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A Report about

COMPHRAHENSIV VIVA
Submitted By

CHANDRA MOHAN REDDY
(Hall Ticket No.: 07D11A0460)

BACHELOR OF TECHNOLOGY IN ELECTRONICS AND COMMUNICATION ENGINEERING

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

TRR ENGINEERING COLLEGE (An ISO 9000: 2000 Certified Institution)

AFFILIATED TO JAWAHARLAR NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD 2007 - 2011

MICROPROCESSORS AND INTERFACING
1. What are Macros? Ans. Macro is a group of instruction. The macro assembler generates the code in the program each time where the macro is called. Macros are defined by MACRO & ENDM directives. Creating macro is similar to creating new opcodes that can be used in the program
• • • • •

INIT MACRO MOV AX, data MOV DS MOV ES, AX ENDM

2. Explain how IRET instruction is executed? A. The IERT instruction is used at the end of the interrupt service routine to return execution to the interrupted program . The 8086 copies return address from stack into IP and CS registers and the stored value of flags back to the flag register .The RET instruction does not copy the flags from the stack back to the flag register. 3. What is the loop instructions of 8086? A. The loop instructions cause the microprocessor to execute a series of instructions repeatedly. Decrements CX by one without affecting flags and performs short jump to the target address if CX is not equal to zero. Loop uses relative addressing mode. MOV CX,0064H ;Initilize counter with 100^10 BACK : ---------------; This section is ; executed 100 ; times,i.e., LOOP BACK 4. What are the features of 8255 PPI? Ans. Three 8-bit Peripheral Ports - Ports A, B, and C ; until CX=0

• • • • •

Three programming modes for Peripheral Ports: Mode 0 (Basic Input/Output), Mode 1 (Strobed Input/Output), and Mode 2 (Bidirectional) Total of 24 programmable I/O lines 8-bit bidirectional system data bus with standard microprocessor interface Controls.

5. What is Interrupt? Ans. The meaning of ‘interrupts’ is to break the sequence of operation.While the cpu is executing a program,on ‘interrupt’ breaks the normal sequence of executionof instructions, diverts its execution to some other program called Interrupt Service Routine (ISR).After executing ISR , the control is transferred back again to the main program. 6. what is type 2 interrupt? A. Non Maskable interrupt is the type 2 interrupt. This interrupt cannot be displayed by any software instruction. This interrupt is activated by low to high transition on 8086 NMI input pin. In response, 8086 will do a type 2 interrupt. 7. what are the types of data communication in 8251? A. 1. Asynchronous transmission 2. Asynchronous reception 3. Synchronous transmission 4. Synchronous reception

8. Register Set of 8051-SFR? Ans. Register Set of 8051-SFR TH0-TL0 and TH1-TL1 16 bit timer registers P0-P3 – port latches SP, PSW, IP – Interrupt Priority, IE – enable TCON – timer/counter control reg to turn on/off the timers, interrupt control flags for ext. int like INT1 and INT0 TMOD – modes of operation of timer/counter SCON – serial port mode control reg

SBUF – serial data buffer for transmit and receive PCON – Power control reg – power down bit, idle bit

MICRO CONTROLLERS AND APPLICATIONS
1. What are 8051 microcontroller’s Internal and External memories? Ans. The 8051 has three very general types of memory. To effectively program the 8051 it is necessary to have a basic understanding of these memory types. The memory types are illustrated in the following graphic. They are: On-Chip Memory, External Code Memory, and External RAM. On-Chip Memory refers to any memory (Code, RAM, or other) that physically exists on the microcontroller itself. On-chip memory can be of several types, but we'll get into that shortly. External Code Memory is code (or program) memory that resides off-chip. This is often in the form of an external EPROM External RAM is RAM memory that resides off-chip. This is often in the form of standard static RAM or flash RAM. 2. How do having separate caches for instruction, data and branch help? A. There are 3 structural units provided in a processor have separate cauches for instruction, data and branch. They are, 1. I-cache (Instruction cache) 2. D-cache (Data cache) 3. BT cache (Branch transfer/Branch target cache). 3. 8051 microcontroller interrupts? Ans. 8051 provides 5 vectored interrupts. They are 1. 2. TF0 3. 4. TF1 5. RI/TI

Out of these, and are external interrupts whereas Timer and Serial port interrupts are generated internally. The external interrupts could be negative edge triggered or low level triggered. All these interrupt, when activated, set the corresponding interrupt flags. Except for serial interrupt, the interrupt flags are cleared when the processor branches to the Interrupt Service Routine (ISR). The external interrupt flags are cleared on branching to Interrupt Service Routine (ISR), provided the interrupt is negative edge triggered. For low level triggered external interrupt as well as for serial interrupt, the corresponding flags have to be cleared by software by the programmer. 4. What is Free running counter in 8051? Ans. The Counter Free-Running block counts up until reaching the maximum value, 2Nbits – 1, where N bits is the number of bits. Then the counter overflows to zero and begins counting up again. After overflow, the counter always initializes to zero. However, if you select the global doubles override, the Counter Free-Running block does not wrap back to zero. 5. How printer inter faces to 8051MCU? Ans. Printer has 8 data lines, and we use two control signals, busy and strobe. Busy pin is made input and strobe as output. First strobe pin is kept high, data to be printed is obtained at particular port then, low to high transition is given to the strobe. then we keep checking the busy pin, if printer is busy then wait, after it becomes free then send next data. for printer interfacing we used DB25 connector. 6. What is Real-Time Operating Systems in Microcontrollers? Ans. Real-time embedded systems serve various purposes, such as to control or process data. A real-time operating system is a piece of software with a set of APIs that developers can use to build applications. RTOSs support the need of some embedded systems to meet deadlines. However, using an RTOS doesn't guarantee that a system will always meet the deadlines, because these systems also depend on the overall system's design. Although RTOSs for embedded systems are predominantly used in high-end microprocessors or microcontrollers with 32-bit CPUs, there is a growing trend to provide these features in mid-range (16-bit and 8-bit) processor systems 7. What are the interrupt vector tables present in the memory map of 80196 A. There are 2 types of interrupt vector tables. They are 1. Lower interrupt vector table 2. Upper interrupt vector table family?

8. What are the addressing modes of ARM MCU? A. The different addressing modes present in ARM MCU are, 1. Register addressing 2. Immediate addressing 3. Indirect base and indexed addressing.

NETWORK ANALYSYS
1. What is Voltage and Current Sources? Ans. Real voltage sources can be represented as ideal voltage sources in series with a resistance r, the ideal voltage source having zero resistance. Real current sources can be represented as ideal current sources in parallel with a resistance r, the ideal current source having infinite resistance. 2. Define Mutual Induction ? Ans. The changing magnetic field created by one circuit (the primary) can induce a changing voltage and/or current in a second circuit (the secondary). The mutual inductance, M, of two circuits describes the size of the voltage in the secondary induced by changes in the current of the primary:
V(secondary) = change in I (primary) - M * ---------------------change in time

The units of mutual inductance are henry, abbreviated "H". 3. Define bandwidth? Ans. The bandwidth of an accelerometer refers to it's useful range of operating frequencies. This is usually defined by the frequency where the amplitude ratio falls to 0.5, the 3 dB point. 4. Define Independent Voltage &? Ans. An ideal independent voltage source is a two-terminal circuit element where the voltage across it a) is independent of the current through it b) can be specified independently of any other variable in a circuit. 5. Maximum Power Transfer Theorem?

Ans..Maximum Power Transfer is another useful analysis method to ensure that the maximum amount of power will be dissipated in the load resistance when the value of the load resistance is exactly equal to the resistance of the power source. The relationship between the load impedance and the internal impedance of the energy source will give the power in the load. 6. What is H - Parameters for two-port network?
Ans. A two-port network (a kind of four-terminal network or quadripole) is an electrical

network or device with two pairs of terminals connected together internally by an electrical network. Two terminals constitute a port if they satisfy the essential requirement known as the port condition: the same current must enter and leave a port.
7. What is Laplace Transform?

Ans. By applying the Laplace transform, one can change an ordinary differential equation into an algebraic equation, as algebraic equation is generally easier to deal with. Another advantage of Laplace transform is in dealing the external force is either impulsive , (the force lasts a very shot time period such as the bat hits a baseball) or the force is on and off for some regular or irregular period of time. 8. What is M-derived filter? Ans. M-derived filters or m-type filters are a type of electronic filter designed using the image method. They were invented by Otto Zobel in the early 1920s. This filter type was originally intended for use with telephone multiplexing and was an improvement on the existing constant k type filter.

CONTROL SYSTEMS
1. what is Open control systems? Ans. In Open-Loop control, no feedback loop is employed and system variations which cause the output to deviate from the desired value are not detected or corrected. 2. How do you construct a signal flow graph from the equations? A. 1. Represent each variable in algebraic equations as a separate node. 2. By using the property of signal flow graph, that the value of any variable (node) is equal to the algebraic sum of entering a signals which are connected to that node. 3. Coefficients of the variables in the algebraic equations are to be represented as the branch gains, which are connecting nodes in the signal flow graph. 4. Show the input and output variables as separate nodes i.e., input node(source)and output node(sink)respectively. 3. The important time response specification of a standard second ordered system to a unit

step input? A. 1. Delay time (Td) 2. Rise time (Tr) 3. Peak time (Tp) 4. Peak overshoot (Mp) 5. Setting time (Ts) 4. What are the limitations of Routh-Hurwitz Criterion? A. 1. This criterion is applicable to only linear and time-invariant systems. 2. This criterion is valid only for characteristics equation which is having real coefficients. 3. This criterion does not give exact locations of the closed loop poles of the system. 4. This criterion does not provide any method to stabilise an unstable system. 5. What is Gain margin? Ans. The gain margin is the amount of gain increase required to make the loop gain unity at the frequency where the phase angle is –180°. In other words, the gain margin is 1/g if g is the gain at the –180° phase frequency. Similarly, the phase margin is the difference between the phase of the response and –180° when the loop gain is 1.0. 6. What is Nyquist Plots? Ans. There are a number of polar graph options for studying control systems including the nyquist, inverse polar plot and the nichols plot. The nyquist open loop polar plot indicates the degree of stability, and the adjustments required and provides stability information for systems containing time delays. Polar plots are not used exclusively because,without powerful computing facilities, they can be difficult to generate at a detailed level and they do not directly yield frequency values. 7. What is lead–lag compensator ? Ans. A lead–lag compensator is a component in a control system that improves an undesirable frequency response in a feedback and control system. It is a fundamental building block in classical control theory. 8. What is state variables? Ans. In Control Engineering and other areas of science and engineering, state variables are used to represent the states of a general system. The state variables can be used to describe the state space of the system. The equations relating the current state and output of a system to its current input and past states are called the state equations. The state equations for a linear time invariant system are expressed with Coefficient matrices.

COMPUTER ORGANIZATION

1. What is digital computer? A. Computer is an programmable machine designed to read and execute sequentially a list of instructions that make it perform arithmetical and logical operations on binary numbers. 2. What is micro-operation? A. Complex digital systems which deals with lots of tasks like logic operation, arithmetic operation contains many hardware whose are interconnected among them is called microoperation. 3. Explain the functions of control unit? A. The functions of the control unit are as follows, 1. Sequencing of Micro-operations. 2. Execution of Micro-operations (a) Hardwired control unit. (b) Micro-programmed control unit. 4. What is decimal arithmetic unit ? Ans. A decimal arithmetic unit is a digital function that performs decimal micro-operations. It can add or subtract decimal numbers, usually by forming the 9's or 10'scomplement of the subtrahend. The unit accepts coded decimal numbers and generates results in the same adopted binary code. A single-stage decimal arithmetic unit consists of nine binary input variables and five binary output variables, since a minimum of four bits is required to represent each coded decimal digit. Each stage must have four inputs for the augend digit, four inputs for the addend digit, and an input-carry. The outputs include four terminals for the sum digit and one for the output-carry. Of course, there is a wide variety of possible circuit configurations dependent on the code used to represent the decimal digits. 5. What is Cache Memory? Ans. A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. As long as most memory accesses are cached memory locations, the average latency of memory accesses will be closer to the cache latency than to the latency of main memory. 6. What are Peripheral devises? Ans. Peripheral devices can be classified according to their functions. Input: Input devices are the type of the computer devices that are used to provide the control signals to the computer. Keyboard and the Mouse are the examples of the input devices.

Output: Output devices are the devices that are used to display the results. Printer, scanner, speaker and the monitor are the examples of the output devices. Storage: A storage device is a device that is used to store the input.

7. What is Parallel processing? Ans. Parallel processing is the simultaneous processing of the same task on two or more microprocessors in order to obtain faster results. The computer resources can include a single computer with multiple processors, or a number of computers connected by a network, or a combination of both. The processors access data through shared memory. Some supercomputer parallel processing systems have hundreds of thousands of microprocessors. 8. What is Interconnection Structures? Ans. A computer consists of a set of components (CPU, memory, I/O) that communicate with each other. The collection of paths connecting the various modules is call the Interconnection Structures. The design of this structure will depend on the exchange that must be made between Modules.

ELECTRONIC DEVICES & CIRCUITS
1. What are Electric and Magnetic fields Ans. Wherever there is electricity, there are also electric and magnetic fields, invisible lines of force created by the electric charges. Electric fields result from the strength of the charge while magnetic fields result from the motion of the charge, or the current. 2. What is the equation of TUF? A. The full form of TUP is Transformer Utilization Factor TUF=Pd.c/Pa.c (rating)

3. What are the different configurations of BJT? A. The three different types of BJT configurations are,

i. Common base configuration ii. Common emitter configuration iii. Common collector configuration.

4. What is biasing? A. The process of obtaining desired Q-point by giving proper supply voltage and resistance is known as biasing. 5. What is Thermal runaway in BJT? Ans. Leakage current increases significantly in bipolar transistors (notably germanium-based bipolar transistors) as they increase in temperature. Depending on the design of the circuit, this increase in leakage current can increase the current flowing through the transistor and with it the power dissipation. 6. What is input impedance? Ans. The input impedance of an electrical network is the equivalent impedance "seen" by a power source connected to that network. If the source provides known voltage and current, such impedance can be calculated using Ohm's Law. The input impedance is the Thévenin's equivalent circuit of the electrical network, modeled by an RL (resistor-inductor) or an RC (resistor-capacitor) combination, with equivalent values that would result in the same response as that of the network. It is also called Z11 in terms of Z-Parameters. 7. What is amplifier gain? Ans. Amplifier gain stands for any of Voltage amplifier, Current amplifier, Trans resistance Trans admittance amplifier

Af =

X X A ; A= 0;β = f 1 + Aβ Xi X0

Xi = Xs − X f

|1 + Aβ | >1 − ve fb , < 1 + ve fb − Ve feed back amplifier depends on  Feed back reduces noise distortion, gain variation due to parameters, increases BW.


+

( 1 + Aβ )

is called de-sensitivity factor.

8. What is Wein Bridge oscillator? Ans. A Wien bridge oscillator is a type of electronic oscillator that generates sine waves. It can generate a large range of frequencies. The circuit is based on an electrical network originally developed by Max Wien in 1891. The bridge comprises four resistors and two capacitors. It can also be viewed as a positive feedback system combined with a band pass filter. Wien did not have a means of developing electronic gain so a workable oscillator could not be realized.

Classic Wien bridge oscillator

PULSE AND DIGITAL CIRCUITS
1. What is high pass RC circuit? A. A circuit which allows high-frequency signals and attenuates or stops the low-frequency signals is called high-pass RC circuit.

2. Explain the non-linear wave shaping? A. “The process where by the form of a sinusoidal or non-sinusoidal signal is altered by transmitting through a non-linear network is called non-linear wave shaping”.

There are 2 types of non-linear wave shaping techniques, 1. Clipping 2. Clamping.

3. What is transistor switch? A. The transistor acts as a switch when it is placed in series with the load and supply voltage.

4. What is multi-vibrator? A. A multi-vibrator is an electronic circuit used to implement a variety of simple two-state systems such as oscillators, timers and flip-flops. 5. What is a voltage time base generator? Ans. A "function generator" generates a voltage equal to some function of time. The most basic models will produce sine, square, and sawtooth waves at different frequencies, but the more expensive models will do all kinds of waves. 6. What is monostable muiltivibrator? Ans. Monostable Multivibrators or "one-shot" pulse generators are used to convert short sharp pulses into wider ones for timing applications. Monostable multivibrators generate a single output pulse, either "high" or "low", when a suitable external trigger signal or pulse T is applied. This trigger pulse signal initiates a timing cycle which causes the output of the monostable to change state at the start of the timing cycle, (t1) and remain in this second state until the end of the timing period, (t1) which is determined by the time constant of the timing capacitor, CT and the resistor, RT. 7. What is sampling gates? Ans. sampling gates are transmission circuits in which the output is an exact replica of input wave from during that selected time interval and is zero otherwise that means only for selected time period the output remains same and for remaining time period the output is zero. 8. What is Diode–transistor logic (DTL)?

Diode–transistor logic (DTL) is a class of digital circuits built from bipolar junction transistors (BJT), diodes and resistors, it is the direct ancestor of transistor–transistor logic. It is called diode–transistor logic because the logic gating function (e.g., AND) is performed by a diode network and the amplifying function is performed by a transistor

LINEAR IC APPLICATIONS
1.Mention the advantages of integrated circuits. Ans. *Miniaturisation and hence increased equipment density. *Cost reduction due to batch processing. *Increased system reliability due to the elimination of soldered joints. *Improved functional performance. *Matched devices. *Increased operating speeds. *Reduction in power consumption. 2. Define an operational amplifier. Ans. An operational amplifier is a direct-coupled, high gain amplifier consisting of one or more differential amplifier. By properly selecting the external components, it can be used to perform a variety of mathematical operations. 3. What is the need for an instrumentation amplifier? Ans. In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help of transducers. The output of transducer has to be amplified So that it can drive the indicator or display system. This function is performed by an instrumentation amplifier. 4. What do you mean by a precision diode? Ans. The major limitation of ordinary diode is that it cannot rectify voltages below the cut – in voltage of the diode. A circuit designed by placing a diode in the feedback loop of an op – amp is called the precision diode and it is capable of rectifying input signals of the order of millivolt. 5. What are the demerits of passive filters? Ans. Passive filters works well for high frequencies. But at audio frequencies, the inductors become problematic, as they become large, heavy and expensive. For low frequency applications, more number of turns of wire must be used which in turn adds to the series resistance degrading inductor’s performance ie, low Q, resulting in high power dissipation. 6. Define capture range of a PLL?

Ans. The range of frequencies over which the PLL can acquire lock with an input signal is called the capture range. It is expressed as a percentage of the VCO free running frequency.

7. Explain in brief the principle of operation of successive Approximation ADC? Ans. The circuit of successive approximation ADC consists of a successive approximation register (SAR), to find the required value of each bit by trial & error. With the arrival of START command, SAR sets the MSB bit to 1. The O/P is converted into an analog signal & it is compared with I/P signal. This O/P is low or High. This process continues until all bits are checked. 8. What is meant by delta modulation? Ans. Delta modulation is a technique capable of performing analog signal quantization with smaller bandwidth requirements. Here, the binary output representing the most recent sampled amplitude will be determined on the basis of previous sampled amplitude levels.

DIGITAL IC APPLICATIONS

1. What is CMOS? Ans. CMOS gates are all based on the fundamental inverter circuit shown to the left. Note that both transistors are enhancement-mode MOSFETs; one N-channel with its source grounded, and one P-channel with its source connected to +V. Their gates are connected together to form the input, and their drains are connected together to form the output. 2. What is TTL logic? Ans. TTL devices make use of bipolar transistors. The main distinguishing features of the basic TTL family is that they demand a power rail which is very close to +5V, and they use a relatively high amount of current to drive their logic levels (below 1V for a logical ‘0’ or ‘low’, and above about 3.5V for a logical ‘1’ or ‘high’).
3. What are Functions and Procedures?

Ans. Functions and procedures in VHDL, which are collectively known as subprograms, are directly analogous to functions and procedures in a high-level software programming language such as C or Pascal. A procedure is a subprogram that has an argument list consisting of inputs and outputs, and no return value. A function is a subprogram that has only inputs in its argument list, and has a return value.

4. What is Structural design elements? Ans. A VHDL architecture that uses components is often called a structural description or Structural design. The important features of structural type of architecture body are, Design hierarchy Components are used Each component is simulated separately In structural modeling, an entity is described as a set of components connected by signals, that is, as a net list. The components used in an architecture may be form a library or may be ones that were previously defined as part of design. 5. What is a decoder? Ans. A decoder is a device which does the reverse of an encoder, undoing the encoding so that the original information can be retrieved. The same method used to encode is usually just reversed in order to decode. 6. What is Barrel Shifter? Ans. A barrel shifter is a digital circuit that can shift a data word by a specified number of bits in one clock cycle. It can be implemented as a sequence of multiplexers (mux.), and in such an implementation the output of one mux is connected to the input of the next mux in a way that depends on the shift distance. 7. What is a shift register? Ans. In digital circuits, a shift register is a cascade of flip flops, sharing the same clock, which has the output of any one but the last flip-flop connected to the "data" input of the next one in the chain, resulting in a circuit that shifts by one position the one-dimensional "bit array" stored in it, shifting in the data present at its input and shifting out the last bit in the array, when enabled to do so by a transition of the clock input. 8. What is SRAM? Ans. Static random-access memory (SRAM) is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit. SRAM exhibits data remanence, but is still volatile in the conventional sense that data is eventually lost when the memory is not powered.

VLSI DESIGN

1. What is BiCMOS? Ans. BiCMOS technology is a combination of Bipolar and CMOS technology. CMOS technology offers less power dissipation, smaller noise margins, and higher packing density. Bipolar technology, on the other hand, ensures high switching and I/O speed and good noise performance. 2. What is Bi-CMOS Inverters? Ans. Two bipolar transistors (T3 and T4), one nMOS and one pMOS transistor (both enhancement-type devices, OFF at Vin=0V)

The MOS switches perform the logic function & bipolar transistors drive output loads Vin = 0 : T1 is off. Therefore T3 is non-conducting T2 ON - supplies current to base of T4 T4 base voltage set to Vdd. T4 conducts & acts as current source to charge load CL towards Vdd. Vout rises to Vdd - Vbe (of T4)

Note :

Vbe (of T4) is base-emitter voltage of T4.

(pullup bipolar transistor turns off as the output approaches 5V - Vbe (of T4)) Vin = Vdd : T2 is off. Therefore T4 is non-conducting.

T1 is on and supplies current to the base of T3 T3 conducts & acts as a current sink to discharge load CL towards 0V. Vout falls to 0V+ VCEsat (of T3) Note : VCEsat (of T3) is saturation V from T3 collector to emitter. 3. What is Stick diagram? Ans. Stick diagrams are commonly used to represent the topology (not the geometry) of CMOS integrated circuits. With a little annotation (FET width and length) they provide adequate information to guide layout and mask generation. Stick diagrams help plan layout quickly – Need not be to scale – Draw with color pencils or dry-erase marker 4.Give the basic process for IC fabrication? Ans.  Silicon wafer Preparation  Epitaxial Growth  Oxidation  Photolithography  Diffusion  Ion Implantation  Isolation technique  Metallization  Assembly processing & Packaging 5. What are gate primitives? Ans. Verilog supports basic logic gates as predefined primitives. Primitive logic function keyword provide the basics for structural modeling at gate level. These primitives are instantiated like modules except that they are predefined in verilog and do not need a module definition. The important operations are and, nand, or, xor, xnor, and buf(non-inverting drive buffer). 6. What is a FPGA?

Ans. A field programmable gate array (FPGA) is a programmable logic device that supports implementation of relatively large logic circuits. FPGAs can be used to implement a logic circuit with more than 20,000 gates whereas a CPLD can implement circuits of upto about 20,000 equivalent gates. 7. Write notes on functionality tests? Ans. Functionality tests verify that the chip performs its intended function. These tests assert that all the gates in the chip, acting in concert, achieve a desired function. These tests are usually used early in the design cycle to verify the functionality of the circuit.. 8. What is fault grading? Ans. Fault grading consists of two steps. First, the node to be faulted is selected. A simulation is run with no faults inserted, and the results of this simulation are saved. Each node or line to be faulted is set to 0 and then 1 and the test vector set is applied. If and when a discrepancy is detected between the faulted circuit response and the good circuit response, the fault is said to be detected and the simulation is stopped.

PROBABILITY THEORY AND STOCHASTIC PROCESSES
1. Define sample space? A. A set of all possible distinct events of a random experiment is known as sample space. Example: The sample space, when a dice is thrown is {1, 2, 3, 4, 5, 6}.

2. Define continous random variable? A. If a random variable ‘X’ takes only of finite or all possible values between certain limits, it is called a continous random variable. Example: Heights, Weights etc.

3. Explain about skew? A. The skew of the density function is a measure of the symmetry of the probability density function fx(x) of random variable X about x=m1.

The skew of a density function is also called as third central movement of the random variable and is given by, µ3= E[(X-m)3].

4. Define conditional probability mass function? Ans. If A and B are 2 random variables. The conditional probability mass function (or) conditional density function of the random variable B, given A=a is, F(b/a)= f(a/b)/g(a), g(a)>0 Where , a,b are arbitrary real numbers f(a,b) is the joint probability density function g(a) is marginal density function of A=a.

5. Write the properties of Gaussian random variables? Ans. The properties of Gaussian random variables are given below, 1. The Gaussian random variables are completely defined through only their means, variances and co-variances. 2. Random variables are said to be statistically independent if they are uncorrelated.

6. Explain the classification of random process? Ans. Random processes are classified into 4 types according to the characteristics of ‘t’ and the random variable X=X(t) at time t. they are, i. Continous random process ii. Discrete random process iii. Continous random sequence iv. Discrete random sequence.

7. State any 1 property of PSD? Ans. For a wide-sense-stationary random process, power spectral density at zero frequency (ω=0) gives the area under the graph of auto correlation.

8. What are the different types of noises? Ans. The various types of noises are, i. Flicker Noise ii. Shot Noise iii. Partition Noise iv. Thermal Noise.

SIGNALS AND SYSTEMS
1. What is SIGNALS AND CLASSIFICATION OF SIGNALS? Ans. A signal is a function representing a physical quantity or variable, and typically it contains information about the behavior or nature of the phenomenon. For instance, in a RC circuit the signal may represent the voltage across the capacitor or the current flowing in the resistor. Mathematically, a signal is represented as a function of an independent variable t. Usually t represents time. Thus, a signal is denoted by x(t). 2. What are the Properties of the Convolution Integral? Ans. The convolution integral has the following properties. I. Commutative: ~ ( t* h) ( t )= h ( t )* ~ ( t ) 2. Associative: { x P )* h l ( 4* h , ( t ) = x ( t )* { h l ( f *) h 2 ( 4) 3. Distributive: x ( t )* { h , ( t ) )+ h N = x ( t )* h l ( t )+ x ( t )* h, ( t ) 3. What are Causal and Stable Systems? Ans. If the system is both causal and stable, then all the poles of H(s) must lie in the left half of the s-plane; that is, they all have negative real parts because the ROC is of the form Re(s) >a max, and since the jo axis is included in the ROC, we must have a,, < 0.

4. Define Z-Transform? Ans. The function H(z) in Eq. (4.2) is referred to as the z-transform of h[n]. For a general discrete-time signal x[n], the z-transform X(z) is defined as m X(Z)= x[n] z - " n= -OD (4.3) The variable z is generally complex-valued and is expressed in polar form as where r is the magnitude of z and R is the angle of z . The z-transform defined in is often called the bilateral (or two-sided) z-transform in contrast to the unilateral. 5. State parseval’s theorem for energy signals? A. The energy of continous time signal x(t) is, E= For energy signal, the average power is zero. Parseval’s theorem for energy signals is, E= Finally, E= 6. What is sampling theorem? A. A continous-time signal can be completely represented in its samples and recovered back, if the sampling frequency ‘fs’ is greater than (or) equal to the twice of highest frequency component of the message signal ‘fm’ i.e., Fs≥2fm 7. What are the types of system? A. A system are of three types. They are, i. Stable system ii. Unstable system iii. Marginally stable system.

8. What are the methods for finding inverse Z-transform? A. Methods for finding inverse Z-transform are as follows, i. Power series expansion or long division method ii. Partial fraction method iii. Residue method.

DIGITAL SIGNAL PROCESSING
1. What is a continuous and discrete time signal? Ans. Continuous time signal: A signal x(t) is said to be continuous if it is defined for all time t. Continuous time signal arise naturally when a physical waveform such as acoustics wave or light wave is converted into a electrical signal. This is effected by means of transducer.(e.g.) microphone, photocell. Discrete time signal: A discrete time signal is defined only at discrete instants of time. The independent variable has discrete values only, which are uniformly spaced. A discrete time signal is often derived from the continuous time signal by sampling it at a uniform rate. 2. What are time invariant systems? Ans. A system is said to be time invariant system if a time delay or advance of the input signal leads to an idenditical shift in the output signal. This implies that a time invariant system responds idenditically no matter when the input signal is applied. It also satisfies the condition R{x(n-k)}=y(n-k). 3. Differentiate between DIT and DIF algorithm Ans. DIT – Time is decimated and input is bi reversed format output in natural order DIF – Frequency is decimated and input is natural order output is bit reversed format. 4. Distinguish analog and digital filters Ans. Analog Filter
1. Constructed using active or passive components and it is

Digital Filter
Consists of elements like adder, subtractor and delay units and it is

described by a differential equation 2. Frequency response can be changed by changing the components 3. It processes and generates analog output 4. Output varies due to external conditions

described by a difference equation Frequency response can be changed by changing the filter coefficients Processes and generates digital output Not influenced by external conditions

5. What is warping effect? Ans. For smaller values of w there exist linear relationship between w and .but for larger values of w the relationship is nonlinear. This introduces distortion in the frequency axis. This effect compresses the magnitude and phase response. This effect is called warping effect 6. Write the steps involved in FIR filter design? Ans.  Choose the desired frequency response Hd(w)  Take the inverse Fourier transform and obtain Hd(n)  Convert the infinite duration sequence 7.What is the principle of designing FIR filter using frequency sampling method? Ans. In frequency sampling method the desired magnitude response is sampled and a linear phase response is specified .The samples of desired frequency response are defined as DFT coefficients. The filter coefficients are then determined as the IDFT of this set of samples. 8. List the on-chip peripherals in 5X. Ans. The C5X DSP on-chip peripherals available are as follows: 1. Clock Generator 2. Hardware Timer 3. Software-Programmable Wait-State Generators 4. Parallel I/O Ports 5. Host Port Interface (HPI) 6. Serial Port 7. Buffered Serial Port (BSP) 8. Time-Division Multiplexed (TDM) Serial Port 9. User-Maskable Interrupts

DIGITAL IMAGE PROCESSING
1. Define Image?

Ans. An Image may be defined as a two dimensional function f(x,y) where x & y are spatial (plane) coordinates, and the amplitude of f at any pair of coordinates (x,y) is called intensity or gray level of the image at that point. When x,y and the amplitude values of f are all finite, discrete quantities we call the image as Digital Image. 2. Write the expression of one-dimensional discrete Fourier transforms Ans. Forward transform The sequence of x(n) is given by x(n) = { x0,x1,x2,… xN-1}. X(k) = (n=0 to N-1) _ x(n) exp(-j 2* pi* nk/N) ; k= 0,1,2,…N-1 Reverse transforms X(n) = (1/N) (k=0 to N-1) _ x(k) exp(-j 2* pi* nk/N) ; n= 0,1,2,…N-1 3. Write the properties of Hadamard transform Ans. 1) Hadamard transform contains any one value. 2) No multiplications are required in the transform calculations. 4) The no: of additions or subtractions required can be reduced from N^2 to about Nlog2N 5) Very good energy compaction for highly correlated images. 4. What is Chromatic Adoption? Ans. The hue of a perceived color depends on the adoption of the viewer. For example, the American Flag will not immediately appear red, white, and blue of the viewer has been subjected to high intensity red light before viewing the flag. The color of the flag will appear to shift in hue toward the red component cyan. 5. How the blur is removed caused by uniform linear motion? Ans. An image f(x,y) undergoes planar motion in the x and y-direction and x0(t) and y0(t) are the time varying components of motion. The total exposure at any point of the recording medium (digital memory) is obtained by integrating the instantaneous exposure over the time interval during which the imaging system shutter is open. 6. What is Image Transform? Ans. An image can be expanded in terms of a discrete set of basis arrays called basis images. These basis images can be generated by unitary matrices. Alternatively, a given NXN image can be viewed as an N^2X1 vectors. An image transform provides a set of coordinates or basis vectors for vector space. 7. Name the categories of Image Enhancement and explain? Ans. The categories of Image Enhancement are 1. Spatial domain 2. Frequency domain

Spatial domain: It refers to the image plane, itself and it is based on direct manipulation of pixels of an image. Frequency domain techniques are based on modifying the Fourier transform of an image. 8. What is Huffman Coding? Ans. Huffman compression reduces the average code length used to represent the symbols of an alphabet. Symbols of the source alphabet, which occur frequently, are assigned with short length codes. The general strategy is to allow the code length to vary from character to character and to ensure that the frequently occurring characters have shorter codes.

ANTENNAS AND WAVE PROPAGATION
1. What is meant by radiation pattern? Ans. Radiation pattern is the relative distribution of radiated power as a function of distance in space .It is a graph which shows the variation in actual field strength of the EM wave at all points which are at equal distance from the antenna. The energy radiated in a particular direction by an antenna is measured in terms of FIELD STRENGTH.(E Volts/m) 2. What is meant by antenna beam width? Ans. Antenna beam width is a measure of directivity of an antenna. Antenna beam width is an angular width in degrees, measured on the radiation pattern (major lobe) between points where the radiated power has fallen to half its maximum value .This is called as “beam width” between half power points or half power beam width.(HPBW). 3.What is meant by uniform linear array.? Ans. An array is linear when the elements of the array are spaced equally along the straight line. If the elements are fed with currents of equal magnitude and having a uniform progressive phase shift along the line, then it is called uniform linear array . 4. List the applications of helical antenna? Ans.The applications of helical antenna are:
 It became the workhouse of space communications for telephone,

television and data, being employed both on satellites and at ground stations
 Many satellites including weather satellites, data relay satellites all have

helical antennas

 It is on many other probes of planets and comets, including moon and mars, being used alone, in arrays or as feeds for parabolic reflectors, its circular polarization and high gain and simplicity making it effective for space application 5. What is meant by Space Wave.? Ans. It is made up of direct wave and ground reflected wave. Also includes the portion of energy received as a result of diffraction around the earth surface and the reflection from the upper atmosphere 6. What is meant by Faraday’ s rotation? Ans. Due to the earth’ s magnetic fields, the ionosphere medium becomes anisotropic and the incident plane wave entering the ionosphere will split into ordinary and extra ordinary waves/modes. When these modes re-emerge from the ionosphere they recombine into a single plane wave again. Finally the plane of polarization will usually have changed, this phenomenon is known as Faraday’ s rotation. 7. Define LUHF? Ans. The lowest useful HF for a given distance and transmitter power is defined as the lowest frequency that will give satisfactory reception for that distance and power. It depends on  The effective radiated power  Absorption character of ionosphere for the paths between transmitter and receiver.  The required field strength which in turn depends upon the radio noise at the receiving location and type of service involved . 8. Define skip distance? Ans. The distance with in which a signal of given frequency fails to be reflected back is the skip distance for that frequency. The higher the frequency the greater the skip distance.

MICROWAVE ENGINEERING
1. Define s-matrix Ans. In a microwave junction there is intersection of three or more components. There will be an output port ,in addition there may be reflection from the junction of other ports. Totally there may be many combinations, these are represented easily using a matrix called S matrix 2. What are ferrites and give its properties? Ans. Ferrites are ceramic like materials. These are made by by sintering a mixture of metallic oxides. Properties  Specific resistivity is may be used as much as 1014 greater than that of metals

 Dielectric constants around 10to 15 or greater  Relative permeability is 1000 3.What is Faraday’s rotation law? Ans. If a circularly polarized wave is made to pass through a ferrite rod which has been influenced by an axial magnetic field B ,then the axis of polarization gets tilted in clockwise direction and amount of tilt depends upon the strength of magnetic field and geometry of the ferrite . What are the assumptions for calculation of RF power in Reflex Klystron? Ans. i) Cavity grids and repeller are plane parallel and very large in extent. ii) No RF field is excited in repeller space iii) Electrons are not intercepted by the cavity anode grid. iv) No debunching takes place in repeller space. v) The cavity RF gap voltage amplitude V, is small compared to the dc beam voltage VO 5. Dicuss the high frequency effects in conventional tubes? Ans. The high frequency effects in conventional tubes are i) Circuit reactance a)Inter electrode capacitance b) Lead inductance ii) Transit time effect iii) Cathode emission iv) Plate heat dissipation area v) Power loss due to skin effect, radiation and dielectric loss 6. What is the purpose of slow wave structures used in TWT amplifiers? Ans. Slow wave structures are special circuits that are used in microwave tubes to reduce wave velocity in a certain direction so that the electron beam and the signal wave can interact. In TWT, since the beam can be accelerated only to velocities that are about a fraction of the velocity of light, slow wave structures are used. 7. What are the applications of TRAPATT devices? Ans. The applications are a)Phased-array Radar systems b)Intermediate frequency transmitters.

c)Proxity fuse sources d)Radio altimeters e)Microwave landing systems. 8.What is negative resistance in gunn diode? Ans. The carrier drift velocity increases linearly from 0 to maximum when the electric field is increased from 0 to threshold value in gunn diodes. When the electric field is beyond the threshold value of 3000v/cm the drift velocity is decreased and the diode exhibit negative resistance.

OPTICAL COMMUNICATION
1. Define Numerical aperture of a step index fiber? Ans. Numerical aperture (N.A) of the fiber is the light collecting efficiency of the fiber and is the measure of the amount of light rays that can be accepted by the fiber. It is equal to the sine of acceptance. N.A= n0 sin θ0max = (n12 - n22)1/2 where n1 and n2 are the refractive indices of core and cladding respectively. 2. What are the uses of optical fibers? Ans. a) To transmit the information which are in the form of coded signals of the telephone communication, computer data, etc. b) To transmit the optical images (Example : Endoscopy) c) To act as a light source at the inaccessible places. d) To act as sensors to do mechanical, electrical and magnetic measurements 3. What is Guide dispersion? Ans. Wave guide dispersion which occurs because of a single mode fiber confines only about 80% of optical power to the core. Dispersion this arises since 20% of light propagates in cladding travels faster than the light confined to the core. Amount of wave-guide dispersion depends on fiber design. Other factor for pulse spreading is inter modal delay 4. Give an account on single mode lasers and modulation of laser diodes.? Ans. Single mode lasers: It is used for long-distance communication. It consists of a single longitudinal mode and single transverse mode. The spectral width is low. Alternative devices developed are

1. Vertical cavity surface emitting lasers 2. Structures that have a built-in frequency-selective grating. 3. Tunable lasers. 5. Define direct band gap materials and indirect band gap materials.? Ans. Direct band gap: In direct band gap materials direct transition is possible from valence band to conduction band. e.g. GaAs, InP, InGaAs Indirect band gap: In indirect band gap materials direct transition is not possible from valence band to conduction. e.g. silicon, germanium. 6. Define internal quantum efficiency. Ans. The internal quantum efficiency is the fraction of the electron-hole pairs that recombine radiatively.If the radiative recombination rate is R and the non radiative recombination rate is Rnr, then the internal quantum efficiency is the ratio of the ratio of the radiative recombination rate to the total recombination rate 7. What is meant by ‘population inversion’? Ans. In thermal equilibrium, the density of excited electrons is very small. Most photons incident on the system will therefore be absorbed, so that stimulated emission is essentially negligible. Stimulated emission will exceed absorption only if the population of the excited states is greater than that of the ground state. This condition is known as population inversion. 8. Write in detail about avalanche photodiodes and explain briefly about photo detector noise and SNR? Ans. Avalanche photodiodes a. Impact ionization b. Avalanche effect c. Reach-through construction d. p+ _ p n+ reach- through structure e. Principle of reach through f. Ionization rate Photo detector noise SNR at output of an optical receiver Condition to achieve a high SNR SNR S = (ip2)M2 N 2q(Ip+ID)M2F(M)+2qILB+4KBTB/RL

EM WAVES AND TRANSMISSION LINES
1. Define conductivity of a material? Ans. According to the Ohms laws, conductivity defined as the current density per unit electric field. Based upon conductivity materials classified into two types, 1. Conductors 2. Non-conductors. Conductivity of the material depends upon the frequency and temperature. 2. Define magnetic flux density? Ans. Magnetic flux constitutes the magnetic lines of force produced by a permanent magnet or a current carrying conductor. In case of current carrying conductor, the magnetic lines of force surround the conductor to form concentric circles and they do not intersect each other. 3. Explain faraday's law for time varying fields? Ans. Faraday's first law of electromagnetic induction states that "When ever the number of magnetic lines of force (called as magnetic flux) passing through a conductor changes, an e.m.f is induced in it". Faraday's second law of electromagnetic induction states that "The magnetic of the induced e.m.f. is proportional to the rate of change of magnetic lines of force". 4. What is meant by the polarization of wave? Ans. By definition, the polarization of a wave is the locus of the tip of the electric field at a given point as a function of time. When two or more waves of the same frequency propagate in the same direction. 5. Define plane of incidence? Ans. If the wave travel through one medium and then enters another medium of infinite extent and is assumed that the interface between the two media is normal to the direction of propagation of the incoming wave is called the incident wave and the medium in which this waves travels is called plane of incidence. 6. Explain the term "conduction current"? Ans. It is the current caused by the applied electric field to any conductor, A.A current through a resistive element is called conduction current. If a constant potential difference is applied across a conductor produces a continuous flow of current of constant value can be termed as conduction current.

7. Define reflection coefficient? Ans. It is the ratio of reflected to incident electric field strength. Reflection coefficient has different values for both parallel and perpendicular polarization. 8. What are equi-potential surfaces? Ans. If the potential throughout the surface is same, then such surface is referred as equipotential surface. The line intersection of an equi-potential surface and a plane results in a path or line known as an equi-potential line.

RADAR SYSTEMS
1. Give the Radar equation? Ans. The power Pr returning to the receiving antenna is given by the radar equation:

2. Write short notes about Noise in Radar? Ans. Signal noise is an internal source of random variations in the signal, which is generated by all electronic components. Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver. 3. What isDoppler effect? Ans. Ground-based radar systems used for detecting speeds rely on the Doppler effect. The apparent frequency (f) of the wave changes with the relative position of the target. The Doppler equation is stated as follows for vobs (the radial speed of the observer) and vs (the radial speed of the target) and f0 frequency of wave :

4. What is FM – CW RADAR? Ans. Frequency Modulated Continuous-wave radar is a short range measuring radar set. This kind of radar is often used as “radar altimeter” to measure the exact height during the landing procedure of aircraft

FMCW) is a radar system where a known stable frequency wave radio energy is modulated by a triangular modulation signal so that it varies gradually and then mixes with the signal reflected from a target object with this transmit signal to produce a beat signal. 5. What is MTI Radar? Ans.
 MTI radars introduce additional loss. The MTI discrimination technique results in

complete loss of sensitivity for certain target values (blind speeds)
 In a radar with overlapping range gates, the gates may be wider than optimum for

practical reasons.
 The additional noise introduced by non – optimum gate width leads to

degradation performance.
 Straddling loss accounts for loss in SNR for targets not at the centre of a range

gate, or at the centre of a filter in a multiple bank processor

6. What is RADAR attrack extraction? Ans. Radar video returns on aircraft can be subjected to a plot extraction process whereby spurious and interfering signals are discarded. A sequence of target returns can be monitored through a device known as a plot extractor. The non relevant real time returns can be removed from the displayed information and a single plot displayed. In some radar systems, or alternatively in the command and control system to which the radar is connected, a radar tracker is used to associate the sequence of plots belonging to individual targets and estimate the targets' headings and speeds. 7. Reduction of interference effects in Radar? Ans. Signal processing is employed in radar systems to reduce the radar interference effects. Signal processing techniques include moving target indication (MTI), pulse Doppler, moving target detection (MTD) processors, correlation with secondary surveillance radar (SSR) targets, space-time adaptive processing (STAP), and track-before-detect (TBD). Constant false alarm rate (CFAR) and digital terrain model (DTM) processing are also used in clutter environments 8. What are the requirements of Radar receiver? Ans. The ideal radar receiver is required to:
• •

amplify the received signals without adding noise or introducing any form of distortion; optimise the probability of detection of the signal by its bandwidth characteristics.

• •

provide a large dynamic range to accommodate large clutter signals; reject interfering signals so that the required information can be optimally detected.

. ANALOG COMMUNICATIONS
1. What is the need for modulation? Ans. Mainly to decrease the antenna size  to increase the bandwidth of the signal  to multiplex the signals  to reduce the interference made when we transmit the signals with nearly same frequency in the audio frequency range (20-20k)kHz.  to favour the complexity of the transmission system

2. What is Costas Loop? Ans. A Costas loop is a phase-locked loop used for carrier phase recovery from suppressedcarrier modulation signals, such as from double-sideband suppressed carrier signals. The primary application of Costas loops is in wireless receivers. Its advantage over the PLL-based detectors is that at small deviations the Costas loop error voltage is sin(2(θi−θf)) vs sin(θi−θf). This translates to double the sensitivity and also makes the Costas loop uniquely suited for tracking Dopplershifted carriers esp. in OFDM and GPS. 3. What is SSB? Ans. Single-sideband modulation (SSB) is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth. It is closely related to vestigial sideband modulation (VSB) Amplitude modulation produces a modulated output signal that has twice the bandwidth of the original baseband signal. Single-sideband modulation avoids this bandwidth doubling, and the power wasted on a carrier, at the cost of somewhat increased device complexity. 4. What is FM? Ans. Frequency modulation (FM) conveys information over a carrier wave by varying its instantaneous frequency. This is in contrast with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant. In analog applications, the difference between the instantaneous and the base frequency of the carrier is directly proportional to the instantaneous value of the input signal amplitude. Digital data can be sent by

shifting the carrier's frequency among a set of discrete values, a technique known as frequencyshift keying. FM is widely used for broadcasting of music and speech, and in two-way radio systems

5. Noise in Analog communication? Ans. Analog systems are less tolerant to noise, make good use of bandwidth, and are easy to manipulate mathematically. However, analog signals require hardware receivers and transmitters that are designed to perfectly fit the particular transmission. If you are working on a new system, and you decide to change your analog signal, you need to completely change your transmitters and receivers.

6. What is a Radio transmitter? Ans. Radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. In addition to their use in broadcasting, transmitters are necessary component parts of many electronic devices that communicate by radio. 7. What is a Radio receiver? Ans. A radio receiver is an electronic circuit that receives its input from an antenna, uses electronic filters to separate a wanted radio signal from all other signals picked up by this antenna, amplifies it to a level suitable for further processing, and finally converts through demodulation and decoding the signal into a form usable for the consumer, such as sound, pictures, digital data, measurement values, navigational positions, etc 8. What is TDM? Ans. Time-division multiplexing (TDM) is a method of putting multiple data streams in a single signal by separating the signal into many segments, each having a very short duration. Each individual data stream is reassembled at the receiving end based on the timing. The circuit that combines signals at the source (transmitting) end of a communications link is known as a multiplexer. It accepts the input from each individual end user, breaks each signal into segments, and assigns the segments to the composite signal in a rotating, repeating sequence.

DIGITAL COMMUNICATIONS
1. What are the advantages of digital communication? Ans. 1. Digital communication is fast and easier. 2. The transmission quality is very high and almost independent of the distance among the terminals. 3. We can increase the capacity for transmission system. 4. The newer types of transmission media such as light beams optical fibers and wave guides operating in the microwave frequency extensively use digital communication. 5. Consistent communication: Very less sensitivity to changes in environmental conditions (temperature and so on.) 6. Then signaling also very easy. 2. What is delta modulation? Ans. Delta modulation (DM or Δ-modulation)is an analog-to-digital and digital-to-analog signal conversion technique used for transmission of voice information where quality is not of primary importance. DM is the simplest form of differential pulse-code modulation (DPCM where the difference between successive samples is encoded into n-bit data streams. In delta modulation, the transmitted data is reduced to a 1-bit data stream. Its main features are:
• • •

the analog signal is approximated with a series of segments each segment of the approximated signal is compared to the original analog wave to determine the increase or decrease in relative amplitude the decision process for establishing the state of successive bits is determined by this comparison

3. What is QPSK? Ans. QPSK, which stands for Quadrature Phase Shift Keying, refers to a type of phase modulation algorithm where there are four states involved. These four states also refer to four phases wherein a particular carrier is sent to QPSK. These states consist of 45, 135, 225, and 315 degrees. QPSK is an algorithm providing procedures used in calculating and finding a specific value. With regards to its encoding, QPSK is capable of processing two bits for each symbol. This is due to the fact that QPSK has four possible states.

QPSK is applied extensively on certain systems. It can be used to maintain the data rate while ensuring that the bandwidth of the signal is stable. This enables the system to efficiently utilize its bandwidth resources.

4. What is baseband signal? Ans. A baseband signal converter device for an impulse radio receiver combines multiple converter circuits and an RF amplifier in a single integrated circuit package. Each converter circuit includes an integrator circuit that integrates a portion of each RF pulse during a sampling period triggered by a timing pulse generator. The integrator capacitor is isolated by a pair of Schottky diodes connected to a pair of load resistors. A current equalizer circuit equalizes the current flowing through the load resistors when the integrator is not sampling. Current steering logic transfers load current between the diodes and a constant bias circuit depending on whether a sampling pulse is present. 5. Define Shannon’s Entropy? Ans. Shannon's entropy represents an absolute limit on the best possible lossless compression of any communication, under certain constraints: treating messages to be encoded as a sequence of independent and identically-distributed random variables, Shannon's source coding theorem shows that, in the limit, the average length of the shortest possible representation to encode the messages in a given alphabet is their entropy divided by the logarithm of the number of symbols in the target alphabet. 6. Define Shannon’s Theorem? Ans. A given communication system has a maximum rate of information C known as the channel capacity. If the information rate R is less than C, then one can approach arbitrarily small error probabilities by using intelligent coding techniques. To get lower error probabilities, the encoder has to work on longer blocks of signal data. This entails longer delays and higher computational requirements. 7. What is linear block codes? Ans. If more error-correcting bits are included with a message, and if those bits can be arranged such that different incorrect bits produce different error results, then bad bits could be identified. In a 7-bit message, there are seven possible single bit errors, so three error control bits could potentially specify not only that an error occurred but also which bit caused the error 8. What is Convolutional Codes? Ans. This chapter describes the encoder and decoder structures for convolutional codes. The encoder will be represented in many different but equivalent ways. Also, the main decoding

strategy for convolutional codes, based on the Viterbi Algorithm, will be described. A firm understanding of convolutional codes is an important prerequisite to the understanding of turbo codes.

TELECOMMUNICATION SWITCHING SYSTEMS

1. Principles of cross bar switching? Ans. A crossbar switch (also known as cross-point switch, crosspoint switch, or matrix switch) is a switch connecting multiple inputs to multiple outputs in a matrix manner. Originally the term was used literally, for a matrix switch controlled by a grid of crossing metal bars, and later was broadened to matrix switches in general. It is one of the principal switch architectures, together with a memory switch and a crossover switch. 2. What is Electronic space division switching? Ans. All the automatic telephone switches, both electromechanical and electronic, discussed up to this point are classified as space-division switches. Space-division switches are characterized by the fact that the speech path through a telephone switch is continuous throughout the exchange. That speech path is a metallic circuit, in the sense that it is provided entirely through the metallic. 3. What is Subscriber loop systems? Ans. Subscriber Loop Carrier (SLC - commonly pronounced "slick") refers to equipment providing central office-like telephone interface functionality. The SLC Remote Terminal (RT) is typically located in a remote (from the telephone company central office) area with a high density of telephone service such as a residential neighborhood. 4. What is Grade of service and blocking probability? Ans. Grade of service is the probability of a call in a circuit group being blocked or delayed for more than a specified interval, expressed as a vulgar fraction or decimal fraction. This is always with reference to the busy hour when the traffic intensity is the greatest. Grade of service may be viewed independently from the perspective of incoming versus outgoing calls, and is not necessarily equal in each direction or between different source-destination pairs. 5. Define network architecture? Ans. Network architecture is the design of a communications network. It is a framework for the specification of a network's physical components and their functional organization and configuration, its operational principles and procedures, as well as data formats used in its operation.

In telecommunication, the specification of a network architecture may also include a detailed description of products and services delivered via a communications network, as well as detailed rate and billing structures under which services are compensated. 6. What is OSI model? Ans. The Open Systems Interconnection model (OSI model) is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a way of subdividing a communications system into smaller parts called layers. A layer is a collection of similar functions that provide services to the layer above it and receives services from the layer below it. On each layer, an instance provides services to the instances at the layer above and requests service from the layer below. 7. What is ISDN? Ans. Integrated Services Digital Network (ISDN) is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.

8. What is cable modem? Ans. A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a HFC and RFoG network. They are commonly deployed in Australia, Europe, Asia and Americas Hybrid fiber-coaxial (HFC) is a telecommunications industry term for a broadband network which combines optical fiber and coaxial cable. Radio Frequency over Glass (RFoG) is a deep fiber network design in which the coax portion of the HFC network is replaced by a single-fiber, passive optical architecture (PON)

CELLULAR AND MOBILE COMMUNICATIONS
1. What is Cellular network? Ans. A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (e.g., mobile phones, pagers, etc.) to communicate with each

other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission 2. What are the elements in Cellular Mobile Radio System Design? Ans. Elements of Cellular Mobile Radio System Design 1 (1) the concept of frequency reuse channels 2 (2) the co‐channel interference reduction factor 3 (3) the desired carrier‐to‐interference ratio 4 (4) the handoff mechanism 5 (5) cell splitting.

3. What is co channel interference? Ans. Co-channel interference with a desired signal in a receiver arrangement of a TDMA cellular radio communications system having two antennas and receivers for providing two received signals is reduced. Two sampled signals are derived from each of the two received signals by sampling the respective received signal at twice the symbol rate of the system and separating alternate samples at twice the symbol rate to produce the two sampled signals each with different samples at the symbol rate, providing a total of four sampled signals from the two antennas. These signals are linearly combined with respective weights to produce an output signal, the weights being determined to reduce co-channel interference with the desired signal represented by the output signal. 4. Discuss the merits of point-to-point model? Ans. 1.The point-to-point provides a more accurate path loss data, while the area-to-area model provides data with 8 bD in case of point-to-point model. 2.The point-to-point prediction model can generate signal coverage maps, interference area maps, hands-off occurrence maps. 5. What is Omni directional antenna?Ans. An omnidirectional antenna is an antenna which radiates power uniformly in one plane, with the radiated power decreasing with elevation angle above or below the plane, dropping to zero on the antenna's axis. Omnidirectional antennas are widely used for radio broadcasting antennas, and in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, Wifi, cordless phones, GPS as well as for base stations that communicate with mobile radios, such as police and taxi dispatchers and aircraft communications. 6. What is Channel allocation?

Ans. In TDMA and FDMA based cellular radio systems and wireless networks, channel allocation schemes are required to allocate channels to base stations and access points and to avoid co-channel interference among nearby cells. A number of approaches have been tried to assign bandwidth to users in an efficient manner while minimizing interference to other users. 7. What is cell splitting? Ans. Cell splitting is one of the concept used to improve the utilization of spectrum efficiency. When the traffic density is more in the system then the frequency channel present in a cell unit provide enough mobile calls, hence the original call be split into smaller cells, which is known as cell splitting. 8. What are GSM channels? Ans. GSM provides a number of different types of channels for user traffic and signaling. These channels are divided into two classes: 1. Traffic channels 2. Signaling channels

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