Planar Transmission Line Planar Transmission Line TechnologiesTechnologies

CMB Polarization Technology WorkshopNIST/Boulder

Edward J. Wollack Observational Cosmology LaboratoryObservational Cosmology Laboratory

NASA Goddard Space Flight CenterNASA Goddard Space Flight CenterGreenbelt, MarylandGreenbelt, Maryland

OverviewOverview

Selected Planar Transmission Line TopologiesSelected Planar Transmission Line TopologiesPlanar Transmission Line ApplicationsPlanar Transmission Line ApplicationsExample: Planar Microwave Filters Example: Planar Microwave Filters Component RepeatabilityComponent RepeatabilitySystem Level ConsiderationsSystem Level ConsiderationsTechnical Readiness Level (TRL) Technical Readiness Level (TRL) Future Development MilestonesFuture Development Milestones

Planar Transmission LinesPlanar Transmission LinesTEMTEM

Conductor

DielectricElectric field

QuasiQuasi--TEMTEM• Phase Velocity• Impedance Level• Number Propagating Modes• Field Configuration

QuasiQuasi--TEMTEM NonNon--TEMTEM

Microstrip

Microstrip with ground plane slot

+

--

Coplanar waveguide

Grounded Coplanar

Finite width Coplanar

Waveguide

Even-mode

Odd-mode

-+

+- -

Stripline

Parallel Plate

Slotline

Finite width Slotline

+ -

+ -

+

-

Planar Transmission Lines: Planar Transmission Lines: Characteristics and ApplicationsCharacteristics and Applications

Blocking FiltersBlocking Filters~0.1 ~0.1 –– 11Medium Medium Strip LineStrip Line

Antennas, Resonance Suppression, Antennas, Resonance Suppression, Filters, TransitionsFilters, Transitions

~0.6 ~0.6 –– 1.81.8MediumMediumMicrostrip LineMicrostrip Linewith ground plane slotwith ground plane slot

Filters, Hybrids, High QFilters, Hybrids, High Q--ResonatorsResonators~0.6 ~0.6 –– 22LowLowCoplanar WaveguideCoplanar Waveguide

Antennas, Transitions, Power Antennas, Transitions, Power CombinersCombiners

~1.2 ~1.2 –– 33HighestHighestFiniteFinite--Width SlotlineWidth Slotline(i.e., Edge(i.e., Edge--Coupled Line)Coupled Line)

Antennas, Phase ShiftersAntennas, Phase Shifters~1.2 ~1.2 –– 2.42.4HighHighSlotlineSlotline

Filters, Hybrids, High QFilters, Hybrids, High Q--ResonatorsResonators~0.2 ~0.2 –– 1.41.4LowLowMicrostrip LineMicrostrip LineAntennas, TransitionsAntennas, Transitions~0.4 ~0.4 –– 1.61.6Low Low ParallelParallel--Plate LinePlate Line

Typical Sensor Circuit Examples:Typical Sensor Circuit Examples:Impedance Impedance [[ZZoo]]

Relative Relative LossLoss

Planar Microwave FiltersPlanar Microwave Filters

Methods to control spurious response and radiationMethods to control spurious response and radiationExtending fundamental propagation mode bandwidth: Extending fundamental propagation mode bandwidth:

Limit width/length ratioLimit width/length ratioThin dielectricThin dielectric

Suppress undesired modes:Suppress undesired modes:Symmetric designSymmetric designPackagingPackagingTransmission zeros insertionTransmission zeros insertionTransmission line alterationTransmission line alterationStepped impedance lineStepped impedance lineDefected ground structureDefected ground structureWiggly coupled linesWiggly coupled linesOtherOther……

Lumped Element FilterLumped Element Filter

CoupledCoupled--Line BandLine Band--pass Filterpass Filter

Quarterwave BandQuarterwave Band--stop Filterstop Filter

Z0

Z0

Tran

smis

sion

(dB)

Frequency (GHz)

Out

In

Actual stop-band responses(with spurious resonance frequencies)

Desirable stop-band frequency response (ideal

lumped-element filter)

10 100 1000

Source: R. K Hoffman, “Handbook of Microwave Integrated Circuits,” Artech House, 1987.

Filter Designs: BandFilter Designs: Band--Pass Pass

Figure 2. Top left: The lumped element model for a 3rd order LC bandpass filter [3,4]. Lower left: The layout for the corresponding SONNET model. Right: The transmittance for the lumped-element model (solid) and the full wave SONNET calculation (dashed).

Figure 1. Upper left: The layout of a resonant stepped impedance filter (GSFC/GATech [2]); Lower left: A lumped element filter with CPW inductors (JPL, [4]); Right: A triplexer (3-element filter bank) connected to a broad band antenna (UC Berkeley, [1]).

Figure 3. FTS Spectra for integrated antenna+filters, from the Berkeley group (Left), and the JPL group (Right). Devices for 90 and 150GHz bands are shown. All spectra are normalized individually. The red curve in the right panel indicates atmospheric transmission at ballooning altitudes.

References:

[1] O’Brient, R. et al., v151, p459, JLTP 2008

[2] U-yen K. et al., v54, i3, p1237, IEEE MTT, 2006.

[3] Goldin, A. et al., v4855, p163, proc. SPIE, 2003

[4] Kuo, C. et al., to appear in proc. SPIE, 2008

Filter Design: Thermal Blocking Filter Design: Thermal Blocking

-100

-80

-60

-40

-20

0

0 10 20 30 40 50Freqeuncy (GHz)

dB|S

21|,

dB|S

11| Measured

EM SimulationCircuit modelS11 meaS11 EMS11 ckt

S11

S21

# 1

# 2

# 3# 4# 5# 6# 7

# 2

# 3# 4 # 5 # 6 # 7

Microwave Blocking filter Enclosed Cavity

Input Pocket

5.85 mm

3.34 mm

13.95 mm

7.8 mm

U-Yen, K. and Wollack, E.J., “Compact Planar Microwave Blocking Filter”, 2008, 38th European Microwave Conference, Amsterdam, Netherlands, accepted.

Process RepeatabilityProcess Repeatability

Process Variations:Process Variations:Component GeometriesComponent Geometries

Conductor Thickness and SlopeConductor Thickness and SlopeSubstrate Thickness and EtchSubstrate Thickness and EtchPackaging Effects and VariationsPackaging Effects and Variations

Material EffectsMaterial EffectsCritical Temperature, Complex Critical Temperature, Complex Surface Impedance, Step CoverageSurface Impedance, Step Coverage……Dielectric ConstantDielectric Constant……

High Material UniformityHigh Material Uniformity……Low Dimensional VariabilityLow Dimensional Variability……

Modeling and Design:Modeling and Design:Circuit Parameter SensitivityCircuit Parameter Sensitivity……Material Parameter KnowledgeMaterial Parameter Knowledge……

Slope

Conductor Thickness

Substrate Over-etch

SEM image of a co-planar waveguide structure

Return loss

Transmission

εr=9.6

εr=7.9

System Level ConsiderationsSystem Level ConsiderationsAdvantages:Advantages:

Compatible with integration on a Compatible with integration on a detector chipdetector chipCan achieve high optical coupling Can achieve high optical coupling efficiencyefficiencyCompact size Compact size Can lead to parts with high Can lead to parts with high repeatability, yield and low process repeatability, yield and low process variation.variation.Does not link frequency and Does not link frequency and angular band definition angular band definition requirementsrequirementsTransmission line thermal Transmission line thermal requirements subdominant to requirements subdominant to detector requirementsdetector requirementsTransmission line loss above gap Transmission line loss above gap frequency limits out of band power frequency limits out of band power Synthesis, modeling, and Synthesis, modeling, and simulation design tools at relatively simulation design tools at relatively mature levelsmature levels

DisadvantagesDisadvantages::Geometries and materials can Geometries and materials can require tighter and greater control require tighter and greater control over process tolerances (relative to over process tolerances (relative to their quasitheir quasi--optical counterparts) to optical counterparts) to insure desired operational insure desired operational performance performance Care must be taken in the overall Care must be taken in the overall design not to allow supporting design not to allow supporting circuitry to drive sensor fabrication circuitry to drive sensor fabrication and test complexity/riskand test complexity/riskEach singleEach single--mode transmission mode transmission line channel experiences an line channel experiences an independent filter which must be independent filter which must be characterized in flightcharacterized in flightPolarimeter implementations Polarimeter implementations which use different filters to form which use different filters to form StokesStokes--Q need wellQ need well--matched matched response to minimize relative response to minimize relative calibration and foreground errorscalibration and foreground errorsCryogenic array characterization Cryogenic array characterization and screening capabilities presently and screening capabilities presently at relatively low level of maturityat relatively low level of maturity

Technical Readiness Level Technical Readiness Level

Prototype variants on the required passive circuit elements to Prototype variants on the required passive circuit elements to support CMB polarization science requirements have or will reachsupport CMB polarization science requirements have or will reachTRL ~ 5 under the on going funding cycle. Examples include:TRL ~ 5 under the on going funding cycle. Examples include:

BandBand--Pass FiltersPass FiltersBolometer to Antenna Thermal Breaks Bolometer to Antenna Thermal Breaks Superconducting Transmission LinesSuperconducting Transmission LinesNormal Metal Absorber Structures and TerminationsNormal Metal Absorber Structures and TerminationsPower CombinersPower CombinersThermal Blocking Filters / Bias ChokesThermal Blocking Filters / Bias ChokesOtherOther……

Continued support in this area will be required to produce high Continued support in this area will be required to produce high optical efficiency sensors and field representative devices in foptical efficiency sensors and field representative devices in fully ully integrated systems. integrated systems. Further design and fabrication iterations will also be required Further design and fabrication iterations will also be required to to validate large numbers fully testable structures with acceptablevalidate large numbers fully testable structures with acceptablelevels of yield and reliability for levels of yield and reliability for spacebornespaceborne applications.... applications....

Future Development MilestonesFuture Development Milestones

So are we ready? Is what we have built what we want?So are we ready? Is what we have built what we want?Production of highest efficiency pixels possible is the key to Production of highest efficiency pixels possible is the key to controlling instrument cost and mission riskcontrolling instrument cost and mission risk within allocated within allocated resources (e.g., design focal plane area, cooling power, resources (e.g., design focal plane area, cooling power, massmass……))Demonstrated filter efficiencies for example are arguably an Demonstrated filter efficiencies for example are arguably an excellent start, however, from a systems perspective one excellent start, however, from a systems perspective one might inquiremight inquire……

Where did the remaining power go?Where did the remaining power go?What is a reasonable target for the filter performance?What is a reasonable target for the filter performance?Given an acceptable target Given an acceptable target –– what design margins are required to what design margins are required to realistically meet the desired instrument sensitivity with this realistically meet the desired instrument sensitivity with this approach?approach?

Planar Circuits: Loss MechanismsPlanar Circuits: Loss Mechanisms

2

20

0

31

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛⋅⋅=

effrad

hkZ

Gε

ηπ

ο

141

−⋅=

rc h

cfε

WZRs

c0

=α

( )( ) δεε

εεα tan

11

20 ⋅−−

⋅⋅=r

eff

eff

rd k

DielectricDielectricConductor Conductor Reactive MismatchReactive MismatchRadiationRadiation

FreespaceFreespace (3D)(3D)Surface Wave (2D) Surface Wave (2D)

Planar Circuits: DesignPlanar Circuits: Design

Material Selection and Fabrication:• Material parameters : εr μr σ• Physical Dimensions and Tolerances• Realizable Topologies

• Number of layers• Apertures, Air Bridges, Vias, etc.• Dimensional Tolerances

Material Selection and Fabrication:Material Selection and Fabrication:• Material parameters : εr μr σ• Physical Dimensions and Tolerances• Realizable Topologies

• Number of layers• Apertures, Air Bridges, Vias, etc.• Dimensional Tolerances

Design and Synthesis:• Extract Circuit Elements

• Impedance Contrast• Propagation Constant

• Transmission Line Model• Full-wave Analysis

Design and Synthesis:Design and Synthesis:• Extract Circuit Elements

• Impedance Contrast• Propagation Constant

• Transmission Line Model• Full-wave Analysis

Circuit Validation:• Compare Models with

Observation• Reliability/Life Testing

Circuit Validation:Circuit Validation:• Compare Models with

Observation• Reliability/Life Testing

Planar Circuits: ExamplesPlanar Circuits: Examples

Hybrids

Filters

Phase Shifters

Bias Chokes

Terminations

Artificial transmission line

Power dividerAntennas