Grid oscillators

In the microwave and millimeter-wave frequency range, solid-state oscillators have limited output power levels. The alternative high-power sources are tubes, which are expensive, bulky, have a limited lifetime and require high-voltage power supplies. Combining a large number of low-power solid-state negative resistance devices becomes attractive. In this work a coherent oscillator that can combine thousands of solid-state devices is presented. The feasibility of a reliable high-power, monolithically integrated microwave and millimeter-wave source is demonstrated. In this approach, the active devices load a two-dimensional metal grid that radiates, and the power combining is done in free-space. Several MESFET grid oscillator designs are presented in this thesis, ranging from a 5 by 5 to a 10 by 10 grid in size. The 100-MESFET hybrid grid oscillator is a planar structure suitable for wafer-scale monolithic integration. This grid locks at 5 GHz, with an ERP of 24 Watts and a conversion efficiency of 20%. An equivalent embedding circuit for the devices in the grid predicts the oscillation frequency. The devices in the grid self-lock with no external locking signal present, but the grid can also be externally injection-locked. Measurements and analysis are presented for the injection-locked planar grid oscillator