CN-121995121-A - Method for detecting electromagnetic leakage signal of display equipment

CN121995121ACN 121995121 ACN121995121 ACN 121995121ACN-121995121-A

Abstract

The invention relates to a detection method of electromagnetic leakage signals of display equipment, which belongs to the technical field of electromagnetic detection, and specifically comprises the steps of firstly collecting space electromagnetic signals through broadband receiving equipment, obtaining baseband complex signals through preprocessing, then finishing primary detection of leakage signals, extraction of core parameters such as pixel clocks and line field synchronization and the like through improving multiple autocorrelation algorithms without prior parameters, then constructing a confidence degree discrimination matrix based on pixel amplitude and phase sequence characteristics, accurately distinguishing effective leakage signals from various interferences, realizing weak signal enhancement through self-adaptive threshold value characteristic preference and confidence degree weighted multi-frame coherent accumulation, and finally finishing detection result output.

Inventors

YANG GUANG
CHEN KAIYUAN
SHI NA
CHEN YUANYUAN
LI HUAXIN
WU QIZHOU
LI KAI
SUN YUFEI

Assignees

中北大学

Dates

Publication Date: 20260508
Application Date: 20260410

Claims (6)

1. A method for detecting electromagnetic leakage signal of display device is characterized by comprising the following steps, S1, broadband electromagnetic signal acquisition and preprocessing, wherein broadband receiving equipment is adopted to acquire space electromagnetic signals of a target monitoring area And sequentially carrying out band-pass filtering, low-noise amplification and quadrature down-conversion treatment on the space electromagnetic signal to obtain a zero intermediate frequency baseband complex signal Then according to the sampling frequency meeting the Nyquist sampling theorem Discrete sampling to obtain a discrete baseband complex signal sequence Wherein N is the total sampling point number; S2, leakage signal detection and core parameter extraction by adopting multiple autocorrelation are carried out, and discrete baseband complex signal sequences are aimed at By using Algorithm computation of order multiple autocorrelation Multiple autocorrelation values are then matched Peak detection is carried out on the order multiple autocorrelation values, and then the pixel clock frequency is obtained Line synchronization frequency Frequency of field synchronization ; S3, constructing a confidence degree discrimination matrix based on pixel amplitude and phase time sequence characteristics, discriminating the confidence degree of the effective leakage signal, and accurately discriminating the effective leakage signal from various interferences; S4, weak signal enhancement is achieved through self-adaptive threshold feature preference and confidence weighting multi-frame coherent accumulation, and finally detection result output is completed.
2. The method according to claim 1, wherein in the step S2, the complex signal sequence is performed for the discrete baseband By using The order multiple autocorrelation algorithm has the following formula: , In the formula, wherein In the form of a discrete amount of delay, For the autocorrelation calculation order, m is the cyclic variable of the cumulative operator pi, n is the discrete sampling point sequence number of the signal sequence, Conjugate operation of complex signal; Is the discrete delay amount Corresponding to A step multiple autocorrelation value; For periodic electromagnetic leakage signals carrying display content, discrete amounts of delay And signal period When the matching is performed, A significant peak occurs, and multiple autocorrelation values of random noise follow the order Is decaying exponentially, thus achieving initial detection of signals at low signal-to-noise ratios.
3. The method for detecting electromagnetic leakage signal of display device according to claim 2, wherein in step S2, the calculation is performed Peak detection is performed by setting a peak value judgment threshold as Extracting a discrete delay amount sequence corresponding to a peak value exceeding a threshold by 3 times of a global average value ; Minimum discrete delay based on periodic level constraints of display device leakage signals Corresponding to the pixel clock period Obtaining the pixel clock frequency ; Integer multiple discrete delay amount Corresponding to the line synchronization period Obtaining the line synchronization frequency ; Integer multiple discrete delay amount Corresponding field synchronization period Obtaining the field synchronous frequency 。
4. The method for detecting electromagnetic leakage signals of a display device according to claim 2, wherein in said step S3, when constructing a confidence judging matrix, the steps are performed as follows, S31, multiplexing the discrete baseband signal sequence By field sync period Dividing into 1 frame to obtain Frame continuous signal, each frame synchronizing period by line Divided into Lines, each line being in pixel clock period Divided into Pixels, get Pixel-level complex signal matrix of frame , Wherein: For the frame number, For the total number of frames, Is the pixel horizontal coordinate; is the pixel vertical coordinate; S32, obtaining Pixel-level complex signal matrix of frame Calculating an amplitude timing sequence And phase timing sequence , , , Wherein, the For the modular operation of the complex signal, Phase angle operation for complex signals; S33, opposite pixels At all Amplitude timing sequence on frames Calculating an amplitude stability factor Characterizing the degree of stability of the inter-frame amplitude: , in the formula, Is the mean value of the time series of pixel amplitudes, Is the standard deviation of the pixel amplitude timing sequence, To prevent the denominator from being 0, the value is fixed ; The range of the values is as follows ; S34, opposite pixels At all On-frame phase timing sequence Calculating a phase coherence factor Characterizing the degree of coherence of the inter-frame phases: , Wherein: is an imaginary unit; the range of the values is as follows The phase of the effective leakage signal has a strong coherence, Approaching 1, while the phase of random disturbance is uniformly distributed, Approaching 0; S35, constructing a confidence degree discrimination matrix, combining an amplitude stability factor and a phase coherence factor, constructing a pixel-level effective leakage signal confidence degree discrimination matrix, and recording that the confidence degree of all frames is the same for the same pixel because the confidence degree is based on the statistical characteristics of all frames , , Wherein the method comprises the steps of , For the amplitude weight to be a weight of the amplitude, Is a phase weight.
5. The method for detecting electromagnetic leakage signal of display device according to claim 4, wherein in step S4, when weak signal enhancement is achieved, the operation is performed according to the following steps, S41, selecting the lowest 10% pixel area in the confidence coefficient judging matrix as a noise reference area, adjusting according to the estimated effective signal duty ratio, and calculating the average value of the confidence coefficient in the noise reference area And standard deviation of Designing an adaptive confidence threshold , In which, in the process, Is a confidence coefficient; S42, confidence of pixel level for all frames To adapt the threshold value The preferential screening is carried out for the reference, and the rejection confidence is lower than Low confidence interference features, false signal features, retaining high confidence effective leakage signal features, obtaining effective feature set , S43, confidence weighting multi-frame coherent accumulation weak signal enhancement aiming at effective feature set The pertinence enhancement of the weak leakage signals is realized by adopting a confidence weighted multi-frame coherent accumulation algorithm for the pixel signals in the filter array, and an enhanced pixel-level complex signal matrix is obtained : , In the formula, To prevent the denominator from being 0, the value is fixed 。
6. The method for detecting electromagnetic leakage signal of display device according to claim 5, wherein in step S4, when outputting the result, the output-based enhanced pixel-level complex signal matrix is performed Finishing final confirmation and output of the detection result, and calculating the signal-to-noise ratio of the enhanced signal : , In the formula, An average power of the effective pixel region; average power for noise reference region; Presetting a detection threshold When (when) If the effective electromagnetic leakage signal exists in the target area, judging that the effective electromagnetic leakage signal exists in the display equipment, otherwise, judging that the effective electromagnetic leakage signal does not exist; If the effective leakage signal is judged to exist, the core parameters of the leakage signal are synchronously output, including the pixel clock frequency, the line synchronization frequency and the field synchronization frequency, so that the full-flow detection is completed.

Description

Method for detecting electromagnetic leakage signal of display equipment Technical Field The invention relates to a method for detecting electromagnetic leakage signals of display equipment, and belongs to the technical field of electromagnetic detection. Background With the rapid development of information technology, display devices such as a display, a notebook computer, an integrated machine and the like are widely applied to confidential information processing scenes such as government affairs, military industry, finance and the like. The display device can generate high-frequency electromagnetic leakage carrying display content information in the image data transmission and pixel driving processes, and can restore the display content in a non-contact manner by receiving and analyzing leakage signals, thereby seriously threatening the security of confidential information. Therefore, the electromagnetic leakage signal detection technology for the display equipment is a core key technology for electromagnetic environment monitoring, information security risk assessment and security protection system construction in a secret place, and has important research value and engineering significance. The existing leakage signal detection method is mainly dependent on priori parameters (such as resolution, pixel clock frequency, line-field synchronous time sequence and the like) of display equipment, signal matching and detection can be completed only by acquiring the equipment parameters in advance, blind detection can not be realized for the display equipment with unknown model and unknown parameters, applicable scenes are severely limited, and the requirements of global electromagnetic environment monitoring in a secret-related place are difficult to meet, a large amount of environment electromagnetic interference, same-frequency-band interference and false synchronous signals exist in the complex electromagnetic environment, the existing detection method does not fully utilize inherent pixel amplitude and phase time sequence characteristics of leakage signals of the display equipment, effective leakage signals and various interferences cannot be accurately distinguished, the detection false alarm rate is high, the reliability of detection results is insufficient, third, under a long-distance or high-interference scene, the attenuation of the leakage signals is serious, the signal to noise ratio is extremely low, the weak leakage signals are extremely easy to be submerged, the existing accumulation method does not distinguish effective signal characteristics from interference characteristics, can not realize weak screening, the detection probability of the effective signals is difficult to be improved, the situation that the detection signals are difficult to be concentrated, the detection process is difficult to be optimized, the detection process is difficult to realize, the detection process is difficult to be optimized, and the detection process is difficult to meet the requirements of the detection process is more than the detection process is difficult to be optimized, and the detection process is difficult to meet the detection has the best, and the detection process is difficult to be has the best. In summary, the prior art lacks a full-flow detection method for electromagnetic leakage signals of display equipment, which does not need prior parameters, has low false alarm rate and high detection sensitivity and adapts to full scenes. Disclosure of Invention In order to solve the technical problems in the prior art, the invention provides a method for detecting electromagnetic leakage signals of display equipment, which can effectively solve the problems that weak leakage signals are submerged by noise and the detection probability is low in a long-distance and high-interference scene. In order to achieve the above object, the present invention adopts a technical scheme that is a method for detecting electromagnetic leakage signals of a display device, comprising the following steps, S1, broadband electromagnetic signal acquisition and preprocessing, wherein broadband receiving equipment is adopted to acquire space electromagnetic signals of a target monitoring areaAnd sequentially carrying out band-pass filtering, low-noise amplification and quadrature down-conversion treatment on the space electromagnetic signal to obtain a zero intermediate frequency baseband complex signalThen according to the sampling frequency meeting the Nyquist sampling theoremDiscrete sampling to obtain a discrete baseband complex signal sequenceWhereinN is the total sampling point number; S2, leakage signal detection and core parameter extraction by adopting multiple autocorrelation are carried out, and discrete baseband complex signal sequences are aimed at By usingAlgorithm computation of order multiple autocorrelationMultiple autocorrelation values are then matchedPeak detection is carried out on the order multiple autocorr