Post on 03-May-2018
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The use of CAD tools in filterdesign for telecommunication
applicationsJ. Kocbach & K. Folgerø
June 3rd 2002
CAD tools in filter design - June 2002
Outline
• Nera Filter applications
• Why do we need CAD tools?
• Use of CAD tools in a typical filter design cycle– Combination with circuit models
– Important requirements for CAD tools
• Application Examples
• Summary
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CAD tools in filter design - June 2002
Nera Filter applications
• Tunable filters:
– Trunk (2 - 15 GHz)
• Tuningless filters & diplexers
– Mobile Infrastructure (15 - 40 GHz)
– Broadband Wireless Access (~40 GHz)
– DVB-RCS (~14 GHz)
CAD tools in filter design - June 2002
Why do we need CAD-tools?
• Generally: Predictable & cost-efficient design– reduce costly prototyping & total development time
• design cycles, time to market– remove uncertainties & risks in development projects
• need predictable design procedures– semi/full automatic design procedures
• directly from specifications -> physical dimensions– optimal integration with radio/antenna
• short filters, folded/cross coupled filters, etc.
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CAD tools in filter design - June 2002
Why do we need CAD-tools?
• Tuneable filters– decide filter tuning range => easier system planning– good initial design gives larger tuning range and/or
less loss
NL 290 Post Filter
CAD tools in filter design - June 2002
Why do we need CAD-tools?
• Tuningfree filters– fast & efficient design of frequency variants– Tolerance analysis using CAD tools:
• Can the filter be made tuningless?• Determine possible production methods
CityLink Iris filters
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CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
CAD tool
CAD tool
Few iterations if:- reliable circuit models- good design methodology- reliable CAD tools
CAD tool
CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
• Example case:– CityLink Filter @ 23 GHz– 560 MHz bandwidth– Tuningfree design - account for prod. tol.
• To be realized as machined Al iris filter– rounded corners, r = 1 mm.
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CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
Insertion loss < 0.8 dB
Return loss > 20 dB
Rejection > 30 dB
CAD tools in filter design - June 2002
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Insertion loss < 0.8 dB
Return loss > 20 dB
Rejection > 30 dB
Temperature variations
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CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
Production tolerances Insertion loss < 0.8 dB
Return loss > 20 dB
Rejection > 30 dB
CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Rin
Rout
M23
M13 M3,n
M12
• Use circuit model to determine– filter topology/filter order– filter bandwidth
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CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Rin
Rout
M23
M13 M3,n
M12
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
7th order
6th order
5th order
CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Rin
Rout
M23
M13 M3,n
M12
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
6th order
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CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Rin
Rout
M23
M13 M3,n
M12
• Apply CAD-tool• Our choice:
– Step-by-step method– Treat each coupling and resonator separately
• Alternatively: Optimization
CAD tools in filter design - June 2002
Rin
Rout
M23
M13 M3,n
M12
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
1 2 3 4 5 6
-18
-16
-14
-12
-10
-8
-6
-4
SimulationCircuit model
Iteration number
S21
[dB
]
Coupling 1
S21 = -5.1 dB
6 full-wavesingle-frequencysimulations at f0with varying irisopening.
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CAD tools in filter design - June 2002
Rin
Rout
M23
M13 M3,n
M12
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
6 7 8 9
-16
-14
-12
-10
-8
-6
-4 S imulationCircuit model
Iteration number
S21
[dB
]
Coupling 2
S21 = -16.4 dB
CAD tools in filter design - June 2002
Rin
Rout
M23
M13 M3,n
M12
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
9 10 11-20.5
-20
-19.5
-19
-18.5
-18
-17.5
-17
-16.5
-16S imulationCircuit model
Iteration number
S21
[dB
]
Coupling 3
S21 = -19.9 dB
10
CAD tools in filter design - June 2002
Rin
Rout
M23
M13 M3,n
M12
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
• Apply this procedure to each coupling– This case: Total of 12 single-frequency simulations– Call EM simulator 12 times
• Calculate resonator lengths based onphase of reflection ( )( )
πλ
φφπ2
0212
1 grl −−=
CAD tools in filter design - June 2002
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Rin
Rout
M23
M13 M3,n
M12
11
CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
• Tolerance analysis:– All dimensions varied– Gaussian distribution (σ = 4 µ m) - based on experience
CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
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CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
Electrical and mechanicalmeasurements
22.4 22.6 22.8 23 23.2 23.4 23.6 23.8 24 24.2-60
-50
-40
-30
-20
-10
0
f [GHz]
S-pa
ram
eter
s [d
B]
CAD tools in filter design - June 2002
Typical Filter Design Cycle
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
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CAD tools in filter design - June 2002
Important CAD tool requirements
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
CA
D tool
• Different types of tools required– Full 3D solvers
• required for complex structures– Mode matching / segmentation approach
• MoM / BIE / FE / FD etc.• required for fast solutions• combine with full 3D solver if possible
• General requirements:– reliable, accurate, fast
CAD tools in filter design - June 2002
• Valued features– combine CAD tool with circuit models– perform tolerance analysis– parametric sweeps– possible to combine different tools– built-in design methodology– use ascii input files for automatic design cycles
• Tools applied at Nera:– WASP-NET, HFSS, WIND, FEST
Filterspecifications
Realization of filterdimensions
Buildprototype(s)
Prototypemeasurements
Final product
Circuit modelcalculations
Tolerance analysis orTuning range analysis
CA
D tool
Important CAD tool requirements
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CAD tools in filter design - June 2002
Realization procedure (typical)
• Step-by-step procedure. Each step:
Example: Cross coupled filter Substructure 1Substructure 2
Substructure 4
Substructure 3
tune
tune
tune
tune
• Global optimization only if necessary -often not required
• See Th-1C-4: Thursday 09.00
– Simple substructures of complete structure– Tune one or a few variables in each step– Calculate for one or a few frequency points– Automatic/semiautomatic if possible– Use circuit model as tuning goal if applicable
CAD tools in filter design - June 2002
Cross coupled filter
• Fast and predictable design (1-2 hours)– step-by-step procedure– Matlab & Wasp-Net
• No global optimization necessary
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CAD tools in filter design - June 2002
Large radii iris filter• Low cost
– tuningfree– 3.0 mm milling radius– 4.0 mm iris length
• Fast & predictable design; minutes– Step-by-step procedure applied– Matlab & Wasp-Net
• No global optimization necessary• Application: DVB/RCS satellite terminal
CAD tools in filter design - June 2002
15.24 15.26 15.28 15.3 15.32 15.34 15.36 15.38 15.4 15.42-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
frequency (GHz)
S (d
B)
Tunable Post filter
• Flexible & reliable design procedure– Step-by-step procedure applied– Calling HFSS from Matlab
• No global optimization necessary• Filter tunable from 14.9 to 15.35 GHz• Application: Trunk product (NL290)
Designed at 15.35 GHzTuned to 15.32 GHz
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CAD tools in filter design - June 2002
Metal Insert Diplexer
• Flexible & reliable design; ~ 12-24 hours– Step-by-step procedure applied; automatic– Matlab & Wasp-Net– Successive optimization runs
• few propagating modes included• Optimization goals for poles of individual filters
CAD tools in filter design - June 2002
Metal Insert Diplexer
• Application: Broadband access product• Tuningfree
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CAD tools in filter design - June 2002
Summary
• Design methods:– required to be reliable & predictable– possibly automatic or semi-automatic
• CAD tools:– reliable, predictable & flexible– different tools necessary:
• Mode matching / segmentation for speed• Full 3D for complex structures
– possible to combine with external programs– closely related to reliable circuit models