Quasi-optical power combining using mutually synchronized oscillator arrays

A quasi-optical method for solid-state power combining with applications to high-power millimeter-wave generation is discussed. The approach uses two-dimensional planar arrays of weakly coupled oscillators. Limiting the strength of the coupling avoids multifrequency moding problems and simplifies the design. A radiating element is embedded in each oscillator so that the power combining is accomplished in free space. The concept which has been demonstrated with two prototype arrays, one using Gunn diodes and the other using MESFETs is discussed. A theoretical description of the coupled-oscillator arrays is presented for design purposes, and is used to investigate phasing problems and stability. Experiments are discussed which indicate that in-phase operation is facilitated by using a quasi-optical reflector element. which influences the operating frequency and coupling between the elements. Equivalent isotropic radiated powers of 22 W at 1% efficiency for a 16-element Gunn array and 10 W at 26% efficiency for a 16-element MESFET array which have been obtained at X-band are discussed.>