Rapid capture implementation method suitable for high-speed spread frequency hopping signals

Abstract

The invention provides a fast capture implementation method suitable for high-speed spread frequency hopping signals, which comprises the following steps of: 1, starting a capture process, and carrying out digital de-hopping; 2, roughly capturing and searching the de-hopped signal; and step 3, finely capturing and searching the de-hopped signal. According to the method provided by the invention, a large-range preliminary search method is used for assisting a small-range fine search method to replace the problem of resource doubling caused by a traditional spread frequency hopping large dynamic interval search method, so that the on-satellite resource consumption is greatly reduced, the capture time is shortened, and the method is insensitive to the transmission rate. The method is suitable for a space environment with a severe signal-to-noise ratio, a complex electromagnetic compatibility environment, an electrostatic discharge environment and a random interference environment, and is also suitable for a complex space environment.

Description

Technical Field

[0001] The invention belongs to the field of communication technology, relates to spread frequency hopping measurement and control, and specifically relates to a fast capture implementation method suitable for high-speed spread frequency hopping signals. Background Art

[0002] With the complexity and diversification of data transmission in aerospace measurement and control systems, the early low-speed spread frequency hopping measurement and control system can no longer meet the needs of the rapidly developing aerospace measurement and control projects. The frequency band of the spread frequency hopping measurement and control system is expanded from S to Ka to have a wider bandwidth and a larger communication capacity. At the same time, the transmission data rate of the spread frequency hopping measurement and control system also needs to be expanded from low to high to meet the complex and diverse measurement and control functions. The high-speed spread frequency hopping measurement and control system has strong anti-interference ability and outstanding anti-interception ability, and can meet most aerospace measurement and control application scenarios. Therefore, the high-speed spread frequency hopping measurement and control mode will be widely used in measurement and control transponders to cope with the increasingly complex space environment. Summary of the invention

[0003] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for realizing fast capture of high-rate spread-hopping frequency signals, so as to solve the technical problem of resource doubling caused by the search method in the prior art.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A fast capture implementation method, the method comprising the following steps:

[0006] Step 1: Start the capture process and perform digital decoding.

[0007] Step 2: Perform a rough capture search on the de-hopping signal.

[0008] Step 3: Perform fine capture and search on the signal after de-hopping.

[0009] Compared with the prior art, the present invention has the following technical effects:

[0010] (I) The method of the present invention uses a large-scale preliminary search method to assist a small-scale fine search method to replace the resource doubling problem caused by the traditional spread-hopping large dynamic interval search method, which greatly reduces the on-board resource consumption and the capture time. The method is insensitive to the transmission rate.

[0011] (II) The present invention can be applied to space environments with poor signal-to-noise ratio, complex electromagnetic compatibility environments, electrostatic discharge environments, random interference environments, and also to complex space environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the principle of the rapid capture implementation method of the present invention.

[0013] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0014] It should be noted that, unless otherwise specified, all algorithms in the present invention adopt algorithms known in the prior art.

[0015] In the present invention, a high-rate spread-frequency hopping signal refers to a spread-frequency hopping signal with a data rate greater than 1 Kbps.

[0016] The fast capture implementation method for high-speed spread frequency hopping signals of the present invention requires that the spread code frequency phase, the frequency hopping carrier phase and the data phase in the spread frequency hopping signal are strictly coherently aligned, that is, T b =MT h =MPT c , that is to say, one data symbol contains a whole M hops, one hop contains a whole P chips, that is, one data symbol contains a whole MP chips.

[0017] Where:

[0018] T b is 1 data symbol width;

[0019] T h is 1 hop width;

[0020] T c It is the width of 1 spreading code chip.

[0021] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0022] Example:

[0023] This embodiment provides a fast capture implementation method suitable for high-speed spread-hopping frequency signals, such as Figure 1 As shown, the method comprises the following steps:

[0024] Step 1: Start the capture process and perform digital decoding:

[0025] Step 101: periodically generate a local frequency hopping carrier according to a changing rule of a frequency hopping pattern.

[0026] Step 102: digitally demodulate the received direct-sequence frequency hopping (DSFH) mixed signal using the local frequency hopping carrier obtained in step 101 and perform low-pass filtering to obtain a filtered signal.

[0027] Step 103, power adjustment is performed on the amplitude of the filtered signal obtained in step 102 through a digital automatic gain control (AGC) algorithm, and the power-adjusted signal is subjected to decimation and speed reduction processing to obtain a de-jumped signal.

[0028] Step 2: Perform a rough capture search on the signal after de-hopping:

[0029] Step 201, generate a local spread spectrum code phase according to the frequency hopping period, and use the local spread spectrum codeword to perform one-channel serial despreading on the de-hopped signal obtained in step 1 to obtain a despread signal.

[0030] Step 202, performing 1 / m-hop integration on the despread signal obtained in step 201 to obtain an integration result.

[0031] in:

[0032] m represents quantity, m=20~60.

[0033] In step 202, the starting code phase of a parallel search of the despread signal is Pn 0 ~Pn i .

[0034] in:

[0035] Pn represents the start code phase;

[0036] i represents the number of code phases for a parallel search, i=1,2,3…n; n≤spread spectrum code period.

[0037] Step 203, perform 2 on the integral result obtained in step 202. n The point discrete Fourier transform (DFT) is padded with zeros and repeated multiple times to obtain multiple discrete Fourier transform results.

[0038] in:

[0039] n represents the exponent of 2, 2 n >m.

[0040] Step 204, accumulating the module values ​​of the multiple discrete Fourier transform results obtained in step 203 to obtain an accumulated result.

[0041] Step 205, performing peak search on the accumulated result obtained in step 204 to obtain coarse-precision chip phase, frequency hopping phase and carrier Doppler shift.

[0042] Step 206, feeding back the coarse-precision chip phase, frequency hopping phase and carrier Doppler shift obtained in step 205 to step 1 to correct the phase of the local frequency hopping carrier.

[0043] In step 2, the local spread spectrum code phase, frequency hopping 30 carrier phase and Doppler frequency deviation are corrected once according to the rough capture search result.

[0044] Step 3: Perform fine capture and search of the signal after de-hopping:

[0045] Step 301, generate a local spread spectrum code phase according to the frequency hopping period, and use the local spread spectrum code to perform 11-channel parallel despreading on the de-hopped signal obtained after the result of step 2 is corrected in step 1 to obtain a despread signal.

[0046] Step 302, performing M-hop integration on each despread signal obtained in step 301 to obtain an integration result.

[0047] in:

[0048] M represents quantity, M≤400.

[0049] Step 303, performing square and sign removal calculation on each integration result obtained in step 302 to obtain a square and sign removal result.

[0050] Step 304, performing a Fast Fourier Transform (FFT) on each square de-signed result obtained in step 303 to obtain a transformed result.

[0051] Step 305, performing peak search on the transformation result obtained in step 304 to obtain a fine chip phase, frequency hopping phase and carrier Doppler shift.

[0052] Step 306, feeding back the fine chip phase, frequency hopping phase and carrier Doppler shift obtained in step 305 to step 1 to correct the phase of the local frequency hopping carrier.

[0053] In step 3, the coarse capture search has narrowed the search range of the spread spectrum code phase, frequency hopping phase and Doppler frequency offset to a relatively small range. The fine capture search only needs to perform a fine search with a step of Δt in a smaller range. The frequency hopping phase performs a sliding search by setting the phase delay output, and the code phase is also adjusted accordingly.

[0054] In step three, based on the primary correction in step two, a secondary correction is performed on the local spread spectrum code phase, the frequency hopping carrier phase and the Doppler frequency offset according to the fine capture search results.

Claims

1. A method for realizing rapid capture, characterized in that: The method comprises the following steps: Step 1: Start the capture process and perform digital decoding; Step 2: Perform a rough capture search on the de-hopping signal; Step 3: Perform fine capture and search on the signal after de-hopping.

2. The fast capture implementation method according to claim 1, characterized in that: The specific process of step one is: Step 101, periodically generating a local frequency hopping carrier according to a change rule of a frequency hopping pattern; Step 102, using the local frequency hopping carrier obtained in step 101 to digitally demodulate the received direct sequence frequency hopping mixed signal and perform low-pass filtering to obtain a filtered signal; Step 103, power-adjusting the amplitude of the filtered signal obtained in step 102 through a digital automatic gain control algorithm, decimating and reducing the power-adjusted signal to obtain a de-jumped signal.

3. The fast capture implementation method according to claim 1, characterized in that: The specific process of step 2 is: Step 201, generating a local spread spectrum code phase according to a frequency hopping period, and performing one-channel serial despreading on the de-hopped signal obtained in step 1 using the local spread spectrum codeword to obtain a despread signal; Step 202, performing 1 / m-hop integration on the despread signal obtained in step 201 to obtain an integration result; in: m represents the quantity, m = 20 to 60; Step 203, perform 2 on the integral result obtained in step 202. n The point discrete Fourier transform is filled with zeros, and repeated multiple times to obtain multiple discrete Fourier transform results; in: n represents the exponent of 2, 2 n >m; Step 204, accumulating the module values ​​of the multiple discrete Fourier transform results obtained in step 203 to obtain an accumulated result; Step 205, performing peak search on the accumulated result obtained in step 204 to obtain coarse-precision chip phase, frequency hopping phase and carrier Doppler shift.

4. The fast capture implementation method according to claim 3, characterized in that: In step 202, the starting code phase of a parallel search of the despread signal is Pn0~Pn i ; in: Pn represents the start code phase; i represents the number of code phases for a parallel search, i=1,2,3...n.

5. The fast capture implementation method according to claim 3, characterized in that: Also includes step 206; Step 206, feeding back the coarse-precision chip phase, frequency hopping phase and carrier Doppler shift obtained in step 205 to step 1 to correct the phase of the local frequency hopping carrier.

6. The fast capture implementation method according to claim 5, characterized in that: The specific process of step three is: Step 301, generating a local spread spectrum code phase according to a frequency hopping period, and using the local spread spectrum codeword to perform 11-channel parallel despreading on the de-hopped signal obtained after the result of step 2 is corrected in step 1, to obtain a despread signal; Step 302, performing M-hop integration on each despread signal obtained in step 301 to obtain an integration result; in: M represents quantity, M≤400; Step 303, performing square and sign removal calculation on each integral result obtained in step 302 to obtain a square and sign removal result; Step 304, performing a fast Fourier transform on each squared de-signed result obtained in step 303 to obtain a transformed result; Step 305, performing peak search on the transformation result obtained in step 304 to obtain a fine chip phase, frequency hopping phase and carrier Doppler shift.

7. The fast capture implementation method according to claim 6, characterized in that: Also includes step 306; Step 306, feeding back the fine chip phase, frequency hopping phase and carrier Doppler shift obtained in step 305 to step 1 to correct the phase of the local frequency hopping carrier.

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