High Speed And High Precision Data Acquisition Technology Research

IF(Intermediate Frequency) receiver is an important component in modern radar and communication system. Quartered demodulating technology is widely applied in modern IF receiver because it can extract phase and amplitude information from the received signal. The quadrature demodulating component in traditional receiver was implemented with analog circuits. Conversion of signals from IF analog into digital samples carrying phase and amplitude information has been traditionally implemented in the form of two parallel IF to baseband converters operated in quadrature each followed by A/D converters which thus provide digitized in-phase(I) and quadrature (Q) components. Because the difference between the two channels exists, the phase error between two channels can be and the stability of the system is not very good. To solve this problem we can use the method of IF sampling and digital quadrature demodulation. The performance of this method is more excellent than the traditional method because the features of the multipliers and filters of the two channels can be identical and an A/D converter can be saved. With the fast development of the software radio technology, the IF receiver system based on software radio technology is presented, thus the function of the hardware platform can be defined by software. In this thesis a kind of IF digitized receiver based on software radio technology is discussed. A new method of using the image spectrum to demodulate the signal is presented in the system realization, thus we can demodulate the signal modulated at high frequency by lower frequency. The experiment's results show that the performance of the system is excellent. The main contents of this thesis include:(1) Analyze the consistency between the traditional receiver and digital receiver in detail. The theory and the excellence of the digital down converter are also analyzed. And introduce the DPD technology based on orthogonal sampling. (2) Discuss the theory of quantification, analyze the method that how to get the effective bits.(3) Introduce the design of the high-speed data acquisition system.The performance of the high-speed data acquisition system is tested and the acquisitive data is analyzed and processed.(4) Introduce the realization of the real_time IF receiver adding the A/D system.The performance of the IF receiver is tested and analyzed.