Phase-controlled magnetron development for SPORTS: Space power radio transmission system

Since the first proposal of a Space Solar Power Station (SPS) in 1968, many different types of SPS have been proposed. Some of them are designed with microwave power transmission (MPT) technology based on a microwave power transmitter with microwave tubes. The microwave tubes, such as klystrons or magnetrons, have high efficiency (> 70%) and high power output (over 1 kW). We show a new concept for a microwave transmitter with phase-controlled magnetrons (PCM), for satisfying both requirements of high efficiency and beam control. We also propose a new phased-array system with the phase-controlled magnetrons for the SPS. We use the injection-locking technique and phase-locked-loop (PLL) feedback by controlling an anode current for the phase-controlled magnetron. We can stabilize and control the frequency and phase of the microwave emission of the phase-controlled magnetron. However, we have a power loss after the phase-controlled magnetron for SPS use, because the output power from one antenna is designed to be less than 1 W in a recent SPS design, and we have to insert a power divider and phase shifters after the phase-controlled magnetron. In order to decrease the power loss after the phase-controlled magnetron, we have recently proposed some new concepts, and have developed a phase-controlled magnetron array called SPORTS (Space Power Radio Transmission System) in FY2000 and FY2001 at Kyoto University.