Study Of Measurement Of Amplitude And Phase Of DBF Systems In Satellite Uplink And Downlink

Design of satellite multi-beam antenna has become a key technology to improvesatellite communicating performance and reduce the cost of the system. With thedevelopment of digital signal processing technology, digital beamforming has becomean important part in the field of array antenna technology. In the multi-beam formingnetwork, factors as mutual coupling of antenna, channel imbalance, unequal length ofcables can lead to channel mismatch of each array channel, and affect the accuracy ofbeam pointing. This paper studies the measurement of amplitude and phase of DBFsystems in satellite uplink and downlink and provide the compensation parameters forchannel calibration of DBF system to ensure the quality of beam forming.This paper studies the measurement of amplitude and phase of DBF systems inthe following five aspects:1) Mathematical model of measurement of amplitude andphase of uplink and downlink DBF systems is established. The deficiencies oftraditional vector network analyzer in amplitude and phase distribution measuring isanalyzed.2) According to theory of Spread Spectrum Communications, measurementscheme of the multi-beam amplitude and phase distribution based on CDMAtechnology is proposed. De-correlation Multi-user detection is used to eliminate themulti-access interference.3) By analyzing the source of channel mismatch, ameasurement scheme of multi-channels DMBF system is proposed, which uses RFelectronic switches to form a virtual multi-channels, and uses band-pass samplingtechnology and ultra-high-speed DA to reduce the source of the channel mismatch.4)The lower bound of the measurement system in theory is deduced. Throughsimulating, the method used in the system is proved to approach the lower bound.5)Hardware design and FPGA algorithm design of the measurement system iscompleted. The test results of the measurement system are presented. Via thecomputer modeling and simulation, and the actual test of the system, the measurementsystem designed by this paper can satisfy the measure accuracy which is0.1dB ofrelative amplitude and1°of relative phase even if the power difference between thestrongest beam and the weakest beam is25dB.