Broadband tuning of Gunn oscillators

The paper discusses the Passive Reactance Compensation technique for tuning Gunn oscillators, after a preliminary discussion of YIG sphere and varactor tuning of Gunn oscillators. The gain frequency response of a parametric amplifier is determined by the reactance slope with frequency of the signal and idler resonant circuits. The reactance compensation technique has been devised to reduce this slope to acceptable levels in the frequency band over which gain is required. A shunt resonant circuit is provided between the series resonant circuit and its load, and the shunt circuit slope is adjusted to reduce the reactance slope over the required frequency range. The technique is applied to the tuning of a Gunn oscillator using a shunt coaxial resonant circuit placed a quarter wavelength from the oscillator. It is shown that the application of this technique to oscillators of moderate tuning range produces a doubling of the tuning range when distributed elements are used for the compensatory circuits.