Development of a Multi-Antenna GPS/Beidou Receiver for Troposphere/Ionosphere Monitoring

摘要

In addition to providing accurate PVT service, GNSSsignals have also been utilized in science research forprobing the earth and atmosphere. Some researchers areinvestigating the strong earthquakes precursor byvariations of the ionospheric total electron content (TEC)observed with GPS signal. In addition, in the Taiwan/USjoint science mission FORMOSAT-3/COSMIC(Constellation Observing System for Meteorology,Ionosphere, and Climate), six satellites are equipped withGPS receiver for Radio Occultation (RO) experiment.This mission has successfully provided a significantamount of RO data for weather forecasting. Several suchkind of GPS signal applications are developing for moreaccurate weather or disaster prediction, especially forweather anomaly. With the emerging of other satellitenavigation system, such as Galileo, GLONASS andCompass, more GPS-like signals are available andprovide more observation on the above researches. Thehigh availability of Beidou signals in Taiwan may lead tomore GNSS-based observations. Indeed, the geometricrelationship between Taiwan and Beidou satellites alsoprovides nice opportunity to observe the severeionospheric anomaly at low latitude region. This paperdescribes the development of a GPS L1/Beidou B1signals receiver. The goal is to receive signals from allsatellites for RO application. As a single antenna cannottrack the satellite over a wide range of azimuths, antennaarray and digital beam forming approach are adopted inthe GPS/Beidou receiver to cope with weak signal of lowelevation or occultation environment. This multi-antennareceiver collects the signals by 4 identical multi-bandGNSS antennas. The captured RF signals aredownconverted and digitized to be IF signals with I/Qcomponents. The IF signals are then weighted andsummed in the digital beamforming approach accordingto the reception pattern control algorithm. This researchemploys convex optimization-based beamformingalgorithm to mitigate the mismatches in the desired signalsteering vector.The validation of this proposed multi-antenna receiveris conducted by receiving real GPS/Beidou signals. Thediscussion compares the performance of one antenna onlyand antenna array with beamforming to understand thebenefit of the proposed approached on GPS signal and theBeidou signal. The research result can provide moreopportunities on troposphere/ionosphere monitoring andprovide ground based RO and weather forecastobservation data.