April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 1 Amplifier-Based Active Antenna Oscillator Design at GHz Isaac Waldron, Ayoob Ahmed, & Sergey Makarov Worcester Polytechnic Institute ECE Department Worcester, MA 01609

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 2 Outline Motivation Oscillator Design Performance Conclusion

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 3 Motivation Self-directed project to design an active antenna using a commercial off-the-shelf RF amplifier IC.

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 4 Antenna Geometry

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 5 Oscillator Linear Model Oscillation prediction follows from Berkhausen criteria: 1 - A(s)H(s) = 0 or |A(s)H(s)| = 1,  A(s)H(s) = 0 

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 6 Oscillator Open-Loop Response The antenna will start to oscillate at approximately the frequency marked by the diamond; at this frequency, a signal traveling around the loop returns in phase.

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 7 Typical Antenna Setup

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 8 Spectrum

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 9 Locking Bandwidth Locking bandwidth of about 100 kHz on each side of the center frequency was observed. Holding bandwidth of about 200 kHz on each side of the center frequency was observed.

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 10 Phase Noise

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 11 Bias Tuning

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 12 Co-polar Radiation Pattern

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 13 Antenna Tuning The oscillation frequency of the antenna linearly depends on the leading patch dimension. It also depends on the ratio between the width and length of the patches. Below a certain patch length, oscillations in the desired mode cease as the coupling between the antenna ports drops below a critical value.

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 14 Antenna Tuning

April 3-7, 2005, Honolulu, HI 2005 IEEE/ACES Int'l Conference on Wireless Communications and Applied Computational Electromagnetics 15 Conclusion Oscillator designed from open-loop transmission. Prototypes match predicted oscillation frequency. Bias and geometric tuning were demonstrated. Regions of operation were determined.