Planar Antennas for CMB Polarimetry

Jamie BockTony Bonetti, Goutam Chattopadhyay, Peter Day, Sunil Golwala, Kent Irwin, Matt Kenyon, Chao-Lin Kuo, Andrew Lange, Rick LeDuc, Hien

Nguyen, Amy Trangsrud, Anthony Turner, Jonas Zmuidzinas

Jet Propulsion Laboratory

CMB Technology WorkshopBoulder CO, 25-28 August 2008

Principle of Operation

Silicon

AR Nb

μ-strip

Back-Illumination

Planar Antenna- Combine sub-slots coherently- Higher forward gain than single slot- E-field distribution defines beamshape

y-pol slots

x-pol slotsx-pol combining network

y-pol combining network

Combiner network

Implementation in a 150 GHz Device

Abs

orbe

r and

TES

Ban

dpas

sFi

lter

180˚

Hyb

rid

Measured Antenna Performance

Measured cross-polar response < 3 %New broad band design

Spectral Response and Optical Efficiency

Measured efficiencies range from 50 – 80 %

Results now for 100 GHz devices as well

35 % BW

Implementation in Focal Plane Arrays

Dual-Pol 150 GHz Pixel

8x8x2 Focal Plane Tile

512 Bolometer Focal Plane

Implementation in Focal Plane Arrays

A Very Flexible Technology

Extended Frequency RangeScale slot array and reroute combiner networkNo problems seen for low frequenciesSpace gets tight for ν > 250 GHz

Highly Tapered BeamsMake d/fλ largerChange combiner network to taper field amplitudeAccount for (known) slot-slot impedance matrix

Non-Telecentric BeamsChange combiner network to produce phase lag

Simultaneous Stokes I, Q & UAdd hybrid and use 4 detectors per pixel, balanced hybrids for band matching

Multiple Bands per AntennaDemonstrated with diplexer in one polarizationKeeping diffraction limit requires beam sharing

Overlapping AntennasIt is possible to recover perfect mapping speed (factor ~3 at 2fλ)Antennas must be large to use entire aperture

Advantages & Disadvantages

AR Coating is Very Simple

Coupling is Lithographic

Minimizes Focal Plane Mass

High Optical Efficiency

Polarized Beam Matching

Beam Control

Flexibility

Need Space for Detectors

Need Better Control of Defects

Advantages Disadvantages

Field focal plane arrays in CMB receiver

Focal plane array demonstration in a single band

Pixel demonstration in multiple bands

Pixel demonstration in a single band

Pixel demonstration in a single band

Pixel demonstration in a single band

Pixel demonstrations at ≤ 30 and ≥ 300 GHz

Field focal plane arrays in a CMB receiver

Pixel demonstration (completed at 100 and 150 GHz)

Milestone

Active device to switch polarization states, RF design

Antenna and combining network design, transmission line density and crossovers

Diplexer design doneDual-polarization design

Antenna and combining network design

Hybrid design and spectral band matching

Antenna and combining network design

Antenna and filter design

Process uniformity and reliability

Antenna and filter design,RF properties and losses

Technical Challenges

Noise stability

System sensitivity

System sensitivity

Use in non-telecentricoptical designs

Systematics control, depends on scan strategy

Sidelobe control for optics without a cold stop

Foreground removal

System sensitivity

Beam formation,polarization analysis,band definition

Advantage for CMBPOL

Polarization modulation

Overlapping antennas

Multiple frequency bands per antenna

Directed beams

Simultaneous Stokes I, Q and U

Highly tapered beams

Frequency coverage

Focal plane arrays

Optical coupling

Capability

2

1

4

2

Attributes Advantageous for CMBPOL

2

2

Attributes Necessary for Some CMBPOL Mission Designs

4

4

5

Attributes Necessary for CMBPOL

TRL?

Technology Readiness and Milestones

Focal Plane Sensitivity Budget

5Psat/QTES safety factor2d/fλBolometer pitch

4 yearsTlifeMission lifetime1.0 %εMirror emissivity at 1 mm

1.414Noise margin60 KToptMirror temperature

30 %Δν/νFractional bandwidth4 KTlensLens temperature

40 %ηoptOptical efficiency0.1 KT0Focal plane temperature

Detector Sensitivities

10

100

1000

10 100 1000

Freq [GHz]

NET

/feed

[uK

s1/

2 ]

Planck-LFIPlanck-HFITFCR-HEMTTFCR-boloEPIC-CSPerfect bolo

Noise Contributions

1

10

100

10 100 1000Freq [GHz]

NEP

[aW

Hz-1

/2]

CMBOptics/BaffleDetectorMarginTotal

EPIC

Sens

itivi

tyA

ssum

ptio

ns

T0 = 250 mK for the Inflation Probe?