Design of an Ultralow Noise Ka-Band Oscillator

Abstract

Oscillator is an integral part of a communication system. Right from tuning a radio to checking the time on the cell phone we rely on a properly working oscillator. Oscillators are highly nonlinear circuits where the most of the nonlinear phenomena of the device are desirable from the designer point of view. The essence of an oscillator lies in the co-existence of the unique and stable periodic oscillations, and an unstable quiescent point. Moreover, the oscillators designed at microwave frequency have more problems of the nonlinear effects, bifurcation from the center frequency and hysteresis. So, designing an oscillator is more an art than science. The thesis analysis the low phase noise push-push oscillator using CFY-25 MESFET transistor for the Ka-Band frequency generation. Non-linear simulation methods, for oscillator analysis and phase noise analysis have been discussed. A low phase noise Ku- Band oscillator has been designed first with the help of Lesson's and Hajimiri phase noise model to give a phase noise response of -79.661dBc/Hz @ 1 KHz and the output power of 8.452dBm at the fundamental tone. Then using two such sub-oscillators a Ka-Band oscillator is designed by the push-push topology. The output power of -6.751dBm is obtained at 25.78 GHz and phase noise of 94.22dBc/Hz @ 1 KHz. Another oscillator design stated here is made with a hairpin resonator in order to curb the disadvantages of an RC resonator and the parallel coupled filter.The transistor model used here is low noise HEMT CFY-67. It uses a hairpin filter with the resonating frequency of 12.5 GHz as a resonator, it also uses the hairpin resonator at the output in order to get pure sinusoidal response. The hairpin filter at the output is designed to resonate at 25 GHz. The output power obtained by this design is -1.154 dBm at 25.678 GHz, but the phase noise is -38.529 dBc/Hz @ 1 KHz.