Characterization and modeling of IMPATT oscillators

A method has been found for large-signal characterization of IMPATT diodes. Waveguides of different heights are used so that the effect on efficiency of load impedance at a fixed oscillation frequency can be observed. Experimental large-signal admittance plane plots for two p-n diodes operating in Ku-band are presented. A nonlinear phenomenological model of an IMPATT oscillator is developed which correctly predicts the experimentally observed dependence of efficiency on load conductance and admittance plane characteristics. In addition to aiding the visualization of oscillator performance, analysis of this parallel circuit model shows that efficiency increases rapidly with small-signal negative conductance.