CN110519003A - A kind of unmanned plane uplink and downlink communication link recognition based on signal characteristic difference - Google Patents
A kind of unmanned plane uplink and downlink communication link recognition based on signal characteristic difference Download PDFInfo
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Abstract
The present invention discloses a kind of unmanned plane uplink and downlink communication link recognition based on signal characteristic difference comprising following sequential steps: the antenna of broadband receiver receives electromagnetic wave signal, amplifies, filters, being mixed and IF process；Treated signal carries out carrier frequency measurement, carries out pulse detection, the pulse repetition period of measuring signal and pulse width parameter in conjunction with narrow-band filtering, with carry out unmanned plane signal whether there is or not anticipation；According to carrier frequency, pulse repetition period and width parameter that measurement obtains, unmanned plane signal can be judged whether there is；If judging, no unmanned plane signal is returned to previous step and continues to test, if tentatively determining whether man-machine signal, detects judgement with regard to the uplink and downlink signals carried out in next step；The uplink signal and downlink signal of unmanned plane are distinguished according to the bandwidth of unmanned plane signal and frequency hopping rate.Concealment of the present invention is strong, does not generate interference, being capable of round-the-clock, all weather operations.
Description
Technical field
The present invention relates to electronic countermeasure technology fields, above and below a kind of unmanned plane based on signal characteristic difference
Row communication link recognition methods.
Background technique
In recent years, the technological break-through along with unmanned plane on low latitude and miniaturization, all kinds of civilian unmanned planes are in the world
Development upsurge is started in range.Unmanned plane is in logistics transportation, geologic prospect, movies-making, agrisilviculture, patrol monitoring, emergency
The application demand rapid growth of rescue etc., attracts more and more science-and-technology enterprises to participate in emerging unmanned plane industry.With
This simultaneously, consumer level civil micro unmanned plane, due to its is easy to operate, price is human-oriented, feeling of freshness and entertainment it is strong the features such as, it is general
All over for it is big it is well-established with pursue, it is growing day by day to buy user.In future, inevitable more wide, the city of the application field of unmanned plane
Field can not estimate.
However as the development of industry, accident relevant to unmanned plane is also frequently occurred among the visual field of people.2017
In April in year, Chengdu airport half a month, interior several unmanned planes of generation interfered flight events, caused society and discussed warmly；2015, U.S.'s law enforcement
Department finds that a frame unmanned plane swarms into the White House；In addition, there is the phenomenon that carrying out criminal activity using unmanned plane in foreign countries, it is above each
The behavior of the improper operation unmanned plane of kind belongs to " black to fly " in itself." black fly " unmanned plane caused various circles of society's concern and
Worry, the demand effectively managed to it are very urgent.However, China relatively lags behind in management unmanned plane industry, mainly
Be embodied in: operator lacks the training of system, and the development of specification unmanned plane, sale, the relevant law that uses are perfect not to the utmost, detection prison
It is immature to control management technical means.
In face of " black fly " unmanned plane, not only specification is set, policies accomplish " not allowing winged ", it will also be on technological layer
It studies anti-means and realizes " dare not fly ".Unmanned plane is broken through, high-power electromagnetic interference is relied primarily at present and destroys nothing
Man-machine communication link.The communication link of unmanned plane includes uplink and downlink, wherein uplink signal is mainly used
It is transmitted in information such as flight control instructions, down link signal is mainly used for the information such as drone status parameter, video image biography
It is defeated.For the military unmanned air vehicle of high threat level, the working frequency of uplink and downlink link is inconsistent.It is breaking through
During unmanned plane, the emphasis of high-power electromagnetic interference is the control instruction signal of uplink, threatens people to cut off
Operation and control of the member to unmanned plane.If cannot the working frequency points of uplink be carried out with accurately frequency sweep compacting interference, arrive
Up to unmanned plane electromagnetic interference signal equivalent radiation power with regard to inadequate, can not just play counter unmanned plane effect.Therefore, needle
To the technological means of electromagnetism compacting interference, most primary problem is exactly the uplink and downlink link signal for perceiving unmanned plane, and area
Divide uplink and downlink link.
Currently, carrying out the technical method of Detection location to unmanned plane mainly includes active radar detection localization method, photoelectricity
Recognition and tracking method, passive acoustics detectiona localization method are detected, the radar target that above-mentioned each method passes through sensorcraft respectively returns
The sound that wave, unmanned plane Infrared Image Features, unmanned plane motor issue is detected, and unmanned plane can not be detected and determine
Uplink and downlink signal, therefore have no idea accurately to guide high-power electromagnetic interference counter unmanned plane, can only can according to unmanned plane
Workable 5~6 frequency dot cycles transmitting, while electromagnetic interference is carried out, therefore interfering signal power is difficult to concentrate, interference is anti-
The effect is unsatisfactory for system.
Summary of the invention
To solve the above problems, the object of the present invention is to provide a kind of unmanned plane uplink and downlinks based on signal characteristic difference to lead to
Believe link recognition, small drone uplink and downlink communication chain under the conditions of non-cooperating is identified using radio detection means
Road guides accurate interference, blocks the unmanned aerial vehicle (UAV) control signal of uplink, provides condition for next step unmanned plane adapter tube；Above-mentioned
Small drone refers to not providing the noncooperative target of identity information, unknown transmission information under non-cooperating condition of acceptance.
For achieving the above object, the present invention adopts the following technical scheme:
A kind of unmanned plane uplink and downlink communication link recognition based on signal characteristic difference comprising following steps:
S1, broadband receiver antenna receive electromagnetic wave signal, amplify, filter, being mixed and IF process；
S2, carrier frequency CF measurement is carried out to step S1 treated signal, carries out pulse detection in conjunction with narrow-band filtering, surveys
Measure signal pulse repetition period PRI and pulse width PW parameter, with carry out unmanned plane signal whether there is or not anticipation；
S3, determine whether unmanned plane signal
Carrier frequency CF, the pulse repetition period PRI and pulse width PW parameter obtained according to step S2 measurement, can
Judge whether there is unmanned plane signal；If judging, no unmanned plane signal is returned to step S2 and continues to test, if tentatively determining whether
Man-machine signal detects judgement with regard to the uplink and downlink signals carried out in step S4；
S4, uplink and downlink signals detection judgement is carried out to unmanned plane signal
After identifying unmanned plane signal, bandwidth and frequency hopping rate to the unmanned plane signal carry out precise measurement and estimate
Meter；
Firstly, accurately estimating the bandwidth of signal, perform the following operation:
1) power spectrum is sought
The data x (n) (n=0,1, L, N-1) for being N by length, is divided into L sections, and every section has M data, and wherein L is not to be overlapped
When each data segment length, L=N/M, the i-th segment data xi(n)=x (n+iM-M) is then added to window function ω (n) each
On data segment, each section of cyclic graph, i-th section of cyclic graph are found out
In formula, U is normalization factor,
Will be approximate irrelevant between each section of cyclic graph, last power Spectral Estimation is
2) wavelet decomposition obtains smooth power spectrum
Wavelet decomposition is carried out to the power spectrum that estimates, is partially separated by the detail section of signal and roughly, then extract slightly
It omits the coefficient of part and power spectrum is reconstructed with this coefficient, eliminate the high frequency detail in power spectrum waveform, obtain smooth waveform；
3) the mobile covariance of smooth power spectrum is calculated
After obtaining smooth power spectrum, the starting point and ending point of passband is extracted to estimate bandwidth；Calculate mobile covariance:
R (k, k+1)=cov (d (k), d (k+1))
(k=1,2, L, N-1) (15)
In formula: d (k) is the reconstruction coefficients that rough part is extracted after wavelet decomposition, and the formula is utilized to traverse all data
Point, what is found out is the mobile covariance between arbitrary neighborhood point；When every p, value can just change, so using
Following formula calculates
In formula, k=1,1+p, L, N-p, the selection of p value, as p=1, are equivalent to by determining the characteristics of actual data point
Formula；
4) estimate bandwidth
The position a and b where maximum 2 mobile covariance values are extracted, and is regarded as the starting point of bandwidth respectively
And cut off, by difference | b-a-1 | as estimation bandwidth；
Cycle-index is set, is repeated the above steps 1)~4 to the L section for the data that length is N), L bandwidth is calculated, then ask
It is average, find out the assembly average of estimation bandwidth, as the precise bandwidth estimated value of unmanned plane signal；
Then, accurately estimate frequency hopping rate, perform the following operation: analyzing signal using Short Time Fourier Transform, obtain at that time
Frequency indicates, recycles wavelet transformation to extract the side information of the time-frequency representation, and then estimate frequency hopping rate using spectrum analysis.
Further, in above-mentioned step S2, the method for unmanned plane signal detection anticipation includes the following steps:
S2a, carrier frequency CF estimation
Rough estimate first is carried out to signal carrier frequency using spectrum peak detection calculations, determines frequency range；Then it recycles
ZFFT further refines frequency spectrum；Finally " fence effect " bring frequency deviation is eliminated using quadratic interpolattion；
To step S1 treated signal, the presence or absence of carrier wave is judged by Threshold detection first, and rough estimate peak value
Position；With xnUnmanned plane baseband signal is represented, if unmanned plane signal sequence to be estimated is
Wherein, A0WithThe respectively amplitude and first phase of carrier signal, if A0=1,f0And fsRespectively wait estimate
The carrier frequency and data sampling rate of signal, N are number of sampling points, and r (n) is white Gaussian noise, if its variance is δr；
Firstly, carrying out FFT transform to signal, it is as follows to obtain its frequency spectrum:
X (k)=FFT { x (n) }, k=0,1 ... N-1 (2)
Then, the ratio for calculating each frequency point signal strength and its neighborhood frequency point signal strength mean value is as follows:
Wherein
M is left and right adjoint point number, if above-mentioned ratio qjMore than setting threshold T, then be determined with carrier signal presence, then with
This value of frequency point and its adjacent time big value of frequency point are reference carrier frequency；If this frequency point and its adjacent time big frequency point respective frequencies difference
For f1 and f2, if f1 < f2, then have | f1-f2|=fs/N；[f1, f2] is signal(-) carrier frequency range to be estimated；
S2b, ultra-narrow low-pass filtering is carried out, specific treatment process is as follows:
Obtaining frequency range by FFT operation is [f1, f2], and the local oscillator complex signal frequency for calculating multiple modulation frequency displacement is
It is obtained shown in frequency shift signal such as formula (6) through multiple modulation, primary frequency feMoved zero-frequency, then at this time former frequency point f1,
F2 is located at zero-frequency two sides and symmetrical about zero-frequency；
Low-pass filtering is carried out to signal using integral operation, in combination with data pick-up, sums to data sectional, takes each section
Data mean value composition extracts signal sequence；If extraction yield is D, the mode of extraction is to take the mean value of D data point as extraction knot
Fruit by way of being segmented summation and taking mean value while realizing low-pass filtering and data pick-up；Signal sampling rate becomes f ' after extractions
=fs/ D, filtering extraction result are as follows:
Finally, envelope detection and pulse detection
After obtaining signal(-) carrier frequency, corresponding signal extraction is come out by envelope detection method, to realize pulse detection
And parameter measurement；The step of envelope detection, is similar with front, i.e., signal is first downconverted to zero intermediate frequency, then passes through segmentation summation
It takes the mode of mean value while realizing low-pass filtering and data pick-up, realize that narrow-band filtering and data volume reduce；I.e. by f in formula (5)e
It changes into
Then repetitive (6)) and the step of formula (7), if obtained result is expressed as x2(n), envelope is taken to it, i.e., to x2
(n) modulus obtains x3(n)=| x2(n)|；
S2c, pulse detection is carried out to envelope waveform and measures related parameter values
Pulse detection is mainly that the detection of rising edge and failing edge is carried out to envelope waveform, using dynamic threshold detection method,
Using the intersection point of envelope and thresholding as rising edge or failing edge；Envelope signal is first divided into M segment signal, Mei Yiduan by dynamic threshold method
Signal is x4m(n), signal is divided into multiple uniform windows by m=1 ..., M, seek the part of signal in each window most
Big value xmax(m)=max (x4m(n)), then generating corresponding thresholding is gm=α xmax(m)；
It is respectively n that the pulse up and down obtained in one-time detection time width, which are located at, along positionupAnd ndown, rise in pulsewidth
Edge and failing edge obtain up and down along position by the way of linear fit interpolation；Specific algorithm is as follows:
Wherein, tup、tdownRespectively rising edge, failing edge correspond to time, BdFor the bandwidth after filtering extraction；Need root
The case where according to pulsewidth negative value, carries out displacement adjustment to rising edge or failing edge；Judge KupA rising edge and KdownA decline
After, the time difference between adjacent rising edges or failing edge is the pulse repetition period, i.e.,
PRI=tup(k+1)-tup(k), k=1,2 ..., K (10)
The failing edge time of pairing is subtracted into rising time, pulsewidth can be obtained, i.e.,
PW=tdown(k)-tup(k), k=1,2 ..., K (11)
In addition, the rising edge of each pulse can be used as its arrival time；
It, can be according to measured signal(-) carrier frequency CF and pulse repetition period after estimating pulse relevant parameter
PRI and pulsewidth PW parameter, are identified and are extracted to unmanned plane signal.
Further, in above-mentioned step S4, accurate the step of estimating frequency hopping rate, is as follows:
1) the Short Time Fourier Transform STFT for receiving signal x (t) is calculatedx；
First assume hop rate estimationIt is to receive the time-frequency representation formula of signal Short Time Fourier Transform known to priori:
Wherein, h (τ-t) is window function, is 1 in (τ-t) ∈ [- Δ/2, Δ/2], other are 0, are set asWith
Ensure at most there is a frequency hopping in the time zone of window function covering；
2) STFT is extractedxTime-frequency crestal line fx(t)；
Secondary treatment is carried out for the time-frequency representation to FH signal, needs to extract its time-frequency crestal line, such as formula (18):
3) f is calculatedx(t) wavelet transformation W (a, t)；
Using wavelet transformation
Wherein, a is scale parameter；It is Haar small echo；
Set the width Delta that scale a is equal to time frequency window, it is ensured that at most have one within the scope of the cover time of wavelet function
Frequency hopping；
4) the amplitude sequence Abs [W (a, t)] of W (a, t) is calculated；
The amplitude sequence Abs [W (a, t)] of W (a, t) is calculated, which is a pseudo-random sequence, i.e. frequency hopping
Occur in nTH(the n ∈ Z) moment；
5) the Fourier transformation FFT of Abs [W (a, t)] is calculated；
6) interval of detection spectrum spike, the interval are the estimation of corresponding hop rate: the wavelet transformation amplitude sequence of time-frequency crestal line
There are discrete spectral lines at hop rate position, can be achieved with the accurate estimation of hop rate by detecting the discrete spectral line.
A kind of unmanned plane uplink and downlink communication link identification device based on signal characteristic difference comprising for receiving electromagnetism
Wave signal simultaneously amplifies signal, filters, being mixed and the broadband receiver of IF process；For at through broadband receiver
Signal after reason carries out carrier frequency CF estimation, pulse detection carried out in conjunction with narrow-band filtering, the pulse repetition period PRI of signal and
The unmanned plane signal detection of pulse width PW parameter measurement prejudges module；For the pulse repetition period PRI to unmanned plane signal
And the unmanned plane signal identification module that pulse width PW parameter is identified；For the bandwidth and frequency hopping rate progress to unmanned plane
Precise measurement and the uplink and downlink signals of estimation detect judgment module.
Due to the adoption of the technical scheme as described above, the present invention has the following advantages:
The unmanned plane uplink and downlink communication link recognition based on signal characteristic difference, uses radio detection technology
To identify unmanned plane uplink, downstream communications link under the conditions of non-cooperating, radio detection technology non-radiating electromagnetic signal, signal biography
Defeated wave-path is the half of radar detection, therefore possesses farther detection range；Radio detection does not emit electromagnetic wave actively, hidden
Covering property is strong, do not generate interference, can round-the-clock, all weather operations, while it is lower compared to active detection method cost；Firstly,
According to unmanned plane signal, there are certain inherent features in time domain and frequency domain, have differences judgement with the other interference signals of same frequency range
Unmanned plane signal whether there is, and then, further according to the feature difference of unmanned plane uplink and downlink link signal, identify uplink and downlink
Link, and the frequency range of uplink and downlink signal is measured, and then advantage power can be concentrated targetedly on unmanned plane
Downlink signal carries out compacting interference.Small drone refers to slipping into military area, test place, command post and security areas
Wait military-civil unmanned vehicle, the wireless signal radiation source etc. of " black to fly " around critical facilities within the scope of 2km, and usual situation
Lower empty weight is no more than 15kg, and take-off weight is no more than 25kg.
Detailed description of the invention
Fig. 1 is the flow chart of the unmanned plane uplink and downlink communication link recognition the present invention is based on signal characteristic difference；
Fig. 2 is unmanned plane uplink signal waveform and spectrogram；
Fig. 3 is unmanned plane downlink signal waveform and spectrogram；
Fig. 4 is unmanned plane uplink signal time frequency distribution map；
Fig. 5 is unmanned plane downlink signal time frequency distribution map.
Specific embodiment
Technical solution of the present invention is described in further detail with reference to the accompanying drawings and examples.
As shown in Figure 1, a kind of unmanned plane uplink and downlink communication link recognition based on signal characteristic difference comprising with
Lower specific steps:
S1, broadband receiver antenna receive electromagnetic wave signal, amplify, filter, being mixed and IF process；So as to
Detection anticipation is carried out to signal in next step；
S2, carrier frequency CF measurement is carried out to step S1 treated signal, carries out pulse detection in conjunction with narrow-band filtering, surveys
Measure signal pulse repetition period PRI and pulse width PW parameter, with carry out unmanned plane signal whether there is or not anticipation；Including having as follows
Body step:
S2a, carrier frequency CF estimation
Rough estimate first is carried out to signal carrier frequency using spectrum peak detection calculations, frequency range is determined, then recycles
(ZFFT is also referred to as Zoom-FFT to ZFFT, the Fast Fourier Transform referred to as refined, also known as choosing band Fast Fourier Transform, is one
Kind complex electromagnetic parameters method) frequency spectrum is further refined, substantially reduce data volume while improving frequency resolution, most
" fence effect " bring frequency deviation is eliminated using quadratic interpolattion afterwards；
To step S1 treated signal, the presence or absence of carrier wave is judged by Threshold detection first, and rough estimate peak value
Position；With xnUnmanned plane baseband signal is represented, if unmanned plane signal sequence to be estimated is
Wherein, A0WithThe respectively amplitude and first phase of carrier signal, to simplify operation, if A0=1,f0And fs
The carrier frequency and data sampling rate of signal respectively to be estimated, N are number of sampling points, and r (n) is white Gaussian noise, if its variance
For δr；
Firstly, carrying out FFT transform to signal, it is as follows to obtain its frequency spectrum:
X (k)=FFT { x (n) }, k=0,1 ... N-1 (2)
Then, the ratio for calculating each frequency point signal strength and its neighborhood frequency point signal strength mean value is as follows:
Wherein
M generally takes the frequency range of left and right 50kHz for left and right adjoint point number to be divided into reference between practical side frequency；On if
State ratio qjMore than setting threshold T, T is 0.28~0.3, then is determined with carrier signal presence, then with this value of frequency point and its
Adjacent time big value of frequency point is reference carrier frequency；If this frequency point and its adjacent time big frequency point respective frequencies are respectively f1 and f2, if
F1 < f2, then have | f1-f2|=fs/N；Due to exist " fence effect ", the actual frequency of signal between f1 and f2, i.e., [f1,
F2] it is signal(-) carrier frequency range to be estimated；
S2b, ultra-narrow low-pass filtering is carried out, specific treatment process is as follows:
Obtaining frequency range by FFT operation is [f1, f2], and the local oscillator complex signal frequency for calculating multiple modulation frequency displacement is
It is obtained shown in frequency shift signal such as formula (6) through multiple modulation, primary frequency feMoved zero-frequency, then at this time former frequency point f1,
F2 is located at zero-frequency two sides and symmetrical about zero-frequency；
On the basis of not influencing filter effect, in order to simplify operation, improve efficiency, signal is carried out using integral operation
Low-pass filtering sums to data sectional in combination with data pick-up, and each segment data mean value composition is taken to extract signal sequence；If taking out
Taking rate is D, and the mode of extraction is to take the mean value of D data point as extraction as a result, same by way of being segmented summation and taking mean value
Shi Shixian low-pass filtering and data pick-up improve processing speed；Signal sampling rate becomes f ' after extractions=fs/ D, filtering extraction knot
Fruit is as follows:
Finally, envelope detection and pulse detection
After obtaining signal(-) carrier frequency, corresponding signal extraction is come out by envelope detection method, to realize pulse detection
And parameter measurement；The step of envelope detection, is similar with front, i.e., signal is first downconverted to zero intermediate frequency, then passes through segmentation summation
It takes the mode of mean value while realizing low-pass filtering and data pick-up, realize that narrow-band filtering and data volume reduce；I.e. by f in formula (5)e
It changes into
Then repetitive (6)) and the step of formula (7), if obtained result is expressed as x2(n), envelope is taken to it, i.e., to x2
(n) modulus obtains x3(n)=| x2(n)|；
S2c, pulse detection is carried out to envelope waveform and measures related parameter values
Pulse detection is mainly that the detection of rising edge and failing edge is carried out to envelope waveform, using dynamic threshold detection method,
Using the intersection point of envelope and thresholding as rising edge or failing edge；Envelope signal is first divided into M segment signal, Mei Yiduan by dynamic threshold method
Signal is x4m(n), signal is divided into multiple uniform windows by m=1 ..., M, seek the part of signal in each window most
Big value xmax(m)=max (x4m(n)), then generating corresponding thresholding is gm=α xmax(m), α=0.5 is generally taken；
It is respectively n that the pulse up and down obtained in one-time detection time width, which are located at, along positionupAnd ndown, in order to further
The measurement accuracy for improving pulsewidth is more accurately obtained in pulsewidth rising edge and failing edge by the way of linear fit interpolation
It rises, failing edge position；Specific algorithm is as follows:
Wherein, tup、tdownRespectively rising edge, failing edge correspond to time, BdFor the bandwidth after filtering extraction；Actually may be used
Can rising edge and failing edge pairing it is wrong, leading to pulsewidth is negative value, it is therefore desirable to the case where according to pulsewidth negative value, to rising edge or
Person's failing edge carries out displacement adjustment；Judge KupA rising edge and KdownAfter a failing edge, between adjacent rising edges or failing edge
Time difference be the pulse repetition period, i.e.,
PRI=tup(k+1)-tup(k), k=1,2 ..., K (10)
The failing edge time of pairing is subtracted into rising time, pulsewidth can be obtained, i.e.,
PW=tdown(k)-tup(k), k=1,2 ..., K (11)
In addition, the rising edge of each pulse can be used as its arrival time；
It, can be according to measured signal(-) carrier frequency CF and pulse repetition period after estimating pulse relevant parameter
PRI and pulsewidth PW parameter, are identified and are extracted to unmanned plane signal.
S3, determine whether unmanned plane signal
According to carrier frequency, pulse repetition period and width parameter that the measurement of step S1, S2 obtains, nobody can be judged whether there is
Machine signal；If judging, no unmanned plane signal is returned to step S2 and continues to test, if tentatively determining whether man-machine signal, with regard to carrying out
Uplink and downlink signals in step S4 detect judgement；
It is 14ms if there is pulse repetition period PRI, pulse width PW is 1ms, 2ms or 10ms；Spectral centroid CF is
The signal of 2.4065GHz or 5.8GHz exists, it will be able to tentatively judge that unmanned plane signal exists；
S4, uplink and downlink signals detection judgement
After identifying unmanned plane signal according to step S3, need to carry out the bandwidth and frequency hopping rate of the unmanned plane signal
Precise measurement and estimation；
Firstly, accurately estimating the bandwidth of signal, perform the following operation:
1) power spectrum is sought
The data x (n) (n=0,1, L, N-1) for being N by length, is divided into L sections, every section has M data, wherein L is not weigh
The length of each data segment, L=N/M, the i-th segment data x when foldedi(n)=x (n+iM-M), is then added to window function ω (n) often
On a data segment, each section of cyclic graph, i-th section of cyclic graph are found out
In formula, U is normalization factor,
Will be approximate irrelevant between each section of cyclic graph, last power Spectral Estimation is
2) wavelet decomposition obtains smooth power spectrum
Although there are many power spectrum smoothing that estimates above, but still include some high fdrequency components, wavelet transformation can be with
The high frequency detail in signal is extracted, so carrying out wavelet decomposition for the detail section of signal and rough portion to the power spectrum estimated
Separation, then extract the coefficient of rough part and power spectrum is reconstructed with this coefficient, so that it may eliminate the high frequency in power spectrum waveform
Details obtains smooth waveform；
3) the mobile covariance of smooth power spectrum is calculated
After obtaining smooth power spectrum, the starting point and ending point of passband need to be extracted to estimate bandwidth, calculate mobile association side
Difference:
R (k, k+1)=cov (d (k), d (k+1))
(k=1,2, L, N-1) (15)
In formula: d (k) is the reconstruction coefficients that rough part is extracted after wavelet decomposition, and the formula is utilized to traverse all data
Point, what is found out is the mobile covariance between arbitrary neighborhood point；When every p, value can just change, so using
Following formula calculates
In formula, k=1,1+p, L, N-p, the selection of p value, as p=1, are equivalent to by determining the characteristics of actual data point
Formula；
4) estimate bandwidth
The position a and b where maximum 2 mobile covariance values are extracted, and is regarded as the starting point of bandwidth respectively
And cut off, by difference | b-a-1 | as estimation bandwidth；Cycle-index is set, these steps is repeated and finds out estimation bandwidth
Assembly average, as the precise bandwidth estimated value of unmanned plane signal；
Then, accurately estimate frequency hopping rate
The estimation of frequency hopping rate needs to analyze signal using Short Time Fourier Transform, obtains its time-frequency representation, recycles small echo
The side information of the time-frequency representation is extracted in transformation, and then estimates hop rate using spectrum analysis；Detailed step is as follows:
1) the Short Time Fourier Transform STFT for receiving signal x (t) is calculatedx；
First assume hop rate estimationIt is to receive the time-frequency representation formula of signal Short Time Fourier Transform known to priori:
Wherein, h (τ-t) is window function, is 1 in (τ-t) ∈ [- Δ/2, Δ/2], other are 0, are set asWith
Ensure at most there is a frequency hopping in the time zone of window function covering；
2) STFT is extractedxTime-frequency crestal line fx(t)；
Secondary treatment is carried out for the time-frequency representation to FH signal, needs to extract its time-frequency crestal line, such as formula (18):
3) f is calculatedx(t) wavelet transformation W (a, t)；
In order to consider the identification of porch, using wavelet transformation,
Wherein, a is scale parameter；It is Haar small echo；
Set the width Delta that scale a is equal to time frequency window, it is ensured that at most have one within the scope of the cover time of wavelet function
Frequency hopping；
4) the amplitude sequence Abs [W (a, t)] of W (a, t) is calculated；
The amplitude sequence Abs [W (a, t)] of W (a, t) is calculated, which is a pseudo-random sequence, i.e. frequency hopping
Occur in nTH(the n ∈ Z) moment, and in nTH(the n ∈ Z) moment is different to establish a capital frequency hopping, the generation of jump whether be with
Machine.
5) the Fourier transformation FFT of Abs [W (a, t)] is calculated；
6) interval of detection spectrum spike, the interval are the estimation of corresponding hop rate, the wavelet transformation amplitude sequence of time-frequency crestal line
There are discrete spectral lines at hop rate position, and the accurate estimation of frequency hopping rate is achieved that by detecting the discrete spectral line.
The uplink signal and downlink letter of unmanned plane are distinguished according to signal bandwidth BW, the two characteristic quantities of frequency hopping rate HP
Number: uplink signal is uplink signal, and general bandwidth is small, is 1.2MHz~2.8MHz, pulse width, and frequency hopping, frequency hopping rate
Comparatively fast；Downlink signal band is roomy, is 9.8MHz~10.2MHz, and pulsewidth is wider, and frequency is stablized in bandwidth, and frequency hopping rate is slower.
Fig. 2 is remote signal (uplink signal) waveform and spectrogram of one of unmanned aerial vehicle example, is based on according to the present invention
The unmanned plane uplink and downlink communication link recognition of signal characteristic difference can extract the recurrent pulse characteristic of remote signal, warp
Estimation, the pulse repetition period is about 14ms, and pulse width respectively may be about 1ms and 2.17ms.
Fig. 3 is figure communication number (downlink signal) waveform and spectrogram of one of unmanned aerial vehicle example, is based on according to the present invention
The unmanned plane uplink and downlink communication link recognition of signal characteristic difference, can extract the recurrent pulse characteristic of figure communication number, nothing
Man-machine downlink signal also has apparent periodic pulse signal characteristic, and the pulse repetition period is about 14ms, and pulse width is about
10ms, spectral centroid are about 2.4065GHz.
Fig. 4, Fig. 5 are the time frequency distribution map of unmanned plane uplink signal and downlink signal respectively, are based on signal according to the present invention
The unmanned plane uplink and downlink communication link recognition of feature difference, available uplink signal time-frequency figure, it is known that its center frequency point
It is constantly jumping, and frequency hopping point is in rule variation；Unmanned plane uplink and downlink communication chain based on signal characteristic difference according to the present invention
Road recognition methods, the frequency hopping rate of uplink signal are 2.14, and the frequency hopping rate of downlink signal is 0.71, the signal band of uplink
Width is 1.2MHz, and the signal bandwidth of downlink is 10MHz.Therefore, according to the bandwidth and frequency hopping rate of signal to be estimated, flexibly
Design a decision threshold, so that it may good differentiation and identification uplink signal and downlink signal.
Invention additionally discloses a kind of unmanned plane uplink and downlink communication link identification device based on signal characteristic difference comprising
For receiving electromagnetic wave signal and amplifying, filter, be mixed and the broadband receiver of IF process to signal；For to warp
Broadband receiver treated signal carries out carrier frequency CF estimation, carries out the pulse of pulse detection, signal in conjunction with narrow-band filtering
Repetition period PRI and the unmanned plane signal detection of pulse width PW parameter measurement prejudge module；For the arteries and veins to unmanned plane signal
Rush repetition period PRI and unmanned plane signal identification module that pulse width PW parameter is identified；For the bandwidth to unmanned plane
The uplink and downlink signals for carrying out precise measurement and estimation with frequency hopping rate detect judgment module.
The foregoing is merely presently preferred embodiments of the present invention, rather than limitation of the present invention, is not departing from essence of the invention
In the case where mind and range, equivalent changes and modifications made according to the patent scope of the present invention should all belong to of the invention special
Within sharp protection scope.
Claims (4)
1. a kind of unmanned plane uplink and downlink communication link recognition based on signal characteristic difference, it is characterized in that: it includes following
Step:
S1, broadband receiver antenna receive electromagnetic wave signal, amplify, filter, being mixed and IF process；
S2, carrier frequency CF measurement is carried out to step S1 treated signal, carries out pulse detection, measurement letter in conjunction with narrow-band filtering
Number pulse repetition period PRI and pulse width PW parameter, with carry out unmanned plane signal whether there is or not anticipation；
S3, determine whether unmanned plane signal
Carrier frequency CF, the pulse repetition period PRI and pulse width PW parameter obtained according to step S2 measurement, can judge
Whether unmanned plane signal is had；If judging, no unmanned plane signal is returned to step S2 and continues to test, if tentatively determining whether man-machine
Signal detects judgement with regard to the uplink and downlink signals carried out in step S4；
S4, uplink and downlink signals detection judgement is carried out to unmanned plane signal
After identifying unmanned plane signal, bandwidth and frequency hopping rate to the unmanned plane signal carry out precise measurement and estimation；
Firstly, accurately estimating the bandwidth of signal, perform the following operation:
1) power spectrum is sought
The data x (n) (n=0,1, L, N-1) for being N by length, is divided into L sections, and every section has M data, and wherein L is every when not being overlapped
The length of a data segment, L=N/M, the i-th segment data xi(n) window function ω (n), is then added to each data by=x (n+iM-M)
Duan Shang finds out each section of cyclic graph, i-th section of cyclic graph
In formula, U is normalization factor,
Will be approximate irrelevant between each section of cyclic graph, last power Spectral Estimation is
2) wavelet decomposition obtains smooth power spectrum
Wavelet decomposition is carried out to the power spectrum that estimates, is partially separated by the detail section of signal and roughly, then extract rough portion
Point coefficient and with this coefficient reconstruct power spectrum, eliminate power spectrum waveform in high frequency detail, obtain smooth waveform；
3) the mobile covariance of smooth power spectrum is calculated
After obtaining smooth power spectrum, the starting point and ending point of passband is extracted to estimate bandwidth；Calculate mobile covariance:
R (k, k+1)=cov (d (k), d (k+1))
(k=1,2, L, N-1) (15)
In formula: d (k) is the reconstruction coefficients that rough part is extracted after wavelet decomposition, traverses all data points using the formula, asks
Out be mobile covariance between arbitrary neighborhood point；When every p, value can just change, so using following formula
It calculates
In formula, k=1,1+p, L, N-p, the selection of p value, as p=1, are equivalent to formula by determining the characteristics of actual data point；
4) estimate bandwidth
The position a and b where maximum 2 mobile covariance values are extracted, and is regarded as the starting point of bandwidth respectively and cuts
Stop, by difference | b-a-1 | as estimation bandwidth；
Cycle-index is set, is repeated the above steps 1)~4 to the L section for the data that length is N), L bandwidth is calculated, then be averaging,
Find out the assembly average of estimation bandwidth, as the precise bandwidth estimated value of unmanned plane signal；
Then, accurately estimate frequency hopping rate, perform the following operation: analyzing signal using Short Time Fourier Transform, obtain its frequency schedule
Show, recycles wavelet transformation to extract the side information of the time-frequency representation, and then estimate hop rate using spectrum analysis.
2. the unmanned plane uplink and downlink communication link recognition according to claim 1 based on signal characteristic difference, special
Sign is: in its step S2, the method for unmanned plane signal detection anticipation includes the following steps:
S2a, carrier frequency CF estimation
Rough estimate first is carried out to signal carrier frequency using spectrum peak detection calculations, determines frequency range；Then ZFFT pairs is recycled
Frequency spectrum further refines；Finally " fence effect " bring frequency deviation is eliminated using quadratic interpolattion；
To step S1 treated signal, the presence or absence of carrier wave, and the position of rough estimate peak value are judged by Threshold detection first；
With xnUnmanned plane baseband signal is represented, if unmanned plane signal sequence to be estimated is
Wherein, A0WithThe respectively amplitude and first phase of carrier signal, if A0=1,f0And fsSignal respectively to be estimated
Carrier frequency and data sampling rate, N are number of sampling points, and r (n) is white Gaussian noise, if its variance is δr；
Firstly, carrying out FFT transform to signal, it is as follows to obtain its frequency spectrum:
X (k)=FFT { x (n) }, k=0,1 ... N-1 (2)
Then, the ratio for calculating each frequency point signal strength and its neighborhood frequency point signal strength mean value is as follows:
Wherein
M is left and right adjoint point number, if above-mentioned ratio qjMore than setting threshold T, then it is determined with carrier signal presence, then with this frequency
Point value and its adjacent time big value of frequency point are reference carrier frequency；If this frequency point and its adjacent time big frequency point respective frequencies are respectively f1
And f2, if f1 < f2, then have | f1-f2|=fs/N；[f1, f2] is signal(-) carrier frequency range to be estimated；
S2b, ultra-narrow low-pass filtering is carried out, specific treatment process is as follows:
Obtaining frequency range by FFT operation is [f1, f2], and the local oscillator complex signal frequency for calculating multiple modulation frequency displacement is
It is obtained shown in frequency shift signal such as formula (6) through multiple modulation, primary frequency feZero-frequency is moved, then original frequency point f1, f2 is located at this time
Zero-frequency two sides and symmetrical about zero-frequency；
Low-pass filtering is carried out to signal using integral operation, in combination with data pick-up, sums to data sectional, takes each segment data
Mean value composition extracts signal sequence；If extraction yield is D, the mode of extraction is to take the mean value of D data point as extraction as a result, logical
Segmentation summation is crossed to take the mode of mean value while realizing low-pass filtering and data pick-up；Signal sampling rate becomes f after extractions'=fs/
D, filtering extraction result are as follows:
Finally, envelope detection and pulse detection
After obtaining signal(-) carrier frequency, corresponding signal extraction is come out by envelope detection method, to realize pulse detection and ginseng
Number measurement；The step of envelope detection, is similar with front, i.e., signal is first downconverted to zero intermediate frequency, is then taken by being segmented summation
The mode of value realizes low-pass filtering and data pick-up simultaneously, realizes that narrow-band filtering and data volume reduce；I.e. by f in formula (5)eIt changes into
Then repetitive (6)) and the step of formula (7), if obtained result is expressed as x2(n), envelope is taken to it, i.e., to x2(n) it takes
Mould obtains x3(n)=| x2(n)|；
S2c, pulse detection is carried out to envelope waveform and measures related parameter values
Pulse detection is mainly that the detection for carrying out rising edge and failing edge to envelope waveform will be wrapped using dynamic threshold detection method
The intersection point of network and thresholding is as rising edge or failing edge；Envelope signal is first divided into M segment signal, each segment signal by dynamic threshold method
For x4m(n), signal is divided into multiple uniform windows, seeks the local maximum of signal in each window by m=1 ..., M
xmax(m)=max (x4m(n)), then generating corresponding thresholding is gm=α xmax(m)；
It is respectively n that the pulse up and down obtained in one-time detection time width, which are located at, along positionupAnd ndown, in pulsewidth rising edge and
Failing edge obtains up and down along position by the way of linear fit interpolation；Specific algorithm is as follows:
Wherein, tup、tdownRespectively rising edge, failing edge correspond to time, BdFor the bandwidth after filtering extraction；It needs according to arteries and veins
The case where wide negative value, carries out displacement adjustment to rising edge or failing edge；Judge KupA rising edge and KdownAfter a failing edge,
Time difference between adjacent rising edges or failing edge is the pulse repetition period, i.e.,
PRI=tup(k+1)-tup(k), k=1,2 ..., K (10)
The failing edge time of pairing is subtracted into rising time, pulsewidth can be obtained, i.e.,
PW=tdown(k)-tup(k), k=1,2 ..., K (11)
In addition, the rising edge of each pulse can be used as its arrival time；
After estimating pulse relevant parameter, can according to measured signal(-) carrier frequency CF and pulse repetition period PRI and
Pulsewidth PW parameter is identified and is extracted to unmanned plane signal.
3. the unmanned plane uplink and downlink communication link recognition according to claim 1 based on signal characteristic difference, special
Sign is: in its step S4, accurate the step of estimating frequency hopping rate, is as follows:
1) the Short Time Fourier Transform STFT for receiving signal x (t) is calculatedx；
First assume hop rate estimationIt is to receive the time-frequency representation formula of signal Short Time Fourier Transform known to priori:
Wherein, h (τ-t) is window function, is 1 in (τ-t) ∈ [- Δ/2, Δ/2], other are 0, are set asTo ensure
At most there is a frequency hopping in the time zone of window function covering；
2) STFT is extractedxTime-frequency crestal line fx(t)；
Secondary treatment is carried out for the time-frequency representation to FH signal, needs to extract its time-frequency crestal line, such as formula (18):
3) f is calculatedx(t) wavelet transformation W (a, t)；
Using wavelet transformation
Wherein, a is scale parameter；It is Haar small echo；
Set the width Delta that scale a is equal to time frequency window, it is ensured that at most there is a frequency within the scope of the cover time of wavelet function
Jump；
4) the amplitude sequence Abs [W (a, t)] of W (a, t) is calculated；
The amplitude sequence Abs [W (a, t)] of W (a, t) is calculated, which is a pseudo-random sequence, i.e., frequency hopping occurs
In nTH(the n ∈ Z) moment；
5) the Fourier transformation FFT of Abs [W (a, t)] is calculated；
6) interval of detection spectrum spike, the interval are the estimation of corresponding hop rate: the wavelet transformation amplitude sequence of time-frequency crestal line is being jumped
There are discrete spectral lines at variable Rate position, can be achieved with the accurate estimation of hop rate by detecting the discrete spectral line.
4. a kind of implement in claims 1 to 33 on the unmanned plane based on signal characteristic difference of any claim the method
Downstream communications link identification device, it is characterized in that: it include for receive electromagnetic wave signal and signal amplified, filter,
The broadband receiver of mixing and IF process；For to through broadband receiver treated signal carry out carrier frequency CF estimation,
The unmanned plane letter of pulse detection, the pulse repetition period PRI of signal and pulse width PW parameter measurement is carried out in conjunction with narrow-band filtering
Number detection anticipation module；For the pulse repetition period PRI and the nothing that is identified of pulse width PW parameter to unmanned plane signal
Man-machine signal identification module；Uplink and downlink signals inspection for bandwidth and frequency hopping rate progress precise measurement and estimation to unmanned plane
Survey judgment module.
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