YIG-sphere-based phase shifter for X-band phased array applications

139 Pages·2015·1.43 MB·English

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Master's Theses Master's Theses and Graduate Research
Fall 2011
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Donald C. Benson
San Jose State University
Follow this and additional works at: https://scholarworks.sjsu.edu/etd_theses
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Benson, Donald C., "YIG-sphere-based phase shifter for X-band phased array applications" (2011).
Master's Theses. 4083.
DOI: https://doi.org/10.31979/etd.p4je-rvaz
https://scholarworks.sjsu.edu/etd_theses/4083
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YIG-SPHERE-BASED PHASE-SHIFTER FOR X-BAND PHASED
ARRAY APPLICATIONS

A Thesis
Presented to
The Faculty of the Department of Electrical Engineering
San José State University

In Partial Fulfillment
of the Requirements for the Degree
Master of Science

by
Donald C. Benson
December 2011
© 2011
Donald C. Benson
ALL RIGHTS RESERVED
The Designated Thesis Committee Approves the Thesis Titled
YIG-SPHERE-BASED PHASE-SHIFTER FOR X-BAND PHASED
ARRAY APPLICATIONS
by
Donald C. Benson
APPROVED FOR THE DEPARTMENT OF ELECTRICAL ENGINEERING
SAN JOSÉ STATE UNIVERSITY
December 2011
Dr. Sotoudeh Hamedi-Hagh Department of Electrical Engineering
Dr. Masoud Mostafavi Department of Electrical Engineering
Dr. Raymond Kwok Department of Physics
ABSTRACT
YIG-SPHERE-BASED PHASE SHIFTER FOR X-BAND PHASED
ARRAY APPLICATIONS
By Donald C. Benson
A novel technique for effecting phase shift of X-band signals has been developed
and analyzed for use with quadrature amplitude modulation (QAM) of signals in a phased
array application, and the impact of this phase shifter on error vector magnitude (EVM)
has been quantified. A commercially available filter consisting of yttrium iron garnet
(YIG) spheres was characterized by means of a network analyzer. The gain and phase
response was measured across a 25 MHz frequency band centered at 10 GHz, while the
filter was tuned in frequency steps such that a 360 range of phase shifts was achieved.
The S-parameters from these measurements were integrated with Matlab representations
of QAM-16 modulation, demodulation, and phased array antennas to model a complete
radio system. The EVM caused by non-ideal gain and phase response of the YIG filter
was determined for various beam angles and data patterns.
It was found that a YIG filter does provide stable phase shift suitable for phased
array applications, with acceptable attenuation so long as the frequency being transmitted
remains within the filter’s pass band. The particular filter analyzed did not contain
sufficient stages to maintain 3 dB flatness across the required 360 tuning range, but
performed satisfactorily for a limited range of beam orientation. The capability to provide
continuously variable phase shift offered by the YIG filter was found to not offer
significant advantage over the discrete steps produced by switched delay lines.
Table of Contents 
I.  Introduction .......................................................................................................... 1 
A.  Background ....................................................................................................... 1 
B.  Related research ................................................................................................ 1 
C.  Selection of YIG sphere technology ................................................................. 3 
II.  Hypothesis ............................................................................................................ 8 
III.  Partition between hardware and mathematical simulation ................................... 9 
IV.  Implementation of YIG phase shifter ................................................................. 11 
D.  Design of a custom filter ................................................................................ 11 
E.  Selection of a commercial filter ..................................................................... 13 
F.  Characterization of filter ................................................................................. 14 
V.  The behavior of phased arrays ........................................................................... 22 
VI.  Simulation of radiation pattern ........................................................................... 24 
VII.  Simulation of modulation/demodulation and error vector magnitude ........... 28 
G.  Baseline model of digital radio with ideal channel ........................................ 28 
H.  Three-bit phase shifter for beam forming ....................................................... 39 
I.  Ideal Butterworth filter phase shifter for beam forming ................................ 40 
J.  Measured YIG filter phase shifter for beam forming ..................................... 44 
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K.  YIG filter phase shifter operated within -3 dB bandwidth ............................. 46 
L.  Swept beam angle using YIG filter phase shifter ........................................... 48 
VIII.  Issues identified in phased array systems ....................................................... 50 
IX.  Potential pitfalls of characterzation and analysis approach ............................... 52 
X.  On implementing an actual system .................................................................... 54 
XI.  Conclusion .......................................................................................................... 55 
APPENDIX A.  Matlab code ........................................................................................ 56 
A.  Radiation pattern ............................................................................................ 56 
B.  Antenna pattern .............................................................................................. 60 
C.  Constructive and destructive interference ...................................................... 61 
D.  Phase shifter .................................................................................................... 63 
E.  Digital radio model and EVM calculation ...................................................... 66 
F.  Idealized Butterworth beam former ................................................................ 84 
G.  Idealized Butterworth phase shifter ................................................................ 86 
H.  Recovery synchronization .............................................................................. 89 
I.  YIG beam former ........................................................................................... 93 
J.  YIG phase shifter ............................................................................................ 96 
K.  Swept beam angle ........................................................................................... 98 
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L.  Read S-parameter files and store in array ....................................................... 99 
M.  Read and plot filter S-parameter across entire passband .............................. 110 
APPENDIX B.  Data files ........................................................................................... 120 
A.  YIG S-parameter .......................................................................................... 120 
References ....................................................................................................................... 128 

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List of Figures 
Figure 1.  Schematic representation of YIG bandpass filter  3 
Figure 2.  Original concept of bi‐directional system  5 
Figure 3.  Transformation of impedance through stages of a filter  11 
Figure 4.  YIG filter  13 
Figure 5.  S‐parameter test setup  15 
Figure 6.  2 ‐ 20 GHz response of YIG filter  17 
Figure 7.  Measured gain and phase of YIG filter across the pass band  18 
Figure 8.  Measured gain and phase of YIG filter across frequency band of radio  20 
Figure 9.  Phase shift vs. beam angle  22 
Figure 10.  Radiation pattern with ideal phase shifters  25 
Figure 11.  Radiation pattern with 3‐bit phase shifters  26 
Figure 12.  Radiation pattern with YIG phase shifters  26 
Figure 13.  Constellation and I/Q modulation of [56A9401237BFEDC8]  33 
Figure 14.  QAM‐16 modulation and frequency content of [56A9401237BFEDC8]  34 
Figure 15.  Recovered constellation, I & Q, and error for [56A9401237BFEDC8]  36 
Figure 16.  Constellation and I/Q modulation of [0F4B87C3D2E1A569]  37 
Figure 17.  QAM‐16 modulation and frequency content of [0F4B87C3D2E1A569]  38 
Figure 18.  Recovered constellation, I & Q, and error for [0F4B87C3D2E1A569]  39 
Figure 19.  Recovered constellation, I & Q, and error, 3‐bit phase shifter  40 
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Figure 20.  Butterworth bandpass filter tuned around 10 GHz to provide phase shift  41 
Figure 21.  Recovered constellation, I & Q, and error, Butterworth phase shifter  43 
Figure 22.  Recovered constellation and delta error YIG vs.  baseline  45 
Figure 23.  Recovered constellation and delta error YIG vs. baseline for small angle  47 
Figure 24.  EVM variation as beam swept from 0 to +90 by YIG phase shifter  49 

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