No abstract

Ahsfrucf -Grid oscillators are an attractive way of obtaining high power levels from solid-state devices, since potentially the output powers of thousands of individual devices can be combined. The active devices do not require an external locking signal and the power combining is done in free space. In this work, 36 transistors are mounted on parallel brass bars, which provide a stable bias and have a low thermal resistance. The output power degrades gradually when devices fail. The grid gives an effective radiated power ( E R P ) of 3 W at 3 GHr. The directivity is 11.3 dB and the dc to RF efficiency is 22 percent. Modulation capabilities of the grid are demonstrated. An equivalent circuit model for the grid is derived, and comparison with experimental results is shown.

Abstract-There is a n increasing demand for compact watt-level CO-herent sources in the millimeter-and submillimeter-wave region. The approach that we have taken to satisfy this need is to fabricate twodimensional grids loaded with oscillators and multipliers for quasi-optical coherent spatial combining of the outputs of large numbers of lowpower devices. This was first demonstrated through the successful fabrication of monolithic arrays with 2000 Schottky diodes. Watt-level power outputs were obtained in doubling to 66 GHz. In addition, a simple transmission-line model was verified with a quasi-optical reflectometer that measured the array impedance. This multiplier array work is being extended to novel tripler configurations employing blocking barrier devices. The technique has also been extended to oscillator configurations where the grid structure is loaded with negative-resistance devices. This was first demonstrated using Gunn devices. More recently, a 25-element MESFET grid oscillating at 10 GHz exhibited power combining and self-locking. Currently, this approach is being extended to a 100-element monolithic array of Gunn diodes. This same approach should be applicable to planar vacuum electron devices such as the submillimeter-wave BWO and vacuum FET.

Semiconductor devices have limited power handling capabilities at high frequencies, particularly at millimeter-wave frequencies. In this paper, we present a method for overcoming this problem by combining the outputs of several devices quasi-optically in a resonator cavity. This method has been applied to a number of solid-state devices, including Gunn diodes and MESFETs. The devices do not require an external locking signal because they lock to a mode of the resonator cavity. Effective radiated powers of 22 watts for a 4x4 array of Gunn diodes and 25 watts for a lOxlO array of MESFETs have been achieved.

No abstract