An active patch antenna topology based on negative resistance FET oscillator design

An active microstrip patch antenna topology is presented which is based on the design principles of FET negative resistance oscillators. The patch operates both as a radiating element and as a one-port resonator for stabilising the oscillation frequency of the FET. The new technique has been compared experimentally at 9.6 GHz with the previously reported technique in which the patch is used as a two-port feedback element for the FET, and the new technique is found to give much improved radiation characteristics.