CN110535543B

CN110535543B - Radio frequency spectrum signal detection threshold calculation method

Info

Publication number: CN110535543B
Application number: CN201910392957.8A
Authority: CN
Inventors: 赵延安; 杜鸿
Original assignee: SHAANXI MONITORING STATION OF STATE RADIO MONITORING CENTER; Chengdu University of Information Technology
Current assignee: SHAANXI MONITORING STATION OF STATE RADIO MONITORING CENTER; Chengdu University of Information Technology
Priority date: 2019-05-13
Filing date: 2019-05-13
Publication date: 2022-01-28
Anticipated expiration: 2039-05-13
Also published as: CN110535543A

Abstract

The invention provides a method for calculating a detection threshold of a radio frequency spectrum signal. The method of the invention carries out the operation of valley removal and exponential smoothing on the frequency spectrum data output by the radio frequency receiver; dividing the frequency spectrum data into frequency spectrum sections according to the frequency intervals, dividing the frequency spectrum sections into subsections, calculating the maximum spectral line level in each subsection, and taking the minimum value of the maximum spectral line level of each subsection as the reference background level of the frequency spectrum section; and finally, taking the minimum value between the spectrum segment data and the segment reference background level as a signal detection threshold. The signal detection threshold calculated by the method can be suitable for detection of various bandwidth signals and weak signals, the algorithm occupies less memory, the calculation cost is low, and the method is suitable for the requirements of various fixed, airborne and vehicle-mounted radio monitoring systems on the calculation performance of the signal detection threshold.

Description

Radio frequency spectrum signal detection threshold calculation method

Technical Field

The invention relates to the technical field of radio frequency spectrum monitoring, in particular to a method for calculating a detection threshold of a radio frequency spectrum signal.

Background

The basic workflow of a radio spectrum monitoring system is to perform spectrum scanning in a monitoring frequency band, detect signals present in a spectrum, and perform statistics and analysis on the detected signals.

The basic workflow of a radio spectrum monitoring system is to perform spectrum scanning in a monitoring frequency band, detect signals present in a spectrum, and perform statistics and analysis on the detected signals. The detection threshold is the basis of signal detection, when the spectrum level of a certain frequency interval is higher than the detection threshold, which means that a signal appears in the frequency interval, the spectrum monitoring system records the frequency, level, bandwidth and other parameters, and further analyzes and classifies the parameters.

The requirements of the frequency spectrum monitoring system on the signal detection threshold algorithm are that the frequency spectrum monitoring system can adapt to the detection of narrowband and broadband signals simultaneously, can adapt to the detection of weak signals, and has dynamic updating capability to adapt to the change of an electromagnetic environment.

The radio frequency receiver hardware determines the level measurement accuracy, dynamic range, and intermodulation and spurious performance of the spectrum monitoring system. Fast fourier transforms that perform time/frequency domain transforms are well established techniques. The quality of the signal detection threshold determines the capability of the spectrum monitoring system for intercepting various bandwidth signals, the capability of intercepting weak signals and the capability of adapting to the change of an electromagnetic environment, thereby finally determining the performance of the spectrum monitoring system.

In the field of radio monitoring technology, signal detection thresholds can be classified into level thresholds, environmental thresholds, and automatic thresholds:

1. level threshold: a fixed level value is assigned by the operator as a signal detection threshold, only for a few specific monitoring tasks.

2. And (3) environment threshold: the maximum retained spectrum for a period of time is used as the signal detection threshold. Primarily for the detection of newly occurring signals after this period.

3. Automatic threshold: and automatically calculating a signal detection threshold according to the frequency spectrum data to serve as a signal detection basis. The automatic threshold is a signal detection threshold with the widest application range.

In the existing frequency spectrum monitoring system, a signal detection threshold is automatically calculated mainly by two methods of 'moving average' or 'amplitude limiting section mean value', and a 'moving average' algorithm is used for calculating the mean value of an adjacent interval of each frequency spectrum point and taking the mean value as the signal detection threshold; the threshold calculated in this way can only be used for detecting narrow-band signals, and the calculation cost is large, and dynamic updating is difficult. The 'amplitude limiting section mean value' algorithm firstly calculates a section mean value, calculates the section mean value again after amplitude limiting is carried out on the frequency spectrum level by using the section mean value, and takes the section mean value after amplitude limiting as a signal detection threshold; when the frequency band has more signals or the signals are wider, the difference between the threshold level calculated in this way and the actual spectrum background is larger, and weak signals are easy to miss in signal detection.

Disclosure of Invention

The invention aims to provide a method for calculating a detection threshold of a radio frequency spectrum signal, which is used for solving the problem that the prior art cannot simultaneously realize broadband energy detection, weak energy detection and dynamic update of the detection threshold.

In order to achieve the purpose, the invention provides the following technical scheme: a method for calculating a detection threshold of a radio frequency spectrum signal comprises the following steps:

s1, setting parameters: setting a median filter window width constant set W_MEDConstant group W of segment bandwidth_SEGSub-segment bandwidth constant set W_BKGThe values of the member nodes in the three arrays are related to the frequency; the exponential smoothing filter coefficient β is set.

S2, receiving data blocks and processing data;

s3, data block segmentation: according to the segment bandwidth array W_SEGAnd frequency interval f of the spectrum data block_B1～f_BKDividing the spectrum data block into N spectrum data segments SEGn, wherein 1 is less than or equal to N; there are P data points in the spectrum data segment SEGn, and the level of each data point is L_S1～L_SP；

S4, subsection division: within SEGn within each spectral data segment, according to the sub-segment bandwidth array W_BKGCenter frequency f of the sum spectrum segment_SEGDividing the frequency spectrum data segment into M subsegments;

s5, obtaining the maximum level of the subsegment: obtaining the maximum level L of the sub-segments by obtaining the maximum spectral line level in M sub-segments_max1～L_maxM；

S6, calculating the reference background level of the spectrum section: obtaining the maximum spectral line level L in M subsections_max1～L_maxMObtaining a spectral band reference background level L_REF；

S7, solving a detection threshold of the frequency spectrum section signal: data point level value L in spectral data segment SEGn_S1～L_SPAnd spectral band reference background level L_REFTaking the minimum value to obtain a detection threshold L of the frequency spectrum section signal_T1～L_TPAs an output;

and S8, repeating the steps from S4 to S7 until all the spectrum data segments are processed.

Preferably, the receiving and processing of the data block in step S2 includes:

s21, receiving data blocks: receiving a wide band spectrum data block B output by a radio frequency receiver_RThe number of spectral data points is K, and the frequency of the data points is f_B1～f_BKLevel of data point is L_B1～L_BK；

S22, valley point filtering: performing median filtering on the valley point in the spectrum data block BR to obtain a spectrum data block B from which the valley point is removed_UThe median filter window length depends on the median filter constant set WMED and the spectral resolution of the spectral data points;

s23, exponential smoothing: for the frequency spectrum data block B_UPerforming exponential smoothing with filter coefficient beta to obtain smoothed spectral data block B_E。

Compared with the prior art, the invention has the beneficial effects that: the embodiment of the invention provides a method for calculating a detection threshold of a radio frequency spectrum signal, wherein valley point filtering is used for eliminating spectral line collapse caused by frequency component loss in frequency spectrum data; exponential smoothing is used to eliminate noise-induced spectral line fluctuations; the exponential smoothing operation only stores one part of data, so that the occupied memory is small, and the calculation cost is low; the data block segmentation plays a role in avoiding overlarge fluctuation of the background level in the calculation frequency spectrum interval; the process of subsection segmentation, subsection maximum level calculation and frequency spectrum section reference background level calculation is an operation independent of signal bandwidth, and reasonable background level can be obtained when narrow-band or wide-band signals exist in frequency spectrum data; in the frequency spectrum section signal detection threshold obtaining process, the minimum value is obtained between the reference background level and the section frequency spectrum data point, and the output signal detection threshold is ensured to be close to the background level, so that the weak signal detection capability is improved; the algorithm of the invention is suitable for the requirements of various fixed, airborne and vehicle-mounted radio monitoring systems on the signal detection threshold calculation performance.

Drawings

Fig. 1 is a schematic flow chart of a method for calculating a detection threshold of a radio spectrum signal according to an embodiment of the present invention.

FIG. 2 is a schematic view of the method of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-2, the present invention provides a technical solution: a method for calculating a detection threshold of a radio frequency spectrum signal comprises the following steps:

s1, setting parameters: setting a median filter window width constant set W_MEDSegment bandwidth constant group W_SEGSub-segment bandwidth constant set W_BKGThe values of the member nodes in the three arrays are related to the frequency; the exponential smoothing filter coefficient β is set.

Wherein;

in the example, the working frequency range of the radio frequency receiver is 30 MHz-6 GHZ, and the medium frequency bandwidth BWIF is 40 MHz; the radio frequency receiver API outputs a fast Fourier transform spectrum data block which is not averaged, and the spectrum resolution used by the monitoring task is 2.4 KHz; setting the coefficient beta of an exponential smoothing filter to be 0.0625 and setting a median filter window width constant set W according to the working conditions of a radio frequency receiver_MEDSet the segment bandwidth constant set W for Table 1_SEGSet the sub-segment bandwidth constant set W for Table 2_BKGIs shown in Table 3:

watch (1)

Frequency value interval (Unit: MHz)	Section bandwidth constant array WSEG (unit: KHz)
		30～80	500.0
80～110	1000.0
		110～500	1500
300～500	5000
		500～6000	40000

Watch (2)

Watch (3)

S2, receiving data blocks and processing data;

wherein, S21, receiving the data block: receiving a wide band spectrum data block B output by a radio frequency receiver_RThe number of spectral data points is K, and the frequency of the data points is f_B1～f_BKLevel of data point is L_B1～L_BK；

Wherein; data block center frequency of F_CFrequency of data points is f_B(k) Where 1 ≦ K ≦ K, the lowest frequency is L_B1Maximum frequency of L_BKLevel of data point is L_B(k)。

S22, valley point filtering: for the frequency spectrum data block B_RPerforming median filtering on the valley point to obtain a frequency spectrum data block B with the valley point removed_UThe window length of the median filter depends on the set of median filter constants W_MEDAnd frequency of the spectral data pointsSpectral resolution;

the pseudo-procedure to implement median filtering is:

for k＝2:K-1

if L_B(k)<L_B(k-1)&&L_B(k)<L_B(k+1)

to W_MEDAs a window, with L_B(k)Sorting the spectral levels of the center points;

L_U(k)sorted level medians;

else

L_U(k)＝L_B(k)；

end

Wherein: the calculation formula of exponential smoothing is:

wherein:

is the last exponential smoothing result of the record;

L_E(k)is the spectral data level;

L_U(k)a median filtered spectral data level;

beta is the filter coefficient;

k is the number of spectral data points.

S3, data block segmentation: according to the segment bandwidth array WSEG and the frequency interval f of the frequency spectrum data block_B1～f_BKDividing the spectrum data block into N spectrum data segments SEGn, wherein 1 is less than or equal to N; there are P data points in the spectrum data segment SEGn, and the level of each data point is L_s(P)；

wherein: m is BW_SEG/W_EKG[j](ii) a Where j is the spectral band block center frequency f_SEGCorresponding W_BKGArray subscripts.

S7, solving a detection threshold of the frequency spectrum section signal: data point level value L in spectral data segment SEGn_S1～L_SPAnd obtaining the minimum value from the spectrum reference background level LREF to obtain the detection threshold L of the spectrum signal_T1～L_TPAs an output;

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.

Claims

1. A method for calculating a detection threshold of a radio frequency spectrum signal is characterized by comprising the following steps: the method comprises the following steps:

s1, setting parameters: setting a median filter window width constant group WMED, a segment bandwidth constant group WSEG and a sub-segment bandwidth constant group WBKG, wherein values of member nodes in the three groups are related to frequency; setting an exponential smoothing filter coefficient beta;

s2, receiving a data block and processing the data, wherein the data block receiving: receiving a wide-band spectrum data block BR output by a radio frequency receiver, wherein the number of spectrum data points is K, the frequency of the data points is fB 1-fBK, the level of the data points is LB 1-LBK, and valley point filtering: performing median filtering on the valley points in the spectral data block BR to obtain a spectral data block BU from which the valley points are removed, the median filter window length depending on the median filter constant set WMED and the spectral resolution of the spectral data points, exponentially smoothing: performing exponential smoothing on the spectrum data block BU, wherein the filter coefficient is beta, and obtaining a smoothed spectrum data block BE;

s3, data block segmentation: dividing the spectrum data block into N spectrum data segments SEGn according to the segment bandwidth arrays WSEG and the frequency interval fB 1-fBK of the spectrum data block, wherein 1 is less than or equal to N is less than or equal to N; p data points exist in the spectrum data segment SEGn, and the level of each data point is LS 1-LSP;

s4, subsection division: in each spectrum data segment SEGn, dividing the spectrum data segment into M subsegments according to the subsegment bandwidth array WBKG and the spectrum segment center frequency fSEG;

s5, obtaining the maximum level of the subsegment: obtaining the maximum spectral line level in M subsections to obtain the maximum level Lmax 1-LmaxM of the subsections;

s6, calculating the reference background level of the spectrum section: solving the minimum value of the maximum spectral line level Lmax 1-LmaxM in the M subsections to obtain the reference background level LREF of the frequency spectrum section;

s7, solving a detection threshold of the frequency spectrum section signal: taking the minimum value from the data point level values LS 1-LSP of the spectrum data segment SEGn and the spectrum reference background level LREF to obtain the spectrum segment signal detection thresholds LT 1-LTP as output;