Software Radio Compass Technology Research

Radio compass is a basic navigation equipment which has the features of cheap price, easy to operate and working steady. It is still widely used as a low price avionics equipment in the Global Positioning System (GPS) world. The traditional radio compasses were implemented with analog circuit, which suffered low precision,low reliability, low yield rate and so on. With the development of technology and the application of high performance DSPs, developing a software radio compass based on DSP technology is imperative which will bring a great improvement to the performance of radio compass.In this thesis, a new software radio compass is presented. The specific technology and the performance characteristic of the software radio compass are described in three aspects, which are mathematic theory, software simulation and hardware implementation.The main innovative works are as follows:1. A new method to implement the carrier synchronization is presented, which can simplify the design of the RF part by reduce the signal channels. The software radio compass meets the same problem as smart antenna technology. When dealing with the signal processing three signals are required, which means three Radio Frequency (RF) channels are needed. A multi-RF-channel technology can solve this problem. Even though the configuration of the multi-RF-channel technology is easy to understand, it has the problem of complex hardware, high cost and hard to miniaturize. The new method takes full advantage of software radio technology. The main idea of this method is to modulate signals in the antenna part, combine three signals, so only one RF channel is needed, which reduces the complicacy of the RF circuits. Most of the demodulation works are done by software in the same software radio platform.2. The front RF circuit of the software radio compass is designed and implemented. Together with the existing antenna part and the software radio platform, an integrated prototype of software radio compass is established. The phase locking loop synthesizer and the super heterodyne dual conversion circuit are designed based on Motorola's MC145170 and MC13030, so any medium wave navigation signal can be convert to a fixed frequency to facilitate the Analog Digital Convertor (ADC) sampling.3. Basing on TMS320C6711 DSP Starter Kit, adding the AD7274 ADC, a software radio compass base band demodulation platform is established. In this platform the demodulation program is coded and the signal demodulation is accomplished. The azimuth results can then be send to the 429 bus with the specific interface, so that software radio compass can communicate with other navigation equipments or other terminal units in a standerd dataformat.