High Power Spatial Combiners: Tile and Tray Approaches
NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF ELECTRICAL ENGINEERING
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Spatial power combining is a method of coherently combining the power of many amplifying devices using free space as the power dividingcombining medium in contrast to traditional circuit based combiners. The spatial combiner is formed from an array of amplifying unit cells, with each cell receiving a signal, amplifying it, and then radiating it into free space. Two methods of spatial power combining, tile and tray, are investigated in this thesis. The tile-based spatial combiner consists of a thick ground plane with receiving microstrip patch antennas on one side and transmitting microstrip patch antennas on the other. In addition, amplifiers are placed on both sides of the thick ground plane, which provides efficient heat removal. This research is focused on the optimal array spacing, biasing, and feeding of tile-based arrays to achieve high output power levels at Ka-band Lockheed Martin was specifically interested in achieving greater than 25 Watts of radiated power under a DARPA MAFET-3 program. Several arrays were developed, consisting of 13, 45, and 98 elements. Noteworthy results were obtained from the experiments with this design approach. A tray-based approach is also investigated in this thesis. This approach differs from the tile-based approach by having multiple ground planes trays containing amplifiers stacked to form an array of amplifying unit cells. In addition, microstrip patch antennas are placed at the ends of the trays and radiate in an end-fire pattern with respect to the tray containing the amplifiers. For this purpose, an approach has been developed for the feeding of the microstrip patch antennas. This feeding mechanism allows the amplifiers and radiating elements to be isolated. Thus more room is allowed for the amplifiers, while minimizing coupling that may cause spurious oscillations. This study examines the effect of device failure on the gain, power output, and radiation pattern.
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