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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
2
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
9
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
10
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
12
• 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
14
Top Layer
LNA Package Layer
Bottom Layer
(Features on backside)
LNA Cap Layer
Second Design Stack-Up
15
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
16
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
19
• 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
20
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
21
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
22
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
23
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
24
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
28
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
29
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
30
• 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