Chaos generation in microwave band using Colpitts circuit

We studied the design of chaotic Colpitts oscillators with fundamental frequency beyond 1 GHz by both circuit simulation and experiment. The BJT (bipolar junction transistor) used in the circuit is Philips´ broadband BJT with threshold frequency of 25 GHz. For the basic configuration of Colpitts circuit with fundamental frequency f* of about 1.6 GHz, broadband continuous power spectra could be obtained from both circuit simulations and experiments. The harmonics of the observed signal from Agilent PSA/ESA Spectrum Analyzer are noticeable as far as 12 GHz, which is the highest one reported till now. We also proposed a modified Colpitts circuit structure employing the parasitic inductance of the BJT. Circuit simulations show that the chaotic attractor and broadband continuous power spectra could be obtained from the modified Colpitts circuit with f* of about 3.5 GHz.