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An all-digital fm/am signal demodulation and analysis method

A technique of signal demodulation and analysis method

Inactive Publication Date: 2018-01-02
THE 41ST INST OF CHINA ELECTRONICS TECH GRP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The demodulation method of this patent has disadvantages such as uncontrollable intermediate frequency bandwidth, does not support AM demodulation, does not support demodulation signal filtering, does not support FFT spectrum output and modulation parameter calculation, etc.
[0004] The existing demodulation method through a dedicated demodulation IC device has disadvantages such as single demodulation format, difficulty in implementing audio filtering, and inability to directly analyze modulation parameters; the existing demodulation method through a dedicated digital down-converter IC device has a bandwidth Narrow, does not support audio spectrum, poor scalability and other shortcomings
The existing demodulation method through FPGA has disadvantages such as uncontrollable intermediate frequency bandwidth, does not support FFT spectrum output and modulation parameter calculation, etc.

Method used

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  • An all-digital fm/am signal demodulation and analysis method
  • An all-digital fm/am signal demodulation and analysis method
  • An all-digital fm/am signal demodulation and analysis method

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Embodiment 1

[0034] The present invention is an all-digital FM / AM signal demodulation and analysis method, such as figure 1 As shown, the details are as follows:

[0035] 1. After the input FM / AM signal passes through the RF conversion module 101, the input RF signal within a certain range is converted to a fixed intermediate frequency signal. The intermediate frequency described in the present invention is 140MHz, and then a 200MHz sampling rate analog-to-digital converter is used Sampling the intermediate frequency signal, the sampling number is 16 bits, and the generated digital signal is output to the digital signal processing FPGA10, which uses the Virtex-5 chip of Xilinx;

[0036] 2. The intermediate frequency sampling input is first processed by the digital down-conversion module 102, that is, the input sampling signal is multiplied by a quadrature digital carrier signal cos and sin in FPGA10, the frequency of the digital carrier signal is 140MHz, and the multiplication is generated I1 a...

Embodiment 2

[0058] On the basis of the foregoing embodiment, an all-digital FM / AM signal demodulation and analysis method includes the following steps:

[0059] Step 1: After the input FM / AM signal is passed through the RF conversion module 101, the input RF signal within a predetermined range is converted to a fixed intermediate frequency signal, and the digital signal is sampled by the analog-to-digital converter and input to the FPGA 10;

[0060] Step 2: After the digital signal input into FPGA10 is processed by digital down-conversion module 102, two baseband signals of I1 and Q1 are generated and sent to decimation and compensation filtering module 103, after HB decimation filtering and CIC decimation filtering, and then FIR filter Complete amplitude compensation filtering to ensure in-band flatness and out-of-band suppression characteristics;

[0061] Step 3: The two baseband signals of I2 and Q2 after filtering and compensation are converted from rectangular coordinates to polar coordinat...

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Abstract

The invention provides an all-digital FM / AM signal demodulation and analysis method, step 1: generate a digital signal and input it into the FPGA; step 2: extract and amplitude compensate the I1 and Q1 two-way baseband signals generated by the digital down-conversion module Filtering; Step 3: Generate the amplitude information and phase information of each sampling point from the filtered and compensated I2 and Q2 baseband signals; Step 4: Perform loadable filtering and trigger processing on the FM or AM demodulated signal to generate a time-domain waveform Step 5: The filtered demodulated signal arrives at the Fourier transform unit at the same time to complete the conversion from the time domain to the frequency domain to generate the spectrum of the demodulated signal. Using the above scheme, the demodulation and analysis of FM and AM signals are realized by using the same processing flow through the operations of intermediate frequency band-limited filtering, audio generation, audio filtering, and audio FFT. The demodulation bandwidth is large and adjustable, and the highest Up to 20MHz, the in-band flatness is extremely high through the CIC frequency response compensation filter technology.

Description

Technical field [0001] The invention belongs to the technical field of electronic measurement, and particularly relates to a method for demodulating and analyzing an all-digital FM / AM signal. Background technique [0002] Frequency modulation (FM) and amplitude modulation (AM) have rapidly become the two most commonly used methods in wireless communication since their appearance in the 1960s. They are widely used in wireless communication equipment such as radio stations, broadcasts, and walkie-talkies. Currently, the International Radio Regulatory Commission stipulates that the maximum value of FM frequency deviation is 6.5MHz, and the emission bandwidth of FM and AM signals is generally below 400kHz, up to about 12MHz. Due to the wide application of FM and AM communication equipment, relevant electronic measuring instruments are needed to test, verify and maintain these equipment. Signal demodulation and modulation parameter analysis are necessary functions of relevant measurin...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L27/06H04L27/10
Inventor 徐群
Owner THE 41ST INST OF CHINA ELECTRONICS TECH GRP