Amplitude modulation signal digital coherent demodulation system and method

Abstract

The invention discloses an amplitude modulation signal digital demodulation system, which comprises an intermediate frequency signal acquisition terminal, an A / D analog-to-digital converter, an FPGA chip and a DSP chip. The invention further discloses an amplitude modulation signal digital demodulation method. The method comprises the steps of 1, collecting an intermediate frequency signal; 2, sending the intermediate frequency signal to the FPGA chip after analog-to-digital conversion, wherein the FPGA chip processes the incoming intermediate frequency signal to generate an I / Q two-path signal; accumulating the I / Q two-path signal, filtering a high-frequency component of the I / Q two-path signals, sampling and outputting; 3, interrupting the acquisition of the intermediate frequency signalby the DSP chip; performing FFT operation on the data sampled and output in the step 2 to realize carrier acquisition; carrying out carrier tracking to obtain an audio signal, and outputting the audio signal; and completing digital demodulation of the amplitude modulation signal. According to the method, the digital demodulation of the amplitude modulation signal is realized, the equipment integration level, the safety and the working reliability are improved, and a more reliable communication means is provided for a user.

Description

technical field [0001] The invention relates to the technical field of radio equipment amplitude modulation signal communication, in particular to a digital coherent demodulation system and method for an amplitude modulation signal. Background technique [0002] When radio equipment communicates with amplitude modulation signals, its receiving channel is a narrowband receiving channel, which converts the radio frequency signal from the antenna into an intermediate frequency signal. When receiving a narrowband (amplitude modulation) signal, the intermediate frequency signal is filtered by a narrowband filter, envelope detected, and amplified by an audio power amplifier. sent to the speaker output. Its principle block diagram is as follows Figure 8 shown. [0003] The entire demodulation of the AM signal of radio equipment is completed by the receiving channel. The receiver uses the envelope detection method for demodulation, and uses separate devices to build hardware circu...

AI Technical Summary

Problems solved by technology

[0003] The entire demodulation of the AM signal of radio equipment is completed by the receiving channel. The receiver uses the envelope detection method for demodulation, and uses separate devices to build hardware circuits such as intermediate frequency amplifiers and low-pass filters, which makes the design circuit complex.

At the same time, in the case of small signal-to-noise ratio, the envelope detector will scramble the useful signal into a noise signal, making the AM call effect in actual use poor

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