Design and optimization of a tunable W-band subharmonic cavity based Gunn diode oscillator using computer-aided design technique

In this work, a systematic computer-aided design technique is proposed to minimize the fabrication iteration for the design and development of W-band subharmonic Gunn diode oscillator with wideband tunable bandwidth at W-band. Gunn diode based single diode oscillator structure was divided into passive and active parts to facilitate the modeling of the component on appropriate simulation environment. Resonating structure and package of Gunn diode are modeled as passive circuit in high frequency structure simulator (HFSS). To satisfy the oscillator design equation, disc-post resonating structure is tuned in HFSS and its S-parameters are collaborated with the model of Gunn diode in advanced design system. Magnitude and phase of reflection coefficient (S11) is observed to ascertain the desired frequency of oscillation. Proper tuning of disc-post structure is done on simulation platform, which reduces the fabrication complexity and cost as well. The measurement results validate the models designed using EM and circuit simulator. The measured maximum stable RF power without any fabrication iteration is 14.2 dBm. A tunable bandwidth of 4 GHz with power output ripple of +/- 1 dB is measured by using a movable backshort.