The PAA consists of four components: module guides, a honeycomb, lower substrates and suspended lines, as shown in Fig. 5. The module guide is a support for the subarrays and is a hexagonal column made of CFRP. Suspended lines are used for the electrical power lines, the local RF signal feeders and the control signal lines. The PAA is reinforced by the honeycomb and the lower substrates, which are in turn connected to each other with an adhesive. The system is designed so as to control the top power of the transmitted microwave with 10 kW at its maximum. Since the SFU solar cells can only generate an electrical power of 1760 W, the microwave transmitter needs a battery system to radiate at 10 kW. Transmission duration in the high power transmmission mode (HPT) is designed to be 0.1 h (6 min). The DOD of the battery is about 82%, although this is restricted by battery weight and the efficiency of the thermal control systems. Using standard switching regulators to regulate electrical power to the HP A would result in an extra weight of over 200 kg—far too high for the SFU mission plan being considered. Power for the HPA will therefore be supplied directly from the battery. This means the effects of input voltage fluctuations on output gain and phase of the HPA must be carefully examined. Effects on the phase of the transmitted wave are especially critical from the point of view of the retrodirective system. On the other hand, electric power supplied to the PCC and PDR cannot be taken directly from the battery but must be regulated by switching regulators due to the PCC/PDR’s severe voltage deviation. A simulated antenna pattern is shown in Fig. 6, where the microwave is transmitted with identical output phases from all antenna elements. The microwave beam can be steered in any direction. The active phase array system also has the capability of focusing microwave energy at a specific point in space by controlling the 4-bit digital phase shifters. Figure 7 shows the distribution of the electric field strengths when the
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