The Research Of The DGPS Transceiver Based On Software Radio

Global position system (GPS) is a navigation satellite system which can position exactly. It attracts the attention from it appeared. But the policy of SA and the influences of the ionosphere, the troposphere, the error of ephemeris and the clock on satellites and so on, these factors depress the civil receiver's precision of position. In order to fully explore and apply the resource of GPS, the scholars and experts from different countries, including some consumers in America, have done much research in this field. Differential GPS is one of the technologies which can effective resolve this problem. Based on this, the paper designs the functions of the DGPS' system to transmit and receive signals.First, the paper introduces the technology of global positioning system (GPS), including the theory of the GPS, the source of the error and influences it brings to the positioning. In allusion to this problem, the paper introduces one way to resolve it-the differential GPS. Then it shows how the three differential technologies work.Then, the paper discusses the material project to implement the DGPS transceiver's functions. Based on its structure, there are two parts to carry out it: the traditional GPS transceiver and the differential link in the DGPS, which can receive the corrector of the data. In the design of the traditional GPS transceiver, the signal we receive has been encoded by PN sequence and then been modulated by BPSK. But in the link of the transmission,the factors of the time-delay and so on caused the signal we receive is unsynchronized with local signal. So the paper designs two module, including the generation of the PN sequence and the PN sequence's capture and decoding. In the differential link, the signal encode by RS code, which is one of the most efficient codes. In order to decode the signal, we do the arithmetic of step-by-step. It has the less quantity of the operation, which different from the standard algebra coding. After the coding, the signal modulated by QPSK. we use the ascend cosine filter, so it can reduce the interfere among separate codes. In order to improve the flexibility, the paper puts forward the design of the adaptive demodulation.At last, the paper introduces the simulating of the design we advanced.