Gate-Feedback MESFET Grids for Microwave Power Combining

Solid-state devices that produce power in the microwave and millimeter-wave region of the spectrum have relatively low power outputs compared to their vacuum tube counterparts. To overcome this limitation, a large variety of power combining schemes have been developed. One of the most promising techniques involves quasi-optical arrays that permit power combining to be done in free space. This approach has a number of advantages over the traditional methods which involve waveguides or hybrids : the losses associated with waveguides and feed networks are eliminated, the power can be distributed over a large number of devices, and an external injection-locking signal is unnecessary. In this paper, we present a quasi-optical power combiner based on integrating MESFETs into a planar grid. An equivalent circuit model for the grid is discussed and used to design a grid oscillator operating at X-band.