Sub-millimetre wave components for steerableantennas with supporting MMIC design

R.Cahill, D.Linton, V. F. Fusco

Overview

• FSS structures• Reflectarray Antennas• Quasi-Optical Switches• V band QPSK MMIC• Conclusions

2

Objectives & Why Liquid Crystal ?

• Objective: Exploit the anisotropic property of Liquid Crystals to create phase shifters for mm & sub –mm wave beamsteering reflectarray antennas which is necessary for space observation objects.

• Why use liquid crystals >100GHz?- Thin tuneable LC film(<50µm) means:

* Low voltage electronic control ---- easy to be digitally controlled

* faster switching speed ---- which is important for some applications

* Device architecture and construction similar to optical LC displays---- fabrication

* Dielectric anisotropy increases & loss decreases with frequency

* Low weight, power consumption and cost

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Frequency Selective Surface Technology

• Single And Dual Polarisation Beamsplitters At Frequencies Over The Range 100 - 470 GHz

• Single and Multilayer Periodic Structures Designed Using CST Microwave Studio

• Fabrication Uses Precision Micromachining Techniques With Submicron Accuracy

• Spectral Response Measured Using 100 -700 GHz VNA and QO Test Bench

Example of a Dual Polarisation (TE & TM, 45° Plane ) FSS; 316.5 -325.5 GHz/ 349.5 -358.5 GHz

300 310 320 330 340 350 360-40

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-5

0

Tran

smis

sion

(dB)

Frequency (GHz)

TE Co meas. TE Co sim. TE X meas. TM Co meas. TM Co sim. TM X meas.

Dickie R, Cahill R, Gamble HS, Fusco VF, Huggard P, Moyna B, Oldfield M, Grant N and de Maagt P: ‘Polarisation Independent bandpass FSS’, IET Electron. Lett., 43, (19), 2007, pp. 1013 – 1015

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Fabrication

• SOI Technology 10μm/2μm/525μm – Suitable for Rapid Prototyping

• Deep Reactive Ion Etching (etch rate 3.5 μm/min) – Patterning and Substrate Removal

• Sputter Coated 0.25μm Copper Seed Layer/1μm Electrodeposited Copper

Freestanding FSS

DRIE etched slots

SOI handle wafer

Substrate removed under mesh

30mm

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Measurement setup

• Transmission Spectra Measured Using 100-540GHz Quasi-Optical Test Bench

- Reflective Focussing Optics Transforms Gaussian Beam –FSS Positioned at Beam Waist

- Dielectric Anisotropy Determined by Applying dc Bias

The DUTBiasingconnection

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Frequency Selective Surface Technology

• Linear Polarised FSS Funded by Centre for Earth Observation Instrumentation (CEOI)

• Transmission in Band 440 – 456 GHz (0.25 dB) & Reflection in Bands 314 – 336 GHz (0.8 dB), 239 – 247 GHz (0.22 dB), 174 – 192 GHz (0.1 dB) , 113 – 123 GHz ) (<0.1 dB)

• Slot Length = 326 μm, Width = 20 μm, Thickness = 12 μm

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-3 0

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0

1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 4 5 0 5 0 0

F re q u e n c y (G H z )

Tran

smis

sion

(dB

)

C S T S 2 1 m e a s 1 1 3 - 1 2 3 m e a s 1 7 4 - 1 9 2 m e a s 2 3 9 -2 4 7m e a s 3 1 4 -3 3 6 m e a s 4 3 0 - 4 7 0

1 1 3 - 1 2 3

1 7 4 - 1 9 2

2 3 9 - 2 4 7

3 1 4 - 3 3 6

4 4 0 - 4 5 6

4 3 0 - 4 7 0

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0

430 435 440 445 450 455 460 465 470Frequency (GHz)

CST_S21 meas

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0

100 150 200 250 300 350 400

Frequency (GHz)

Ref

lect

ion

(dB

)

CST S11 meas 113 - 123 meas 174 - 192meas 239 - 247 meas 314 - 336

113 - 123174 - 192

239 - 247

314 - 336

Spectral Transmission

Spectral Reflection

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Theory of Operation (1)Liquid Crystal

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Phase Agile Reflectarray Antennas Based on Liquid Crystals

• Phase Shifters are Created By Exploiting the Dielectric Anisotropy Property Of Liquid Crystals

• Parallel Plate Topology Is Suitable for Reflectarray Antenna Design

• Reconfigurable Radiation Patterns Are Generated By Applying A Small Bias Voltage

• Sum and Difference Radiation Pattern Switching Demonstrated At 10 GHz

• Beam Steering Antenna Measured At 94 GHz

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0

-90 -70 -50 -30 -10 10 30 50 70 90Angle (deg)

Pow

er (d

B)

10.3 GHz - difference pattern

10.3 GHz - sum pattern

Alignment layer Electrode

mm wave E field ε⊥

No Biasing Field

⊥−=Δ εεε //eff

mm wave E field∼

With Biasing Field

V ε//

Hu W, Ismail MY, Cahill R, Encinar JA, Fusco V F, Gamble H S, Linton D, Dickie R, Grant N and Rea S P: ‘Liquid crystal based reflectarray antenna with electronically switchable monopulse patterns’, IET Electron. Lett., 43, (14), 2007, pp. 744 -745

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Electronically Reconfigurable Quasi – Optical Switches

• A Tunable Bandpass FSS Is Created By Inserting A Thin Layer Of Liquid Crystals Between Two Screens

• Dynamically Switching The Transmitted Signal Between ‘ON’ and ‘ OFF’ States Has Been Demonstrated At 145 GHz

• This Structure Can Be Used To Determine The Permittivity, Dielectric Anisotropy And Loss Tangent Of Tunable Liquid State Materials

Dynamic transmission range

Biasingconnection

Y

XZ

Hu W, Dickie R, Cahill R, Gamble H S, Ismail MY, Fusco V F, Linton D, Rea S P and Grant N: ‘ D-Band Tunable Frequency Selective Surface Based on Liquid Crystals’, Proc. IEEE Microwave and Wireless Components Letters, 17, (9), September 2007, pp. 667- 700

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Summary

Broadband millimetre wave QPSK Modulator

• Frequency span, 35GHz~65 GHz

• The phase errors are ±15°

• The amplitude errors are ±1dB

• The insertion loss is 9 ±1.5 dB

• The input return loss is below -10 dB

• The output return loss is below -10 dB

• The input 1 dB compression power is 18 dBm

• The DC power consumption is below 60mW

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V band QPSK Modulator MMIC

• MMIC broadband QPSK modulator

• 0.15 um pHEMT technology

• the chip size is 2.7mm*1mm

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MMIC Measurement

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35.0G 40.0G 45.0G 50.0G 55.0G 60.0G 65.0G-60

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0

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(phase(S(43))-phase(S(21)))_Simu (phase(S(65))-phase(S(21)))_Simu (phase(S(87))-phase(S(21)))_Simu (phase(S(43))-phase(S(21)))_Meas (phase(S(65))-phase(S(21)))_Meas (phase(S(87))-phase(S(21)))_Meas

Pha

se(d

egre

e)

Freq(Hz)

The QPSK four states simulated and measured phase performances vs. Carrier frequency for QPSK

modulator

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35.0G 40.0G 45.0G 50.0G 55.0G 60.0G 65.0G-15

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-7In

serti

on L

oss(

dB)

Freq(Hz)

dB(S(2,1)) dB(S(4,3)) dB(S(6,5)) dB(S(8,7))

The QPSK four states insertion loss vs. Carrier frequency for QPSK modulator

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40 45 50 55 6035 65

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0

freq , G Hz

dB(S

(1,1

))dB

(S(3

,3))

dB(S

(5,5

))dB

(S(7

,7))

The QPSK four states input return loss vs. Carrier frequency for QPSK modulator

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40 45 50 55 6035 65

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0

freq, GHz

dB(S

(2,2

))dB

(S(4

,4))

dB(S

(6,6

))dB

(S(8

,8))

The QPSK four states output return loss vs. Carrier frequency for QPSK modulator

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Conclusions

• 450 GHz Bandpass FSS filter with an insertion loss of 0.2 dB

• Sum and difference LC Radiation Pattern demonstrated at 10 GHz

• Beam Steering LC planar array demonstrated at 94 GHz

• Quasi-optical switch demonstrated at 145 GHz

• Broadband millimetre wave QPSK MMIC modulator demonstrated 35 – 65 GHz

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Many thanks for your attention

Any questions?

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