Millimeterwave high power pulsed silicon IMPATT oscillator modelling

The first results of a theoretical study devoted to the modelling and optimization of millimeter wave high power pulsed IMPATT oscillator are presented. A new time-domain pulsed oscillator model is described. This model accounts in a self consistent manner for both the diode non linear, large signal and temperature dependent operation and passive load circuit frequency behaviour. A simple RLC RF load circuit has been up to now considered. The diode epitaxial structure, the load impedance and bias current pulse shape have been optimized for stable and high power generation at 94 GHz. Despite of the development of the transistor technology, the IMPATT diode still remains the most powerful semiconductor structure for the realization of millimeter-wave solid state high power pulsed sources. By contrast with CW operation and because the thermal limitation can be overcome at narow pulse width (50-100 ns at 94 GHz) and low duty factor, the bias current density and diode area can be strongly increased to the benefit of the emitted power level (theoretically at 94 GHz, CW : 1W, pulsed : 40-50 W). However the optimum design and use of such oscillators remain complicated because of the diode non linear, large signal and temperature dependent operation leading to frequency chirp and instantaneous emitted power level variations. This constitutes the purpose of this paper devoted to the study and optimization of 94 GHz silicon pulsed IMPATT diode oscillators.