CN114706046A - Harmonic envelope adaptive weighting-based frequency modulation fuse anti-interference method - Google Patents

Harmonic envelope adaptive weighting-based frequency modulation fuse anti-interference method Download PDF

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CN114706046A
CN114706046A CN202210401685.5A CN202210401685A CN114706046A CN 114706046 A CN114706046 A CN 114706046A CN 202210401685 A CN202210401685 A CN 202210401685A CN 114706046 A CN114706046 A CN 114706046A
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郝新红
周文
闫晓鹏
董二娃
郑胜
刘冰
陈彦君
杨瑾
段乐帆
贾瑞丽
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Beijing Institute of Technology BIT
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Abstract

The invention relates to a harmonic envelope adaptive weighting-based frequency modulation fuse anti-interference method, and belongs to the technical field of information countermeasure. According to the method, the frequency modulation fuse difference frequency signal is subjected to fast Fourier transform to obtain each subharmonic coefficient containing target information, the corresponding harmonic position is determined according to the preset explosion height, the real target signal is identified by combining self-adaptive weighting processing between two adjacent subharmonics and threshold judgment and utilizing the logic characteristics in the bullet meeting process, and the accurate control of explosion points is realized. According to the method, the crossing information from far to near contained in the real target echo signal is obtained through the combined extraction of the harmonic envelope corresponding to the preset explosion height and the adjacent higher harmonic envelope, and the interference signal which does not meet the logic characteristic can be inhibited; by multiplying the two paths of harmonic envelopes, the relative correlation side lobe level is reduced, clutter interference is inhibited, and the target detection precision is improved.

Description

Harmonic envelope adaptive weighting-based frequency modulation fuse anti-interference method
Technical Field
The invention relates to a harmonic envelope adaptive weighting-based frequency modulation fuse anti-interference method, and belongs to the technical field of information countermeasure.
Background
The frequency modulation fuse utilizes the frequency difference value of the transmitting signal and the echo signal to carry out distance measurement, and has the characteristics of high distance measurement precision and reliable performance compared with a continuous wave Doppler fuse due to simple algorithm and easy realization of hardware. At present, a great number of countries are equipped with radio fuses, and in recent years, the equipment is mainly frequency modulation fuses which can be obtained according to the development context of the fuses of the countries, and the frequency modulation fuses are one of the main objects of research and equipment of the countries.
The frequency modulation fuse transmits a constant amplitude continuous wave signal with frequency change controlled by a modulation signal to a target, the frequency of the transmitted signal is a function of time, the time delay from the target to a path is determined by measuring the main frequency component of an intermediate frequency signal obtained after the target echo and a reference signal are mixed, and then the relative distance from the target can be obtained, so that whether a starting signal is output or not is determined.
In general, the detection distance of the conventional ammunition radio fuse is relatively short, and ideally, the explosion point control is realized by judging the single harmonic envelope threshold corresponding to the preset explosion height in the difference frequency signal. In the complex electromagnetic environment of a battlefield, however, the various active electronic devices cause severe interference to the frequency-modulated fuses. Taking a typical frequency-sweeping interference as an example, the frequency-sweeping bandwidth of the jammer generally covers the working frequency band of the fuze, when the frequency of the interference signal enters the receiving bandwidth of the fuze, the frequency-sweeping interference signal difference frequency spectrum can cover the whole real target signal spectrum of the fuze to influence the amplitude distribution of each subharmonic in the intermediate frequency signal, and the energy of the interference signal is generally higher than that of the real target echo signal, so that a pressing type covering effect is generated on the frequency spectrum of the real target echo difference frequency signal, a large number of abnormal false peaks are generated, and the explosion judging effect of the traditional frequency modulation fuze based on the extracted harmonic envelope characteristic is influenced, thereby causing the explosion or misfire.
The traditional frequency modulation fuse difference frequency signal processing method only carries out simple threshold judgment according to single harmonic envelope corresponding to the preset burst height, and the risk of performance reduction or even failure exists in a complex electromagnetic environment of a battlefield. Under the promotion of demand traction and technology, the confronting characteristics of the frequency modulation fuse are changed and are changing in an accelerated way, the anti-interference capability of the frequency modulation fuse is forced to be greatly improved by the development of the frequency modulation fuse interference technology, and the method has great significance for ensuring the normal work of the frequency modulation fuse and playing the best damage efficiency of ammunition.
Disclosure of Invention
The invention aims to provide a frequency modulation fuse anti-interference method based on harmonic envelope adaptive weighting, which is characterized in that the difference frequency signal of the frequency modulation fuse is subjected to fast Fourier transform to obtain each subharmonic coefficient containing target information, the corresponding harmonic position is determined according to the preset explosion height, the adaptive weighting processing between two adjacent subharmonics is combined with threshold judgment, the logic characteristic in the missile meeting process is utilized to reduce the level of related sidelobes, a real target signal is identified, the accurate control of explosion points is realized, and the problem of insufficient anti-interference capability of the frequency modulation fuse is solved.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a frequency modulation fuse anti-interference method based on harmonic envelope adaptive weighting, which comprises the following steps:
the method comprises the following steps: the method comprises the following steps of carrying out fast Fourier transform processing on a frequency modulation fuse difference frequency signal according to an integer multiple data length of a modulation period to obtain each harmonic containing target distance information, and specifically comprises the following substeps:
step 1.1, Fourier transformation of the frequency modulation fuse difference frequency signal:
frequency modulated fuze transmission signal xt(t) is represented by the formula (1):
Figure BDA0003600330770000021
wherein f is0Transmitting an initial frequency of a signal for the frequency-modulated fuse, T being the corresponding time of the current signal, TmFor the modulation period, β is the frequency modulation slope, rect () is a rectangular window function, and n is 1,2,3, which is the relative period ordinal number;
true target echo signal xr(t) is represented by the formula (2):
Figure BDA0003600330770000022
wherein tau is the relative path time delay between the bullets;
further, ignoring the effect of the irregular region, the frequency modulated fuse difference frequency signal xΔf(t) is represented by the formula (3):
Figure BDA0003600330770000023
furthermore, frequency-adjusting fuse difference frequency signal xΔf(t) performing Fourier transform, as shown in formula (4):
Figure BDA0003600330770000024
wherein, X (kf)m) For frequency-modulated fuse difference frequency signal xΔf(t) the fourier transform result, k being 1, 2., N being the corresponding harmonic ordinal number, N being the signal length;
step 1.2, extracting a modulus value of a Fourier transform result:
frequency modulation fuse difference frequency signal xΔfFourier transform result X (kf) of (t)m) Extracting Fourier transform result X (kf) in complex formm) Modulus value of (c) | X (kf)m) L as shown in formula (5):
Figure BDA0003600330770000025
wherein, Re [ X (kf)m)]As a result of Fourier transformation X (kf)m) Real part of (i), Im [ X (kf)m)]As a result of Fourier transformation X (kf)m) An imaginary part of (d);
step 1.3, extracting harmonic envelopes with different periods:
repeating the step 1.1 and the step 1.2 for the frequency modulation fuze difference frequency signal data of each period in the bullet-and-eye intersection process, wherein the module value of each harmonic of different periods is the harmonic envelope, as shown in the formula (6):
Figure BDA0003600330770000031
step two: determining the difference frequency of a corresponding frequency modulation fuse difference frequency signal according to the preset explosion height, extracting harmonic waves of corresponding times and adjacent higher harmonic waves in the step one, and extracting two paths of harmonic envelopes through low-pass filtering, wherein the method specifically comprises the following substeps:
step 2.1, extracting the corresponding harmonic envelope of the preset explosion height and the envelope of the adjacent higher harmonic:
according to the practical process that the missile and the target meet from far to near and the difference frequency of the frequency modulation fuse difference frequency signal corresponding to the preset explosion height, the corresponding harmonic envelope and the adjacent higher harmonic envelope in the step one are extracted at the same time, and according to the formula (6), the relation between the preset explosion height and the harmonic frequency k where the harmonic envelope peak value in the frequency modulation fuse difference frequency signal is located is shown as the formula (7):
Figure BDA0003600330770000032
wherein R is a preset explosive height, and c is the propagation speed of the electromagnetic wave in the free space;
step 2.2, two-path harmonic enveloping low-pass filtering treatment:
carrying out low-pass filtering processing on the harmonic envelope corresponding to the preset explosion height extracted in the step 2.1 and the adjacent higher harmonic envelope thereof, and reducing the influence of abnormal peak values caused by background noise;
step three: and (3) performing adaptive weighting processing on the two harmonic envelopes extracted in the step two, which specifically comprises the following substeps:
step 3.1 determining the optimal delay time:
delaying the envelope of adjacent higher harmonics by an optimum delay time taudAs shown in formula (8)
Figure BDA0003600330770000033
Wherein, VrThe relative speed of the shot eyes is B, and the modulation bandwidth of the transmitted signal is B;
step 3.2, self-adaptive weighting processing:
delaying adjacent high-order harmonic envelopes, and multiplying the delayed high-order harmonic envelopes as self-adaptive weight by a harmonic envelope corresponding to the preset explosion height;
the two harmonic envelopes comprise logic characteristics in the process of intersecting the bullet eyes from far to near;
step four: and (3) amplitude threshold judgment:
performing threshold judgment on the result of the self-adaptive weighting processing, judging as a target signal if the result meets the minimum threshold requirement, and outputting detonation information to the next stage; and if the minimum threshold requirement is not met, judging that no target exists, and waiting for judging next frame data.
Has the advantages that:
1. according to the frequency modulation fuse anti-interference method based on the harmonic envelope adaptive weighting, the intersection information from far to near contained in the real target echo signal is obtained through the combined extraction of the harmonic envelope corresponding to the preset burst height and the adjacent higher harmonic envelope, and the interference signal which does not meet the logic characteristic can be inhibited;
2. according to the frequency modulation fuse anti-interference method based on the harmonic envelope adaptive weighting, the relative correlation side lobe level is reduced, clutter interference is inhibited, and the target detection precision is improved through multiplication of two paths of harmonic envelopes.
Drawings
FIG. 1 is an overall flow chart of a frequency modulation fuse anti-interference method based on harmonic envelope adaptive weighting according to the present invention;
FIG. 2 is a flow chart of harmonic envelope adaptive weighting processing of a frequency modulation fuze anti-interference method based on harmonic envelope adaptive weighting according to the present invention;
FIG. 3 is a schematic diagram of the information about the 6 th harmonic envelope and the 7 th harmonic envelope;
FIG. 4 is a graph illustrating the low pass filtering results for the 6 th harmonic envelope and the 7 th harmonic envelope;
fig. 5 is a schematic diagram of a comparison of a single channel harmonic envelope processing result and a dual channel harmonic envelope weighting processing result.
Detailed Description
For a better understanding of the objects and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example 1:
in this embodiment, the predetermined burst height is 9m, the transmission signal is a sawtooth wave frequency modulation continuous wave signal, the modulation period is 100KHz, and the modulation bandwidth is 100 MHz. Firstly, performing fast fourier transform with the length of 1 period on an input frequency modulation fuse difference frequency signal to obtain a global fourier spectrum of the frequency modulation fuse difference frequency signal, extracting a harmonic envelope corresponding to a preset explosion height and an adjacent higher harmonic envelope, performing certain delay on the higher harmonic envelope, multiplying the higher harmonic envelope by the harmonic envelope corresponding to the preset explosion height, outputting the higher harmonic envelope, finally judging the higher harmonic envelope by a preset threshold, if the higher harmonic envelope is higher than the minimum threshold requirement, judging a target signal, and outputting a starting signal to a next stage, wherein the method specifically comprises the following steps as shown in fig. 1:
the method comprises the following steps: the method comprises the following steps of carrying out fast Fourier transform processing on a frequency modulation fuze difference frequency signal according to an integer multiple data length of a modulation period to obtain each harmonic containing target distance information, and specifically comprises the following sub-steps:
step 1.1, Fourier transformation of the frequency modulation fuse difference frequency signal:
frequency modulated fuze transmission signal xt(t) is represented by the formula (1):
Figure BDA0003600330770000041
wherein f is0Transmitting an initial frequency of a signal for the frequency-modulated fuse, T being the corresponding time of the current signal, TmFor the modulation period, β is the frequency modulation slope, rect () is a rectangular window function, and n is 1,2,3, which is the relative period ordinal number;
true target echo signal xr(t) is represented by the formula (2):
Figure BDA0003600330770000042
wherein tau is the relative path time delay between the bullets;
further, ignoring the effect of the irregular region, the frequency modulated fuse difference frequency signal xΔf(t) is represented by the formula (3):
Figure BDA0003600330770000051
furthermore, frequency-adjusting fuse difference frequency signal xΔf(t) performing Fourier transform, as shown in formula (4):
Figure BDA0003600330770000052
wherein, X (kf)m) For frequency-modulated fuse difference frequency signal xΔf(t) the fourier transform result, k being 1, 2., N being the corresponding harmonic ordinal number, N being the signal length;
step 1.2, extracting a modulus value of a Fourier transform result:
frequency modulation fuse difference frequency signal xΔf(t) Fourier transform result X (kf)m) In complex form, extracting FourierTransformation result X (kf)m) Modulus value of (c) | X (kf)m) L as shown in formula (5):
Figure BDA0003600330770000053
wherein, Re [ X (kf)m)]As a result of Fourier transformation X (kf)m) Real part of (i), Im [ X (kf)m)]Fourier transform result X (kf)m) An imaginary part of (d);
step 1.3, extracting harmonic envelopes with different periods:
repeating the step 1.1 and the step 1.2 for the frequency modulation fuze difference frequency signal data of each period in the bullet-and-eye intersection process, wherein the module value of each harmonic of different periods is the harmonic envelope, as shown in the formula (6):
Figure BDA0003600330770000054
step two: determining the difference frequency of a corresponding frequency modulation fuse difference frequency signal according to the preset explosion height, extracting harmonic waves of corresponding times and adjacent higher harmonic waves in the step one, and extracting two paths of harmonic envelopes through low-pass filtering, wherein the method specifically comprises the following substeps:
step 2.1, extracting the corresponding harmonic envelope of the preset explosion height and the envelope of the adjacent higher harmonic:
according to the practical process of intersection of the shots from far to near and the difference frequency of the frequency modulation fuse difference frequency signal corresponding to the preset burst height, the corresponding harmonic envelope and the adjacent higher harmonic envelope in the step one are extracted at the same time, and according to the formula (6), the relation between the preset burst height and the harmonic frequency k where the harmonic envelope peak value in the frequency modulation fuse difference frequency signal is located is shown as the formula (7):
Figure BDA0003600330770000055
wherein R is the preset explosion height, and c is the propagation speed of the electromagnetic wave in the free space;
in an embodiment, the predetermined burst height R is 9 m;
extracting a harmonic envelope corresponding to the preset explosion height according to the formula (7), and simultaneously extracting an adjacent higher harmonic envelope;
with reference to the specific parameters of this embodiment, a 6 th harmonic envelope corresponding to a predetermined burst height of 9m and an adjacent 7 th harmonic envelope in the fft result are extracted, respectively, as shown in fig. 3;
step 2.2, two-path harmonic enveloping low-pass filtering treatment:
low-pass filtering the 6 th harmonic envelope and the 7 th harmonic envelope extracted in step 2.1 to reduce the influence of abnormal peaks caused by background noise, as shown in fig. 4;
step three: and (3) performing adaptive weighting processing on the two harmonic envelopes extracted in the step two, which specifically comprises the following substeps:
step 3.1 determining the optimal delay time:
delaying the envelope of adjacent higher harmonics by an optimum delay time taudAs shown in formula (8)
Figure BDA0003600330770000061
Wherein, VrThe relative speed of the shot eyes is B, and the modulation bandwidth of the transmitted signal is B;
in the examples, the relative speed V of the eyesr300m/s, the modulation bandwidth B of the transmitted signal is 100MHz, and the optimal delay time tau is determineddIs 5 ms;
step 3.2 adaptive weighting:
delaying adjacent high-order harmonic envelopes, and multiplying the delayed high-order harmonic envelopes as self-adaptive weight by a harmonic envelope corresponding to the preset explosion height;
the 7 th harmonic envelope is delayed by 5ms after low-pass filtering, and is output after being correspondingly multiplied by the 6 th harmonic envelope through a multiplier, and a decibel chart obtained after the peak value normalization of the obtained result is shown in fig. 5: the relative sidelobe of the output result of the single harmonic envelope is higher and is-9.95 dB, the relative sidelobe of the output result of the two-path self-adaptive weighted harmonic envelope is only-18.72 dB, and the two-path harmonic self-adaptive weighted processing method has stronger clutter suppression capability;
step four: and (3) amplitude threshold judgment:
performing threshold judgment on the output result, wherein the specific value of the judgment threshold is related to the performance of the front-end antenna;
in the embodiment, the judgment threshold is set to be 0.01V, if the requirement of the lowest threshold is met, a target signal is judged, if the requirement of the lowest threshold is not met, no target is judged, and the judgment of the next frame data is waited;
in the embodiment, the peak value of the self-adaptive weighted harmonic envelope is 0.012V, meets the requirement of the minimum threshold, and is judged as a real target corresponding to the 9m blast height, which is consistent with the actual situation;
the output results of the two paths of self-adaptive weighted harmonic envelopes comprise the logic characteristics of a real target in the crossing process from far to near, the anti-interference capability is enhanced, the relevant side lobes are inhibited through self-adaptive weighted multiplication, the selection of the lowest threshold value is facilitated, and the robustness is higher compared with the traditional one-path harmonic envelope threshold judgment.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (4)

1. A frequency modulation fuse anti-interference method based on harmonic envelope adaptive weighting is characterized in that: the method comprises the following steps:
the method comprises the following steps: carrying out fast Fourier transform processing on the frequency modulation fuse difference frequency signal according to the integral multiple data length of the modulation period to obtain each subharmonic containing target distance information;
step two: determining the difference frequency of the corresponding frequency modulation fuse difference frequency signal according to the preset explosion height, extracting the harmonic waves of corresponding times and adjacent higher harmonic waves in the step one, and extracting two paths of harmonic envelopes through low-pass filtering;
step three: carrying out self-adaptive weighting processing on the two paths of harmonic envelopes extracted in the step two;
step four: and (3) amplitude threshold judgment:
performing threshold judgment on the result of the self-adaptive weighting processing, judging as a target signal if the result meets the minimum threshold requirement, and outputting detonation information to the next stage; and if the minimum threshold requirement is not met, judging that no target exists, and waiting for judging next frame data.
2. The harmonic envelope adaptive weighting-based frequency modulated fuze interference rejection method according to claim 1, characterized in that: in the first step, the following substeps are specifically included:
step 1.1, Fourier transformation of the frequency modulation fuse difference frequency signal:
frequency modulated fuze transmission signal xt(t) is represented by the formula (1):
Figure FDA0003600330760000011
wherein f is0Transmitting an initial frequency of a signal for the frequency-modulated fuse, T being the corresponding time of the current signal, TmFor the modulation period, β is the chirp rate, rect () is a rectangular window function, and n is 1,2,3.
True target echo signal xr(t) is represented by the formula (2):
Figure FDA0003600330760000012
wherein tau is the relative path time delay between the bullets;
further, ignoring the effect of the irregular region, the frequency modulated fuse difference frequency signal xΔf(t) is represented by the formula (3):
Figure FDA0003600330760000013
further, frequency-modulated fuze difference frequency signal xΔf(t) performing Fourier transform, as shown in formula (4):
Figure FDA0003600330760000014
wherein, X (kf)m) For frequency-modulated fuse difference frequency signal xΔf(t) the fourier transform result, k being 1, 2., N being the corresponding harmonic ordinal number, N being the signal length;
step 1.2, extracting a modulus value of a Fourier transform result:
frequency modulation fuse difference frequency signal xΔfFourier transform result X (kf) of (t)m) Extracting Fourier transform result X (kf) in complex formm) Modulus value of (c) | X (kf)m) L as shown in formula (5):
Figure FDA0003600330760000021
wherein, Re [ X (kf)m)]As a result of Fourier transformation X (kf)m) Real part of (c), Im [ X (kf) ]m)]As a result of Fourier transformation X (kf)m) An imaginary part of (d);
step 1.3, extracting harmonic envelopes with different periods:
repeating the step 1.1 and the step 1.2 for the frequency modulation fuze difference frequency signal data of each period in the bullet-and-eye intersection process, wherein the module value of each harmonic of different periods is the harmonic envelope, as shown in the formula (6):
Figure FDA0003600330760000022
3. the harmonic envelope adaptive weighting-based frequency modulated fuze interference rejection method according to claim 1, characterized in that: in the second step, the following substeps are specifically included:
step 2.1, extracting the corresponding harmonic envelope of the preset explosion height and the envelope of the adjacent higher harmonic:
according to the practical process that the missile and the target meet from far to near and the difference frequency of the frequency modulation fuse difference frequency signal corresponding to the preset explosion height, the corresponding harmonic envelope and the adjacent higher harmonic envelope in the step one are extracted at the same time, and according to the formula (6), the relation between the preset explosion height and the harmonic frequency k where the harmonic envelope peak value in the frequency modulation fuse difference frequency signal is located is shown as the formula (7):
Figure FDA0003600330760000023
wherein R is the preset explosion height, and c is the propagation speed of the electromagnetic wave in the free space;
step 2.2, two-path harmonic enveloping low-pass filtering processing:
and (4) carrying out low-pass filtering processing on the harmonic envelope corresponding to the preset burst height extracted in the step (2.1) and the adjacent high-order harmonic envelope thereof, and reducing the influence of abnormal peaks caused by background noise.
4. The harmonic envelope adaptive weighting-based frequency modulated fuze interference rejection method according to claim 1, characterized in that: in the third step, the method specifically comprises the following substeps:
step 3.1 determining the optimal delay time:
delaying the envelope of adjacent higher harmonics by an optimum delay time taudAs shown in formula (8)
Figure FDA0003600330760000024
Wherein, VrThe relative speed of the shot eyes is B, and the modulation bandwidth of the transmitted signal is B;
step 3.2 adaptive weighting:
delaying adjacent high-order harmonic envelopes, and multiplying the delayed high-order harmonic envelopes as self-adaptive weight by a harmonic envelope corresponding to the preset explosion height;
the two-way harmonic envelope contains the logical characteristics of the bullet during the intersection from far to near.
CN202210401685.5A 2022-04-18 2022-04-18 Harmonic envelope adaptive weighting-based frequency modulation fuse anti-interference method Pending CN114706046A (en)

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CN116910452A (en) * 2023-07-21 2023-10-20 郑州铁路职业技术学院 Hazardous waste aseptic treatment risk prediction evaluation method based on big data

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* Cited by examiner, † Cited by third party
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CN116910452A (en) * 2023-07-21 2023-10-20 郑州铁路职业技术学院 Hazardous waste aseptic treatment risk prediction evaluation method based on big data
CN116910452B (en) * 2023-07-21 2024-04-26 郑州铁路职业技术学院 Hazardous waste aseptic treatment risk prediction evaluation method based on big data

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