| This thesis analyzes the principle and architecture of twin-satellite positioning system and investigates the related circuits. Twin-satellite positioning system's test signal source, demodulate circuit, despread circuit are modeled and realized with simulation tool, SystemView. The acquisition and tracking of spreading signal are simulated and investigated in great detailst.Sliding correlation method and advance-delay tracking method are applied in the acquisition and tracking of spread spectrum signal. The relation between circuit parameter and system performance is simulated and investigated. The focus of investigation is on the effect of circuit parameters to the performance of carrier recovery circuit and PN sequence tracking circuit under large noise and high dynamic range environment, such as acquisition bandwidth, tracking bandwidth, phase jitter, etc. The simulationn result shows that sliding correlation method and advance-delay tracking method have excellent performance. Circuit parameters such as decision threshold of spread sequence acquisition circuit under low SNR and high doppler shift environment are obtained, which provide foundation and optimizing principal for the hardware design. In order to realize the position funcrion under high doppler shift, this thesis proposes extended acquisition method under high doppler shift condition, i.e. scan method and frequency reseting method. These two methods all can reduce initial frequency difference between satellite signal and receiver DCO by adjusting receiver DCO' s frequency range, therefore extending theacquisition bandwidth of receiver significantly. Simulated result shows that these two methods do accomplish positioning under high dynamic environment.In order to provide simulating positioning signal, a simulating signal source is designed and analyzed. In addition, variable-rate simulating tokens and others are also designed by programing in SystemView for the demand of simulation.
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