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Design of Multilayer Balun for Balanced Mixers
using HFSS and Ansoft DesignerNikolay Ilkov – Synergy Microwave Research
Ansoft „Partners in Design“ WorkshopMunich, 8/11/2004
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Synergy Microwave Research GmbHFounded in 2003 by Prof. Ulrich L. RohdeOffers R&D services in microwave and RF technology• RFIC and MMIC design in Si, SiGe and GaAs
• Modules on PCB, ceramic, LTCC• RF and Microwave measurements• Component development and modeling
Contact:Synergy Microwave Research GmbHPotsdamer Str. 18A, 14513 TeltowTel. 03328 351 771E-mail : [email protected]
Internet: www.synergymwavegmbh.com
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B a
l u n
RF
Balun
LO
Balun
IF
There are two major challenges when designing a balanced mixer:
2. Designing the balun and passive matching circuit
1. Selection/design of the nonlinear elements
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Balun Design Considerations
Technical Economic
Bandwidth
Matching
Loss
Symmetry
Size
Cost
Yield
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The major design challenge for the balun is to minimizecoupling to the common mode.
BALUN+ +
-
In Differential Out
common mode
Odd (Differential) Mode Even (Common) Mode
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0
0
IZ=0Ohm
PNUM=1RZ=50Ohm Port1
IZ=0Ohm
PNUM=2RZ=50Ohm Port2
IZ=0Ohm
PNUM=3RZ=50OhmPort3
P=length
W=width
P=length
W=width
Differential
+-
Single Ended
The performance of the Marchand balun is less sensitive to low even modeimpedance than many other balun configurations.
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0
0
IZ=0Ohm
PNUM=1RZ=50Ohm Port1
IZ=0Ohm
PNUM=2RZ=50Ohm Port2
IZ=0Ohm
PNUM=3RZ=50OhmPort3
P=length
W=width
P=length
W=width
λ /4 λ /4
Zoe2=Zse *Zd /2
Even, Zin = 8Even, Zin = 8 Odd, Zin ˜ 50?
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• A practical implementation requires bent coupled lines inorder to reduce size.
• Microstrip to stripline transitions may cause non-idealbehavior
• Finite ground size and via connections between striplinegrounds may be critical to performance.
Analytic estimates are useful for theinitial design. However….
Integration of circuit and full-wave models must be efficientlycombined for design and verification.
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1. Copper thickness is comparable to the gap between coupled lines.
Other issues that are not easilyhandled by the circuit simulator
2. Lack of circuit models for inhomogeneous stripline.
copperε r1
εr2
εr1
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Designer circuit model
Comparison of Circuit model and transmission line model based on 2-Dfull-wave port solution
I n s e r t i o n L o s s
R e t ur nL o s s
Freq (GHz)
Transmission linemodel from HFSS
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Using the dynamic link the exact trace width and length can be
easily optimized
00
0
IZ=0Ohm
PNUM=1RZ=50Ohm
IZ=0Ohm
PNUM=2RZ=50Ohm
IZ=0Ohm
PNUM=3RZ=50Ohm
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
WavePort1 WavePort2
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Optimisation result. The ground and the feeds are ideal.
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HFSS model of the module edge. The antipad size and the
stripline width are optimized for good return loss
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Optimized HFSS model of the module edge together with
the solder pad
MS return loss
SL return loss
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HFSS model of the differential port transition
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HFSS model of the differential port transition
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HFSS model of the single-ended port transition
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More realistic Designer simulation including the feeds and the via
IZ=0Ohm
PNUM=2RZ=50Ohm
IZ=0Ohm
PNUM=3RZ=50Ohm
IZ=0Ohm
PNUM=1RZ=50Ohm
Port3
Port4 Port5
Port6
M S
S L
M S
S L
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
M
S
S L
Coup1:T1
Coup1:T2
Coup2:T1
Coup2:T2
SingleLine
Coup1:T1
Coup1:T2
Coup2:T1
Coup2:T2
U n c o u p: T 1
U n c o u p: T 2
1
2
3
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More realistic Designer simulation including the feeds and the viabut the coupler is not folded.
Full 3D
Designer
(no bends)
Diff to commonmodeconversion
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HFSS broadside-coupled bend modelDifferential S-parameters
R e t ur nL o s s
I n s e r t i o n
L o s s
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Complete balun model in Designer
IZ=0Ohm
PNUM=2RZ=50Ohm
IZ=0Ohm
PNUM=3RZ=50Ohm
IZ=0Ohm
PNUM=1RZ=50Ohm
Port3
Port4 Port5
Port6
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
C o u p 1 : T 1
C o u p 1 : T 2
C o u p 2 : T 1
C o u p 2 : T 2
S i n g l e L i n e
Coup1:T1
Coup1:T2
Coup2:T1
Coup2:T2
U n
c o u p: T 1
U n
c o u p: T 2
123
Port1:T1
Port1:T2P
o r t 2 : T
1
P o r t 2 : T
2P or t 1 : T 1
P or t 1 : T 2
Port2:T1
Port2:T2
W a v e
P o r t 1 : T
1
W a v e
P o r t 1 : T
2
W a v e
P o r t 2 : T
1
W a v e
P o r t 2 : T
2
W a v e
P o r t 1 : T
1
W a v e
P o r t 1 : T
2
W a v e
P o r t 2 : T
1
W a v e
P o r t 2 : T
2 P o r t 1 : T
1
P o r t 1 : T
2
P o r t 2 : T 1
P o r t 2 : T 2
P o r t 1 : T 1
P o r t 1 : T 2P
or t 2 : T 1
P or t 2 : T 2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
P or t 1 : T 1
P or t 1 : T 2
Port2:T1
Port2:T2
Port1:T1
Port1:T2P
o r t 2 : T 1
P o r t 2 : T 2
W av eP
or t 1 : T 1
W av eP
or t 1 : T 2
W av eP
or t 2 : T 1
W av eP
or t 2 : T 2
W a v e P o r t 1 : T
1
W a v e
P o r t 1 : T
2
W a v e
P o r t 2 : T
1
W a v e P o r t 2 : T
2
P o r t 1 : T
1
P o r t 1 : T
2
P o r t 2 : T 1
P o r t 2 : T 2
P o r t 1 : T 1
P o r t 1 : T 2P
or t 2 : T 1
P or t 2 : T 2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
Port1:T1
Port1:T2P
o r t 2 : T
1
P o r t 2 : T
2 W a v e
P o r t 1 : T
1
W a v e
P o r t 1 : T
2
W a v e
P o r t 2 : T
1
W a v e P o r t 2 : T
2 P o r t 1 : T
1
P o r t 1 : T
2
P o r t 2 : T 1
P o r t 2 : T 2
W a v e P o r t 1 : T 1
W a v e P o r t 1 : T 2
W a v e P o r t 2 : T 1
W a v e P o r t 2 : T 2
WavePort1:T1
WavePort1:T2
WavePort2:T1
WavePort2:T2
P or t 1 : T 1
P or t 1 : T 2
Port2:T1
Port2:T2
W a v e
P o r t 1 : T
1
W a v e
P o r t 1 : T
2
W a v e
P o r t 2 : T
1
W a v e P o r t 2 : T
2
P o r t 1 : T 1
P o r t 1 : T 2P
or t 2 : T 1
P or t 2 : T 2
W a v e P o r t 1 : T 1
W a v e P o r t 1 : T 2
W a v e P o r t 2 : T 1
W a v e P o r t 2 : T 2
M S
S L
M S
S L
M S
S L
The same HFSS Modes are reusedwithin the dynamic link
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Designer model performance vs. HFSS simulation (full)
Designer
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Complete Marchand balun in HFSS
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Possible explanation for the matching discrepancy
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Complete Marchand balun in HFSSStraightforward solution of the problem
The HFSS editor is very slow for complicated drawings
2h 20min to solve on 2.8GHz Xeon
Marchand balun in Designer using direct link to HFSS
Need 3 to 15min to solve depending on the parameter
No „debugging“ possibilities – easy to make mistakes