1. A Phase Noise Study on Coupled Oscillator Arrays Summer 2002 SURE Program Jack Chao, Univ. of Michigan - Ann Arbor Advisors: Dr. L. Wilson Pearson, Chris Tompkins

2. Outline zBasic concepts zCircuit fabrication zPhase noise measurements zConclusions zFuture work

3. Beam Steering zRotate beam axis by changing phase delay between elements

4. Motivation zBeam steering currently uses phase shifter for each element zBecomes complex for large arrays at millimeter wavelengths zCoupled oscillator arrays: less complex circuitry for beam steering

5. Antennas Oscillators Coupled Oscillator Array zPhase difference between adjacent oscillators can be controlled zLess complex circuitry for beam steering

6. * H.-C. Chang, et. al., “Phase Noise in Externally Injection-Locked Oscillator Arrays,” IEEE Trans. Microwave Theory Tech., vol. 45, pp. 2035-2042, Nov. 1997. A Problem: Phase Noise zProblem: All oscillator signals have phase fluctuation (phase noise or “jitter”) zProposed solution: Injection lock at multiple points in array* z Summer objective: verify multi-point injection locking reduces phase noise

7. Injection Locking Injection Locking a Single Voltage-Controlled Oscillator Free RunningSignal InjectionInjection Locked Oscillates at  0 More Phase Noise External Signal at  1 (  1 close to  0 ) Oscillates at  1 Less Phase Noise

8. Fabrication zOscillator layer (oscillates ~10 GHz) zNon-overlapping oscillation ranges ySettled on 5-element array instead of 9-element

9. Fabrication (cont’d) zTransmit layer

10. Injection Locking Setup Antennas Oscillators Clean Source Signal Phase-shifters zElements 3,5,7 were injection locked in various combinations zAntenna received array’s combined signal 357

11. Measurement Process zFind array’s free-running frequency yTune individual oscillators zInjection lock desired oscillators zMeasure phase noise for each injection combination

12. View from Spectrum Analyzer

13. Results - Injection Schemes

14. Results - Injection Power

15. Conclusions zExperimentally verified increasing number of injection ports decreases phase noise yDiminishing returns with increase in ports zIncreasing injection power decreases phase noise yGreater effect on phase noise with less ports

16. Future Work zLower noise floor of measurement setup zMeasure phase noise for 5-element array under beam steering conditions zDebug and test entire 9-element array zFabricate and test two-dimensional array

17. Acknowledgements zDr. Jim Harriss zXing Wang

18. Questions?