electrical engineering
Content
Practical Aspects of Microwave Filter Design and Realization
IMS’05 Workshop-WMB
Microstrip Filter Design
Jia-Sheng Hong
Heriot-Watt University Edinburgh, UK
[email protected]
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
1
Outline
Introduction Design considerations Design examples Summary
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
2
Introduction- Driving forces
Recent development of microstrip filters has been driven by applications Wireless communications Wireless sensor/radar systems …….
Driven by technologies High temperature superconducting Micromachining LTCC Ferroelectric …….
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
3
Introduction- Microstrip Filter Publications
Total 600+ in recent 10 years
120 100
Search from IEEE Xplore
N u m b e r
80 60 40 20 0
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
4
Design Considerations- Topologies
l1 l2 ln l n+1
WC WL l1 l2 l3 l4 l5 l6 l7
Y0
W1 s1 W1
W2 s2 W2
C2 L2 Z0 L1 L3
C4 L4 L5 C6 Z0
W1 W2 W3 Wn
Wn sn Wn
Wn+1 sn+1 Wn+1
Y0
CL1 CL2
l g0/4 l g0/4
CL3
CLn-1 CLn
l1
l2
l3
ln
0 1 2 3
q0
n-1
n
n+1
l1h
l2h
l3h
l4h
l5h
Yt qt
Y1
Yn
Yt
l1v s1 s2 l2v s3
l3v s5 s4 l4v
l5v W
YA
s1,2 s2,3 sn-1,n
~λ/4
YA
~λ/4
~λ/4
~λ/4
Via hole grounding
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
5
Design Considerations- Topologies
The choice of a topology depends on Characteristics of filters, such as chebyshev or elliptic Bandwidth Size Power handling
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
6
Design Considerations- Substrates
The choice of a substrate depends on Size Higher-order modes Surface wave effects Implementations – couplings, line/spacing tolerances, … Dielectric loss Temperature stability Power handling – dielectric strength (breakdown), thermal conductivity
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
7
Design Considerations- Higher-order modes
Keep operating frequencies below the cutoff frequency of c the 1st higher-order mode, f c =
ε r (2W + 0.8h )
90 W = 1.0 mm 90
Cutoff frequency fc (GHz)
70 60 50 40 30 20 0.2 0.4 0.6 0.8 1.0 1.2
εr = 6.15 εr = 10.8
Cutoff frequency fc (GHz)
80
εr = 3
80 70 60 50 40 30 20 10
εr = 10.8
W=0.5 mm W=1.0 mm W=1.5 mm
1.4
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Substrate thickness h (mm)
Substrate thickness h (mm)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
8
Design Considerations- Surface waves
Keep operating frequencies below the threat frequency of the lowest surface wave mode,
c tan −1 ε r fs = 2πh ε r − 1
700
Threat frequency fs (GHz)
600 500 400 300 200 100 0 0.2 0.4 0.6 0.8 1.0
εr = 3 εr = 6.15 εr = 10.8
at which the surface mode couples strongly to the dominant mode of microstrip because the phase velocities of the two modes are close.
1.2
1.4
Substrate thickness h (mm)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
9
Design Considerations- Losses
There are three major losses in a microstrip resonator: Conductor loss Dielectric loss Radiation loss
⎛ h ⎞ ⎛ 377Ω ⎞ Qc ∝ π ⎜ ⎟ ⋅ ⎜ ⎜ R ⎟ ⎝λ⎠ ⎝ s ⎟ ⎠
Qd ∝
1 tan δ
1 1 1 1 = + + Qu Qc Qd Qr
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
10
Design Considerations- Power handling
Peak power handling capability –
when the breakdown occurs in substrate
Vo2 Pp ∝ 2Z c
Vo is the maximum breakdown voltage of the substrate Zc is the characteristic impedance of the microstrip
Narrower band filters result in higher electric field density, leading to a lower peak power handling
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
11
Design Considerations- Temperature effect
Temperature characteristic of a microstrip half-wavelength resonator on RT/Duroid substrate with εr = 10.2, h = 1.27 mm Copper CTE (coefficient of thermal expansion) = 17 ppm/oC Substrate CTE = 24 ppm/oC Substrate TCK (thermal coefficient of εr) = −425 ppm/oC
At 23 oC At 73 oC for copper CTE only At 73 oC for substrate thickness CTE only At 73 oC for substrate TCK only At 73 oC (consider all) f0 = 1929.8 MHz f0 = 1928.1 MHz f0 = 1929.9 MHz f0 = 1949.4 MHz f0 = 1947.8 MHz ∆f = 0 ∆f = −1.7 MHz ∆f = 0.1 MHz ∆f = 19.6 MHz ∆f = 18.0 MHz
Frequency variation versus temperature is mainly due to dielectric constant change vs temperature
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
12
Design Examples- Open-loop filters
1 2
4 3
1
2 3
5 4
6
(a)
1 1 2 3 4 6 5 7 8 2
( b)
8 3 4 6 5 7
( c)
( d)
From: Jia-Sheng Hong and M.J.Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons. Inc. New York, 2001
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
13
Design Examples- Open-loop filters
Specifications:
Center frequency Fractional Bandwidth 40dB-Rejection Bandwidth Passband Return loss 985MHz 10.359% 125.5MHz −20dB
Design parameters for an 8-pole filter:
M 1, 2 = M 7 ,8 = 0.08441 M 3, 4 = M 5, 6 = 0.05375 M 3, 6 = −0.01752 M 2,3 = M 6, 7 = 0.06063 M 4,5 = 0.0723 Qei = Qeo = 9.92027
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
14
Design Examples- Open-loop filters
Realisation 1
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm. Each resonator has a size of 16 by 16 mm.
0 -5 Insertion/Return Loss (dB) -10 -15 -20 -25 -30 -35 -40 925 950 975 1000 1025 1050
Insertion loss Return loss
0
-20 Insertion Loss (dB)
-40
-60
-80
600
800
1000
1200
1400
Frequency (MHz)
Frequency (MHz)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
15
Design Examples- Open-loop filters
Realisation 2
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
16
Design Examples- Trisection open-loop filters
Midband or centre frequency Bandwidth of pass band Return loss in the pass band : 905MHz : 40MHz : < −20dB
f 01 = f 03 = 899.471 MHz f 02 = 914.713 MHz Qei = Qeo = 15.7203 M 12 = M 23 = 0.04753 M 13 = −0.02907
0 -10 Magnitude (dB) -20 -30 -40
Rejection : > 20dB for frequencies ≥ 950MHz
S21 S11
-50 700 750 800 850 900 950 1000 1050 1100 Frequency (MHz)
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm
Measured response
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
17
Design Examples- Trisection open-loop filters
Midband or centre frequency Bandwidth of pass band Return loss in the pass band : 910MHz : 40MHz : < −20dB
f 01 = f 03 = 916.159 MHz f 02 = 905.734 MHz Qei = Qeo = 14.6698 M 12 = M 23 = 0.05641 M 13 = 0.01915
0 -10 Magnitude (dB) -20 -30 -40 -50 -60 700 750 800 850 900 950 1000 1050 1100 S21 S11
Rejection : > 35dB for frequencies ≤ 843MHz
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm
Frequency (MHz)
Measured response
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
18
Design Examples- Trisection open-loop filters
0 case 1 case 2 case 3 case 4
Insertion Loss (dB)
-20
0
-40
Insertion Loss (dB)
-20
-60
-40
-80 200 400 600 800 1000 1200
Frequency (MHz)
-60
Measured wideband response
-80 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 Frequency (GHz)
Experimental results on extra transmission zeros, where case 1 to 4 indicate the increase of direct coupling between the two feed lines.
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
19
Design Examples- Multi-layer filters
Magnetic Coupling Aperture
Dielectric Substrate Common Ground Plane
Electric Coupling Aperture
I/O Ports
Microstrip Open-Loop Resonator
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
20
Design Examples- Multi-layer filters
0 Transmission/Return Loss (dB) -10 -20 -30 -40 -50 -60 850 Chebyshev Elliptic Linear Phase 900 950 1000 1050 1100 Qu=200
Frequency (MHz)
(a)
35 30 Group Delay (ns) 25 20 15 10 5 0 940 950 960 970 Chebyshev Elliptic Linear Phase 980 990 Qu=200
Frequency (MHz)
(b)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
21
Design Examples- Multi-layer filters
Experimental results
0 -10 0 -10
0 -10
Transmission (dB)
Transmission (dB)
Transmission (dB)
-20 -30 -40 -50 -60 850
-20 -30 -40 -50 -60 850
-20 -30 -40 -50 -60
900
950
1000
1050
1100
900
950
1000
1050
1100
850 Group delay (ns)
40 30 20 10 0 940
900
950
1000
1050
1100
Frequency (MHz) Group delay (ns)
30 20 10 0 940 950 960 970 980 990 1000
Frequency (MHz) Group delay (ns)
40 30 20 10 0 940 950 960 970 980 990 1000
Frequency (MHz)
40
950
960
970
980
990
1000
Frequency (MHz)
Frequency (MHz)
Frequency (MHz)
(a)
(b)
(c)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
22
Design Examples- Slow-wave filters
Capacitively loaded line resonator
I1 d Za, ba V1 CL/2 CL/2 V2
w2 L2
7 6 Frequency (GHz) 5 4 3 2 1 0 0 1 2 3 4 5 6 Loading capacitance (pf) f0 f1 f1 / f0 3.25 3.00 2.75 f1 / f0 2.50 2.25 2.00 1.75 1.50
Microstrip slow wave resonator (I)
d wa L1 w1
f0 f1 f1 / f0 3.25 3.00 2.75 f1 / f0 2.50 2.25 2.00 1.75 1.50 0 1 2 3 4 5 6 7 8 9 10 11 Open-stub length, L (mm)
I2
Wa=1 mm, w1=2 mm, w2=3 mm, d=16 mm on RT/Duroid 6010
7 6 Frequency (GHz) 5 4 3 2 1 0
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
23
Design Examples- Slow-wave filters
Centre Frequency : 1335 MHz 3dB Bandwidth : passband Loss : 30 MHz 3dB Max.
Min. stopband rejection : D.C. to 1253 MHz 60dB 1457 to 2650 MHz 60dB 2650 to 3100 MHz 30dB 60dB Bandwidth : 200 MHz Max. On RT/Duroid 6010 substrate
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
24
Design Examples- Slow-wave filters
0
37.75mm
Transmission (dB)
-20
0.5mm
-40
-60
Substrate: εr=10.8 h=1.27mm
-80 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Frequency (GHz)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
25
Design Examples- Dual-mode filters
Type I dual-mode resonator
D ≈ 1.84λg 0 π D ≈ λg 0 2
C1
(a)
D ≈ λg 0 π D ≈ λg 0 4
L1
Mode 1
L2
Mode 2
C2
(b)
D < λg 0 4
( c)
(d)
(e)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
26
Design Examples- Dual-mode filters
0 16 mm -10 Amplitude (dB) -20 -30 -40 -50 1.3 Port 2 S21 S11
dxd Port 1
1.4
1.5
1.6
1.7
1.8
1.9
Frequency (GHz)
d =2 mm on RT/Duroid 6010 substrate
2.5% bandwidth at 1.58 GHz
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
27
Design Examples- Dual-mode filters
20 mm
1 mm Port 1
Port 2
On RT/Duroid 6010 substrate
Centred at 820 MHz
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
28
Design Examples- Dual-mode filters
Type II dual-mode resonator
Y
⎛ a a⎞ ⎜ ⎟ , ⎟ ⎜ ⎝2 3 2⎠
Electric Field Pattern @ Mode 1
1
@ Mode 2
0 0.5 0.5 1 1.5 2 2.5 3 3.5 4 2.5 2 0.5 0.5 2 1 2.5
2 2.5
1 .5 1
0.5 0
0.5
1
0
0.5
0
1
0
1.5
⎞ ⎛ a , 0⎟ ⎜− 3 ⎠ ⎝
Z
2.5
2 1.5 1
0.5 0
0.5
1
0
0.5
1
1.5
X
2 1.5 1
3
0.5
0
0.5
1
a
E
Ed
0.5 0 0.5 1 1.5 2 2.5 3 3.5
4
a⎞ ⎛ a ,− ⎟ ⎜ ⎝2 3 2⎠
Equilateral triangular microstrip patch resonator
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
29
Design Examples- Dual-mode filters
1
J0,1
L1 C1
J1,3
3
w
b
INPUT
0
J0,3
2
OUTPUT
a
J0,2 L2
J2,3 C2
0
Circuit model (No coupling between the two modes)
|S11| (Theory) |S21| (Theory)
Magnitude (dB)
-10
-20
-30
|S11| (EM) |S21| (EM)
Frequency response
(a = 15 mm and b = 11.25 mm on a 1.27mm thick dielectric substrate with a relative dielectric constant of 10.8)
-40
-50 3.0 3.5 4.0 4.5 5.0
Frequency (GHz)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
30
Design Examples- Dual-mode filters
10 0
Magnitude (dB)
-10 -20 -30 -40 -50 -60 -70 2.8 3.2 3.6 4.0 4.4 4.8
w
b
|S11| (Theory) |S21| (Theory) |S11| (Simulation) |S21| (Simulation)
a
a = 15 mm and b = 14 mm on a 1.27mm thick dielectric substrate with a relative dielectric constant of 10.8
Frequency (GHz)
Frequency response
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
31
Design Examples- Dual-mode filters
Four-pole dual-mode filters
On a substrate with a relative constant of 10.8 and a thickness of 1.27 mm
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
32
Design Examples- Dual-mode reject filters
s
0 Magnitude (dB) -10 -20 -30 -40 3.6 3.8 4.0 4.2 4.4 S11 S21
l W g a
Single dual-mode resonator
1
Frequency (GHz)
PORT 1
2
PORT 2
The details to be presented in another session (WE4C) at IMS2005
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
33
Design Examples- Extract-pole filters
Ls
=
zin
J=1
zin
Cs
L=Cs
C=Ls
l1 ≈λg/4
l2 s
zin
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
l3 ≈λg/2
34
Design Examples- Extract-pole filters
On RT/Duroid 6010 substrate
EM simulated performance
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
35
Design Examples- Extract-pole filters
On RT/Duroid 6010 substrate
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
36
Design Examples- CQ filters
PORT 1
PORT 2
8 pole 5MHz wideband S21 res ponse 65K S21
dB 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100
Start: 1.880000 GHz
Stop: 2.200000 GHz
Another 18-pole filter of this type with group delay equalisation will be presented in TH1F session at IMS2005
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
37
Design Examples- CQT filters
PORT 1
10
PORT 2
dB 0 -10 -20 -30 -40 -50 -60 -70
S11
S21
1
dB 0 -5 -10 -15 -20 -25 -30 -35
1
-80 -90 -100 Start: 1.960000 GHz
S21 1.974000 GHz -0.7590 dB
-40 -45 -50
Stop: 1.985000 GHz
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
38
Design Examples- Wideband filters
Optimum stub bandpass or pseudo highpass
2θc 2θc
0.9 23.8 2.0 23.0 2.8 22.7 Unit: mm
y0=1 y1 θc
y1,2 y2 yn-1
yn-1,n yn
y0=1
4.9
13.9
13.5
13.2
30
Via hole grounding
150
Short-circuited stub of electrical length θc
θc π/2 π−θc π 3π/2
On substrate: εr = 2.2, h = 1.57 mm
θ
Amplitude (dB) 0 -10 -20 -30 -40 -50 -60 0 1 2 3 4 5 6 7 Frequency (GHz) S21 S11
|S21|
fc
(π/θc −1)fc
f
EM simulated performance
From: Jia-Sheng Hong and M.J.Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons. Inc. New York, 2001
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
39
Summary
Microstrip filter designs involve a number of considerations, including careful choice of topologies and substrates. Some design examples of new topologies with advanced filtering characteristics have been described, including –
Open-loop resonator filters Multilayer filters Slow-wave filters Dual-mode filters Extract pole, Trisection, CQ and CQT filters Optimum wideband stub filters
Driven by applications and emerging device technologies, many new and advanced microstrip filters have been developed and their designs are available in open literatures.
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
40
IMS’05 Workshop-WMB
Microstrip Filter Design
Jia-Sheng Hong
Heriot-Watt University Edinburgh, UK
[email protected]
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
1
Outline
Introduction Design considerations Design examples Summary
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
2
Introduction- Driving forces
Recent development of microstrip filters has been driven by applications Wireless communications Wireless sensor/radar systems …….
Driven by technologies High temperature superconducting Micromachining LTCC Ferroelectric …….
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
3
Introduction- Microstrip Filter Publications
Total 600+ in recent 10 years
120 100
Search from IEEE Xplore
N u m b e r
80 60 40 20 0
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
4
Design Considerations- Topologies
l1 l2 ln l n+1
WC WL l1 l2 l3 l4 l5 l6 l7
Y0
W1 s1 W1
W2 s2 W2
C2 L2 Z0 L1 L3
C4 L4 L5 C6 Z0
W1 W2 W3 Wn
Wn sn Wn
Wn+1 sn+1 Wn+1
Y0
CL1 CL2
l g0/4 l g0/4
CL3
CLn-1 CLn
l1
l2
l3
ln
0 1 2 3
q0
n-1
n
n+1
l1h
l2h
l3h
l4h
l5h
Yt qt
Y1
Yn
Yt
l1v s1 s2 l2v s3
l3v s5 s4 l4v
l5v W
YA
s1,2 s2,3 sn-1,n
~λ/4
YA
~λ/4
~λ/4
~λ/4
Via hole grounding
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
5
Design Considerations- Topologies
The choice of a topology depends on Characteristics of filters, such as chebyshev or elliptic Bandwidth Size Power handling
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
6
Design Considerations- Substrates
The choice of a substrate depends on Size Higher-order modes Surface wave effects Implementations – couplings, line/spacing tolerances, … Dielectric loss Temperature stability Power handling – dielectric strength (breakdown), thermal conductivity
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
7
Design Considerations- Higher-order modes
Keep operating frequencies below the cutoff frequency of c the 1st higher-order mode, f c =
ε r (2W + 0.8h )
90 W = 1.0 mm 90
Cutoff frequency fc (GHz)
70 60 50 40 30 20 0.2 0.4 0.6 0.8 1.0 1.2
εr = 6.15 εr = 10.8
Cutoff frequency fc (GHz)
80
εr = 3
80 70 60 50 40 30 20 10
εr = 10.8
W=0.5 mm W=1.0 mm W=1.5 mm
1.4
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Substrate thickness h (mm)
Substrate thickness h (mm)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
8
Design Considerations- Surface waves
Keep operating frequencies below the threat frequency of the lowest surface wave mode,
c tan −1 ε r fs = 2πh ε r − 1
700
Threat frequency fs (GHz)
600 500 400 300 200 100 0 0.2 0.4 0.6 0.8 1.0
εr = 3 εr = 6.15 εr = 10.8
at which the surface mode couples strongly to the dominant mode of microstrip because the phase velocities of the two modes are close.
1.2
1.4
Substrate thickness h (mm)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
9
Design Considerations- Losses
There are three major losses in a microstrip resonator: Conductor loss Dielectric loss Radiation loss
⎛ h ⎞ ⎛ 377Ω ⎞ Qc ∝ π ⎜ ⎟ ⋅ ⎜ ⎜ R ⎟ ⎝λ⎠ ⎝ s ⎟ ⎠
Qd ∝
1 tan δ
1 1 1 1 = + + Qu Qc Qd Qr
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
10
Design Considerations- Power handling
Peak power handling capability –
when the breakdown occurs in substrate
Vo2 Pp ∝ 2Z c
Vo is the maximum breakdown voltage of the substrate Zc is the characteristic impedance of the microstrip
Narrower band filters result in higher electric field density, leading to a lower peak power handling
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
11
Design Considerations- Temperature effect
Temperature characteristic of a microstrip half-wavelength resonator on RT/Duroid substrate with εr = 10.2, h = 1.27 mm Copper CTE (coefficient of thermal expansion) = 17 ppm/oC Substrate CTE = 24 ppm/oC Substrate TCK (thermal coefficient of εr) = −425 ppm/oC
At 23 oC At 73 oC for copper CTE only At 73 oC for substrate thickness CTE only At 73 oC for substrate TCK only At 73 oC (consider all) f0 = 1929.8 MHz f0 = 1928.1 MHz f0 = 1929.9 MHz f0 = 1949.4 MHz f0 = 1947.8 MHz ∆f = 0 ∆f = −1.7 MHz ∆f = 0.1 MHz ∆f = 19.6 MHz ∆f = 18.0 MHz
Frequency variation versus temperature is mainly due to dielectric constant change vs temperature
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
12
Design Examples- Open-loop filters
1 2
4 3
1
2 3
5 4
6
(a)
1 1 2 3 4 6 5 7 8 2
( b)
8 3 4 6 5 7
( c)
( d)
From: Jia-Sheng Hong and M.J.Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons. Inc. New York, 2001
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
13
Design Examples- Open-loop filters
Specifications:
Center frequency Fractional Bandwidth 40dB-Rejection Bandwidth Passband Return loss 985MHz 10.359% 125.5MHz −20dB
Design parameters for an 8-pole filter:
M 1, 2 = M 7 ,8 = 0.08441 M 3, 4 = M 5, 6 = 0.05375 M 3, 6 = −0.01752 M 2,3 = M 6, 7 = 0.06063 M 4,5 = 0.0723 Qei = Qeo = 9.92027
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
14
Design Examples- Open-loop filters
Realisation 1
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm. Each resonator has a size of 16 by 16 mm.
0 -5 Insertion/Return Loss (dB) -10 -15 -20 -25 -30 -35 -40 925 950 975 1000 1025 1050
Insertion loss Return loss
0
-20 Insertion Loss (dB)
-40
-60
-80
600
800
1000
1200
1400
Frequency (MHz)
Frequency (MHz)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
15
Design Examples- Open-loop filters
Realisation 2
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
16
Design Examples- Trisection open-loop filters
Midband or centre frequency Bandwidth of pass band Return loss in the pass band : 905MHz : 40MHz : < −20dB
f 01 = f 03 = 899.471 MHz f 02 = 914.713 MHz Qei = Qeo = 15.7203 M 12 = M 23 = 0.04753 M 13 = −0.02907
0 -10 Magnitude (dB) -20 -30 -40
Rejection : > 20dB for frequencies ≥ 950MHz
S21 S11
-50 700 750 800 850 900 950 1000 1050 1100 Frequency (MHz)
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm
Measured response
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
17
Design Examples- Trisection open-loop filters
Midband or centre frequency Bandwidth of pass band Return loss in the pass band : 910MHz : 40MHz : < −20dB
f 01 = f 03 = 916.159 MHz f 02 = 905.734 MHz Qei = Qeo = 14.6698 M 12 = M 23 = 0.05641 M 13 = 0.01915
0 -10 Magnitude (dB) -20 -30 -40 -50 -60 700 750 800 850 900 950 1000 1050 1100 S21 S11
Rejection : > 35dB for frequencies ≤ 843MHz
On RT/Duroid substrate with a relative dielectric constant of 10.8 and a thickness of 1.27mm
Frequency (MHz)
Measured response
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
18
Design Examples- Trisection open-loop filters
0 case 1 case 2 case 3 case 4
Insertion Loss (dB)
-20
0
-40
Insertion Loss (dB)
-20
-60
-40
-80 200 400 600 800 1000 1200
Frequency (MHz)
-60
Measured wideband response
-80 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 Frequency (GHz)
Experimental results on extra transmission zeros, where case 1 to 4 indicate the increase of direct coupling between the two feed lines.
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
19
Design Examples- Multi-layer filters
Magnetic Coupling Aperture
Dielectric Substrate Common Ground Plane
Electric Coupling Aperture
I/O Ports
Microstrip Open-Loop Resonator
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
20
Design Examples- Multi-layer filters
0 Transmission/Return Loss (dB) -10 -20 -30 -40 -50 -60 850 Chebyshev Elliptic Linear Phase 900 950 1000 1050 1100 Qu=200
Frequency (MHz)
(a)
35 30 Group Delay (ns) 25 20 15 10 5 0 940 950 960 970 Chebyshev Elliptic Linear Phase 980 990 Qu=200
Frequency (MHz)
(b)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
21
Design Examples- Multi-layer filters
Experimental results
0 -10 0 -10
0 -10
Transmission (dB)
Transmission (dB)
Transmission (dB)
-20 -30 -40 -50 -60 850
-20 -30 -40 -50 -60 850
-20 -30 -40 -50 -60
900
950
1000
1050
1100
900
950
1000
1050
1100
850 Group delay (ns)
40 30 20 10 0 940
900
950
1000
1050
1100
Frequency (MHz) Group delay (ns)
30 20 10 0 940 950 960 970 980 990 1000
Frequency (MHz) Group delay (ns)
40 30 20 10 0 940 950 960 970 980 990 1000
Frequency (MHz)
40
950
960
970
980
990
1000
Frequency (MHz)
Frequency (MHz)
Frequency (MHz)
(a)
(b)
(c)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
22
Design Examples- Slow-wave filters
Capacitively loaded line resonator
I1 d Za, ba V1 CL/2 CL/2 V2
w2 L2
7 6 Frequency (GHz) 5 4 3 2 1 0 0 1 2 3 4 5 6 Loading capacitance (pf) f0 f1 f1 / f0 3.25 3.00 2.75 f1 / f0 2.50 2.25 2.00 1.75 1.50
Microstrip slow wave resonator (I)
d wa L1 w1
f0 f1 f1 / f0 3.25 3.00 2.75 f1 / f0 2.50 2.25 2.00 1.75 1.50 0 1 2 3 4 5 6 7 8 9 10 11 Open-stub length, L (mm)
I2
Wa=1 mm, w1=2 mm, w2=3 mm, d=16 mm on RT/Duroid 6010
7 6 Frequency (GHz) 5 4 3 2 1 0
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
23
Design Examples- Slow-wave filters
Centre Frequency : 1335 MHz 3dB Bandwidth : passband Loss : 30 MHz 3dB Max.
Min. stopband rejection : D.C. to 1253 MHz 60dB 1457 to 2650 MHz 60dB 2650 to 3100 MHz 30dB 60dB Bandwidth : 200 MHz Max. On RT/Duroid 6010 substrate
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
24
Design Examples- Slow-wave filters
0
37.75mm
Transmission (dB)
-20
0.5mm
-40
-60
Substrate: εr=10.8 h=1.27mm
-80 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Frequency (GHz)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
25
Design Examples- Dual-mode filters
Type I dual-mode resonator
D ≈ 1.84λg 0 π D ≈ λg 0 2
C1
(a)
D ≈ λg 0 π D ≈ λg 0 4
L1
Mode 1
L2
Mode 2
C2
(b)
D < λg 0 4
( c)
(d)
(e)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
26
Design Examples- Dual-mode filters
0 16 mm -10 Amplitude (dB) -20 -30 -40 -50 1.3 Port 2 S21 S11
dxd Port 1
1.4
1.5
1.6
1.7
1.8
1.9
Frequency (GHz)
d =2 mm on RT/Duroid 6010 substrate
2.5% bandwidth at 1.58 GHz
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
27
Design Examples- Dual-mode filters
20 mm
1 mm Port 1
Port 2
On RT/Duroid 6010 substrate
Centred at 820 MHz
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
28
Design Examples- Dual-mode filters
Type II dual-mode resonator
Y
⎛ a a⎞ ⎜ ⎟ , ⎟ ⎜ ⎝2 3 2⎠
Electric Field Pattern @ Mode 1
1
@ Mode 2
0 0.5 0.5 1 1.5 2 2.5 3 3.5 4 2.5 2 0.5 0.5 2 1 2.5
2 2.5
1 .5 1
0.5 0
0.5
1
0
0.5
0
1
0
1.5
⎞ ⎛ a , 0⎟ ⎜− 3 ⎠ ⎝
Z
2.5
2 1.5 1
0.5 0
0.5
1
0
0.5
1
1.5
X
2 1.5 1
3
0.5
0
0.5
1
a
E
Ed
0.5 0 0.5 1 1.5 2 2.5 3 3.5
4
a⎞ ⎛ a ,− ⎟ ⎜ ⎝2 3 2⎠
Equilateral triangular microstrip patch resonator
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
29
Design Examples- Dual-mode filters
1
J0,1
L1 C1
J1,3
3
w
b
INPUT
0
J0,3
2
OUTPUT
a
J0,2 L2
J2,3 C2
0
Circuit model (No coupling between the two modes)
|S11| (Theory) |S21| (Theory)
Magnitude (dB)
-10
-20
-30
|S11| (EM) |S21| (EM)
Frequency response
(a = 15 mm and b = 11.25 mm on a 1.27mm thick dielectric substrate with a relative dielectric constant of 10.8)
-40
-50 3.0 3.5 4.0 4.5 5.0
Frequency (GHz)
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
30
Design Examples- Dual-mode filters
10 0
Magnitude (dB)
-10 -20 -30 -40 -50 -60 -70 2.8 3.2 3.6 4.0 4.4 4.8
w
b
|S11| (Theory) |S21| (Theory) |S11| (Simulation) |S21| (Simulation)
a
a = 15 mm and b = 14 mm on a 1.27mm thick dielectric substrate with a relative dielectric constant of 10.8
Frequency (GHz)
Frequency response
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
31
Design Examples- Dual-mode filters
Four-pole dual-mode filters
On a substrate with a relative constant of 10.8 and a thickness of 1.27 mm
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
32
Design Examples- Dual-mode reject filters
s
0 Magnitude (dB) -10 -20 -30 -40 3.6 3.8 4.0 4.2 4.4 S11 S21
l W g a
Single dual-mode resonator
1
Frequency (GHz)
PORT 1
2
PORT 2
The details to be presented in another session (WE4C) at IMS2005
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
33
Design Examples- Extract-pole filters
Ls
=
zin
J=1
zin
Cs
L=Cs
C=Ls
l1 ≈λg/4
l2 s
zin
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
l3 ≈λg/2
34
Design Examples- Extract-pole filters
On RT/Duroid 6010 substrate
EM simulated performance
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
35
Design Examples- Extract-pole filters
On RT/Duroid 6010 substrate
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
36
Design Examples- CQ filters
PORT 1
PORT 2
8 pole 5MHz wideband S21 res ponse 65K S21
dB 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100
Start: 1.880000 GHz
Stop: 2.200000 GHz
Another 18-pole filter of this type with group delay equalisation will be presented in TH1F session at IMS2005
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
37
Design Examples- CQT filters
PORT 1
10
PORT 2
dB 0 -10 -20 -30 -40 -50 -60 -70
S11
S21
1
dB 0 -5 -10 -15 -20 -25 -30 -35
1
-80 -90 -100 Start: 1.960000 GHz
S21 1.974000 GHz -0.7590 dB
-40 -45 -50
Stop: 1.985000 GHz
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
38
Design Examples- Wideband filters
Optimum stub bandpass or pseudo highpass
2θc 2θc
0.9 23.8 2.0 23.0 2.8 22.7 Unit: mm
y0=1 y1 θc
y1,2 y2 yn-1
yn-1,n yn
y0=1
4.9
13.9
13.5
13.2
30
Via hole grounding
150
Short-circuited stub of electrical length θc
θc π/2 π−θc π 3π/2
On substrate: εr = 2.2, h = 1.57 mm
θ
Amplitude (dB) 0 -10 -20 -30 -40 -50 -60 0 1 2 3 4 5 6 7 Frequency (GHz) S21 S11
|S21|
fc
(π/θc −1)fc
f
EM simulated performance
From: Jia-Sheng Hong and M.J.Lancaster, Microstrip Filters for RF/Microwave Applications, John Wiley & Sons. Inc. New York, 2001
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
39
Summary
Microstrip filter designs involve a number of considerations, including careful choice of topologies and substrates. Some design examples of new topologies with advanced filtering characteristics have been described, including –
Open-loop resonator filters Multilayer filters Slow-wave filters Dual-mode filters Extract pole, Trisection, CQ and CQT filters Optimum wideband stub filters
Driven by applications and emerging device technologies, many new and advanced microstrip filters have been developed and their designs are available in open literatures.
Dr. Jia-Sheng Hong Department of Electrical, Electronic and Computer Engineering Heriot-Watt University, UK [email protected]
40
