CN117375771B - Frame header detection method and device for IFF mode five signals and signal receiver - Google Patents
Frame header detection method and device for IFF mode five signals and signal receiver Download PDFInfo
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Abstract
The invention provides a frame header detection method of an IFF mode five signal, which comprises the following steps: performing phase alignment on the received leading pulse sequence and two paths of in-phase and quadrature reference leading pulse sequences generated locally, and then performing correlation processing to obtain two paths of correlation signals; calculating the time domain correlation accumulation envelope of the two paths of correlation signals, and performing autocorrelation calculation on the pulse signals to obtain detection decision quantity; and judging the leading pulse sequence according to the detection judgment quantity and a preset threshold value, confirming that the maximum correlation peak of the pulse signal is detected, and then confirming that the leading pulse sequence of the IFF mode five signals is detected according to the time interval and the number of the maximum correlation peak of the pulse signal. The invention also provides a frame header detection device and a signal receiver of the IFF mode five signals. The invention can realize the frame head detection of the five signals in the IFF mode, and effectively improves the accuracy of acquiring the position of the front-end data pulse.
Description
Technical Field
The application relates to the technical field of receiver communication, in particular to an IFF mode five-signal frame header detection method and device and a signal receiver.
Background
The IFF signal (i.e. "friend-of-foe identification signal") is a signal for identity identification and information exchange between an aircraft and a ground station, and is mainly applied to the fields of electronic reconnaissance, electronic countermeasure, and the like. The method is beneficial to counting the characteristics of the local aircraft and important information such as travel and the like by identifying and demodulating the intercepted IFF mode five signals, and plays a role in promoting the victory or defeat of war situation.
The IFF signal includes multiple signal types, wherein the mode five signal mainly includes three signals, i.e., an inquiry signal, a response signal_lever1, and a response signal_lever2. The existing method for detecting the frame head of the five signals in the IFF mode generally adopts digital down-conversion to a baseband, carries out envelope detection to form pulse signals, adopts a gate detection method to detect pulses existing in the signals and find out the frame head, then extracts domain parameters such as pulse width, amplitude, arrival time and interval, and the like, and although the existing preamble pulse detection method can realize the frame head detection, the detection accuracy is not high and can cause higher bit error rate in the demodulation process of the five signals in the mode; the existing method for detecting the frame head realizes the preamble pulse detection and signal identification of the mode five signals by adopting a synchronous pulse correlation method, and the method is quick and effective, but can not be simultaneously suitable for the detection and identification of the signals of other modes of MARKX IIA; therefore, how to detect the leading pulse of the five signals in the IFF mode and improve the accuracy of detection is a technical problem to be solved.
Patent document with publication number CN113030870A discloses a method for blind recognition of IFF mode 5 signals based on time domain features, and specifically discloses a method for inputting pulse frame search through processing results of two paths of signals to realize leading pulse sorting and mode five signal recognition of the mode 5 signals, but in an actual detection environment, IFF mode five signals, especially the number of response signals is huge, various pulse aliasing conditions can occur, and the method simply depends on the pulse frame search and matching, so that not only can the accuracy rate in the leading pulse sorting process be low, but also a certain degree of false alarm can be caused.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a frame header detection method, a frame header detection device and a signal receiver for an IFF mode five signal, wherein the method is applied to an IFF mode 5 query signal and a response signal, can realize the frame header detection of the IFF mode five signal and the bit synchronization of the IFF mode five signal, not only effectively improve the accuracy of acquiring the position of a front-end data pulse, but also improve the error rate of the receiver for realizing the demodulation of the IFF mode five signal to be as low as 5e-4 in an 8dB signal-to-noise ratio environment.
The technical scheme of the invention is as follows:
a frame header detection method of IFF mode five signals includes the following steps:
the received pulse signals are respectively correlated with the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence which are generated locally, so that two paths of correlated signals are obtained;
calculating time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a time domain correlation accumulation envelope value and a detection decision quantity;
and judging the time correlation accumulation envelope value according to the detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of the pulse signal, and then confirming the frame head of the detected IFF mode five signals according to the time interval and the number of the maximum correlation peak of the pulse signal.
Further, the received pulse signal is respectively correlated with the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence generated locally to obtain two paths of correlated signals, which specifically comprises:
Receiving a pulse signal, wherein the pulse signal is a time-varying phase modulation signal;
Locally generating two reference preamble pulse sequences with phase information being an initial phase and a modulated time-varying phase, the two reference preamble pulse sequences comprising an in-phase reference preamble pulse sequence and a quadrature reference preamble pulse sequence;
and multiplying the pulse signals with two paths of reference leading pulse sequences respectively, and integrating the pulse signals with integration length being a plurality of symbol widths to obtain two paths of related signals.
According to the invention, the correlation processing is carried out on the leading pulse sequence and the local two paths of reference leading pulse sequences after the time-varying phase is remodulated, so that the IFF mode five signals can still effectively detect the leading pulse under the condition of signal overlapping.
Further, the time-varying phase modulation of the pulse signal specifically includes:
integrating the plurality of code elements and multiplying the integrated code elements by a fixed constant to obtain a first integration result;
Multiplying the sequence number value of the last code element by the symbol width, dividing the difference between the product and the current time value by the symbol width to obtain a second symbol width;
and multiplying the last code element, the second code element width and a fixed constant, and adding the product of the multiplying and the first integral result to obtain the time-varying phase of the pulse signal at any time.
Further, calculating a time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a detection decision quantity, which specifically comprises:
The two paths of related signals are respectively squared and then added to obtain time domain related accumulated envelope values of the two paths of related signals;
After square the pulse signal, integrating with a plurality of symbol widths as integration length, and finally dividing by the plurality of symbol widths to obtain an autocorrelation value of the pulse signal;
and calculating the ratio between the time domain correlation accumulation envelope value and the autocorrelation value, and multiplying the ratio by the noiseless correlation coefficient to obtain the detection decision quantity.
Through the autocorrelation calculation and the detection decision quantity acquisition, the IFF mode five signals can still be effectively detected under the conditions of signal overlapping and low signal-to-noise ratio, and the accuracy of searching the preamble pulse is effectively improved.
Further, the calculation of the noiseless correlation coefficient specifically includes:
Under the condition of no noise, the square of the two paths of related signals is respectively carried out and then added, and finally, the product of the square of the signal amplitude and the first related coefficient is obtained, and the product is a second time domain related accumulated envelope value;
Under the condition of no noise, the square of the signal amplitude is multiplied by a second correlation coefficient, and the product is a second autocorrelation value, wherein the product is obtained by integrating a plurality of symbol widths after the square of the pulse signal and dividing the pulse signal by the plurality of symbol widths;
And calculating the ratio between the second time domain correlation accumulated envelope value and the second autocorrelation value to obtain a noise-free correlation coefficient.
By calculating the noiseless correlation coefficient, the accuracy of detection decision quantity can be effectively improved, and accurate detection and search of the position of the leading pulse are facilitated.
Further, according to the detection decision quantity and a preset threshold value, deciding the time-correlated accumulation envelope value to obtain a maximum correlation peak of the pulse signal, and then according to the time interval and the number of the maximum correlation peak of the pulse signal, confirming the frame head of the detected five signals in the IFF mode, which specifically comprises:
acquiring a detection judgment quantity and presetting a threshold value, comparing the detection judgment quantity with the threshold value, and confirming that the maximum correlation peak of the pulse signal is detected under the condition that the detection judgment quantity is larger than the preset threshold value and the maximum value of the detection judgment quantity is acquired;
And acquiring the number and time interval of the detected maximum correlation peaks of the continuous pulse signals, and confirming that the leading pulse sequence of the IFF mode five signals is detected under the condition that the number and time interval of the maximum correlation peaks of the pulse signals meet the signal specification.
The invention also provides a frame head detection device of the IFF mode five signals, which comprises:
the first correlation processing module is used for performing correlation processing on the received pulse signals and the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence which are generated locally respectively to obtain two paths of correlation signals;
the second correlation processing module is in communication connection with the first correlation processing module and is used for calculating time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a time domain correlation accumulation envelope value and a detection judgment quantity;
the detection judgment module is in communication connection with the second correlation processing module and is used for judging the time-correlated accumulation envelope value according to the detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of the pulse signal, and then confirming the frame head of the detected IFF mode five signals according to the time interval and the number of the maximum correlation peak of the pulse signal.
Further, the first correlation processing module includes:
the modulating unit is used for receiving the pulse signal and modulating the time-varying phase of the pulse signal;
The local signal generating unit is in communication connection with the modulating unit and is used for locally generating two paths of reference leading pulse sequences with the initial phase and the modulated time-varying phase as phase information;
the first correlation processing unit is in communication connection with the local signal generating unit and is used for multiplying pulse signals with two paths of reference leading pulse sequences respectively and then integrating the pulse signals with integration lengths being a plurality of symbol widths to obtain two paths of correlation signals.
Further, the second correlation processing module includes:
the second correlation processing unit is used for respectively squaring and then adding the two paths of correlation signals to obtain time domain correlation accumulated envelope values of the two paths of correlation signals;
The third correlation processing unit is in communication connection with the second correlation processing unit and is used for squaring the pulse signal, then integrating the pulse signal by taking a plurality of symbol widths as integration lengths and finally dividing the pulse signal by the plurality of symbol widths to obtain an autocorrelation value of the pulse signal;
The detection decision calculating unit is in communication connection with the third correlation processing unit and is used for calculating the ratio between the time domain correlation accumulated envelope value and the autocorrelation value, and then multiplying the ratio by the noiseless correlation coefficient to obtain the detection decision.
The detection judgment module comprises:
The pulse correlation peak confirming unit is used for acquiring the detection judgment quantity and presetting a threshold value, comparing the detection judgment quantity with the threshold value, and confirming that the maximum correlation peak of the pulse signal is detected under the condition that the detection judgment quantity is larger than the preset threshold value and the maximum value of the detection judgment quantity is acquired;
The pulse frame head confirming unit is in communication connection with the pulse correlation peak confirming unit and is used for acquiring the number and time interval of the detected continuous pulse signal maximum correlation peak, and if the number and time interval of the pulse signal maximum correlation peak meet the signal specification, the leading pulse sequence of the IFF mode five signals is confirmed to be detected.
The invention also provides a signal receiver, which comprises the frame header detection device of the IFF mode five signals.
The invention firstly carries out phase alignment on the received leading pulse sequence and two paths of in-phase and quadrature reference leading pulse sequences generated locally, then carries out correlation processing to obtain two paths of correlation signals, calculates the time domain correlation accumulation envelope of the two paths of correlation signals, carries out autocorrelation calculation on the pulse signals to obtain detection judgment quantity, finally judges the leading pulse sequence according to the detection judgment quantity and a preset threshold value to obtain a plurality of pulse correlation peaks, and confirms that the leading pulse sequence is detected according to the interval and the number of the maximum correlation peak of the pulse signals, thereby achieving the aim of detecting and searching the frame head of the five signals in the IFF mode, not only effectively improving the accuracy rate of acquiring the pulse position of the leading data, but also still being capable of realizing effective detection in the signal-to-noise ratio environment of 8dB, greatly reducing the demodulation error rate of the five signals in the mode, and being capable of reducing the demodulation error rate to 5e-4.
The invention has the beneficial effects that:
1. the frame head detection method can realize effective detection under the conditions of signal overlapping and low signal-to-noise ratio, and can reduce the demodulation error rate of five signals in the IFF mode.
2. Compared with the mode of firstly determining the correlation peak and calculating the correlation value amplitude and then carrying out threshold judgment in the prior art, the method and the device can effectively detect and search the position of the preamble pulse and improve the detection efficiency and accuracy by confirming the maximum correlation peak of the preamble pulse in a mode that the detection judgment quantity is larger than the preset threshold value and the maximum detection judgment quantity is obtained.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
Fig. 1 is a flowchart of a frame header detection method of an IFF mode five signal according to an embodiment of the present invention;
FIG. 2 is a diagram of an IFF mode five-signal specification according to an embodiment of the present invention, wherein 2A is a diagram of an IFF mode five-query signal specification, 2B is a diagram of an IFF mode five-response signal_lever1 specification, and 2C is a diagram of an IFF mode five-response signal_lever2 specification;
Fig. 3 is a schematic diagram of an IFF mode five-signal frame header detection device according to an embodiment of the present invention.
Detailed Description
Embodiments of the invention are described in detail below with reference to the attached drawings, but the invention can be implemented in a number of different ways, which are defined and covered by the claims.
As shown in fig. 1, a method for detecting a frame header of an IFF mode five signal includes the following steps:
S01, carrying out correlation processing on the received pulse signals and the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence which are generated locally respectively to obtain two paths of correlation signals.
S101, receiving a pulse signal, wherein the pulse signal is a time-varying phase modulation signal, and the time-varying phase modulation process of the pulse signal is as follows: first, a plurality of symbols a k are integrated and multiplied by a fixed constantObtaining a first integration result; secondly, multiplying the sequence number value of the last code element by the symbol width, and dividing the difference between the product and the current time value by the symbol width to obtain a second symbol width; finally, the last code element is multiplied by the width of the second code element and the fixed constant, and the product is added with the first integral result to obtain the time-varying phase. In summary of the above steps, the expression for the computation of the time-varying phase is:
(1) Where a k is the symbol, T is the symbol width, a n-1 is the last symbol, Is the second symbol width.
The received pulse signal S pre has the expression:
(2) In the method, in the process of the invention, For initial phase,/>For the timing phase, f c is the carrier frequency.
S102, locally generating two paths of in-phase and quadrature reference leading pulse sequences, wherein the expression is as follows:
(3) In the formula (I) and (4), For time-varying phase, f c is the carrier frequency.
S103, multiplying the received pulse signals with two paths of reference leading pulse sequences respectively, and integrating the integrated length into a plurality of symbol widths to obtain two paths of related signals, wherein the expressions of the two paths of related signals are as follows:
(5) In the formulas (1) and (6), a is the signal amplitude.
S02, calculating time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a time domain correlation accumulation envelope value and a detection decision quantity; step S02 may be specifically divided into the following steps:
s201, respectively squaring and then adding the two paths of related signals to obtain a time domain related accumulated envelope value M 1 of the two paths of related signals, wherein the expression is as follows:
S202, squaring the pulse signal, integrating by taking a plurality of symbol widths as integration lengths, and dividing by the plurality of symbol widths to obtain an autocorrelation value M 2 of the pulse signal; the expression of the autocorrelation value M 2 is as follows:
(8) In the method, in the process of the invention, Is the timing phase, f c is the carrier frequency,/>R is the symbol width for the initial phase;
S203, calculating the ratio between the time domain correlation accumulated envelope value M 1 and the autocorrelation value M 2 Then multiplying the ratio by a noise-free correlation coefficient, wherein in the embodiment, the noise-free correlation coefficient is 2, so as to obtain a detection decision quantity/>Specifically, the noise-free correlation coefficient is calculated as follows:
S2031, under the condition of no noise, when the phases of the received pulse signals and the phases of two paths of locally generated reference leading pulse sequences are completely aligned, respectively squaring and then adding the two paths of related signals to finally obtain the product of the square of the signal amplitude and the first related coefficient, wherein the product is a second time domain related accumulated envelope value; specifically, when the phases of the received pulse signals are completely aligned with the phases of the two locally generated correlated signals, respectively, the second time domain correlation accumulated envelope value is calculated as follows:
(9) Wherein I accum2 and Q accum2 are two paths of correlation signals under the condition of no noise influence, and the first correlation coefficient calculated by the embodiment is A is the signal amplitude, so the second time domain correlation accumulated envelope value is/>
S2032, under the condition of no noise, performing integration of a plurality of symbol widths after squaring a pulse signal, dividing the pulse signal by the plurality of symbol widths, and finally obtaining a product of the square of the signal amplitude and a second correlation coefficient, wherein the product is a second autocorrelation value; the specific calculation process is that the calculation formula of the second autocorrelation value is as follows:
(10) In this embodiment, the calculated second correlation coefficient is A is the signal amplitude, so the second autocorrelation value is/>
S2033, calculating the ratio between the second time domain correlation accumulated envelope value and the second autocorrelation value to obtain a noise-free correlation coefficientIn this embodiment, the calculated noise-free correlation coefficient is 2.
S03, judging a time correlation accumulation envelope value according to a detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of a pulse signal, and then confirming the frame head of the detected IFF mode five signals according to the time interval and the number of the maximum correlation peak of the pulse signal, wherein the method specifically comprises the following steps:
s301, acquiring a detection judgment quantity and presetting a threshold value, comparing the detection judgment quantity with the threshold value, and confirming that a maximum correlation peak of a pulse signal is detected under the condition that the detection judgment quantity is larger than the preset threshold value and the maximum value of the detection judgment quantity is acquired; specifically, in this embodiment, the detection decision amount is The preset threshold value is 0.6; when the detection decision quantity is detected by the threshold, if the detection decision quantity is larger than a preset threshold value, recording the detection decision quantity exceeding the threshold; and if the maximum value of the detection judgment quantity is selected from the detection judgment quantity which continuously exceeds the threshold for a plurality of times, confirming that the maximum correlation peak of the pulse signal is detected.
S302, acquiring the number and time interval of the detected maximum correlation peaks of the continuous pulse signals, and confirming that the leading pulse sequence of the IFF mode five signals is detected under the condition that the number and time interval of the maximum correlation peaks of the pulse signals meet the signal specification.
Specifically, the signal specifications are a mode 5 interrogation signal pulse structure, a mode 5 reply signal_lever1 pulse structure, and a mode 5 reply signal_lever2 pulse structure; for example, as shown in fig. 2, in the pattern 5 interrogation signal pulse structure, the four preceding pulses P1 to P4 are synchronous pulses, L1/L2 is a sidelobe suppression pulse, D1 to D11 are data pulses, the interval of the four preceding synchronous pulses is variable, and the variation amounts S1 to S3 are determined by data provided by an encryptor; the width of each pulse is 1us, the code element rate is 16Mbps, and the 16bit of the first four synchronous pulses is fixed to 0111100010001001; in the mode 5 response signal_lev1 pulse structure, the front P1 pulse and the front P2 pulse are synchronous pulses, the pulse width is 1us, the rear 9us long pulse is a data pulse, the interval between the synchronous pulses P1 and P2 is a variable, and the range is 0-1.875 us; in the mode 5 response signal_lev2 pulse structure, four sync pulses P1 to P4 (pulse width of 1 us), 1 long data pulse (pulse width of 33 us), and the first four sync pulses have a content identical to that of the interrogation signal fixed to 0111100010001001.
In this embodiment, according to the pattern 5 interrogation signal pulse structure, if the number of detected consecutive preamble pulse correlation peaks matches the four preceding synchronization pulses P1 to P4 in the pattern 5 interrogation signal pulse structure and the time interval of the preamble pulse correlation peaks matches the time interval data of the four synchronization pulses in the pattern 5 interrogation signal, it can be determined that the preamble pulse sequence of the IFF pattern five interrogation signal, that is, the frame header of the IFF pattern five interrogation signal has been detected.
If the number of detected continuous leading pulse correlation peaks accords with the interval data of the two P1 to P2 synchronous pulses in the mode 5 response signal_lever1 pulse structure and the interval of the leading pulse correlation peaks accords with the two synchronous pulses in the mode 5 response signal_lever1 pulse structure, the leading pulse sequence of the detected IFF mode five response signal_lever1 pulse, namely the frame head of the IFF mode five response signal, can be judged.
If the number of detected continuous front pulse correlation peaks accords with four synchronization pulses from P1 to P4 in the mode 5 response signal_lever2 pulse structure and the interval of the front pulse correlation peaks accords with interval data of four synchronization pulses in the mode 5 response signal_lever2 pulse structure, the front pulse sequence of the detected IFF mode five response signal_lever2 pulse, namely the frame head of the IFF mode five response signal, can be judged.
The frame header detection method of five signals in the IFF mode includes the steps of firstly, carrying out phase alignment on a preamble pulse sequence and a local reference preamble pulse sequence, then carrying out correlation processing to obtain two paths of correlation signals, then carrying out time domain correlation accumulation envelope calculation of the two paths of correlation signals and carrying out autocorrelation calculation on the preamble pulse sequence to obtain a detection judgment quantity, and finally judging the preamble pulse sequence according to the detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of the pulse signal; finally, according to the number and time interval of the maximum correlation peaks of the pulse signals and according to the specification of the mode 5 signals, whether the leading pulse sequence of the five signals of the IFF mode is detected is confirmed, so that the purposes of frame head detection of the five signals of the IFF mode and bit synchronization of the five signals of the IFF mode are achieved; by the frame header detection method, the accuracy of acquiring the position of the front-end data pulse is effectively improved, and the error rate of IFF mode five signals is reduced to 5e-4 in an 8dB signal-to-noise ratio environment, so that compared with the prior art, the demodulation error rate is greatly reduced.
The embodiment of the invention also provides a frame head detection device of the IFF mode five signals, which comprises:
The first correlation processing module is used for performing correlation processing on the received pulse signals and the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence which are generated locally respectively to obtain two paths of correlation signals; the second correlation processing module is in communication connection with the first correlation processing module and is used for calculating time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a time domain correlation accumulation envelope value and a detection judgment quantity; the detection judgment module is in communication connection with the second correlation processing module and is used for judging the time-correlated accumulation envelope value according to the detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of the pulse signal, and then confirming the frame head of the detected IFF mode five signals according to the time interval and the number of the maximum correlation peak of the pulse signal.
The first correlation processing module includes: the modulating unit is used for receiving a pulse signal, wherein the pulse signal is a time-varying phase modulating signal; the local signal generating unit is in communication connection with the modulating unit and is used for locally generating two paths of reference leading pulse sequences with the initial phase and the modulated time-varying phase as phase information; the first correlation processing unit is in communication connection with the local signal generating unit and is used for multiplying pulse signals with two paths of reference leading pulse sequences respectively and then integrating the pulse signals with integration lengths being a plurality of symbol widths to obtain two paths of correlation signals.
The second correlation processing module includes: the second correlation processing unit is used for respectively squaring and then adding the two paths of correlation signals to obtain time domain correlation accumulated envelope values of the two paths of correlation signals; the third correlation processing unit is in communication connection with the second correlation processing unit and is used for squaring the pulse signal, then integrating the pulse signal by taking a plurality of symbol widths as integration lengths and finally dividing the pulse signal by the plurality of symbol widths to obtain an autocorrelation value of the pulse signal; the detection decision calculating unit is in communication connection with the third correlation processing unit and is used for calculating the ratio between the time domain correlation accumulated envelope value and the autocorrelation value, and then multiplying the ratio by the noiseless correlation coefficient to obtain the detection decision.
The detection judgment module comprises: the pulse correlation peak confirming unit is used for acquiring the detection judgment quantity and presetting a threshold value, comparing the detection judgment quantity with the threshold value, and confirming that the maximum correlation peak of the pulse signal is detected under the condition that the detection judgment quantity is larger than the preset threshold value and the maximum value of the detection judgment quantity is acquired; the pulse frame head confirming unit is in communication connection with the pulse correlation peak confirming unit and is used for acquiring the number and time interval of the detected continuous pulse signal maximum correlation peak, and if the number and time interval of the pulse signal maximum correlation peak meet the signal specification, the leading pulse sequence of the IFF mode five signals is confirmed to be detected.
The embodiment of the invention also provides a signal receiver which comprises the frame header detection device of the IFF mode five signals.
The frame header detection device and the signal receiver in the embodiments of the present invention are the same technical concept as the frame header detection method, and have the same technical effects, and are not described here again.
Claims (8)
1. A method for detecting a frame header of an IFF mode five signal, the method comprising the steps of:
the received pulse signals are respectively correlated with the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence which are generated locally, so that two paths of correlated signals are obtained;
calculating time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a time domain correlation accumulation envelope value and a detection decision quantity;
Judging the time correlation accumulation envelope value according to the detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of the pulse signal, and then confirming the frame head of the detected IFF mode five signal according to the time interval and the number of the maximum correlation peak of the pulse signal;
the method comprises the steps of carrying out correlation processing on a received pulse signal and a locally generated in-phase reference leading pulse sequence and a locally generated quadrature reference leading pulse sequence respectively, and specifically comprises the following steps:
Receiving a pulse signal, wherein the pulse signal is a time-varying phase modulation signal;
Locally generating two reference preamble pulse sequences with phase information being an initial phase and a modulated time-varying phase, the two reference preamble pulse sequences comprising an in-phase reference preamble pulse sequence and a quadrature reference preamble pulse sequence;
Wherein, the time-varying phase modulation of the pulse signal specifically comprises:
integrating the plurality of code elements and multiplying the integrated code elements by a fixed constant to obtain a first integration result;
Multiplying the sequence number value of the last code element by the symbol width, dividing the difference between the product and the current time value by the symbol width to obtain a second symbol width;
and multiplying the last code element, the second code element width and a fixed constant, and adding the product of the multiplying and the first integral result to obtain the time-varying phase of the pulse signal at any time.
2. The frame header detection method of five signals in IFF mode according to claim 1, wherein the correlation processing is performed on the received pulse signal with the locally generated in-phase reference preamble pulse sequence and the quadrature reference preamble pulse sequence, respectively, to obtain two paths of correlation signals, and specifically comprising:
and multiplying the pulse signals with two paths of reference leading pulse sequences respectively, and integrating the pulse signals with integration length being a plurality of symbol widths to obtain two paths of related signals.
3. The frame header detection method of five signals in IFF mode according to claim 2, wherein calculating a time-domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a detection decision value comprises:
The two paths of related signals are respectively squared and then added to obtain time domain related accumulated envelope values of the two paths of related signals;
After square the pulse signal, integrating with a plurality of symbol widths as integration length, and finally dividing by the plurality of symbol widths to obtain an autocorrelation value of the pulse signal;
and calculating the ratio between the time domain correlation accumulation envelope value and the autocorrelation value, and multiplying the ratio by the noiseless correlation coefficient to obtain the detection decision quantity.
4. A method for detecting a frame header of an IFF mode five signal as claimed in claim 3, in which the calculation of the noiseless correlation coefficient comprises:
Under the condition of no noise, the square of the two paths of related signals is respectively carried out and then added, and finally, the product of the square of the signal amplitude and the first related coefficient is obtained, and the product is a second time domain related accumulated envelope value;
Under the condition of no noise, the square of the signal amplitude is multiplied by a second correlation coefficient, and the product is a second autocorrelation value, wherein the product is obtained by integrating a plurality of symbol widths after the square of the pulse signal and dividing the pulse signal by the plurality of symbol widths;
And calculating the ratio between the second time domain correlation accumulated envelope value and the second autocorrelation value to obtain a noise-free correlation coefficient.
5. The method for detecting a frame header of five signals in an IFF mode according to claim 4, wherein the determining the accumulated envelope value of the time correlation according to the detection decision amount and the preset threshold value, obtains the maximum correlation peak of the pulse signal, and then confirms the frame header of five signals in the IFF mode according to the time interval and the number of the maximum correlation peak of the pulse signal, specifically comprising:
acquiring a detection judgment quantity and presetting a threshold value, comparing the detection judgment quantity with the threshold value, and confirming that the maximum correlation peak of the pulse signal is detected under the condition that the detection judgment quantity is larger than the preset threshold value and the maximum value of the detection judgment quantity is acquired;
And acquiring the number and time interval of the detected maximum correlation peaks of the continuous pulse signals, and confirming that the leading pulse sequence of the IFF mode five signals is detected under the condition that the number and time interval of the maximum correlation peaks of the pulse signals meet the signal specification.
6. An IFF mode five-signal frame header detection apparatus, comprising:
the first correlation processing module is used for performing correlation processing on the received pulse signals and the in-phase reference leading pulse sequence and the quadrature reference leading pulse sequence which are generated locally respectively to obtain two paths of correlation signals;
the second correlation processing module is in communication connection with the first correlation processing module and is used for calculating time domain correlation accumulation envelope of two paths of correlation signals and performing autocorrelation calculation on pulse signals to obtain a time domain correlation accumulation envelope value and a detection judgment quantity;
The detection judgment module is in communication connection with the second correlation processing module and is used for judging the time-correlated accumulation envelope value according to the detection judgment quantity and a preset threshold value to obtain a maximum correlation peak of the pulse signal, and then confirming the frame head of the detected IFF mode five signals according to the time interval and the number of the maximum correlation peak of the pulse signal; wherein the first correlation processing module comprises:
A modulation unit for receiving a pulse signal, the pulse signal being a time-varying phase modulation signal;
The local signal generating unit is in communication connection with the modulating unit and is used for locally generating two paths of reference leading pulse sequences with the initial phase and the modulated time-varying phase as phase information;
the first correlation processing unit is in communication connection with the local signal generating unit and is used for multiplying the pulse signals with two paths of reference leading pulse sequences respectively and then integrating the pulse signals with integration lengths being a plurality of symbol widths to obtain two paths of correlation signals;
Wherein, the time-varying phase modulation of the pulse signal specifically comprises:
integrating the plurality of code elements and multiplying the integrated code elements by a fixed constant to obtain a first integration result;
Multiplying the sequence number value of the last code element by the symbol width, dividing the difference between the product and the current time value by the symbol width to obtain a second symbol width;
and multiplying the last code element, the second code element width and a fixed constant, and adding the product of the multiplying and the first integral result to obtain the time-varying phase of the pulse signal at any time.
7. The frame header detection apparatus of claim 6, wherein said second correlation processing module comprises:
the second correlation processing unit is used for respectively squaring and then adding the two paths of correlation signals to obtain time domain correlation accumulated envelope values of the two paths of correlation signals;
The third correlation processing unit is in communication connection with the second correlation processing unit and is used for squaring the pulse signal, then integrating the pulse signal by taking a plurality of symbol widths as integration lengths and finally dividing the pulse signal by the plurality of symbol widths to obtain an autocorrelation value of the pulse signal;
the detection decision amount calculating unit is in communication connection with the third correlation processing unit and is used for calculating the ratio between the time domain correlation accumulated envelope value and the autocorrelation value, and then multiplying the ratio by the noiseless correlation coefficient to obtain a detection decision amount;
the detection judgment module comprises:
The pulse correlation peak confirming unit is used for acquiring the detection judgment quantity and presetting a threshold value, comparing the detection judgment quantity with the threshold value, and confirming that the maximum correlation peak of the pulse signal is detected under the condition that the detection judgment quantity is larger than the preset threshold value and the maximum value of the detection judgment quantity is acquired;
The pulse frame head confirming unit is in communication connection with the pulse correlation peak confirming unit and is used for acquiring the number and time interval of the detected continuous pulse signal maximum correlation peak, and if the number and time interval of the pulse signal maximum correlation peak meet the signal specification, the leading pulse sequence of the IFF mode five signals is confirmed to be detected.
8. A signal receiver comprising the IFF mode five signal frame header detection arrangement of any one of claims 6 to 7.
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