Numerical investigation and experimental demonstration of chaos from two-stage Colpitts oscillator in the ultrahigh frequency range

Abstract

A hardware prototype of the two-stage Colpitts oscillator employing the microwave BFG520 type transistors with the threshold frequency of 9 GHz and designed to operate in the ultrahigh frequency range (300-1000 MHz) is described. The practical circuit in addition to the intrinsic two-stage oscillator contains an emitter follower acting as a buffer and minimizing the influence of the load. The circuit is investigated both numerically and experimentally. Typical phase portraits, Lyapunov exponents, Lyapunov dimension and broadband continuous power spectra are presented. The main advantage of the two-stage chaotic Colpitts oscillator against its classical single-stage version is in the fact that operating in a chaotic mode it exhibits higher fundamental frequencies and smoother power spectra.