filterdesign and hfss ho[1]
TRANSCRIPT
Filter Design and Ansoft Tools
1-1ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.
Anders EdquistField Application Engineer
Introduction
Courtesy of Microdata Telecom Innovation
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Courtesy of Powerwave Technologies
Courtesy of Powerwave Technologies
Introduction - Traditional Filter Synthesis
…The majority of modern microwave filters are designed by using the insertion-loss method, whereby the amplitude response of the filter is approximated by using network synthesis techniques that have been extended to accommodate microwave distributed circuit elements. A general four-step procedure is followed: determination of filter specifications, design of a low-pass prototype filter, scaling and transforming the filter , and implementation (conversion of lumped elements to distributed elements)…
LP
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A group of traditional filter designers…
BP
Introduction - Prototype Filter Networks
- M - M
M
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⋅=⋅=
12
21
iMjv
iMjv
ωω
v1
-L0-L0
L0 L0 v2i1 i2
M
MK ω=
kLMK 0ωω ==
M M M M
R1 R2
M01M12
M13
M23 M34
C2 C3C1 L0L0 L0
v1 v2i0 i1 i2 i3 i4
⋅= 1011 iMjv ω
Introduction - Prototype Filter Networks
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iKu ⋅⋅= 0Ljω
( )( )
( )
⋅
−−
−=
−
−
−
4
3
2
1
0
34
341
0032313
231
00212
13121
00101
01
0
2
1
0000
0
00
0
0000
0
0
0
i
i
i
i
i
k
kjQkk
kjQk
kkjQk
k
Lj
v
v
ωδωδ
ωδω
( )( )( )( )( )( )
⋅=⋅+⋅−+⋅=
⋅+⋅−+⋅=
⋅+⋅−+⋅=
⋅=
−
−
−
4342
43431
0030223
32321
0020112
21211
0010001
1011
0
0
0
iMjv
iMjijQLjiMj
iMjijQLjiMj
iMjijQLjiMj
iMjv
ωωωδωωωωδωωωωδωω
ω
2
20
0 1ωωδ i
i −=
Introduction – The Coupling Matrix
R1 R2
M01M12
M13
M23 M34
C2 C3C1 L0L0 L0
v1 v2i0 i1 i2 i3 i4
iKu ⋅⋅= Ljω
2
20
0 1ωωδ i
i −=
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( )( )
( )
−
= −
00000
01000
00100
00010
00000
0000
0
00
0
0000
10
34
34032313
230212
13120101
01
jQ
k
kkk
kk
kkk
k
ωδωδ
ωδK
Resonant frequency
Coupling coefficients
Q-values
Coupling Matrix
iKu ⋅⋅= 0Ljω
Introduction – Modern Filter Synthesis (example)
Output from synthesis tool
Is the Coupling Matrix
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Courtesy of Guided Wave Technology
[1] R.J. Cameron, "Advanced coupling matrix synthesis techniques for microwave filters", IEEE Trans. Microwave Theory Tech., vol 51, pp. 1-10, Jan 2003.
[2] R.J. Cameron, "General coupling matrix synthesis methods for Chebyshev filtering functions", IEEE Trans. Microwave Theory Tech., vol 47, pp. 433-442, Apr 1999.
[3] A.E Atia and A.E. Williams, "New types of bandpass filters for satellite transponders", "COMSAT Tech. Rev., vol 1, no. 1, pp. 21-43, Fall 1971.
[4] Cameron, Kudsia, Mansour, "Microwave Filters for Communication Systems", Wiley-Interscience, 2007
[5] G. Macchiarella, S.C.D'Oro, "Design of Generalized Comb Filters With Asymmetric Transmission Zeroes Using Arbitrary Cascaded Triplet and Quadruplet Sections",
28th EUMC, Amsterdam 1998, pp. 179-183.
System Analysis
A prototype filter network based on the synthesised coupling matrix is easy to build
for use as a building block in a system simulation
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The filters can be optimised based on the cascaded system performance.
System Analysis – Optimisation
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Filter Realisation – Coupling Extraction
The key to the realisation of a synthesised prototype network:
– How to extract the mutual couplings between resonators of an arbitrary 3D geometry?
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Design variables
v.s
Coupling coefficients?
Generalized bandpass filter circuit with admittance inverters
J01 J12 J23 Jn,n+1
GA GB
B1(ω)
Coupling coefficients can be calculated from (MYJ) External Q-values can be calculated from (Ness)
B2(ω) Bn(ω)
Coupling Extraction – Theory
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[1] G.L. Matthaei, L. Young and E.M.T. Jones, Microwave Filters, Impedance-Matching Networks and Coupling Structures. New York: McGraw-Hill, 1964
[2] John B. Ness, A Unified Approach to the Design, Measurement, and Tuning of Coupled-Resonator Filters. IEEE Transactions on Microwave Theory and Techniques, vol 46, No 4, April 1998
( )
( )ω
ω
ωω
∂∂∠−=Γ
⋅Γ=
11
00
4
S
Q
d
de
020
1
11
1,1,
ff
jj
n
jjj
jjjj
df
dBfb
bb
Jk
=
−
=+
++
⋅=
=
Place lumped ports at every resonator1
Coupling Extraction – Implementation
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Y11+Y12 Y22+Y12
J = -Y12-Y12
Y11 Y22
020
1
11
1,1,
ff
jj
n
jjj
jjjj
df
dBfb
bb
Jk
=
−
=+
++
⋅=
=
))((
)(
,
,,
jjj
jiji
Yimderivb
YimJ
=
=
Coupling Extraction – Port Re-normalisation
Port 1
(Zp = 50 Ω)
Port 2
(Zp = 50 Ω)
Port 3
(Zp = 50 Ω)Example:
Q = R / ω L
f0=1GHz
L = 1 nH
Q = 3000
R 3000 *2pi
R = 50 ohm
Q 50/2pi
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Znorm = 1010 Ω(open)
Znorm = 10-10 Ω(short)
Port 1
(Zp = 50 Ω)
(open)
S11
Q 50/2pi
(HFSS > Results > Output Variables)
dBdB
Create Output Variables2
Coupling Extraction – Implementation
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df
dB
df
dBBk jjii
jijiBW,,
,,, 2 ⋅⋅=
( )2
00 fQ d
e
⋅⋅Γ= πω
Coupling Extraction
Extracted couplings
Design variables
Extract Couplings for a given set of
Design variables3
(Analytical derivatives*)
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*) The estimated aperture heights from a single extraction using Analytical Derivatives and
“Report Tuning” resulted in couplings within approx 5% from synthesis
Coupling Optimisation
Optimise all couplings simultaneously4
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If making variants of the filter, getting the “designs curves” it’s
probably more preferable to run a parametric sweep rather than
multiple optimisations.
+
Verification – Virtual Tuning
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oDynamic Link between Ansoft Designer and HFSS
oPlace capacitors at resonator ports
oInterpolate or Solve missing solutions
Good correspondence with synthesis
apart from at the transmission zeros.
WHY ???
HFSS
synthesis
Coupling Extraction – Parasitic Couplings
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Main couplings Parasitic couplings
How large impact does the parasitic
couplings have on the ideal synthesised
response?
Port Tuning
Modify the prototype network built from synthesis and include the spurious coupling
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Modify the prototype network built from synthesis and include the spurious coupling
Port Tuning
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HFSS
(synthesis)
Synthesis
with parasitics
Summary
• A prototype filter network was built in Ansoft Designer based on a
synthesised coupling matrix and used in a system simulation.
• Based on the system simulations, a modified coupling matrix was retrieved.
• An efficient method of coupling extraction was implemented in HFSS for the
realisation of the coupling matrix.
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realisation of the coupling matrix.
• The results from HFSS was dynamically linked into Ansoft Designer and the
filter was ”virtually tuned”.
• It was shown that parasitic couplings can have huge impact on the filter
performance.– The method for coupling extraction makes it possible to calculate these parasitics. Therefore, it is possible to
account for parasitics in an early stage of the design.
Thank You!
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Thank You!