Six-Port Junctions for the Control of Phased Array Antennas on Microwave Power Satellites FADHEL M. GHANNOUCHI, YVES CASSIVI & RENATO G. BOSISIO1 SUMMARY This paper shows that six-port techniques can he used for the control of phased array antennas on microwave power satellites. The relative amplitude and phase of each microwave signal, generated by one radiator, can be measured by inserting a six-port junction between the radiator and the generator and coding the signal using low frequency amplitude modulation (kHz). This configuration requires NxM six-port junctions for an array of NxM radiators. A second configuration without modulation requiring M(N-l) + N(M-1) six-port junctions is also presented. This paper also shows that the use of six-port junctions enhances the precision of phase and amplitude control of the signals present at each radiating element. In addition, the use of analogue voltage controlled phase shifters and attenuators without precalibration is possible by the appropriate use of such junctions. Introduction The use of microwave energy in space power transmission systems has already been proposed in previous work [1-2]. In some cases, high power microwave beams are generated from a large number of microwave radiators placed in a phased array antenna configuration. The microwave energy is then converted at the receiving end into DC energy with a rectenna array [3], The direction of the generated microwave beam is dependent on control of the individual phases and amplitudes of the signals at each radiating element [4]. For space power satellites, it is usually preferable to operate the power generators in the non-linear region to obtain maximum efficiency in power conversion and the maximum possible ratio of microwave power to generator weight. In a large signal operating mode, the phase of the generated microwave signal is very sensitive to variation of the operating parameters, i.e. RF power level, DC voltages, load impedances, etc. It is therefore desirable to measure and then control, as required, the phases and the amplitudes of all the microwave signals reaching the radiating elements in the antenna array. This paper examines the potential use of six-port junctions to make such measurements. Linear six-port circuits have been widely used at low power levels and in some cases at relatively high power levels (1 kW at 2450 MHz) [5-6]. In order to generate a 1 GW beam of microwave power, it would be necessary to operate a 1000 x 1000 element array of 1 kW radiators. t Electrical and Computer Engineering Department, Microwave Research Laboratory, Ecole Polytechnique de Montreal, P.O. Box 6079, Station A, Montreal, Quebec, Canada H3C 3A7.
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