HTML5 Webook

131/182

1Introductione WINDS APAA (Active Phased Array Antenna) has a function to point its antenna beam in an arbitrary direc-tion towards the earth from geostationary orbit. is an-tenna consists of a receiver and a transmitter, both of which have 128 antenna elements, an amplier and a BFN (Beam Forming Network). Both the receiving and the transmitting systems can form two beams simultaneously. ese two beams share antenna elements and the amplier, while separate BFN is installed for each beam. A soundness verication test for long-term operation is required because, in general, the APAA is composed of many parts and it has not been used for the Ka band of a satellite before. In this paper, we report on the results of a soundness verication test for long-term WINDS APAA operation by applying an in-orbit rotating element electric eld vector method [1] to measure the feed amplitude and feed phase. In addition, we also report on the results of a phase compensation experiment that maximizes the antenna gain by correcting APAA systematic errors as an application of the REV method.e REV evaluation of the WINDS APAA was also performed by JAXA [2].2Outline of WINDS APAAA function block diagram of the RF system of the APAA is shown in Fig. 1. Both the receiving and transmit-ting systems consist of a small horn antenna with 128 ele-ments that are aligned in a plane, an amplier and two systems of BFN (Beam Forming Network). e BFN con-sists of phase shiers, multiplexers or dividers. Each phase shier is an analog phase shier of 5 bits and it can shi a phase by 11.25° by one bit. In the receiving system, the phase of signals received by antennas of 128 elements are shied to an appropriate phase by the phase shier in BFN. en, the signals are synthesized by the multiplexer to form a receiving beam to be input to a down-converter. In the transmitting system, the transmitted signals from the up-converter are distributed to 128 elements by the divider to be input to the phase shier. e transmitted signals pass through the phase shier from the transmission beam by being radiated from the 128 antenna elements.3Outline of REVe merit of the REV method is that it enables simul-taneous measurement of the feed amplitude and feed phase of the antenna array by measuring only the amplitude using a facing antenna pair, using the phase shier installed in the antenna. Moreover, it enables retrieving an optimized feed phase that maximizes antenna gain as compensation phase. Also, the REV method enables failure diagnosis of elements by applying the method to all the APAA elements.Here, an outline of the REV method is described using 3-7 Experimental Reports of APAA Health TestAkira AKAISHI, Mitsugu OHKAWA, and Takashi TAKAHASHIAs a health test of the WINDS APAA, Rotating Element Electric Field Vector Method (REV) was applied between the satellite and the earth station. This report shows the problems on orbit REV, the data acquisition method, the data evaluation method and the phase compensation experiment. The REV problems on orbit are that the clocks of the satellite and the earth station are not synchronized and the received REV signal fluctuates due to the atmospheric disturbance. We have resolved those problems that the two times measurements for a phase setting are applied for the non-synchronization, and the averaging method is applied for the signal fluctuation.As the results of the trend assessments for the measured data, the relative amplitudes and the relative phases for the all antenna elements were almost reappeared for the beginning data. The health of the WINDS APAA was confirmed consequently.1273 Ultra-High-Speed Satellite Communication Technology