A gated tunnel diode has been introduced into a wave-guide oscillator circuit and the gate is used to tune the oscillation frequency and to turn the oscillator on and off. Oscillators with oscillation frequencies in the range of 9-22 GHz with a typical oscillator output power about -20 dBm have been fabricated. We found that the output power remains essentially constant over a gate bias range (about -260 to 200 mV at V-c = 1.0 V in one oscillator), while it rapidly drops to the noise level over a gate bias range of less than 60 mV above or below the threshold, respectively. In the region with constant power, a total frequency tuning of about 30% is achieved. The maximum oscillation frequency. f(max) (osc), of the gated tunnel diode is set by the tunnel diode and the gate-collector capacitance, and does not depend on the gate-emitter capacitance. This oscillator implementation, in particular, eliminates the need for a separate switch in the realisation of oscillator-based ultra-wide band impulse radios. (C) 2009 Elsevier Ltd. All rights reserved.