Negative Resistance Oscillators, Multipliers and BWOs

To understand how a negative resistance oscillator works, it is easiest to consider the electrical characteristics of the waveguide cavity in which the device is housed. A waveguide cavity is in its simplest form a short piece of transmission line terminated in a short-circuit at one end and an impedance matching device coupled to the rest of the circuit at the other end (Section 2.1). 

The cavity so formed has both inductive and capacitive properties which, coupled together make the circuit resonant at a particular frequency or frequencies. The cavity also has resistive loss that must be overcome before the circuit can oscillate. In low-frequency circuits this can be achieved with an amplifier whose gain is greater than the resistive attenuation of the circuit. In a negative resistance oscillator the attenuation is overcome by the negative resistance of the diode. 

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