IQ demodulation method and system without local oscillator signal

Abstract

The invention discloses an IQ demodulation system without a local oscillator signal. The IQ demodulation system without the local oscillator signal realizes IQ demodulation without the local oscillator signal by using a specific relationship between a digital module (ADC) sampling rate and an intermediate frequency carrier signal. The modulation method comprises the following steps: S1, inputtingan analog intermediate frequency signal, and utilizing a frequency relationship between a digital module and a front-end input signal, i.e., the sampling frequency not only meets a Nyquist sampling theorem, but also is twice of the carrier frequency of the front-end analog input intermediate frequency signal; enabling the digital module to be homologous with the clock of the front-end emission source; S2, inputting the analog intermediate frequency signal into a digital module for sampling to obtain a digital intermediate frequency signal; and S3, performing binary amplitude modulation processing on the data in a processing module to obtain an I-path signal, and performing Hilbert conversion to obtain a Q-path signal, thereby finishing digital demodulation of a local-oscillator-free signal. According to the invention, real-time processing of the process can be realized by adopting a programmable logic device and the like, hardware resources are saved, and the processing speed is improved.

Description

technical field [0001] The invention relates to the field of using IQ demodulation, in particular to a system that needs IQ demodulation technology and real-time processing technology to realize speed measurement, phase measurement and imaging. Background technique [0002] With the development of electronic information technology, IQ demodulation technology is applied in communication, radar, medical treatment, security inspection, military and non-destructive testing and other fields. It is an important component module in the system and a key technology that determines the performance of the system. IQ demodulation is usually used to perform quadrature coherent demodulation on the received signal, that is, to mix the received signal through two local oscillator signals with a phase difference of 90°, so that the received signal is divided into two mutually orthogonal IQ channels, retaining the Amplitude and phase information of the signal. Currently, the echo processing...

AI Technical Summary

Problems solved by technology

However, there are still some problems in the traditional digital IQ demodulation method. The numerically controlled oscillator in the digital demodulation process is usually realized by table look-up method or CORDIC iterative algorithm; but with the continuous improvement of signal accuracy, no matter which method is used Both of these methods occupy a large amount of hardware resources, which bring great pressure to the system design and also affect the speed of signal demodulation

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