5-10 Ghz YIG-tuned tunnel-diode oscillator

A previously reported YIG-tuned tunnel diode oscillator was limited in its upper frequency of oscillation by the resonance of the diode capacitance with the inductance of the YIG coupling loop. The oscillator described here was designed to operate above this resonance, which is one of the causes of the curvature at the low frequency end of the tuning curve. The tunnel diode used is a Microwave Associates MA 4655 Gallium-Arsenide diode, having an operating (large signal) self-resonance at 10.3 GHz. It has a peak current of 25 mA and a resistive cutoff frequency of 25 GHz. The YIG sphere has a diameter of 0.040 inch and a saturation magnetization of 1750 gauss. It was oriented with one of the easy axes parallel to the applied magnetic field. The magnetic field was varied from 1120 to 3360 gauss in order to tune the oscillator from 5.1 to 10.2 GHz.