recent advances in the development of a lightweight, flexible 16x16 antenna array … ·...

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Recent Advances in the DevelopmentRecent Advances in the DevelopmentOf a Lightweight, Flexible 16x16 AntennaOf a Lightweight, Flexible 16x16 Antenna

Array with RF MEMS Phase ShiftersArray with RF MEMS Phase Shiftersat 14 GHzat 14 GHz

David Chung1, Swapan Bhattacharya1, G. Ponchak2

and John Papapolymerou1*

*Associate Professor

1School of Electrical & Computer EngineeringGeorgia Institute of Technology, Atlanta, GA 30332

2NASA Glenn Research Center, Cleveland, OH 44135

ESTO Conference June 2008

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Outline

• Introduction

• RF MEMS Switches and Low Loss Phase Shifters on LCP

• 3-D Integrated RF MEMS Phased Array Module (2x2)

• Recent Results on Large Antenna Array

• Conclusions

3

• Introduction

• RF MEMS Switches and Low Loss Phase Shifters on LCP

• 3-D Integrated RF MEMS Phased Array Module (2x2)

• Recent Results on Large Antenna Array

• Conclusions

4

• Objective

– Develop a large lightweight and deployable phased array using RF-MEMS.

Integration with other passive and active circuits.

• Challenges

– Obtain desired beam-steering for earth coverage, with the desired radiation

pattern and return loss characteristics

– Low cross-polarization and back-sidelobe level

– Low loss

– Compact Structure

– High Degree of Integration

– Expandable Design

– Flexibility

• Proposed Solution

– Aperture-fed microstrip patch antennas

– Corporate feed network

– A 3-D System-on-a-Package Approach

192mm

192mm

256 elements

16 4x4 tiles

8 4x8 tiles

Introduction

5

SOP RF Front End Evolution

LTCC

PWB

RF MEM

S

3D

Digital & Analog IC

RF MEMS

CircuitHermetic

Packagingˇ

RF Passives

AntennaDigital & Analog IC

RF MEMS

CircuitHermetic

Packagingˇ

RF Passives

Antenna

• Lower Cost

• Smaller Size/Weight

• Better Performance

• Multi Functionality “Best of Breed” Solution

Hybrid Solution

Reconfigura

ble

LCP

μBGA

BGA

Filter Antenna

μBGA

BGA

Filter Antenna

Epoxy

Ceram

ic

Organic

Thin F

ilms

Nanomate

rials

6

Patch Antennas

10mils LCP

Apertures

Vias to Attenuators

Attenuators

Phase Shifter

MEMS of

Phase Shifter

MEMS DC PadsBottom LCP substrate

used in 16x16 design

(no metal on this layer)

DC pad of

Phase Shifter

Holes in bottom

substrate to bias

the switches

Attenuators

MEMS Switches

Sub-Array 3-D Integration

7

• Introduction

• RF MEMS Switches and Low Loss Phase Shifters on LCP

• 3-D Integrated RF MEMS Phased Array Module (2x2)

• Recent Results on Large Antenna Array

• Conclusions

8

Top Plate Top PlatePull-Down Electrode

and Bottom Plate

Dielectric

Air-bridge

RF In RF OutPull-Down

Electrode

Cantilever beam

Electrostatic actuation

Low loss and low cost

High linearity – no distortion

No power consumption

Switching time 1-50 μs

Reliability & RF power?

Packaging?

Enabling technologies:

RF MEMS and micromachining

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RF MEMS Switch on LCP

The springs anchor the

membrane to the finite ground

coplanar waveguide’s (FGC’s)

ground planes [not shown]. A

special process was developed

to fabricate the MEMS switches

on and LCP substrate.

Dark brown – electroplated gold

Yellow – evaporated gold

Membrane

Signal Line

Signal Line

SpringSpring

Switching speed ~ 12 usec

Actuation voltage: 20-40 V

More than 0.5B Cycles

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Fabricated 4-bit Phase Shifter

270o

90o

180o

0o

67.5o

45o

0o

22.5o

Capable of phase shifts from 0o to 337.5o in 22.5o increments

LCP

Gold

MEMS Switches

6.3 mm

10.6 mm

11Packaged

MEMS on LCP

0.343.968.25Phase Error

(deg)

-0.72-1.02-1.29S21 (dB)

-49.83-35.74-25.63S11 (dB)

Best

Case

AverageWorst

Case

Isolation and Insertion Loss Measurements

Packaging of 4-bit Phase Shifter

N. Kingsley and J. Papapolymerou, “Organic Wafer Scale Packaged Miniature

Four-Bit RF MEMS Phase Shifter,” IEEE Transactions on

Microwave Theory and Techniques, Vol. 54, No. 3, pp. 1229-1236, March 2006

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• Introduction

• RF MEMS Switches and Low Loss Phase Shifters on LCP

• 3-D Integrated RF MEMS Phased Array Module (2x2)

• Recent Results on Large Antenna Array

• Conclusions

13

LNA

LNA

RF IN

RF IN

Antenna

&

MEMS

Phase Shifter

Design#2

Signal

coupled

down

Signal

coupled

up

Antenna

&

MEMS

Phase Shifter

Integrated RF Module on Multilayer Organics

Design#1

• 2x2 patch antenna design with two 1-bit MEMS phase shifters

• LNA on same layer and different layer

• Multilayer LCP design

N. Kingsley, G. Ponchak and J. Papapolymerou, “Reconfigurable RF MEMS Communication Module on LCP Substrate,”

IEEE Transactions on Antennas and Propagation, January 2008

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Top Layer

LNA Package Layer

Bottom Layer

(Features on backside)

LNA Cap Layer

Second Design Stack-Up

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DC pads

for RF

MEMS

DC pads

for LNA

Off-chip

capsRF IN

LNA

RF MEMS

Phase Shifter

2x2 phased

array

Fist Design Photo

N. Kingsley, G. Ponchak and J. Papapolymerou, “Reconfigurable RF MEMS Communication Module on LCP Substrate,”

IEEE Transactions on Antennas and Propagation, January 2008

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DC pads

for RF

MEMS

DC pads

for LNA

Alignmen

t holes

RF IN

The LNA and off-chip capacitors are located on an embedded layer.

They are fed via aperture coupling.

RF MEMS

Phase Shifter

2x2 phased

array

Aperture

coupling

down

Aperture

coupling

up

Second Design Photo

17

Left

82o

Center

90o

Right

94o

Radiation Patterns (Design#1)

Beam Steering Range: 12 degrees

Measured Antenna Efficiency ~ 80%

18

Left

86oCenter

92o

Right

98o

Radiation Patterns (Design#2)

Beam Steering Range: 12 degrees

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• Introduction

• RF MEMS Switches and Low Loss Phase Shifters on LCP

• 3-D Integrated RF MEMS Phased Array Module (2x2)

• Recent Results on Large Antenna Array

• Conclusions

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Embedded feed lines

Main feed point

Vias from bottom LCP to

embedded substrate

Exposed (bottom) feed lines

DC bias pads and holes

down to the bottom substrate

Space for passives (21 x 5 mm2)

Complete Phased Array Layout

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Cross-Sectional View of stitched 4x8 structure

Patch Radiator

Microstrip to CPW transition

Via is sputtered 5 micron Copper

Patch radiator

Ground plane

Microstrip line #1

Microstrip line #2

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13.213.413.613.814.014.214.414.614.813.0 15.0

-25

-20

-15

-10

-5

-30

0

S11

Metal back

GIT Fabricated Stitched 4X8 Array

Resonance at 13.75 GHz is suppressed by metal grounding

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8x8 8x8 with PS

4x8 180-270R

16x16 with PS

4x8 0-90R

4x8

4x8 0-04x8 270-270

4x8 0-90L

Design and Layout of Large Panel

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Metro Circuit Fabricated Panel

- Patch Radiator Side

25

Metro Circuit Fabricated Panel

- CPW transition through plated vias

Calibration

Lines

26

13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6 14.813.0 15.0

-25

-20

-15

-10

-5

-30

0

Sputtered

Metro

Metro Circuit Fabricated Panel

vs GIT Fabricated 4x8 array

GIT FabMetro Fab

27

13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6 14.813.0 15.0

-25

-20

-15

-10

-5

-30

0

S11

Metal back

Metro Circuit Fabricated Panel

4x8 with Phase Shifter 0-0 Degree

Gain ~ 15 dB

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Metro Circuit Fabricated Panel

4x8 with Phase Shifter 0-90 Degree

S11

Metal back

13.213.413.613.814.014.214.414.614.813.0 15.0

-25

-20

-15

-10

-5

-30

0

freq, GHz

S1

1 (

dB

)

4x8 w PS 0-90 degree

Gain ~ 14.5 dB

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13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6 14.813.0 15.0

-25

-20

-15

-10

-5

-30

0

S11

Metal back

Metro Circuit Fabricated Panel 8x8

with Phase Shifter 0-0 Degree

Gain ~ 17 dB

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• LCP provides technology platform for low cost multilayer lowloss microwave circuits (f>10 GHz)

• Packaged RF MEMS switches and low loss phase shifters (1 dBat 14 GHz) have been developed for the first time

• First demonstration of a low loss 14 GHz phased array LCP RFmodule with amplifier and RF MEMS phase shifters (12 degreessteering)

• Development of low loss stitching technique for multilayer largearrays above 10 GHz

• Very encouraging results for stitched 4x8 and 8x8 sub-arrays at14 GHz

• Feeding network design very important for overall lossminimization

Conclusions