DC to 40 GHz Phase Shifter

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DC to 40 GHz Phase Shifter Powered By Docstoc
					10 to 30 GHz RF MEMS True
Time Delay Phase Shifter
By Mark Hampson

In Conjunction With Prof. Milton Feng and
the High Speed Integrated Circuits Group
What is a Phase Shifter?
Q: Why a Phase Shifter?
A: Radar!   (don’t mess with the US)
Layout
90 Degree Phase Shifter   Center Frequency: 20 GHz
                          -3 dB BW: ~20 GHz
Transmission Line Theory
Making the Phase Shifter Work
Simulated Phase Shifter Insertion Loss
(All Simulations Used HP Advanced Design System)
Simulated Phase Shifter Return Loss
Simulated Phase Plots
Test Structures
                             Test Line




                  Test Tee
RF MEMS Switches
Advantage of MEMS
Switches

 •Low insertion loss  less
 than 0.1dB (compared to
 0.6 to 1 dB for FET
 switch)
 •Low power
 requirements (<0.25 mW)
Switch RF Characterization
Single Switch Insertion Loss (“up state”)
Switch RF Characterization
Single Switch Insertion Loss (“down state”)
Switch RF Characterization
Single Switch Return Loss (“down state”)
MEMS Switch Reliability Testing
“Cold testing”
•Strictly tests mechanical reliability
•Activate and deactivate switch until visual failure
•Tested to last about 800 million cycles


 “Hot testing”
 •Tests mechanical reliability and electrical isolation
 at the same time
 •Failure is defined by loss of electrical isolation seen on
 oscilloscope no visual check necessary
 •Tested to last around 1 million cycles
Example of Hot Test
Summary
Successes
•Achieved desired insertion loss over 20 GHz bandwidth
•Achieved desired phase shift at design frequency
•Achieved desired return loss at design frequency


Problems
•Device was not fabricated in time
•Phase was not linear over entire 20 GHz bandwidth (it was “jumpy”)
•Shunt switch requires λ/4 stub  hurts phase performance/wastes space

Future Possibilities
•Use a series switch to eliminate need for λ/4 stub
•Measure actual fabricated device!
•Shorten lengths of input lines to help phase
performance
Acknowledgements
This project would not exist if not for the sound advice and MEMS
   processing expertise of the following people:


  Richard Chan
  Robert Lesnick
  Doris Chan
  Jeff Feng
  Dave Becher
  Milton Feng
  Mike Hattendorf
  Mac Hafez

				
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posted:2/13/2013
language:English
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