Abstract
ABSTRACT A signal system for improving the code acquisition complexity of Global Navigation Satellite System (GNSS) receiver is proposed and the receiving correlator scheme is presented accordingly. The proposed signal system is a hierarchical code type with a duplexing configuration which consists of the Zadoff-Chu (ZC) code having a good auto-correlation characteristic and the Pseudo Random Noise (PRN) code for distinguishing satellites. The receiving correlator has the scheme that consists of the primary correlator for the ZC code and the secondary correlator which uses the PRN code for the primary correlation results. The simulation results of code acquisition using the receiving correlator of the proposed signal system show that the proposed signal scheme improves the complexity of GNSS receiver and has the code acquisition performance comparable to the existing GNSS signal system using Coarse/Acquisition (C/A) code. Keywords: Zadoff-Chu sequence, GNSS, acquisition search space the spread spectrum signal generated at each satellite has different sign. When this code for each satellite is received in a mixed form, the code that minimizes the cross-correlation value between the signals is used, and the Coarse/Acquisition (C/A) code of Global Positioning System (GPS) is a representative code for this purpose. Also, for the additional reduction of cross-correlation value, the code period is generally maximized within the limit that minimizes the effect of Doppler shift due to the movements of satellite and receiver. The Doppler shift due to the relative movements of satellite and receiver which is observed at the receiver could be a major factor for degrading the correlation performance of receiving correlator. Therefore, regarding the Doppler shift which is dispersed over a range of more than several kHz, a typical GNSS receiver uses the method that obtains the correlation value by changing the frequency of correlator.Based on the above discussion, Fig. 1 shows the search range of receiving correlator for the satellite signal acquisition of typical GNSS receiver. The frequency search interval by the Doppler shift is generally 500Hz, and the number of satellites that a GPS has at present is about 30.
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