26
RF MEMS SWITCHES AND PHASE SHIFTERS FOR MICROWAVE APPLICATIONS SUKOMAL DEY CENTRE FOR APPLIED RESEARCH IN ELECTRONICS INDIAN INSTITUTE OF TECHNOLOGY DELHI March 2016
RF MEMS SWITCHES AND PHASE SHIFTERS
FOR MICROWAVE APPLICATIONS
SUKOMAL DEY
CENTRE FOR APPLIED RESEARCH IN ELECTRONICS
INDIAN INSTITUTE OF TECHNOLOGY DELHI
March 2016
© Indian Institute of Technology Delhi (IITD), New Delhi, 2016
RF MEMS SWITCHES AND PHASE SHIFTERS
FOR MICROWAVE APPLICATIONS
by
SUKOMAL DEY
Centre for Applied Research in Electronics
Submitted
in fulfillment of the requirements of the degree of
DOCTOR OF PHILOSOPHY
to the
INDIAN INSTITUTE OF TECHNOLOGY DELHI
MARCH 2016
DEDICATION
This dissertation is dedicated to my parents and to my wife for their immense love and support.
EPIGRAPH
“Take up one idea. Make that one idea your life - think of it, dream of it, live on that idea. Let the brain,
muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is
the way to success”
……………….Swami Vivekananda
CERTIFICATE
This is to certify that the thesis entitled, “RF MEMS SWITCHES AND PHASE SHIFTERS FOR
MICROWAVE APPLICATIONS”, being submitted by Mr. Sukomal Dey for the award of the degree
of Doctor of Philosophy to the Centre for Applied Research in Electronics, Indian Institute of
Technology Delhi, New Delhi, is a record of bonafide research work carried out by him under
my guidance and supervision.
Mr. Sukomal Dey has fulfilled the requirements for the submission of this thesis, which to our
knowledge has reached the requisite standard. The results contained in this thesis have not been
submitted in part or in full to any other university or institute for the award of any degree or
diploma.
Date: (Dr. Shiban. K. Koul)
Place: New Delhi Professor
Centre for Applied Research in Electronics
Indian Institute of Technology Delhi
Hauz Khas, New Delhi-110016, India
iii
ACKNOWLEDGEMENTS
This dissertation would not be possible without the help and support of many people. First, I
would like to thank my advisor, Prof. Shiban. K. Koul, for allowing me to continue with this
thesis topic. His technical insight complimented with his understanding and patience make him
one of the remarkable persons I have ever met. I sincerely thank him for his contributions to my
personal and professional growth.
I would also thank Prof. Sudhir Chandra and Prof. G. S. Visweswaran for taking the time to
serve on my dissertation committee. I also thankful for technical discussions held with Prof.
Ananjan Basu and for agreeing to chair my dissertation committee. I appreciate their
contributions for reviewing this dissertation and participating in the oral presentation.
Thanks are also due to Mr. Vedula Kirty, senior general manager of Astra Microwave Product
Limited (AMPL), Hyderabad, India, for helping me during the process of fabrication, mounting
of the devices in the test jigs and device characterization up to a reasonable extent.
I want to sincerely thank Dr. Mahesh P. Abegaonkar and Dr. Karun Rawat from RF and
Microwave group, CARE, for their advice and motivation towards my research goals.
I would like to take this opportunity to thank National Programme on Micro and Smart Materials
and Systems (NPMASS) for providing the financial support during my stay at IIT Delhi as a full
time research scholar.
I would like to express my profound gratitude to Prof. K. N. Bhat, Prof Navakant Bhat and
research staffs in the Centre for Nanoscience and Engineering, Indian Institute of Science (IISc),
Bangalore, for their help in characterizing the devices at their facility.
I am extremely grateful to Mr. Surela Hari, technical staff at AMPL for helping me during power
handing, temperature and 3-axis vibration testing on the MEMS phase shifter.
Next, I would like to thank all of my colleagues here in the RF and Microwave group for making
this journey a pleasant experience, including, Dr. Preeti Sharma, Dr. Manoj Singh Parihar, Dr.
Madhur Deo Upadhyay, Dr. Ritabrata Bhattacharya, Dr. Lalithendra Kurra, Sanjeev Kumar,
Srujana Kagita, Saurabh Pegwal, Ankita Katyal, B. Gawrish, Rajesh, Robin, Deepika,
iv
Anushruti, Ayushi, Amit, Pranav, Harikesh and Shakti. Their friendships made this journey
enjoyable and will make my graduation memorable.
I would like to thank Mrs Sneh Kapoor, Mr. S. P. Chakraborty and Mr. Ashok Pramanik for
their support and help rendered during my research work.
I would also like to express my gratitude to all respected faculty and staffs members from the
CARE at IIT Delhi, for all of the support that they have given me during my dissertation period.
Finally, I would like to thank my family for their steadfast support – particularly my parents, Mr.
Swapan Ranjan Dey and Mrs. Pranati Dey and my wife, Nibedita. They encouraged me at
every step by investing their considerable time and never doubted on my ability to complete the
task. I needed it the most and I will forever be grateful to them.
...........................................
Sukomal Dey
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ABSTRACT
This dissertation presents design and measurement of RF MEMS metal-contact switches
and phase shifters. This thesis broadly divided into three parts. The first part of the thesis
concentrates on the metal-contact switch functionalities in-terms of mechanical behaviour,
electrical behaviour, transient analysis, linearity, power handling, temperature, S-parameter and
cold-switched reliability. All these switch performances are critically evaluated for developing
high performance and reliable MEMS switch.Different switching networks like series/shunt
configuration, single-pole-double-throw (SPDT) and single-pole-four-throw (SP4T) are presented
for application in multi-bit digital phase shifters, which is the primary goal of this thesis.
Next part of this thesis concentrates on the design and development of narrow-band
MEMS 5-bit phase shifters driven by an electrostatic actuation. Chapter 3 to Chapter 5 deals with
five 5-bit MEMS phase shifters that work over a 500 MHz bandwidth. Initially, 5-bit phase shifter
operation was checked on a conventional switched line topology and discussed. Later, a DMTL
5-bit phase shifter using MEMS bridge and MAM capacitors is designed, developed and tested.
Finally, an improved version of a 5-bit narrow-band phase shifter is developed using four MEMS
SP4T and two SPDT switches. This novel topology drastically improved the device reliability
with return loss of better than 20 dB, average insertion loss of 2.65 dB and excellent phase
accuracy within a 13 mm2 area. The performance of this phase shifter is very much comparable
with the present state-of-the-art digital phase shifter performances.
Next and last phase of this dissertation deals with a wide band digital phase shifter using
a push-pull type beam topology. Initially, the working functionalities of the push-pull bridge are
extensively investigated using analytical method, validation using simulation and followed by
experimental investigation. Later, the utility of this beam design is validated and tested on a
simple DMTL configuration where 11 push-pull bridges are used in a periodic placement.
Finally, a modified version of the push-pull actuator is used to design a frequency reconfigurable
5-bit phase shifter over a wide band of spectrum of 10 – 25 GHz. The concept of the frequency
reconfiguration is clearly mentioned and validated with exhaustive measurement process. This 5-
bit phase shifter is capable enough of providing 32 phase states with constant resolution over the
vi
10 – 25 GHz band. Initially, to validate frequency reconfiguration, all primary unit cells are
fabricated and tested. Later, a complete 5-bit phase shifter is developed, tested and discussed in
details with its microwave and reliability performances. The performance of the phase shifter is
also compared with the present state-of-the-art digital phase shifter.
Finally, in addition to all these, a low cost module is developed using gold coated brass
material to observe optimum device performance for end user applications and two phase
shifters (a narrow-band (Chapter 5) and a wide-band (Chapter 7)) are tested over large cycles
including life cycle, power handling, temperature stability and qualification testing such as 3-axis
vibration.
vii
TABLE OF CONTENTS
Certificate ...................................................................................................................................................... i
Acknowledgements .................................................................................................................................. iii
Abstract ......................................................................................................................................................... v
Table of Contents..................................................................................................................................... vii
List of Figures .......................................................................................................................................... xiii
List of Tables ......................................................................................................................................... xxiii
Chapter 1: Introduction........................................................................................................................... 1
1.1. MEMS Overview......................................................................................................................1
1.2. RF MEMS Switch.......................................................................................................... ............2
1.3. RF MEMS Phase Shifters.........................................................................................................6
1.4. Major Application of RF MEMS Phase Shifters...................................................................9
1.5. Scope and Objectives of the Work………………………………………………………...10
1.6. Thesis Organization………………………………………………………………………...12
Chapter 2:RF MEMS Metal Contact Switches and Switching Networks ....................................... 14
2.1. Introduction............................................................................................................................14
2.2. Device Structure.....................................................................................................................14
2.3. Switch Model Design.............................................................................................................15
2.4. Switch Electromagnetic Analysis.........................................................................................16
2.5. Fabrication...............................................................................................................................18
2.6. Measurements............................................................................................................ ............21
2.6.1. DC Measurement..................................................................................................21
2.6.2. Mechanical Measurement....................................................................................22
2.6.3. Switching and Release Time Measurement......................................................22
viii
2.6.4. Temperature Measurement.................................................................................23
2.6.5. S-parameter Measurement..................................................................................24
2.6.6. Linearity Measurement........................................................................................25
2.6.7. RF Power Handling Measurements...................................................................26
2.6.8. Reliability Measurements....................................................................................27
2.7. Switching Networks………………………………………………………………………..28
2.7.1. Series/Shunt Switch Design and Measurement……………………………..28
2.7.2. SPDT Switch Design and Measurement………………………………………29
2.7.3. SP4T Switch Design and Measurement…………………………………….....31
2.8. Conclusion.............................................................................................................. ................35
Chapter 3: Design and Development of 5-Bit Switched line Phase Shifters using MEMS
Metal Contact Switches ........................................................................................................................... 36
3.1. Introduction............................................................................................................... .............36
3.2. Switched line Phase Shifter Design.....................................................................................37
3.3. MEMS Switch Design............................................................................................................38
3.4. MEMS Switch Results............................................................................................................39
3.5. MEMS Primary Bit Phase Shifter Fabrication and Measurements.................................42
3.6. 5-bit Switched-line Phase Shifters Fabrication and Measurements................................45
3.6.1. 5-bit Phase Shifter using SW 1: Phase 1.............................................................45
3.6.2. 5-bit Phase Shifter using SW 2: Phase-2............................................................48
3.7. Reliability Measurements.....................................................................................................51
3.8. Conclusion..............................................................................................................................53
Chapter 4: X-Band 5-Bit DMTL Phase Shifter using MEMS Bridge and MAM Capacitors.....54
4.1. Introduction............................................................................................................................54
4.2. Unit Cell Phase Shifter Design and Modelling..................................................................55
4.3. Fabrication and Measurements............................................................................................60
4.3.1. Unit Cell Phase Shifter Measurements and Results........................................60
ix
4.3.2. Primary Phase Bits Measurement Results........................................................64
4.3.3. Complete 5-Bit Phase Shifter Measurements and Results..............................67
4.4. Reliability Measurements and Results................................................................................69
4.4.1. Reliability Measurements of the MEMS Bridge...............................................69
4.4.2. Reliability Measurements of the 5-bit Phase Shifter........................................71
4.5. Conclusion.................................................................................. ............................................73
Chapter 5: Ku-Band 5-Bit Phase Shifters using MEMS SP4T and SPDT Switches .................. 74
5.1. Introduction............................................................................................................... .............74
5.2. Phase Shifter Design Topology............................................................................................75
5.3. 2-bits and 1-bit Phase Shifter Design and Analysis: Phase-I...........................................76
5.4. 2-bits and 1-bit Phase Shifters Measurements: Phase-I....................................................78
5.5. Design and Measurements of the 5-bit Phase Shifter: Phase-I........................................81
5.6. Reliability Measurements of the SPST and SP4T Switches: Phase-I...............................83
5.6.1. Temperature Stability Measurements on the MEMS Switch.........................84
5.6.2. Power Handling Measurements on the MEMS Switch..................................86
5.6.3. Cold-Switched Reliability Measurements on the MEMS Switches...............89
5.6.4. Creep Measurements on the MEMS Switch.....................................................91
5.7.Reliability Measurements of the Phase Shifter: Phase-I....................................................91
5.7.1. Phase Shifter Testing on a Chip and within Module......................................92
5.7.2. Phase Shifter Reliability Measurements under Different Temperatures.....93
5.7.3. Phase Shifter Reliability under Cold Switched Condition.............................93
5.8. Design Modification and Measurements of the Phase Shifter: Phase-II........................95
5.9. Reliability Measurements of Switches: Phase-II..............................................................101
5.9.1. Temperature Measurements on the MEMS Switch.......................................101
5.9.2. Power Handling Measurements on the MEMS Switches.............................101
5.9.3. Cold-Switched Reliability Measurements.......................................................102
5.9.4. Hot-Switched Reliability Measurements........................................................103
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5.10. Reliability Measurements of the Phase Shifter: Phase-II..............................................104
5.10.1. Phase Shifter Reliability under Cold Switched Condition.........................106
5.10.2. Phase Shifter Reliability under Hot Switched Condition...........................106
5.10.3. Phase Shifter Testing Under Prolonged Actuation......................................107
5.11. Qualification Testing of the Phase Shifter: 3-Axis Vibration.......................................108
5.12. Failure Analysis of the 5-Bit MEMS Phase Shifter........................................................110
5.13. Conclusion.............................................................................................................. ............111
Chapter 6: DMTL Type Analog Phase Shifter using MEMS Push Pull Actuator ................... 113
6.1. Introduction..........................................................................................................................113
6.2. Operating Principle of the Push-Pull Bridge...................................................................114
6.2.1. Analysis of Bridge Pull-in Voltage using Quasi Static Approximation......115
6.2.2. Modelling of the Push-Pull Bridge...................................................................121
6.3. DMTL Unit Cell Phase Shifter Design and Modelling...................................................123
6.4. Fabrication............................................................................................................. ................125
6.5. Measurements......................................................................................................................126
6.5.1. Mechanical Measurements................................................................................126
6.5.2. Electrical Measurements....................................................................................130
6.5.3. S-parameter Measurements of the Unit Cell Phase Shifter..........................131
6.5.4. Measurements of the Complete Analog Phase Shifter..................................132
6.6. Discussions on the Push-Pull Bridge Performances.......................................................135
6.7. Conclusion.............................................................................................................. ..............136
Chapter 7: 10 – 25-GHz Frequency Reconfigurable MEMS 5-Bit Phase Shifter using Push-
Pull Actuators .......................................................................................................................................... 137
7.1. Introduction................................................................................................................. .........137
7.2. Design and analysis of the Phase Shifter using Push-Pull Actuator............................138
7.2.1. Analysis of the Push-Pull Actuator under Step and Modulated
Voltage Responses........................................................................................................140
xi
7.2.2. Design and Analysis of the Push-Pull Voltages and a Travel Range..........144
7.2.3. Design of Primary Cell Phase Shifters.............................................................147
7.2.4. Overall RF MEMS Phase Shifter Design.........................................................151
7.3. Measurements of the Push-Pull Actuator and Primary Phase Bits..............................151
7.3.1. Mechanical Measurement of the Push-Pull Actuator...................................154
7.3.2. Vpull, Vpush and Capacitance Measurements...................................................155
7.3.3. Response Time Measurements of the Push-Pull Actuator...........................155
7.3.4. S-Parameter Measurements..............................................................................156
7.4. Measurements of the Complete 5-Bit Phase Shifter........................................................159
7.5. Power Handling and Reliability Measurements.............................................................162
7.6. Conclusion.............................................................................................................. ..............169
Chapter 8: Conclusions and Future Scope ...................................................................................... 170
8.1. Summary of the Thesis........................................................................................................170
8.2. Future Scope of the Work...................................................................................................171
References ............................................................................................................................................. ...175
Appendix – A .......................................................................................................................................... .182
Publications ............................................................................................................................................ .185
Brief Bio-Data of the Author ............................................................................................................... .187
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LIST OF FIGURES
Fig. 1.1. SEM images of (a) silicon micro-mirror by Alcatel-Lucent and (b) an accelerometer by
Analog devices................................................................................................................................1
Fig. 1.2. Suspended MEMS bridge in shunt configuration over a CPW transmission line and its
circuit model.............................................................................. ......................................................4
Fig. 1.3. Suspended MEMS bridge in shunt configuration over a CPW transmission line and its
circuit model................................................................................. ...................................................4
Fig. 1.4. Examples of RF MEMS devices - (a) clock-wise from top left: Raytheon [1], MIT-LL [1],
UCSD [1], and Wi Spry capacitive devices [1]; and (b) Radant (left) [1] and UCSD (right)
[57] metal-contact switches.............................................................................................. ..............5
Fig. 1.5. Photomicrographs of (a) MEMS SPDT switch, and (b) a one-bit Ka-band MEMS TTD
phase shifters [29]............................................................................................................. ...............7
Fig. 1.6. Photographs of the (a) SP4T switch and (b) 2-bit phase shifter; [30].......................................7
Fig. 1.7. Top view of a CPW line periodically loaded by shunt MEMS bridges; where, W, S are
the CPW line width and spacing, w and l are the MEMS bridge width and length,
respectively, and s is the spacing between two consecutive MEMS bridges.........................8
Fig. 1.8. Schematic of a beam-steering front-end based phased-array antenna.................................10
Fig. 2.1. Top view and cross section of the MEMS SPST switch...........................................................15
Fig. 2.2. Lumped representation of MEMS switch in saber architect.................................................16
Fig. 2.3. Equivalent circuit model of the metal-contact MEMS switch................................................17
Fig. 2.4. Simulated S-parameter performance of the metal-contact MEMS SPST switch.................18
Fig. 2.5. Fabrication process steps of MEMS SPST switch.....................................................................19
Fig. 2.6. Microscopic image of the SPST MEMS switch.........................................................................20
Fig. 2.7. Measured interferometer profile of the cantilever switch after release................................20
Fig. 2.8. CV measurements of MEMS switch showing pull-in at 40 V and pull-out at 26.4 V.........21
Fig. 2.9. Vibration spectrum of the switch showing resonance at 9.8 kHz, inset shows first
mode of vibration..........................................................................................................................22
Fig. 2.10. Measured switching and release time is 78 µsec and 118 µsec............................................23
xiv
Fig. 2.11. Measured temperature versus Vp and Vr................................................................................24
Fig. 2.12. Measured S-parameter response of the fabricated MEMS switch.......................................25
Fig. 2.13. Measured IIP3 of the MEMS switch.........................................................................................25
Fig. 2.14. Measured power versus pull-in and release voltages...........................................................26
Fig. 2.15. Measured change in Vp and contact resistance with time....................................................27
Fig. 2.16. (a) Micro fabricated image of the high isolation SPST switch and (b) its equivalent
circuit model..................................................................................................................................28
Fig. 2.17. Measured S-parameter response of high isolation SPST switch..........................................29
Fig. 2.18. (a) Micro-photograph image of the SPDT switch and (b) its equivalent circuit
model..............................................................................................................................................30
Fig. 2.19. Measured versus simulated loss (a) input to port 1 and (b) input to port 2, of the
SPDT switch...................................................................................................................................31
Fig. 2.20. Schematic and equivalent circuit representation of SP4T Switch (P1-P2 connected).......32
Fig. 2.21. Equivalent circuit model of the MEMS metal contact switch. It is also represented by
‘Block A’ in the equivalent circuit model of the SP4T Switch................................................33
Fig. 2.22. Microscopic images of the fabricated SP4T RFMEMS switch. Inset shows SEM image
of the SP4T central junction where all four SPST switches are closely packed...................34
Fig. 2.23. Measured S-parameter performances of SP4T RFMEMS switch.........................................34
Fig. 3.1. Design schematic of a switched line phase shifter...................................................................37
Fig. 3.2. Top view of the MEMS SPST switch (SW1)..............................................................................38
Fig. 3.3. Microscopic image of the MEMS switch (SW 1). Inset shows the side view of the
MEMS switch.................................................................................................................................39
Fig. 3.4. Measured S-parameter of SW1 switch versus circuit model and FEM based
simulation (a) Return loss and insertion loss (b) Isolation, over 13 – 18 GHz...................41
Fig. 3.5. Measured S-parameter of SW2 switch versus circuit model and FEM based
simulation (a) Return loss and insertion loss (b) Isolation, over 13 – 18 GHz...................41
Fig. 3.6. SEM image of two back to back SW1 SPST switches...............................................................42
xv
Fig. 3.7. SEM images of five primary bit individual switched-line phase shifter bits using SW1
switches. (a) 11.250, (b) 22.50, (c) 450, (d) 900 and (e) 1800 phase bits......................................43
Fig 3.8. Measured versus simulation results of individual-bits phase shifter (a) 11.250, (b) 22.50,
(c) 450, (d) 900, (e) 1800, phase bits and (f) measured phase shift versus frequency
characteristics.................................................................................................................................44
Fig.3.9. SEM images 900 CPW bend at the corner of the phase shifter................................................45
Fig. 3.10. SEM image of complete 5-bit phase shifter (PS1) using SW1 switches fabricated from
phase 1............................................................................................................................................47
Fig. 3.11 (a) Measured return loss from 32-states of complete 5-bit phase shifter and
(b) Measured and simulated average insertion loss from 32-states of phase-1 5-bit
phase shifter...................................................................................................................................47
Fig. 3.12. SEM images of the 5-bit phase shifter using SW2 switch fabricated from phase-2..........49
Fig. 3.13 (a) Measured return loss from 32-states of complete 5-bit phase shifter and
(b) Measured simulated average insertion loss from 32-states of phase-2 5-bit
phase shifter……………………………………………………………………………………...49
Fig. 3.14. Schematic of the reliability measurement set up for the 5-bit phase shifter......................52
Fig. 3.15. Measured cold switched reliability results of the 5-bit MEMS phase shifter with
0.1 – 1 W of incident RF power at 17.25 GHz frequency.........................................................53
Fig. 4.1 (a) SEM image and (b) equivalent circuit model of the unit cell DMTL phase shifter........55
Fig. 4.2. Simulated (a) S-parameter and (b) phase shift versus frequency response of the
unit cell...........................................................................................................................................59
Fig. 4.3. Complete schematic of 5-bit DMTL phase shifter where bias lines are indicated
with red lines.................................................................................................................................60
Fig. 4.4. (a) Capacitance versus voltage measurement shows pull-in and pull-out at 54 V
and 34 V, respectively, and (b) Vibration spectrum of the MEMS bridge shows a
resonance at 47 kHz, inset shows fundamental mode shape of the mechanical
vibration.........................................................................................................................................61
Fig. 4.5. Measured VPI and Vr versus incident RF power at 10 GHz at room temperature..............61
xvi
Fig. 4.6. Measured versus simulated S-parameter response of the unit cell, (a) return and
insertion loss and (b) phase versus frequency response…………………………………….62
Fig. 4.7. Microscopic images of individual phase bits (a) 11.250, (b) 22.50, (c) 450, (d) 900and (e)
1800.............................................................................................................................. ....................64
Fig. 4.8. (a) Measured loss of the individual phase bits when structure is tuned to 53 Ω.
Measured versus simulated phase shift of the individual phase bits (b) 11.250(c) 22.50
(d) 450 (e) 900 and (f) 1800.............................................................................................................65
Fig. 4.9. SEM image of fabricated phase shifter structure where all functional blocks are
marked............................................................................................................................................67
Fig. 4.10. Measured S-parameter response of the 5-bit phase shifter (a) return loss (b) insertion
loss is verified with simulated average loss..............................................................................68
Fig. 4.11. Measured phase versus frequency characteristics of the complete cells............................68
Fig. 4.12. Measured VPI and Vr versus (a) extended continuous actuation, and (b) temperature,
at 0.1 W of RF power at 10 GHz..................................................................................................70
Fig. 4.13. Reliability measurements of the 5-bit phase shifter under (a) 1 W of RF power and
(b) 40 0C – 70 0C temperature variation with 0.1 W of RF power...........................................72
Fig. 5.1. Schematic diagram of the 5-bit phase shifter using four SP4T and two SPDT switches....75
Fig. 5.2. Microscopic images of fine and coarse bit sections of the 5-bit phase shifter......................77
Fig. 5.3. Simulated coupling among the delay lines (a) fine-bit section and (b) coarse-bit
section.............................................................................................................................................78
Fig. 5.4. Microscopic image of 1-bit section of the 5-bit phase shifter.................................................78
Fig. 5.5. Measured versus simulated S-parameters of the individual fine-bit section, (a) Return
loss and (b) Insertion loss, over the entire Ku-band................................................................79
Fig. 5.6. Measured versus simulated S-parameters of the individual coarse-bit section,
(a) Return loss and (b) Insertion loss, over the entire Ku-band.............................................80
Fig. 5.7. Measured versus simulated S-parameters of the individual 1-bit section, (a) Return
loss and (b) Insertion loss, over the entire Ku-band................................................................80
xvii
Fig. 5.8. Measured versus simulated phase versus frequency response of (a) fine-bit,
(b) coarse- bit and (c) 1-bit sections, over the entire Ku-band................................................80
Fig. 5.9. Microscopic image of the Ku-band 5-bit TTD phase shifter fabricated under
Phase-I.............................................................................................................................................81
Fig. 5.10. Effect of different connecting line lengths on S-parameters.................................................82
Fig.5.11. Measured S-parameter response of PS1 (a) Return loss from 0 – 18 GHz , (b) Insertion
loss, (c) Phase versus frequency response of primary phase bits over 13 – 18GHz, (d)
measured group delay performance at different phase states of the complete 5-bit
phase shifter...................................................................................................................................83
Fig. 5.12. Measured pull-in (Vp) and pull-out (Vr) voltage versus (a) temperature and
(b) power at different temperatures for the switch..................................................................85
Fig. 5.13.Simulated heat dissipations on the "dc" contact switch at 2 GHz and 17 GHz
frequencies.....................................................................................................................................87
Fig. 5.14. Simulated variation of switch insertion loss with (a) 0.1 – 2 W of RF power and
(b) with 0.5 – 2 W of power at three different temperatures..................................................88
Fig. 5.15. Simulated current distributions on the SP4T switch at 2 GHz and 17 GHz with
0.1 W of incident RF power at 2730K temperature...................................................................89
Fig. 5.16.Measured contact resistance versus applied voltage for the switch....................................90
Fig. 5.17.Measured (a) SPST and (b) SP4T switch reliability, with different incident RF power…90
Fig. 5.18. Test setup for the reliability measurement of phase shifter where it is mounted
on a test jig......................................................................................................................................92
Fig. 5.19. (a) Phase shifter reliability performances on a chip and within a module, and
(b) Phase shifter reliability at different temperature at 17 GHz.............................................92
Fig. 5.20. Phase shifter cold switched reliability performance with 500 mW, 800 mW and
1 W of power..................................................................................................................................94
Fig. 5.21. Measured S-parameter response of the (a) SP4T switch, (b) return loss, (c) insertion
loss, and (d) phase versus frequency responses of individual sections of 5-bit phase
shifter..............................................................................................................................................97
xviii
Fig. 5.22. Microphotograph images of fine and coarse bit sections of the 5-bit phase shifter..........97
Fig. 5.23. Microscopic image of the Ku-band 5-bit phase shifter fabricated from Phase II..............98
Fig. 5.24. Schematic of the complete 5-bit phase shifter at 00 (reference) state...................................99
Fig. 5.25. (a) Measured return loss performance of 5-bit phase shifter up to 18 GHz and
(b) Measured versus simulated average insertion loss over 13 – 18 GHz..........................100
Fig. 5.26. (a) Measured pull-in and release voltages of SPST switch versus temperatures and
(b) Switch power handling response at different temperature scales.................................101
Fig. 5.27. Cold switched reliability of the SPST and SP4T switches at 25 0C....................................102
Fig. 5.28. Reliability of (a) SPST and (b) SP4T switches for 0.1 – 1 W of RF power at 50 0C (top)
and 70 0C (bottom) with 70 V actuation voltage.....................................................................103
Fig. 5.29. (a) Reliability performances of individual sections of the 5-bit phase shifter and (b)
performance comparison of the 5-bit phase shifter on a chip and on a package,
at 17 GHz with 0.1 W of RF power...........................................................................................105
Fig. 5.30. Simulated performance variation between chip and module where (a) return
and insertion loss and (b) phase, at reference state of the phase shifter.............................105
Fig. 5.31. Reliability of the phase shifter with (a) 0.5 – 2 W of power under cold-switched
and (b) for 0.5 – 1 W of power and at two different temperatures (50 0C and 70 0C)
under hot-switched conditions.................................................................................................106
Fig. 5.32. Measured change in loss and phase error at (a) 250C and (b) 500C; over 6 h of
prolonged actuation (ON-state) with 0.1 W of power at 17 GHz........................................107
Fig. 5.33. Power spectral density versus frequency for shaker table testing under 0.04 g2 Hz-1
PSD................................................................................................................................................108
Fig. 5.34. Schematics of individual switch actuations from the 5-bit phase shifter over one
complete cycle..............................................................................................................................110
Fig. 6.1.Schematic of the top surface of the push-pull type MEMS bridge.......................................114
Fig. 6.2.Schematic of (a) Beam lifted upward due to Vpush (b) beam snaps down due to Vpull,
under different applied forces...................................................................................................115
Fig. 6.3. 3D model of the push-pull MEMS bridge...............................................................................116
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Fig. 6.4. Lumped representation of the push-pull MEMS bridge in Saber Architect......................122
Fig. 6.5.Variation of gap height with applied (a) Vpull and (b) Vpush voltages. Inset shows
beam upward and downward deflections..............................................................................123
Fig. 6.6.Vibration spectrum of the beam shows the fundamental frequency at 4.86 kHz..............123
Fig. 6.7.SEM Images of Micro-fabricated unit cell phase shifter using MEMS push-pull bridge..126
Fig. 6.8.Vibration spectrums of the push-pull bridge, where, (a) pull state shows a resonance at
4.012 kHz (b) push state shows a resonance peak at 5.29 KHz. Inset shows the
measured shape of the bridge...................................................................................................127
Fig. 6.9. Snap shot of one mode of vibration under in-plane and out of plane bending motions.129
Fig. 6.10. Capacitance versus voltage variations at (a) Pull and (b) push stages.............................130
Fig. 6.11. Measured versus simulated S-parameter response of a unit cell, (a) return loss
and (b) insertion loss performance...........................................................................................132
Fig. 6.12. Layout of complete TTD phase shifter, inset shows the saw-shaped CPW.
Complete area of the phase shifter is 8.5 mm2........................................................................133
Fig. 6.13. (a)Top and (b) cross section SEM images of the distributed MEMS phase shifter.........133
Fig. 6.14. Measured versus simulated S-parameter responses of the distributed cell,
(a) return loss and (b) Insertion loss.........................................................................................134
Fig. 6.15.Measured variation of phase shift with applied bias at (a) pull and (b) push states,
respectively, at 40 GHz frequency............................................................................................134
Fig. 7.1 (a) Top view of the unit cell phase shifter using push-pull actuator and
(b) its equivalent circuit model............................................................................................... ..138
Fig. 7.2. Calculated rotation angle versus under quasi-static, step and modulated applied
voltages.........................................................................................................................................143
Fig. 7.3. (a) Simulated bridge gap height versus applied Vpull and Vpush voltages and
(b) Variation of bridge pull-in voltages with various mobile electrodes and fixed
electrodes lengths........................................................................................................................145
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Fig. 7.4. (a) Variation of bridge pull-in voltages versus torsional spring lengths with different
bridge torsional spring widths and (b) Variation of bridge pull-in voltages versus
torsional spring thickness with different bridge gap height values....................................145
Fig. 7.5. Simulated bridge gap height variation with applied Vpull and Vpush....................................146
Fig. 7.6. Simulated S-parameter response of the unit cell phase shifter............................................148
Fig. 7.7. Layout of the 5-bit reconfigurable phase shifter. Total area of the phase shifter is
15.6 mm2.......................................................................................................................................151
Fig. 7.8.Simulated performance of the RF MEMS phase shifter for 5-bit operation in all 36
states at (a) 10 GHz, (b) 12 GHz, (c) 17.2 GHz and (d) 25 GHz, respectively,
over 500 MHz bandwidth..........................................................................................................152
Fig. 7.9. Measured 3D profile of the fabricated unit cell phase shifter..............................................153
Fig. 7.10. Microphotograph of (a) 22.50, (b) 450, (c) 900 and (d) 1800 phase shifters.........................153
Fig. 7.11. (a) Measured (10.68 KHz) versus simulated (14.8 KHz) mechanical resonance
frequency where (b) push and (c) pull stages response of the bridge.................................154
Fig. 7.12.Comparison between capacitance values from DC and RF measurements......................155
Fig. 7.13. (a) Measured switching and release time response in pull stage, extracted from
DSO and (b) Changes in response time with applied Vpush and Vpull voltages...................156
Fig. 7.14. Measured loss performances of 11.250 phase shifter at different bias voltage................156
Fig. 7.15. Measured differential phase shifts of 11.250 unit cell at (a) 10, (b) 12, (c) 17.2 and
(d) 25 GHz....................................................................................................................................157
Fig. 7.16. S-parameters of 22.50 phase shifter when it is reconfigured at (a) 12, (b) 17.2,
(c) 25 and (d) 10 GHz frequencies over 500MHz bandwidth...............................................158
Fig. 7.17. S-parameters of 1800 phase shifter when it is reconfigured at (a) 12 GHz,
(b) 17.2 GHz, (c) 25 GHz and (d) 10 GHz frequencies over 500MHz bandwidth.............159
Fig. 7.18. Measured S-parameter response of the RF MEMS 5-bit phase shifter when it is
reconfigured over 500 MHz bandwidth at three sample frequencies over the
X – K band (12 – 25 GHz), (a) 12 GHz (X-band), (b) 17.2 GHz (Ku-band) and
(c) 25 GHz (K-band)....................................................................................................................160
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Fig. 7.19. Measured phase improvement of the MEMS 5-bit phase shifter when it is
reconfigured between Vpush and Vpull actuation states at (a) 10 GHz, (b)17.2 GHz
and (c) 25 GHz, over 500 MHz bandwidth.............................................................................161
Fig. 7.20. Measured (a) loss and (b) phase response of the RF MEMS 5-bit phase shifter
when it is reconfigured between Vpush and Vpull actuation states at 10 GHz over
500 MHz bandwidth...................................................................................................................161
Fig. 7.21. Measured pull-in (Vp) and release (Vr) voltages versus incident power level at
pull and push stages...................................................................................................................163
Fig. 7.22. (a) Measured loss versus incident RF power at different Vpull voltages, and
(b) Measured Vpush voltage versus incident RF power...........................................................163
Fig. 7.23. Reliability measurement of unit cell MEMS phase shifter with single push-pull
actuator at (a) 10 GHz, (b) 17.2 GHz and (c) 25 GHz.............................................................165
Fig. 7.24. Measured cold switched reliability result of the 5-bit MEMS phase shifter with
0.1 – 2 W of incident RF power at 17.2 GHz frequency.........................................................166
Fig. 8.1. Schematics of a 5-bit MEMS phase shifter using two SP8T and two SP4T switches........172
Fig. 8.2. Block diagram of 3-bit or 4-bit phase shifters using MEMS SP8T or SP16T switching
network.........................................................................................................................................173
Fig. 8.3. Block diagram of a K-band frequency reconfigurable phase shifter using two
MEMS SP4T switches and four DMTL phase shifters...........................................................174
Fig. A.1. Schematic view of micro-fabrication process steps..............................................................182
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LIST OF TABLES
TABLE 1.1: Performance Comparison of FETs, PIN Diodes and RF MEMS
Electrostatic Switches.......................................................................................................3
TABLE 3.1: Switch Mechanical Performance........................................................................ ..........40
TABLE 3.2: Switch Electrical Performance......................................................................................40
TABLE 3.3: Individual Primary Phase Bits Performance Over 17 – 17.5 GHz...........................45
TABLE 3.4: Performance Summery of the Phase 1 5-Bit Phase Shifter Over 17 – 17.5 GHz…48
TABLE 3.5: Performance Summery of the Phase 2 5-Bit Phase Shifter Over 17 – 17.5 GHz…50
TABLE 3.6: Performance Comparison between Phase-1 and Phase-2 Phase shifter
Over 17 – 17.5 GHz.........................................................................................................50
TABLE 4.1: Dimensions of the Unit Cell Phase Shifter..................................................................58
TABLE 4.2: Simulated and Measured Circuit Parameters of the Unit Cell Phase Shifter........63
TABLE 4.3: Simulated and Measured Q Factor Loss Component at 10 GHz for
Individual Phase Bits in the Actuated State................................................................66
TABLE 4.4: Measured Individual Primary Phase Bits Performance Over 8 – 12 GHz.............66
TABLE 4.5: Performance Summery of the 5-Bit Phase Shifter Over 8 – 12 GHz........................69
TABLE 5.1: Performance Comparison between Phase-1 and Phase-2 Phase Shifters
at 17 GHz.........................................................................................................................99
TABLE 5.2: Performance Summery of the 5-Bit Phase Shifter Over 8 – 12 GHz......................100
TABLE 5.3: State-of-the-art Reliability Comparison of the MEMS SPST Switches
over Last Four Years.....................................................................................................104
TABLE 5.4: State-of-the-art Comparison of MEMS SP4T Switches over Last Four Year……104
TABLE 5.5: Comparison of State-of-the-Art MEMS Phase Shifters over last decade..............109
TABLE 5.5: Comparison of State-of-the-Art Phase Shifters over last decade...........................109
TABLE 5.7: Reliability Comparison between Two Reported Phase Shifters at 17 GHz.........109
TABLE 6.1: Designed Dimensions of the Push-Pull Bridge........................................................120
TABLE 6.2: Material Properties of the MEMS Push-Pull Bridge................................................121
TABLE 6.3: Material Properties of the MEMS Push-Pull Bridge................................................129
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TABLE 7.1: Designed Dimensions of the Push-Pull Bridge........................................................141
TABLE 7.2: Optimized Circuit Model of the Unit Cell DMTL Phase Shifter...........................149
TABLE 7.3: List of Designed Parameters of the Unit Cell DMTL Phase Shifter......................149
TABLE 7.4: Summary of the Simulation Results of The Primary Cell Phase Shifter at
a Four Sample Frequencies over 10 – 25 GHz band................................................150
TABLE 7.5: Measured Single-Bit Phase Shifter Performance Parameters.................................157
TABLE 7.6: List of Final Designed Parameters of the Unit Cell DMTL Phase Shifter.............158
TABLE 7.7: 5-bit Phase Shifter Performance Comparison at Different Voltage States...........162
TABLE 7.8: 5-bit Phase Shifter Cold-Switched Reliability Results Over 10 – 25 GHz............167
TABLE 7.9: S-Parameters Results of the Phase Shifter during Cold-Switched Reliability
Cycles............................................................................................... ...............................167
TABLE 7.10: Comparison of State-of-the-Art Phase Shifters Over Last Decade........................168
TABLE 8.1: 5-Bit MEMS Phase Shifter Performance Summery..................................................171
TABLE A-1: Characteristic of substrate material...........................................................................182
