RF excitation of an oscillator with several tunneling devices in series

An oscillator with several tunneling devices connected in series has a demanding excitation condition due to the DC instability of the series connection. An RF source with a frequency close to the oscillation frequency may be used to overcome this problem. The experimental demonstration of an RF source excitation of an oscillator with two tunnel diodes in series at 2 GHz is described here. The RF power necessary for the excitation is about 15 dB lower than the output power of the oscillator.>