Computer-aided analysis and improvement of an 8 to 18 GHz YIG-tuned FET oscillator

Enhancing the performance of a wideband yttrium-aluminium-garnet (YIG) oscillator requires a comprehensive model of the circuit so that simulation accurately reflects its behavior in the laboratory. The authors have developed a comprehensive model of a production YIG sphere oscillator using both commonly available CAD tools and specialized measurement fixtures to enhance the accuracy of the circuit simulation. Because of this accuracy, they have achieved very close agreement between simulated and actual results over the broad tuning bandwidth of the circuit. Measured data were used for the YIG sphere resonator and coupling loop combination, obtained with a Wiltron 360 network analyzer and a specially modified 3680 K microstrip test fixture. This fixture was also used to measure and evaluate passive networks such as spiral inductors for bias and feedback elements in a new oscillator topology.<>