The Reserch And Development Of BD2-based GNSS Receiver

Based on the BD2(Beidou-2, "Compass II") satellite navigation system, this paper focused on the research and development of the Compass II software receiver. The software receiver collects the data of the Beidou satellite through the RF front end and converts the data into a digital intermediate frequency signal, then through the USB interface of data acquisition card collected data will be transmitted to the PC machine, and digital signal processing will accomplish on the PC machine finally. The base band signal processing and position solution is realized by software, this improved the flexibility of the Compass II software receiver greatly, and reduced the cost effectively.The research and development of GNSS receiver is introduced in this paper. From the beginning, this paper introduces four kinds of satellite navigation systems, and the significance of the development of the Beidou satellite navigation system, and introduces the research of GNSS software receiver both at home and abroad. Then, it describes the research and integration of RF front-end hardware, the acquisition and implementation of the baseband signal, and the navigation data demodulation and position solution. At last, the design and implementation of the GNSS software receiver is accomplished based on the research of RF front end processing, base band signal processing and user location solution, and the whole performance of GNSS software receiver is tested.In the process of design and development of the whole GNSS receiver, the work below is done:1) On the basis of analyzing the characteristics of the Beidou antenna, the performance and the internal functions of the RF chip MAX2769, the front-end is integrated and the data acquisition function is completed.The designtion, integrattion RF front-end circuit board is completed, and with the control program program downloading into the board, the if data is acquisited.2) Acquisition and implementation of baseband signal.Based on the study of the sliding correlation acquisition algorithm and the cyclic convolution algorithm based on FFT, combined with the BD signal acquisition algorithm based on compressed sensing, a new termination criterion proposed in the five criteria of the existing GPRS algorithm. Experiment shows that, with the termination criterion proposed in this paper, the reconstruction accuracy of GPRS algorithm is slightly better than the known algorithm.3) Study of the location solution algorithm of the user’sThe user’s location information solved using the least square method and Calman filter. During this period, two processes are completed, that is estimated time to update and estimate measurement to update. To achieve the estimated time to update, the recursive prediction method is used, thus it can mend the current state of the amount. In the process of locating, the signal of the GNSS reciever may not stable, and the deviation value of the result of Calman filter is too large. At this time, we have to return to the least square algorithm.Thus, Calman filter and least square method will be closely linked, so that the user can get an optimal positioning results.4) The frame structure design of GNSS software receiver software system is carried out. Based on the structure of GNSS receiver and the working principle of GNSS receiver, the task mechanism of GNSS software receiver is divided.The software flow of the software receiver designed in this paper showes as follow:(1)Signal acquisition module first acqure signal, that is, the satellite distribution in the IF signal, as well as signal 1 carrier and pseudo code phase of each satellite.(2)Use the information above to initialize the multi channel correlator,preparing for the tracking of the signal, and finally achieve the positioning and navigation solution.(3)Based on the above, complete the test of signal tracking module of the software receiver, and finish the analysis of the results of the positioning accuracy. Verification of the design of the GNSS software receiver can work properly, and meet the positioning requirements of the receiver.