Novel interferometric frequency discriminators for low noise microwave applications

New configurations of interferometric frequency discriminators (FD) for fre quency stabilization of microwave oscillators are examined. The new FDs are arranged in single directional (SD) (patented), hi-directional (BD) (paten t pending), and dual reflection (DR) (patent pending) configurations. In th e SD configuration, the signals reflected off and transmitted through the r esonator separately pass through different arms of the interferometer. In t he ED configuration, microwaves pass in both directions through each arm of the interferometer. In the DR configuration, microwaves are reflected from the resonator as well as the compensating arm. The FD sensitivity is compa red with that for the conventional interferometric FD and found to be 6 dB greater in the ED configuration. Because no circulator is required within t he interferometer in either the ED or the DR FD, the discriminator's phase noise floor is not limited by the circulator contribution.