Digital Receiver, The I / Q Demodulation Algorithm Research

The receiver system is the most important part in communication systems and radar systems. The traditional analog technology can't meet the requirement of the modern war. Thus, it is a necessary trend to study the technology for digitalization. Digital signal processing includes A/D convert and how to get I/Q signal, the main content is to discuss how to get the baseband I-Q signal in digital domain under the existed condition of parts. In this thesis, we introduced several methods about getting digital I/Q signal, Based on direct-IF sampling structure,we discussed several digital quadrature demodulation techniques such as low-pass filter,Hilbert transform and interpolation. According to the radar system performance target, we designed a receiver scheme which is testified by computer simulation. In addition, we discuss the amplitude and phase unbalances of I/Q demodulators and the difference of error analyse between narrow-band systems and wide-band systems, and provide reference for correcting the errors in quadrature receivers. The principle of IF digitlization is introduced at the first. Then, from a general point, we summarized the theory and structure of I/Q demodulating algorithms, and compared the performance of every kinds of algorithms,and discussed a mehod to design a kind of IF digitlized receiver based on polyphase filters and find a simpler way to get I-Q signal. Last, the affection of imbalance to the narrow-band system and the wide-band system are analyzed, one method of calibrating of amplitude and phase imbalances is introduced and the result of computer simulation is given.