Efficient power transfer through small apertures

Efficient power transfer through a small slot in the ground plane separating a microstrip patch oscillator from a quasioptical cavity resonator has been achieved by empirically optimising the dimensions of the coupling aperture and the substrate thickness. The design of a power combining circuit based upon the use of slot coupled microstrip sources is discussed in terms of an electrical equivalent circuit and results are presented that confirm the theoretical prediction that a high power transfer efficiency is possible with such an arrangement. The purpose of the paper is to discuss some fundamental aspects for the design of an efficient power combining cavity which in principle could be used to generate a single highly directional free space output beam from a planar multielement array of self-oscillating sources, or might alternatively be arranged to couple power into a conventional waveguide mode