Experimental and Numerical Studies on the Dynamics of X-Band Gunn Oscillator Based Angle Modulator–Demodulator System with Chaotic Modulating Signal

Abstract

We have studied the performance of a Gunn oscillator (GO) based angle modulator–demodulator system in transmitting chaotic signals in the X-band microwave frequency channel. The principle of bias tuning of a GO is employed to implement the angle modulator used in the transmitter. The said GO is operated in a free running condition and then in a frequency synchronized condition to an external microwave signal, thus generating frequency modulated (FM) and phase modulated (PM) signals, respectively. The demodulator circuit is implemented with a GO phase synchronized to the incoming modulated signal, followed by a microwave mixer multiplying the input and the output signals of the GO and a low pass filter. The response of the system is analytically established, numerically examined and experimentally verified. The obtained results confirm that in the limit of low modulation index and in the linear range of operation of the bias tuned modulator and the phase synchronized detector, a chaos signal can be transmitted and recovered through a microwave channel using the technique of angle modulation.