CN110336583A - A kind of quick catching device and method of Direct Sequence Spread Spectrum Signal - Google Patents
A kind of quick catching device and method of Direct Sequence Spread Spectrum Signal Download PDFInfo
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- CN110336583A CN110336583A CN201910280880.5A CN201910280880A CN110336583A CN 110336583 A CN110336583 A CN 110336583A CN 201910280880 A CN201910280880 A CN 201910280880A CN 110336583 A CN110336583 A CN 110336583A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7075—Synchronisation aspects with code phase acquisition
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/709—Correlator structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
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Abstract
The present invention provides a kind of quick catching device of Direct Sequence Spread Spectrum Signal, the digital down converter and m-sequence generator for multiplying module including a conjugate complex and being connected by two FFT correlators with two input terminals that conjugate complex multiplies module, the output end that conjugate complex multiplies module are connected with iFFT correlator, memory, FFT correlator, auto-correlation accumulation module, wave detector and judging module in turn.The present invention also provides a kind of quick capturing methods.The present invention uses FFT, and the method that secondary FFT and auto-correlation accumulation combine not will cause frequency deviation sensitivity since FFT has circumference correlation；And secondary M point FFT and simplified auto-correlation are accumulated and are used in combination, further eliminating clutter influences, and avoids the Square loss for causing accumulation；Further, since secondary M point FFT and simplified auto-correlation accumulation avoid Gaussian spectrum and are superimposed as conjugation spectrum, the later period is easy to handle so that bottom is made an uproar due to being substantially also coherent accumulation.
Description
Technical field
The invention belongs to UAV Communication technical fields, and in particular to a kind of fast Acquisition dress of Direct Sequence Spread Spectrum Signal
It sets and method.
Background technique
Unmanned plane due to its " not manned " speciality, compared to have it is man-machine have in modern Aviation field widely answer
With development prospect is inestimable.No matter in aeroplane photography, mapping, traffic monitoring, the civil fields such as Investigating, still
It is hit in fight, communication relay, the military aspect such as interference detection, unmanned plane all plays an increasingly important role.Due to
Special operations field, UAV system requirement concealed for equipment is very high, in addition to the features such as coating, noise need to reinforce
Other than hidden design, wireless communication section is also required to the characteristic for having hidden, to hide the electronic reconnaissance of enemy.
Existing UAV system generally uses between Direct Sequence Spread Spectrum Signal (DSSS) Lai Jinhang unmanned plane and earth station
Link communication.Direct Sequence Spread Spectrum Signal has the characteristics that power spectral density is low, therefore has for the angle of radio
The strong advantage of concealment, this is readily applicable under special operations background, the link communication between unmanned plane and earth station.Make in special type
It, not only will be by way of improving pseudo- bit rate, reducing transmission power in the unmanned plane Direct Sequence Spread Spectrum Communication fought under environment
The power spectral density of signal of communication is reduced, i.e., reduces the probability found by enemy from frequency domain, while also being needed prominent using short frame
The mode of hair reduces the probability being found from time-domain.
Simultaneous techniques is the key that direct sequence spread spectrum skill, simultaneous techniques and can be further divided into capture technique and
Tracking technique.Capture technique is substantially a signal detection problem, i.e. receiver detects directly under the conditions of noise background
Sequence spread spectrum signal；Tracking technique is substantially a signal estimation, i.e. receiver is accurate to estimate under the conditions of noise background
The carrier phase and code phase of the Direct Sequence Spread Spectrum Signal received out.In order to allow receiver tracking loop circuit successfully to track
Signal, the carrier wave and C/A code signal of receiver inside institute initial replication must coincide to a certain extent with signal is received, otherwise,
If difference the leading into range more than track loop between replica signal and reception signal, loop would generally be to signal losing lock.
Therefore, ground receiver is before starting aircraft signal trace, it is necessary first to estimate the carrier frequency of reception signal (in other words
Carrier Doppler shift) and code phase the two parameters, track loop then is initialized according to these Signal parameter estimation values, with
Help receiving channel to be unfolded tracking to signal, and the purpose of signal capture precisely in order to obtain the carrier frequency for receiving signal and
The rough estimate value of code phase.Capture is generally divided into relevant, accumulation and judgement three phases.
Traditional thick simultaneous techniques is under the requirement of fast Acquisition, often in such a way that FFT circumference correlation combines a variety of accumulations
(single is adjudicated, and is adjudicated for M/N time, is sentenced for 1+M/N times for (coherent accumulation, non-coherent accumulation, differential coherent accumulative etc.) and judgement mode
Certainly, Tong judgement etc.), but it is directed to unmanned plane covert communications background demand under the conditions of low carrier-to-noise ratio, it is relevant tired according to FFT+
Product is to be captured, and sensitive to frequency deviation although capture rate is high, accumulated time is unsuitable too long, limits to a certain extent
The improvement degree of signal-to-noise ratio；For FFT+ non-coherent accumulation due to having carried out a square processing to detected value, the noise being superimposed on signal is equal
Value is no longer zero, can introduce Square loss, and especially under the conditions of low carrier-to-noise ratio, correlation energy is difficult to be superimposed out effective correlation
Peak；FFT+ differential coherent accumulative can make white noise spectrum become conjugation spectrum from Gaussian spectrum after treatment, and the later period is difficult.It is same with this
When, common high decision rate such as Tong decision method, although function admirable, due to the increasing of operand, to power consumption and hard
Part is more demanding.
Therefore, the thick simultaneous techniques of tradition is in the small-sized reconnaissance version unmanned plane Military Application field of the low carrier-to-noise ratio of the low dynamic of low speed
It is difficult to reach current operational need.
Summary of the invention
The purpose of the present invention is to provide a kind of direct sequence expansions suitable for small and medium size unmanned aerial vehicles under low carrier-to-noise ratio environment
The quick capturing method of frequency signal, it is sensitive to avoid frequency deviation is caused, and eliminate clutter influence.
To achieve the goals above, the present invention provides a kind of quick catching device of Direct Sequence Spread Spectrum Signal, including one
A conjugate complex multiplies module and defeated by the first FFT correlator and the 2nd FFT correlator and the conjugate complex multiply module two respectively
Enter end connected digital down converter and m-sequence generator, conjugate complex, which multiplies module also, has an output end, and the output end is successively
It is connected with iFFT correlator, memory, the 3rd FFT correlator, auto-correlation accumulation module, wave detector and judging module.
For the judging module tool there are two output end, one of output end passes through a control module and digital down converter
It is connected, another output is used to export the corresponding frequencies value and phase value that capture obtains.
The digital down converter includes two multipliers, a carrier wave NCO and a low-pass filter, the carrier wave
NCO tool there are two orthogonal output end, one of input terminal of each multiplier with one of them orthogonal output of carrier wave NCO
End is respectively connected with, another input terminal for receiving the Direct Sequence Spread Spectrum Signal, the input terminal of the low-pass filter with
Two multipliers are connected, and output end multiplies module with the conjugate complex and is connected.
The digital down converter is connected by the carrier wave NCO with the control module.
The conjugate complex multiplies module and includes tool there are two the multiple multiplication device of input terminal and be connected to the multiple multiplication device
Conjugate operation device on one of input terminal, the conjugate complex multiply module and pass through the input terminal and first of the multiple multiplication device
FFT correlator is connected, and is connected by the conjugate operation device with the 2nd FFT correlator.
On the other hand, the present invention provides a kind of quick capturing method of Direct Sequence Spread Spectrum Signal, comprising:
S1: down coversion and low-pass filtering treatment are carried out to Direct Sequence Spread Spectrum Signal using a digital down converter and used
One the oneth FFT correlator carries out FFT, while locally generating m pseudo-code sequence and carrying out FFT using the 2nd FFT correlator, then adopts
Multiply module with a conjugate complex both are carried out conjugate complex and multiplied by the signal that FFT is concerned with, obtains N number of symbol.
S2: correlated results is obtained using an iFFT correlator is relevant to N number of symbol progress iFFT, and correlated results is stored
Into a memory.
S3: again to this N number of correlated results zero padding to M, secondary FFT is carried out using one the 3rd FFT correlator, wherein M is 2
Secondary number formulary；
S4: the result after secondary FFT is carried out using auto-correlation accumulation module to simplify auto-correlation accumulation；
S5: auto-correlation accumulation results are sent into a wave detector, are compared using a judging module and a threshold value, and root
It according to comparison result, adjusts the digital down converter and repeats step S1-S5, or capture obtains corresponding frequencies value and phase value simultaneously
Output.
In the step S1, the Direct Sequence Spread Spectrum Signal and the m pseudo-code sequence are when carrying out the FFT to adopt
Sampling search is carried out with identical sample rate.
The Direct Sequence Spread Spectrum Signal is through aircraft signal by digital signal through BPSK modulation and LmPosition m-sequence spread spectrum
What processing obtained.
In step s 2, the correlated results is stored in u-th of area block of memory, v-th of symbol, first yard
The cell x of phasel,v,uIn, wherein 0≤l≤Lk- 1,1≤v≤V, 1≤u≤U, Lk, V, U be respectively code phase search length,
Accumulate symbolic number and frequency search interval number.
In the step S3, the result after the secondary FFT are as follows:
Several and area block ordinal number, Lk, V, U be respectively code phase search length, accumulation symbolic number and frequency search interval number.
In the step S4, the auto-correlation accumulation results z (l, m, u) are as follows:
Z (l, m, u)=yα(l,m,u)*yβ(l,m,u)
In formula, yα(l,m,u)、yβ(l, m, u) indicates the result after secondary FFT.
The digital down converter includes two multipliers, a carrier wave NCO and a low-pass filter；In the step
In S5, if being more than threshold value, obtains corresponding frequencies value and phase value and export；Otherwise, number is adjusted using a control module
The carrier wave NCO of low-converter, repeats step S1-S5.
The quick catching device of Direct Sequence Spread Spectrum Signal of the invention uses FFT, and secondary FFT and auto-correlation accumulation combine
Method, due to FFT have circumference correlation, corresponding pseudo-code after FFT accumulates retain phase characteristic simultaneously adjacent frequency deviation
Superposition is eliminated, and not will cause frequency deviation sensitivity；And due to FFT do not have modulus value characteristic, while correlated noise due to without it is good from
Correlation, therefore secondary M point FFT and simplified auto-correlation are accumulated and are used in combination, and clutter influence, the influence so that bottom is made an uproar can be further eliminated
Small, relevant peaks are sharply obvious, avoid the Square loss for causing accumulation；Further, since secondary M point FFT and simplified auto-correlation are tired
Product is avoided using noise caused by differential coherent accumulative due to being also substantially coherent accumulation by common Gaussian spectrum
It is superimposed as conjugation spectrum, the later period is easy to handle so that bottom is made an uproar.In addition, the present invention is adjudicated using single, operand is small, to power consumption and hardware
It is required that low.
Detailed description of the invention
Fig. 1 is the structural representation according to the quick catching device of the Direct Sequence Spread Spectrum Signal of one embodiment of the present of invention
Figure.
Fig. 2A is to be shown according to the principle of the quick capturing method of the Direct Sequence Spread Spectrum Signal of one embodiment of the present of invention
Be intended to, wherein left side be frequency domain search and code phase search two-dimensional search module, right side be each area block under to frequency domain into
Row fine search；
Fig. 2 B be according to the simplification of the quick capturing method of the Direct Sequence Spread Spectrum Signal of one embodiment of the present of invention from
The operation schematic diagram of related progressive.
Fig. 3 A-3C is to be captured according to the quick capturing method of the Direct Sequence Spread Spectrum Signal of one embodiment of the present of invention
The analogous diagram of correlated results when success, wherein Fig. 3 A shows correlated results with the situation of change of frequency domain, and Fig. 3 B shows phase
Result is closed with the situation of change in code phase domain, Fig. 3 C shows correlated results with the situation of change of frequency domain and code phase domain.
Specific embodiment
Below in conjunction with specific embodiment, the present invention will be further described.It should be understood that following embodiment is merely to illustrate this
The range of invention and is not intended to limit the present invention.
As shown in Figure 1 for according to the quick catching device 100 of the Direct Sequence Spread Spectrum Signal of one embodiment of the present of invention,
It includes that a conjugate complex multiplies module 101 and respectively by the first FFT correlator 104 and the 2nd FFT correlator 105 and the conjugation
Multiply two input terminals of module 101 connected digital down converter 102 and m-sequence generator 103 again, conjugate complex multiplies module 101
Also have an output end, the output end be connected in turn iFFT correlator 106, memory 107, the 3rd FFT correlator 108,
Auto-correlation accumulates module 109, wave detector 110 and judging module 111.There are two output ends for the tool of judging module 111, wherein one
A output end is connected by a control module 112 with digital down converter 102, and another output is for exporting capture result.
Wherein, the conjugate complex multiplies module 101 and includes tool there are two the multiple multiplication device 1011 of input terminal and be connected to this
Conjugate operation device 1012 on one of input terminal of multiple multiplication device 1011, it is multiple by this that the conjugate complex multiplies module 101
The input terminal of multiplication device 1011 is connected with the first FFT correlator 104, and passes through the conjugate operation device 1012 and described second
FFT correlator 105 is connected.
Digital down converter 102 includes two multipliers, 1021, carrier wave NCO (numerically-controlled oscillator) 1022 and one
A low-pass filter 1023, the digital down converter 102 are connected by the carrier wave NCO1022 with the control module 112,
The carrier wave NCO 1022 tool there are two orthogonal output end, one of input terminal of each multiplier 1021 with carrier wave NCO
The orthogonal output end of one of them of 1022 is respectively connected with, another signal input part is then used to receive the Direct Sequence Spread Spectrum letter
Number.The input terminal of the low-pass filter 1023 is connected with two multipliers 1021, and output end and the conjugate complex multiply module 101
It is connected.
Based on the quick catching device of Direct Sequence Spread Spectrum Signal described above, the present invention also provides a kind of direct sequences
The quick capturing method of column spread-spectrum signal uses secondary M point FFT to accumulate+simplify auto-correlation and accumulate and is used in combination, specifically includes following
Step:
Step S1: Direct Sequence Spread Spectrum Signal is carried out at down coversion and low-pass filtering using a digital down converter 102
Reason, and FFT is carried out using one the oneth FFT correlator 104, while generating m pseudo-code sequence simultaneously using a m-sequence generator 2 is local
FFT is carried out using the 2nd FFT correlator 105, module 101 is then multiplied using a conjugate complex, both is passed through into the letter that FFT is concerned with
Number carry out conjugate complex multiply, obtain N number of symbol.Wherein, Direct Sequence Spread Spectrum Signal is to be passed through by digital signal through aircraft signal
BPSK modulation and LmPosition m-sequence spread processing obtains.Direct Sequence Spread Spectrum Signal and m pseudo-code sequence are when carrying out the FFT
To carry out sampling search using identical sample rate.
The quick relevant and code phase correlated process of spread-spectrum signal is realized by FFT as a result, first time FFT is to frequency
Inclined rough estimate.In code phase correlated process, to guarantee that low-pass filtered rear code is estimated partiallyA symbol (chip)
Between, when to carry out sampling search using identical sample rate, the code phase search length L of single symbolkIt is set asWherein, LmFor the length of m pseudo-code sequence used, no fixed numbers requirement need to use m pseudo-code sequence according to user
It depending on column length, and is L to the elongated degree of single symbol zero paddingψ(LψValue be 2 secondary number formulary) with realize V point FFT be concerned with；Meanwhile
Frequency domain is also according to single character rate RBLow pass Nyquist Bandwidth fstep=RB/ 2 steppings are ± f in Doppler shiftd
When, frequency search interval number is U=[2fd/(RB/2)+1]。
Step S2: correlated results is obtained using an iFFT correlator 106 progress iFFT is relevant to N number of symbol, and will be related
As a result it stores into a memory 107.
Wherein, as shown in Fig. 2, in step s 2, the correlated results be stored in memory 107 u-th of area block,
The cell x of v-th of symbol, first code phasel,v,uIn, wherein 0≤l≤Lk- 1,1≤v≤V, 1≤u≤U, Lk- 1, V, U points
It Wei not code phase search length, accumulation symbolic number and frequency search interval number.
Step S1 and step S2 utilizes circumference correlation theorem as a result, will receive signal and related turn of the local time domain of pseudo-code
It changes the conjugate multiplication of frequency domain into, and correlated results is converted into dividing after time domain by area block and is stored.
Step S3: again to this N number of correlated results zero padding to M, carrying out secondary FFT using the 3rd FFT correlator 108,
The secondary number formulary that middle M is 2；
Result after the secondary FFT are as follows:
In formula,
L, v, u are code phase ordinal number, symbol ordinal sum area block sequence respectively
Number, m are fine frequency ordinal number, Lk- 1, code phase search length when V, U are respectively secondary FFT, accumulates symbolic number and frequency is searched
Rope interval number.
Second of FFT further can carefully estimate frequency deviation on the basis of the rough estimate of first time FFT as a result,.
Step S4: the result after secondary FFT is carried out to simplify auto-correlation accumulation, further to eliminate the noisy wave in bottom；
The auto-correlation accumulation results z (l, m, u) are as follows:
Z (l, m, u)=yα(l,m,u)*yβ(l, m, u),
In formula, yα(l,m,u)、yβ(l, m, u) indicates after secondary FFT as a result, l, m, u are respectively auto-correlation accumulation knot
Code phase ordinal number, the fine frequency ordinal sum area block ordinal number of fruit z (l, m, u).
Hereby it is achieved that secondary FFT and simplified auto-correlation accumulation, so that Overlay is significant.This secondary FFT is simultaneous to be simplified certainly
Related progressive is original creation of the present invention, and the method is substantially exactly auto-correlation accumulation.It is simplified from phase by being introduced after secondary FFT
Accumulation (simple from multiplication and accumulation) is closed, compared with existing some auto-correlation Cumulate algorithms, operand is small, and consumption resource is few,
Achieve the effect that required auto-correlation accumulation can handle in front again on the basis of, is suitable for this application.
The correlated results of the conjugate multiplication of frequency domain after temporarily being pressed area block and dividing preservation by step S3 and step S4, tired
It realizes that secondary M point FFT and simplified auto-correlation are accumulated and be used in combination using FFT circumference correlation theorem again during product, further eliminates
Clutter influences, and relevant peaks is allowed to become apparent from.
Step S5: auto-correlation accumulation results z (l, m, u) is sent into a wave detector 110, using a judging module 111 and door
Limit value is compared, and according to comparison result, is adjusted the digital down converter 102 and repeated step S1-S5, or capture obtains
Corresponding frequencies value and phase value simultaneously export.
Here capture rate needed for the basis of design of threshold value and false alarm rate requirement.If being more than threshold value, acquisition success is obtained
It to corresponding frequencies value and phase value and exports, the frequency values and phase value of output are sent into tracking module, wherein the frequency exported
The area block ordinal number u and fine frequency ordinal number m of auto-correlation accumulation results when being worth by acquisition success determine that is, frequency values calculate
When, u determines a big frequency, and m determines a thinner frequency values, and the two is added the precise frequencies value that capture can be obtained, phase
The code phase ordinal number l of auto-correlation accumulation results when place value is by acquisition success is determined；If capturing failure not above threshold value,
A control module is fed back to, thus using the carrier wave NCO 1022 of the control module 112 adjustment digital down converter 102, so that
The frequency values and phase value searched for are adjusted according to a default stepping, repeat step S1-S5.Hereby it is achieved that single
Judgement, operand is small, low with hardware requirement to power consumption.
Simulation result
Using algorithm designed by this patent, the simulating, verifying in matlab.The modulation methods employed in the simulated example
Formula is common BPSK/DSSS, and frequency deviation is that the common low dynamic unmanned plane internal crystal oscillator of goods shelf products generates maximum frequency deviation redundancy
Range ± 5KHz.Carrier-to-noise ratio selects lower 34dB to verify within the scope of general low carrier-to-noise ratio 34-40dB；Other parameters are made
Convertible numerical value sets itself needed for example has generality.Technical indicator condition see the table below 1.
The technical indicator of the quick capturing method of 1 Direct Sequence Spread Spectrum Signal of table
| Parameter or index name | Numerical value |
| Modulation system | BPSK/DSSS |
| The spreading code period | 1023m sequence |
| Information rate | 1000bps |
| Spreading rate | 1.023Mchip/s |
| Sample rate | 2.046MHz |
| Carrier Doppler frequency range | ±5KHz |
| Carrier-to-noise ratio | 34dB |
| Accumulate symbolic number | 32 |
| Capture time | <150ms |
| Test deviation distortion degree | < 10% |
| Test code bias distortion degree | < 5% |
As shown in figs. 3 a-3 c, the acquisition success when carrier-to-noise ratio cnr is 34dB, search for frequency deviation is obtained simulation result
6993.1641Hz, the frequency deviation being calculated are 6671.875Hz, and practical Doppler shift is 6676Hz, and deviation distortion degree is about
4.7%；Searching for code bit is 7242, and actual noise head length is 7284, and code bias distortion degree is about 0.5%.It can be seen that of the invention
Algorithm for design is suitable for the synchronization acquistion of low speed small and medium size unmanned aerial vehicles direct sequence signal, catches in the case where the capture of low carrier-to-noise ratio weak signal requires
It is obvious to obtain effect, it is with the obvious advantage.
Above-described, only presently preferred embodiments of the present invention, the range being not intended to limit the invention, of the invention is upper
Stating embodiment can also make a variety of changes.Made by i.e. all claims applied according to the present invention and description
Simply, equivalent changes and modifications fall within the claims of the invention patent.The not detailed description of the present invention is
Routine techniques content.
Claims (10)
1. a kind of quick catching device of Direct Sequence Spread Spectrum Signal, which is characterized in that multiply module (101) including a conjugate complex
It is defeated by the first FFT correlator (104) and the 2nd FFT correlator (105) and the conjugate complex multiply module (101) two respectively
Enter end connected digital down converter (102) and m-sequence generator (103), the output end that conjugate complex multiplies module (101) successively connects
It is connected to iFFT correlator (106), memory (107), the 3rd FFT correlator (108), auto-correlation accumulation module (109), wave detector
(110) and judging module (111).
2. the quick catching device of Direct Sequence Spread Spectrum Signal according to claim 1, which is characterized in that the judgement mould
There are two output end, one of output ends to pass through a control module (112) and digital down converter (102) phase for block (111) tool
Even, another output is used to export the corresponding frequencies value and phase value that capture obtains.
3. the quick catching device of Direct Sequence Spread Spectrum Signal according to claim 2, which is characterized in that under the number
Frequency converter (102) includes two multipliers (1021), a carrier wave NCO (1022) and a low-pass filter (1023), described
Carrier wave NCO (1022) tool there are two orthogonal output end, one of input terminal of each multiplier (1021) with carrier wave NCO
(1022) the orthogonal output end of one of them is respectively connected with, another input terminal is used to receive the Direct Sequence Spread Spectrum Signal,
The input terminal of the low-pass filter (1023) is connected with two multipliers (1021), and output end and the conjugate complex multiply module
(101) it is connected, the digital down converter (102) is connected by the carrier wave NCO (1022) with the control module (112).
4. the quick catching device of Direct Sequence Spread Spectrum Signal according to claim 1, which is characterized in that the conjugate complex
Multiplying module (101) includes having the multiple multiplication device (1011) there are two input terminal and being connected to this to answer its of multiplication device (1011)
In conjugate operation device (1012) on an input terminal, the conjugate complex multiplies module (101) and passes through multiple multiplication device (1011)
Input terminal be connected with the first FFT correlator (104), and pass through the conjugate operation device (1012) and the 2nd FFT correlator
(105) it is connected.
5. a kind of quick capturing method of Direct Sequence Spread Spectrum Signal characterized by comprising
Step S1: down coversion and low-pass filtering treatment are carried out to Direct Sequence Spread Spectrum Signal using a digital down converter (102)
And FFT is carried out using one the oneth FFT correlator (104), while locally generating m pseudo-code sequence and using the 2nd FFT correlator
(105) FFT is carried out, module (101) is then multiplied using a conjugate complex, both is subjected to conjugate complex by the signal that FFT is concerned with
Multiply, obtains N number of symbol.
Step S2: correlated results is obtained using an iFFT correlator (106) is relevant to N number of symbol progress iFFT, and correlation is tied
Fruit stores in a memory (107).
Step S3: again to this N number of correlated results zero padding to M, carrying out secondary FFT using one the 3rd FFT correlator (108),
The secondary number formulary that middle M is 2；
Step S4: the result after secondary FFT is carried out using auto-correlation accumulation module (109) to simplify auto-correlation accumulation；
Step S5: sending auto-correlation accumulation results into a wave detector (110), using a judging module (111) and a threshold value into
Row compares, and according to comparison result, adjusts the digital down converter (102) and repeat step S1-S5, or capture obtains accordingly
Frequency values and phase value simultaneously export.
6. the quick capturing method of Direct Sequence Spread Spectrum Signal according to claim 5, which is characterized in that in the step
In S1, the Direct Sequence Spread Spectrum Signal and the m pseudo-code sequence are adopted when carrying out the FFT with the identical sample rate of use
Sample search, the Direct Sequence Spread Spectrum Signal are through aircraft signal by digital signal through BPSK modulation and LmPosition m-sequence spread spectrum
What processing obtained.
7. the quick capturing method of Direct Sequence Spread Spectrum Signal according to claim 5, which is characterized in that in step S2
In, the correlated results is stored in the cell of u-th of area block of memory (107), v-th of symbol, first code phase
xl,v,uIn, wherein 0≤l≤Lk- 1,1≤v≤V, 1≤u≤U, Lk, V, U be respectively code phase search length, accumulation symbolic number and
Frequency search interval number.
8. the quick capturing method of Direct Sequence Spread Spectrum Signal according to claim 7, which is characterized in that in the step
Result in S3, after the secondary FFT are as follows:
In formula,L, v, u are code phase ordinal number, symbol ordinal sum area block sequence respectively
Number, Lk, V, U be respectively code phase search length, accumulation symbolic number and frequency search interval number.
9. the quick capturing method of Direct Sequence Spread Spectrum Signal according to claim 8, which is characterized in that in the step
In S4, the auto-correlation accumulation results z (l, m, u) are as follows:
Z (l, m, u)=yα(l,m,u)*yβ(l,m,u)
In formula, yα(l,m,u)、yβ(l, m, u) indicates the result after secondary FFT.
10. the quick capturing method of Direct Sequence Spread Spectrum Signal according to claim 5, which is characterized in that the number
Low-converter (102) includes two multipliers (1021), a carrier wave NCO (1022) and a low-pass filter (1023)；
In the step S5, if being more than threshold value, obtains corresponding frequencies value and phase value and export；Otherwise, using a control
Molding block (112) adjusts the carrier wave NCO (1022) of digital down converter (102), repeats step S1-S5.
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| CN112839001A (en) * | 2020-12-30 | 2021-05-25 | 南京天际易达通信技术有限公司 | Airborne measurement and control terminal of unmanned aerial vehicle |
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