AN OPTICALLY-SWITCHED TRANSMIT/RECEIVE LENS ARRAY FOR BEAM-SPACE ADAPTIVE COMMUNICATION SYSTEMS by JAMES EDWIN VIAN B.S., University of Colorado at Boulder, 1994 M.S., University of Colorado at Boulder, 1996 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Electrical and Computer Engineering 2000 This thesis entitled: An Optically-Switched Transmit/Receive Lens Array for Beam-Space Adaptive Communication Systems written by James Edwin Vian has been approved for the Department of Electrical and Computer Engineering Zoya Popovi´c Louis Scharf Date The final copy of this thesis has been examined by the signatories; and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline HRC Protocol iii Vian, James Edwin (Ph.D., Electrical Engineering) AnOptically-SwitchedTransmit/ReceiveLensArrayforBeam-SpaceAdaptiveCom- munication Systems Thesis directed by Professor Zoya Popovi´c With the growth in todays modern communication world, multiple user and multi-path environments are becoming an ever increasing problem. These en- vironments reduce the quality of the communication link through multiple users interfering with each other or self interference in multi-path environments. A com- mon technique used to combat these environments, is to use a planar antenna array that steer its receptivity pattern in the direction of the desired user. The receptivity patterns for the arrays are control through adaptive algorithms that adjust the mag- nitude and phase of each received signal at each element in the planar array before coherently combining the signals. The magnitude and phase adjustments (complex weights) reverse the phase shifts induced in the signals as they propagate across the surface of the planar array. The disadvantage of this technique is that it requires significant amounts of computational processing power for large arrays containing manyantennaelements. Byusingamicrowavelensarrayinsteadofaplanararrayin the communication system, the received signals are transformed from a phase-space representation to a beam-space representation, which can reduce the processing load for the algorithm and may increase the overall signal to noise ratio (SNR) through partial beam-forming before the noise is added to the system. For these reasons, an optically controlled transmit/receive lens array is developed. The optical control of thelensarrayallowsthearraytoswitchbetweentransmitandreceivemodesrapidly withnegligibleinterferencetothemicrowavesignals. Alowopticalpowersinglepole double throw switch is developed for routing the transmit and receive signals in the iv array that has insertion loss of 0.3 dB and isolation of 36 dB. To model the per- formance of lens arrays for wireless communication systems, code is developed that calculates the imaging properties of lens arrays under different design conditions. The lens array modeling code is used in conjunction with a modified Least Mean Square(LMS)algorithmthatturnsoff small valuedcomplex weights, to improve the overall SNR and adaptation rate for the communication system. DEDICATION Dedication ...This thesis is dedicated to my family. To parents, Wayne and Sharon Vian, who are my first teachers that made me excited about the world of science. To my sister, Carol Vian, for the healthy competition while growing up. And finally to my loving wife, Trina Vian, who helped me keep everything in perspective. vi ACKNOWLEDGMENTS Acknowledgments ...This work would not be possible without the men- torship of my advisor Prof. Zoya Popovi´c. Besides her day-to-day support and encouragement, it is her unwavering dedication to developing and maintaining a top quality research laboratory that made this work possible. Note that this work was supported ONR and the Office of the Secretary of Defense through the MURI program grant N00014-97-1006. I would also like to thank the past and present members of Zoya Popovi´c’s research group. To Stein Hollung, whose work on transmit/receive lens arrays is the bases for my work research. To Eric Bryerton, Joe Tustin, Michael Forman, Todd Marshall, Manoja Weiss and Jan PeetersWeem, whose conservations on on electro- magnetic theory (among other things) help me to better understand this difficult topic. A special thanks to Shawn Stone, Pete Kirkpatrick and Paul Smith, who help with the buying, building and testing of many of the items in this thesis. I would also like to thank Michael Forman, Todd Marshall and Jan PeetersWeem for their time and patience in teaching me the ways of Linux and LaTex which made the writing of this thesis possible. In addition to the members of Zoya Popovi´c’s group, I would like to thank Prof. Dana Anderson, Prof. Kelvin Wagner and their research groups (Edeline Fotheringham, Leslie Czaia, Greg Kriehn, Ken Anderson, Friso Schlottau, Andrew Kiruluta, Paulo Silveria) for there help and guidance in the world of optics. I am also grateful to Prof. Lloyd Griffiths for his help on adaptive arrays and the LMS algorithm. I want to thank our administrative assistants, Helen Frey and Rachel Tearle, who often went out of their way to make sure that our day-to-day operations vii ran smoothly. CONTENTS CHAPTER 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Adaptive Communication Systems . . . . . . . . . . . . . . . . . 1 1.2 Adaptive Planar Array Communication Systems . . . . . . . . . 5 1.3 Adaptive Lens Array Communication Systems . . . . . . . . . . 8 1.4 Fast Optical Control of Lens Arrays . . . . . . . . . . . . . . . . 9 1.5 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2 8 GHZ RESONANT SWITCH AND UNIT CELL DESIGN . . . . . 13 2.1 Microwave Switches Background . . . . . . . . . . . . . . . . . . 13 2.2 Photonic Switches Background . . . . . . . . . . . . . . . . . . . 18 2.3 Developing Photonic Switch . . . . . . . . . . . . . . . . . . . . 19 2.3.1 Techniques for Optical Control. . . . . . . . . . . . . . . 20 2.3.2 InvestigatingOpticalDevicesUsedasMicrowaveSwitch Components . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3.3 InvestigatingOpticalDevicesThatBiasMicrowaveSwitch Component . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3.4 Investigating Optical Devices That Control the Bias of Microwave Switch Component . . . . . . . . . . . . . . . 23 2.3.5 Photo-MESFET . . . . . . . . . . . . . . . . . . . . . . . 23 2.3.6 Resonant Switch Operation . . . . . . . . . . . . . . . . 29 2.4 SPDT Switch Design . . . . . . . . . . . . . . . . . . . . . . . . 30 2.4.1 Manufacturing Tollerances . . . . . . . . . . . . . . . . . 31 2.4.2 Four Different SPDT Switch Designs . . . . . . . . . . . 35 ix 2.4.3 Effects of Optical Control . . . . . . . . . . . . . . . . . 35 2.5 Unit Cell Array Element Design . . . . . . . . . . . . . . . . . . 38 2.5.1 Low Noise Amplifier and Power Amplifier . . . . . . . . 40 2.5.2 Bias Line Design . . . . . . . . . . . . . . . . . . . . . . 43 2.5.3 Antenna Design . . . . . . . . . . . . . . . . . . . . . . . 44 2.5.4 Slot Coupler vs. Vias Feed . . . . . . . . . . . . . . . . . 47 2.5.5 Unit Cell Layout . . . . . . . . . . . . . . . . . . . . . . 48 2.5.6 Testing Unit Cell . . . . . . . . . . . . . . . . . . . . . . 50 3 10GHZ CHIP-PIN DIODE SPDT SWITCH . . . . . . . . . . . . . . 52 3.1 Improved Switch Design . . . . . . . . . . . . . . . . . . . . . . 52 3.1.1 MA4GP032 Chip PIN diode . . . . . . . . . . . . . . . . 53 3.1.2 High Pass Filter . . . . . . . . . . . . . . . . . . . . . . . 59 3.1.3 Low Pass Filter . . . . . . . . . . . . . . . . . . . . . . . 61 3.1.4 Simulation of Transient Response of SPDT Switch . . . 63 3.2 Optimized SPDT Switch Design . . . . . . . . . . . . . . . . . . 65 3.2.1 Estimation of Switching Current Isolation . . . . . . . . 68 3.2.2 Maximum Input Power for SPDT Switch . . . . . . . . . 70 3.3 Switch Rate Measurements . . . . . . . . . . . . . . . . . . . . . 70 3.3.1 Optical Test Setup . . . . . . . . . . . . . . . . . . . . . 71 3.3.2 Calibration of the Optical Setup . . . . . . . . . . . . . . 77 3.3.3 Measured Switch Rate Performance . . . . . . . . . . . . 79 4 10GHZ UNIT CELL AND LENS ARRAY . . . . . . . . . . . . . . . 81 4.1 Unit Cell Construction . . . . . . . . . . . . . . . . . . . . . . . 81 4.1.1 Unit Cell Layout . . . . . . . . . . . . . . . . . . . . . . 82 4.1.2 RF Mount Design . . . . . . . . . . . . . . . . . . . . . . 85 4.1.3 Optical Mount Design . . . . . . . . . . . . . . . . . . . 85 4.2 Unit Cell Testing . . . . . . . . . . . . . . . . . . . . . . . . . . 86 x 4.3 Array Design and Testing . . . . . . . . . . . . . . . . . . . . . . 87 4.3.1 Optical Control Problems with the Array Measurements 88 4.3.2 Array Pattern Measurements. . . . . . . . . . . . . . . . 92 4.4 Shaped Pulse Control of SPDT Switch . . . . . . . . . . . . . . 98 5 LENS ARRAYS DESIGN. . . . . . . . . . . . . . . . . . . . . . . . . 101 5.1 Constrained Lens Array Theory . . . . . . . . . . . . . . . . . . 101 5.2 Lens Array Modeling . . . . . . . . . . . . . . . . . . . . . . . . 106 5.2.1 Physical Bases for the Numerical Model . . . . . . . . . 107 5.2.2 Antenna Element Models . . . . . . . . . . . . . . . . . . 111 5.2.3 Numerical Model Structure. . . . . . . . . . . . . . . . . 117 5.3 Lens Simulation Results . . . . . . . . . . . . . . . . . . . . . . 120 5.3.1 F/D versus θ . . . . . . . . . . . . . . . . . . . . . . . . 122 0 5.3.2 Lens Abberations . . . . . . . . . . . . . . . . . . . . . . 126 5.3.3 Lens Array Loss under Scaling . . . . . . . . . . . . . . . 130 6 SIMULATIONOFBEAM-SPACEADAPTIVELENSARRAYSYS- TEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 6.1 The LMS Algorithm. . . . . . . . . . . . . . . . . . . . . . . . . 133 6.2 Sampling the Lens Array Focal Surface . . . . . . . . . . . . . . 137 6.3 Numerical Experiments on Lens Array Systems . . . . . . . . . 143 6.3.1 SNR vs. Number of Signals . . . . . . . . . . . . . . . . 145 6.3.2 SNR vs. Lens Array Size . . . . . . . . . . . . . . . . . . 155 6.3.3 Adaptation Rate Vs. Number of Signals . . . . . . . . . 156 7 FUTURE WORK AND CONCLUSIONS . . . . . . . . . . . . . . . . 158 7.1 Optically Controlled Lens Arrays . . . . . . . . . . . . . . . . . 158 7.1.1 Future Work for Optically Controlled Lens Arrays . . . . 158 7.1.2 Conclusion for Optically Controlled Lens Arrays . . . . . 159 7.2 Modeling of Lens Arrays . . . . . . . . . . . . . . . . . . . . . . 160