CN112152735A - Broadband real-time APD (avalanche photo diode) measuring method based on STFFT (fast Fourier transform algorithm) - Google Patents
Broadband real-time APD (avalanche photo diode) measuring method based on STFFT (fast Fourier transform algorithm) Download PDFInfo
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- CN112152735A CN112152735A CN202010934341.1A CN202010934341A CN112152735A CN 112152735 A CN112152735 A CN 112152735A CN 202010934341 A CN202010934341 A CN 202010934341A CN 112152735 A CN112152735 A CN 112152735A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/10—Monitoring; Testing of transmitters
- H04B17/15—Performance testing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/20—Monitoring; Testing of receivers
- H04B17/29—Performance testing
Abstract
The invention discloses a broadband real-time APD measuring method based on STFFT, which comprises the steps of carrying out frequency conversion on an input signal to intermediate frequency through a mixer, carrying out digital sampling on the intermediate frequency signal after intermediate frequency filtering to obtain a digital intermediate frequency signal, carrying out IQ conversion on the digital intermediate frequency to obtain intermediate frequency IQ data, carrying out traditional detection measurement on one path of IQ data, carrying out envelope extraction on the other path of IQ data, carrying out STFFT conversion to obtain multi-channel data of a broadband signal, and then carrying out parallel statistical measurement on the multi-channel data to obtain an APD statistical measurement result of the broadband multi-frequency point. The method can realize real-time measurement of the APD of the broadband interference, simultaneously counts and measures data of 200MHz bandwidth and 800 frequency points, improves the test speed by 320 times compared with the traditional single-frequency-point APD measurement method, has high test efficiency, does not lose data in the broadband interference test, and has more accurate test result.
Description
Technical Field
The invention relates to the technical field of real-Time APD measurement, in particular to a broadband real-Time APD measurement method based on Short-Time Fast Fourier Transform (STFFT).
Background
The traditional peak value and quasi-peak value measuring methods cannot reflect the influence of disturbance on the performance of the digital communication system, cannot accurately evaluate and analyze the disturbance efficiency and the performance of the communication system, and particularly cannot analyze the influence of the disturbance of the pulse property on the performance of the digital communication system. The Amplitude Probability Distribution (APD) measurement can accurately evaluate the interference influence and reflect the error rate, so that the APD is adopted by a new electromagnetic compatibility standard and becomes an important function of an EMI receiver. However, the current APD measurement receiver only supports single-frequency point measurement, each frequency point needs to reside for more than 120s, the sampling clock is not lower than 10MHz, and a single-channel register is used for address mapping and accumulation calculation after ADC sampling, so as to realize statistical measurement. For the measurement of interference signals in a bandwidth range, frequency points need to be scanned and measured one by one to complete the APD measurement of a full frequency band, the test time is long, the test efficiency is low, interference information can be lost when the frequency and bandwidth-varying broadband random interference is scanned for a long time, and the statistical characteristics of the interference cannot be fully reflected.
Disclosure of Invention
The invention provides a broadband real-time APD measuring method based on STFFT, which adopts a multi-frequency-point high-speed parallel processing structure to realize broadband APD measurement of maximum 800 frequency points and maximum 20MHz (10kHz intermediate frequency bandwidth) bandwidth, thereby being capable of quickly and seamlessly measuring the statistical characteristics of broadband interference, having short testing time and high efficiency, realizing seamless statistical measurement on broadband random interference and accurately evaluating and analyzing the influence of electromagnetic interference on the performance of a digital communication system.
The technical scheme of the invention is as follows: a broadband real-time APD measuring method based on STFFT comprises the following steps:
step 1: an input signal passes through an attenuator and a mixing filter, is subjected to frequency conversion to intermediate frequency through a mixer, and is subjected to intermediate frequency filtering through an anti-aliasing filter, and then the intermediate frequency signal is subjected to digital sampling to obtain a digital intermediate frequency signal;
step 2: digital intermediate frequency signals are subjected to NCO digital quadrature frequency mixing to obtain IQ quadrature digital signals, IQ quadrature digital carriers are removed, and digital I-path signals and digital Q-path signals are obtained;
and step 3: I. the Q digital signal is divided into two paths for processing, wherein one path is used for carrying out traditional detection measurement, and the basic test function of the EMI test receiver is realized;
and 4, step 4: carrying out envelope detection and low-pass filtering on the other path of I, Q data to obtain a video envelope signal;
and 5: performing STFFT (fast Fourier transform) on the video envelope signals to obtain a plurality of parallelized channel frequency domain signals;
step 6: sending the multi-channel frequency domain signal to a multi-channel parallel parameter statistical module for carrying out the statistical calculation of APD, wherein the calculation process is as follows: mapping the multi-channel frequency domain signal to corresponding elements of an M x N-dimensional pixel matrix A, wherein the frequency of the frequency domain signal corresponds to an x axis of a horizontal coordinate, the amplitude of the signal corresponds to a y axis of a vertical coordinate, a frequency domain signal sequence generated by each STFFT corresponds to a two-dimensional chromatogram, adding 1 to the element value of the pixel position corresponding to the frequency and the amplitude in the chromatogram, and the others are 0; then, after each STFFT conversion, performing one-time addition and 1 updating on the chromatogram, and performing T-time acquisition calculation and element updating in one-time measurement;
and 7: the (m,
n) element values of
Each column vector of B corresponds to one APD curve for the current frequency.
In the above, in step 1, when the intermediate frequency signal is digitally sampled, the sampling clock is not lower than 10MHz, and the quantization is not lower than 14 bits.
The method can realize real-time APD measurement of broadband interference, improves the test speed by hundreds of times compared with the traditional single-frequency-point APD measurement method, has high test efficiency, does not lose data in broadband interference test, and has more accurate test result.
Drawings
FIG. 1 is a block diagram of a broadband real-time APD measurement system according to the present invention.
FIG. 2 is a schematic diagram of a PDF statistical process according to the present invention.
Detailed Description
In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
An embodiment of the invention is that a system structure block diagram of a broadband real-time APD measuring method based on STFFT is shown in fig. 1, a broadband real-time APD testing receiver comprises a radio frequency input, an attenuator, a filter, a mixer, an anti-aliasing filter, an AD sampler, a local digital oscillator NCO, a low-pass forming filter, an envelope detector, an STFFT module, a parallel statistical parameter measuring module and the like, and the realization of the broadband real-time APD measurement mainly depends on the STFFT module to perform multi-channel parallel processing on broadband signal envelopes, and then performs statistical calculation through the parallel statistical parameter measuring module. After an interference signal is input by radio frequency, an attenuator controls a signal gain level, a mixer performs frequency mixing after filtering to obtain an intermediate frequency signal, an anti-aliasing filter filters out an out-of-band spurious signal, the out-of-band spurious signal is sent to an AD converter for high-speed data sampling (a sampling clock is not lower than 10MHz, and the quantization is not lower than 14bit), a digital intermediate frequency signal is obtained, a digital clock NCO performs I, Q two-path digital orthogonal frequency mixing to obtain a digital I path signal and a digital Q path signal, the I, Q digital signal is divided into two paths for processing, and one path is subjected to traditional detection measurement to realize the basic test function of an EMI test receiver; and carrying out envelope detection and low-pass filtering on the other path to obtain a video envelope signal, then carrying out STFFT (fast Fourier transform) on the broadband envelope signal to obtain a multichannel signal, then sending the multichannel signal to a multichannel parallel parameter statistical module, carrying out APD (avalanche photo diode) statistical calculation, and outputting a measurement result.
A broadband real-time APD measuring method based on STFFT comprises the following specific steps:
step 1: an input signal passes through an attenuator and a mixing filter, is subjected to frequency conversion to an intermediate frequency by a mixer, and is subjected to intermediate frequency filtering by an anti-aliasing filter, and the intermediate frequency signal is subjected to digital sampling (a sampling clock is not lower than 10MHz, and the quantization is not lower than 14 bits) to obtain a digital intermediate frequency signal;
step 2: digital intermediate frequency signals are subjected to NCO digital quadrature frequency mixing to obtain IQ quadrature digital signals, IQ quadrature digital carriers are removed, and digital I-path signals and digital Q-path signals are obtained;
and step 3: I. the Q digital signal is divided into two paths for processing, wherein one path is used for carrying out traditional detection measurement, and the basic test function of the EMI test receiver is realized;
and 4, step 4: carrying out envelope detection and low-pass filtering on the other path of I, Q data to obtain a video envelope signal;
and 5: performing STFFT (fast Fourier transform) on the video envelope signals to obtain a plurality of parallelized channel frequency domain signals;
step 6: sending the multi-channel frequency domain signal to a multi-channel parallel parameter statistical module for performing statistical calculation of the APD, wherein the process is as shown in fig. 2: mapping the multi-channel frequency domain signal to corresponding elements of an M x N dimensional pixel matrix A, wherein the frequency of the frequency domain signal corresponds to an x axis of a horizontal coordinate, the amplitude of the signal corresponds to a y axis of a vertical coordinate, a frequency domain signal sequence generated by each STFFT corresponds to a two-dimensional chromatogram, the element value of the pixel position corresponding to the frequency and the amplitude in the chromatogram is added with 1, and the others are 0; then, after each STFFT conversion, performing one-time addition and 1 updating on the chromatogram, and performing T-time acquisition calculation and element updating in one-time measurement;
and 7: the (m, n) th element value of the matrix B is obtained by carrying out column calculation operation on the element values of the chromatogram matrix A
Each column vector of B corresponds to one APD curve for the current frequency.
The method can realize real-time APD measurement of broadband interference, improves the test speed by hundreds of times compared with the traditional single-frequency-point APD measurement method, has high test efficiency, does not lose data in broadband interference test, and has more accurate test result.
The technical features mentioned above are combined with each other to form various embodiments which are not listed above, and all of them are regarded as the scope of the present invention described in the specification; also, modifications and variations may be suggested to those skilled in the art in light of the above teachings, and it is intended to cover all such modifications and variations as fall within the true spirit and scope of the invention as defined by the appended claims.
Claims (2)
1. A broadband real-time APD measuring method based on STFFT is characterized by comprising the following steps:
step 1: an input signal passes through an attenuator and a mixing filter, is subjected to frequency conversion to intermediate frequency through a mixer, and is subjected to intermediate frequency filtering through an anti-aliasing filter, and then the intermediate frequency signal is subjected to digital sampling to obtain a digital intermediate frequency signal;
step 2: digital intermediate frequency signals are subjected to NCO digital quadrature frequency mixing to obtain IQ quadrature digital signals, IQ quadrature digital carriers are removed, and digital I-path signals and digital Q-path signals are obtained;
and step 3: I. the Q digital signal is divided into two paths for processing, wherein one path is used for carrying out traditional detection measurement, and the basic test function of the EMI test receiver is realized;
and 4, step 4: carrying out envelope detection and low-pass filtering on the other path of I, Q data to obtain a video envelope signal;
and 5: performing STFFT (fast Fourier transform) on the video envelope signals to obtain a plurality of parallelized channel frequency domain signals;
step 6: sending the multi-channel frequency domain signal to a multi-channel parallel parameter statistical module for carrying out the statistical calculation of APD, wherein the calculation process is as follows: mapping the multi-channel frequency domain signal to corresponding elements of an M x N-dimensional pixel matrix A, wherein the frequency of the frequency domain signal corresponds to an x axis of a horizontal coordinate, the amplitude of the signal corresponds to a y axis of a vertical coordinate, a frequency domain signal sequence generated by each STFFT corresponds to a two-dimensional chromatogram, adding 1 to the element value of the pixel position corresponding to the frequency and the amplitude in the chromatogram, and the others are 0; then, after each STFFT conversion, performing one-time addition and 1 updating on the chromatogram, and performing T-time acquisition calculation and element updating in one-time measurement;
and 7: the (m, n) th element value of the matrix B is obtained by carrying out column calculation operation on the element values of the chromatogram matrix A
Each column vector of B corresponds to one APD curve for the current frequency.
2. The STFFT-based wideband real-time APD measurement method of claim 1, in which in step 1, when the intermediate frequency signal is digitally sampled, the sampling clock is not lower than 10MHz and the quantization is not lower than 14 bits.
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| CN114826307A (en) * | 2022-06-28 | 2022-07-29 | 中星联华科技（北京）有限公司 | Digital channelized receiver, signal acquisition playback system and method |
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