A Doppler capture method, apparatus and storage medium

Abstract

This invention provides a Doppler acquisition method, apparatus, and storage medium to achieve successful Doppler acquisition in scenarios without synchronization sequences, thereby providing a data foundation for demodulation in subsequent communication systems. The method includes: preprocessing the received signal to obtain an initial target signal; sampling the initial target signal to obtain a first target signal; performing a first coarse acquisition on the first target signal; if the first coarse acquisition is successful, sampling the initial target signal to obtain a second target signal; performing a second coarse acquisition on the second target signal; if the second coarse acquisition is successful, determining the chip offsets of the first and second coarse acquisitions based on the final correlation peaks in the first and second coarse acquisitions, respectively; determining the chip offset difference based on the chip offsets of the two coarse acquisitions; if the difference is less than a preset threshold, ending the coarse acquisition; if the difference is not less than the preset threshold, repeating the second coarse acquisition.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a Doppler capture method, apparatus, and storage medium. Background Technology

[0002] The Doppler effect refers to the difference between the received and transmitted signals caused by factors such as the distance between the transmitting and receiving devices and their relative motion during propagation. Furthermore, crystal oscillator errors in the transmitting and receiving clocks can lead to code offsets in the received signal. On one hand, the first point of the information data is not the first point sampled at the receiving end; on the other hand, the received data has a corresponding widening compared to the transmitted data. To compensate for the impact of frequency and code offsets caused by relative motion on the modulated signal and to achieve synchronization in high-dynamic, large-frequency-offset spread spectrum systems, the commonly used algorithm is the FFT-based acquisition algorithm, which is relatively easy to implement in hardware. It utilizes the circular shift correlation theorem to convert the time-domain correlation calculation of the received signal and the local PN code into a frequency-domain multiplication. The FFT acquisition algorithm significantly reduces acquisition time through fast FFT computation, resulting in more accurate acquisition results. The FFT acquisition algorithm uses the synchronization sequence of all 0s or all 1s in the frame format to accumulate signal energy and extract frequency and code phase information. However, when there is no synchronization sequence of all 0s or all 1s in the frame format, traditional acquisition algorithms cannot directly capture the frequency offset and code phase, thus affecting the demodulation of the communication system. Therefore, there is still a lack of effective means to solve the problem of not being able to directly capture frequency offset and code phase in scenarios without synchronization sequences under spread spectrum systems. Summary of the Invention

[0003] This invention provides a Doppler acquisition method, apparatus, and storage medium to achieve successful Doppler acquisition in a scenario without a synchronization sequence under spread spectrum, thereby providing a data foundation for demodulation of subsequent communication systems.

[0004] In a first aspect, the present invention provides a Doppler capture method, comprising:

[0005] The received signal is preprocessed to obtain the initial target signal;

[0006] The initial target signal is sampled to obtain the first target signal;

[0007] A first coarse acquisition is performed on the first target signal;

[0008] When the first coarse acquisition is confirmed to be successful, the initial target signal is sampled to obtain the second target signal;

[0009] A second coarse acquisition is performed on the second target signal;

[0010] When the second coarse acquisition is confirmed to be successful, the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition are determined based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively.

[0011] The chip offset difference is determined based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition.

[0012] If the chip offset difference is less than a preset threshold, the second coarse acquisition ends; if the chip offset difference is not less than the preset threshold, the second coarse acquisition is performed again.

[0013] In one implementation, coarse capture is performed according to the following procedure:

[0014] Based on a preset duration, the total duration of the first target signal is segmented to obtain several segments of target signal with preset durations;

[0015] Each target signal of a preset duration is translated according to a first preset translation method to obtain a preset number of translated target signals corresponding to each target signal segment.

[0016] Based on the initial spreading code and the translation target signal of several target signals, determine the correlation value between the initial spreading code and the translation target signal in the time domain;

[0017] Differential coherent accumulation is performed on the correlation values ​​between the initial spreading code and the translation target signal in the time domain to obtain the positive and negative correlation peaks of the first target signal under each translation mode;

[0018] The final correlation peak is determined based on the positive and negative correlation peaks of the first target signal under each translation mode; and the success of coarse acquisition is determined according to the following procedure:

[0019] Determine whether the peak value of the final correlation peak is greater than the coarse capture decision threshold;

[0020] If so, then the coarse capture was successful;

[0021] If not, then coarse capture has failed.

[0022] In one implementation, after the second coarse capture is completed, the process further includes:

[0023] The carrier Doppler compensation and synchronization head variation are determined based on the final correlation peak in the coarse acquisition.

[0024] The first target signal and the second target signal are compensated according to the carrier Doppler compensation amount to obtain the input signal;

[0025] Based on the chip offset of the second coarse acquisition and the second preset translation method, the input signal is translated to obtain the first translation signal, the second translation signal, and the third translation signal respectively;

[0026] Based on the changes in the synchronization header, determine the first synchronization header and the second synchronization header;

[0027] Based on the initial spreading code, the first spreading code and the second spreading code are determined according to the first synchronization header and the second synchronization header, respectively.

[0028] The first translation signal, the second translation signal, and the third translation signal are multiplied by the first spreading code and the second spreading code respectively, and then coherently accumulated to obtain the corresponding spreading sequence;

[0029] Perform a Fast Fourier Transform (FFT) on each spread spectrum sequence;

[0030] Take the square of the modulus of each sequence after FFT;

[0031] Determine the maximum value among the squares of the moduli of all sequences;

[0032] Determine if the maximum value is greater than the decision threshold;

[0033] If so, then the capture was successful;

[0034] If not, the fine capture fails.

[0035] In one implementation, the received signal is preprocessed to obtain an initial target signal, specifically including:

[0036] The received signal is down-converted, and the resulting baseband signal is expressed by the following expression: y(t)=Ad(t)c(t-τ)cos(ω0+ω d )t+n(t);

[0037] The baseband signal is sampled to obtain the sampled signal;

[0038] The sampled signal is low-pass filtered to obtain the initial target signal;

[0039] Where y(t) is the baseband signal, A is the signal amplitude, d(t) is the modulation data information, c(t-τ) is the initial spreading code, ω0 is the carrier frequency, and ω d denoted as Doppler shift, and n(t) as additive white Gaussian noise.

[0040] In one implementation, the correlation value between the initial spreading code and the translated target signal in the time domain is determined based on the initial spreading code and several segments of target signal, specifically including:

[0041] A two-dimensional parallel time-frequency search is performed on each segment of the target signal for different translational target signals to determine the correlation value between the initial spreading code and the translational target signal in the time domain.

[0042] In one implementation, the correlation value between the initial spreading code and the translation target signal in the time domain is determined by the following formula:

[0043]

[0044]

[0045] Where y(m) is the m-th element in the sequence, c(mn) is the initial spreading code shifted n bits to the right based on the m-th element, N is the number of points in the time-domain discrete signal, and k is the number of the frequency-domain signal, with a value range of 0 ≤ k ≤ N-1, e -2πjkn / N e -2πjkm / N and e 2πjk(m-n) / N Let z(n) be an orthogonal basis in N-dimensional complex space, z(n) be the result of the convolution operation between the initial spreading code and the target signal in the time domain, Z(k) be the correlation value in the frequency domain, Y(k) be the received signal in the frequency domain, and C(k) be the initial spreading code signal in the frequency domain.

[0046] In one implementation, differential coherent accumulation is performed on the correlation values ​​between the initial spreading code and the translation target signal in the time domain to obtain the positive and negative correlation peaks of the first target signal under each translation mode, specifically including:

[0047] For each translation mode, the correlation values ​​between the initial spreading code in the time domain and the corresponding translated target signal in each segment of the target signal are accumulated. The positive and negative accumulation results of the first target signal under each translation mode are determined by the following formula:

[0048]

[0049]

[0050] Based on the positive and negative cumulative results of the first target signal under each translation mode, the positive and negative correlation peaks of the first target signal under each translation mode are determined by the following formula:

[0051]

[0052] in, This indicates the positive accumulation of the correlation value in differential coherent demodulation. This indicates the negative accumulation of correlation values ​​in differential coherent demodulation, where yk represents the k-th coherent accumulation result. Let represent the conjugate of the (k+1)th coherent accumulation result, L represent the number of coherent accumulations, CB represent the correlation peak, V represent the differential coherent demodulation correlation accumulation, and E(V) represent the expectation of the differential coherent demodulation correlation accumulation.

[0053] In a second aspect, the present invention provides a Doppler capture device, comprising:

[0054] The preprocessing module preprocesses the received signal to obtain the initial target signal;

[0055] The sampling module is used to sample the initial target signal to obtain the first target signal; when the first coarse acquisition is successful, the initial target signal is sampled to obtain the second target signal.

[0056] The coarse acquisition module is used to perform a first coarse acquisition process on the first target signal and a second coarse acquisition process on the second target signal; when the chip offset difference is not less than a preset threshold, the second coarse acquisition is performed again.

[0057] The first determining module is used to determine the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively; and to determine the chip offset difference based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition.

[0058] The first judgment module is used to determine whether the chip offset difference is less than a preset threshold.

[0059] The termination module is used to end the second coarse capture when the chip offset difference is less than a preset threshold.

[0060] In one embodiment, the coarse capture module includes:

[0061] The duration segmentation submodule is used to segment the total duration of the first target signal into several segments of the target signal with a preset duration based on a preset duration.

[0062] The translation submodule is used to translate each target signal of a preset duration according to a first preset translation method to obtain a preset number of translated target signals corresponding to each target signal segment;

[0063] The first determining submodule is used to determine the correlation value between the initial spreading code and the translated target signal in the time domain based on the initial spreading code and the translated target signal of several segments of target signal;

[0064] The coherent accumulation submodule is used to perform differential coherent accumulation on the correlation values ​​between the initial spreading code and the translation target signal in the time domain, so as to obtain the positive correlation peak and negative correlation peak of the first target signal under each translation mode.

[0065] The second determining submodule is used to determine the final correlation peak based on the positive and negative correlation peaks of the first target signal under each translation mode;

[0066] The judgment submodule is used to determine whether the peak value of the final correlation peak is greater than the coarse capture decision threshold; if yes, the coarse capture is determined to be successful; otherwise, the coarse capture is determined to be unsuccessful; and,

[0067] The coarse acquisition module is specifically used to perform a first coarse acquisition process on the first target signal and a second coarse acquisition on the second target signal through each sub-module; when the chip offset difference is not less than a preset threshold, the second coarse acquisition is performed again.

[0068] In one embodiment, the device further includes:

[0069] The second determining module is used to determine the carrier Doppler compensation amount and synchronization header change based on the final correlation peak in the coarse acquisition.

[0070] The compensation module is used to compensate the first target signal and the second target signal according to the carrier Doppler compensation amount to obtain the input signal;

[0071] The translation module is used to translate the input signal based on the chip offset of the second coarse capture and the preset translation mode, to obtain the first translation signal, the second translation signal, and the third translation signal, respectively.

[0072] The third determining module is used to determine the first synchronization head and the second synchronization head based on the change of the synchronization head;

[0073] The fourth determining module is used to determine the first spreading code and the second spreading code based on the initial spreading code and according to the first synchronization header and the second synchronization header, respectively.

[0074] The arithmetic module is used to coherently accumulate the first translation signal, the second translation signal, and the third translation signal after multiplying them with the first spreading code and the second spreading code, respectively, to obtain the corresponding spreading sequence; perform a Fast Fourier Transform (FFT) on each spreading sequence; take the square of the modulus of each sequence after FFT; and determine the maximum value among the squares of the moduli of all sequences.

[0075] The second judgment module is used to determine whether the maximum value is greater than the decision threshold; if so, the fine capture is successful; otherwise, the fine capture fails.

[0076] In one embodiment, the preprocessing module includes:

[0077] The frequency conversion submodule is used to down-convert the received signal. The baseband signal obtained after down-conversion is expressed by the following expression: y(t)=Ad(t)c(t-τ)cos(ω0+ω d)t+n(t);

[0078] The sampling submodule is used to sample the baseband signal to obtain the sampled signal;

[0079] The filtering submodule is used to perform low-pass filtering on the sampled signal to obtain the initial target signal;

[0080] Where y(t) is the baseband signal, A is the signal amplitude, d(t) is the modulation data information, c(t-τ) is the initial spreading code, ω0 is the carrier frequency, and ω d denoted as Doppler shift, and n(t) as additive white Gaussian noise.

[0081] In one implementation, the first determining submodule is specifically used to perform a time-frequency two-dimensional fully parallel search on different translation target signals of each segment of target signal to determine the correlation value between the initial spreading code and the translation target signal in the time domain.

[0082] In one implementation, the first determining submodule is specifically used to determine the correlation value between the initial spreading code and the translation target signal in the time domain using the following formula:

[0083]

[0084]

[0085] Where y(m) is the m-th element in the sequence, c(mn) is the initial spreading code shifted n bits to the right based on the m-th element, N is the number of points in the time-domain discrete signal, and k is the number of the frequency-domain signal, with a value range of 0 ≤ k ≤ N-1, e -2πjkn / N e -2πjkm / N and e 2πjk(m-n) / N Let z(n) be an orthogonal basis in N-dimensional complex space, z(n) be the result of the convolution operation between the initial spreading code and the target signal in the time domain, Z(k) be the correlation value in the frequency domain, Y(k) be the received signal in the frequency domain, and C(k) be the initial spreading code signal in the frequency domain.

[0086] In one implementation, the coherent accumulation submodule includes:

[0087] The arithmetic unit is used to perform an accumulation operation on the correlation value between the initial spreading code in the time domain and the corresponding translated target signal in each segment of the target signal under each translation mode. The positive accumulation result and negative accumulation result of the first target signal under each translation mode are determined by the following formula:

[0088]

[0089]

[0090] Furthermore, based on the positive and negative cumulative results of the first target signal under each translation mode, the positive and negative correlation peaks of the first target signal under each translation mode are determined using the following formula:

[0091]

[0092] in, This indicates the positive accumulation of the correlation value in differential coherent demodulation. This indicates the negative accumulation of the correlation value in differential coherent demodulation, y k This represents the k-th coherent cumulative result. Let represent the conjugate of the (k+1)th coherent accumulation result, L represent the number of coherent accumulations, CB represent the correlation peak, V represent the differential coherent demodulation correlation accumulation, and E(V) represent the expectation of the differential coherent demodulation correlation accumulation.

[0093] Thirdly, the present invention provides a computing device, characterized in that it includes at least one processor and at least one memory, wherein the memory stores a computer program that, when executed by the processor, causes the processor to perform the steps of the Doppler capture method provided in the first aspect.

[0094] Fourthly, a computer-readable medium is provided, characterized in that it stores a computer program executable by a terminal device, which, when run on the terminal device, causes the terminal device to perform the steps of the Doppler capture method provided in the first aspect.

[0095] This invention provides a Doppler acquisition method, apparatus, and storage medium. By down-converting the received signal to baseband and then low-pass filtering the baseband waveform, coarse acquisition of the pre-processed digital baseband signal is achieved, enabling acquisition of frequency offset and code phase even without an all-zero or all-one synchronization sequence. Further, by using the correlation value between the spreading code and the target signal, and coherently accumulating the result, the peak-to-average power ratio (PAPR) is calculated and compared with a threshold value to determine whether the signal has been acquired. Based on this, the synchronization sequence estimated from the coarse acquisition is used for fine acquisition, further correcting the signal's frequency offset and code phase. The acquired signal is then subjected to subsequent processing such as tracking, demodulation, frame synchronization, and decoding to demodulate the signal. Thus, through the above processing, acquisition can be successfully completed even without a synchronization sequence in the data link frame format, obtaining data with a very small residual frequency offset, thereby providing a data foundation for the communication system and assisting the receiver in subsequent correct demodulation.

[0096] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0097] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0098] Figure 1 This is a flowchart illustrating a Doppler capture method according to an embodiment of the present invention.

[0099] Figure 2 This is a schematic diagram of the coarse acquisition process in a Doppler acquisition method according to an embodiment of the present invention;

[0100] Figure 3 This is a schematic diagram of the fine capture process in a Doppler capture method according to an embodiment of the present invention;

[0101] Figure 4 This is a schematic diagram of a Doppler capture device according to an embodiment of the present invention. Detailed Implementation

[0102] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. "A plurality or several" as used herein refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone.

[0103] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Furthermore, the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0104] The technical solutions provided in the various embodiments of this specification are described in detail below with reference to the accompanying drawings.

[0105] Example 1

[0106] This invention provides a Doppler capture method, such as... Figure 1 A flowchart illustrating a Doppler capture method according to an embodiment of the present invention is shown, comprising:

[0107] S11. Preprocess the received signal to obtain the initial target signal.

[0108] In practice, in scenarios where there is no synchronization sequence of all 0s or all 1s in the frame format, the received signal is preprocessed to obtain a processed digital baseband signal.

[0109] In one embodiment, step S11 specifically includes:

[0110] Step 1: Down-convert the received signal. The baseband signal obtained after down-conversion is expressed by the following expression: y(t)=Ad(t)c(t-τ)cos(ω0+ω d )t+n(t);

[0111] Where y(t) is the baseband signal, A is the signal amplitude, d(t) is the modulation data information, c(t-τ) is the spreading code, ω0 is the carrier frequency, and ω d For Doppler shift, n(t) represents additive white Gaussian noise;

[0112] Step 2: Sample the baseband signal to obtain the sampled signal;

[0113] Step 3: Perform low-pass filtering on the sampled signal to obtain the initial target signal.

[0114] In practice, the received signal is down-converted to baseband. The baseband signal obtained after down-conversion can be represented by the above expression. The baseband signal is sampled to obtain y(n). y(n) is then low-pass filtered to remove high-frequency components and out-of-band noise. The digital baseband signal obtained after the above processing is the initial target signal.

[0115] S12. Sample the initial target signal to obtain the first target signal.

[0116] The initial target signal obtained in step S11 is sampled to obtain the first target signal as the input data for the first coarse acquisition.

[0117] It should be noted that sampling the initial target signal can yield the first target signal, the second target signal, or any target signal.

[0118] S13. Perform the first coarse acquisition on the first target signal.

[0119] The first target signal obtained in step S12 is subjected to the first coarse acquisition process.

[0120] In one implementation, coarse capture is performed according to the following procedure:

[0121] Step 1: Based on the preset duration, the total duration of the first target signal is divided into segments to obtain several segments of target signal with preset duration.

[0122] The first target signal is divided into several segments based on its total time length according to a preset duration. The preset duration can be determined based on empirical values, actual scenario requirements, etc.

[0123] Step 2: Translate each target signal segment of a preset duration according to the first preset translation method to obtain a preset number of translated target signals corresponding to each target signal segment.

[0124] Specifically, the preset number is determined based on the preset translation method. Different translation methods correspond to different frequency offsets. Each segment of the target signal obtained in step one above is translated according to the preset translation method, that is, a different frequency offset is set for each segment of the target signal. For example, suppose the preset translation methods are to shift left by 1, 2...k positions, to the right by 1, 2...k positions, and to shift right by 0 positions, for a total of 2k+1 possibilities. Then, each segment of the target signal is translated according to the preset translation method, and each segment of the target signal is translated to obtain 2k+1 different translated target signals with different frequency offsets.

[0125] Step 3: Determine the correlation value between the initial spreading code and the translated target signal in the time domain based on the initial spreading code and several segments of target signal.

[0126] In practice, based on the initial spreading code and the translation target signals of several target signals obtained in step two above, the correlation value between the initial spreading code and each translation target signal in the time domain is determined. The spreading code can be calculated using a local pseudocode.

[0127] In one implementation, the correlation value between the initial spreading code and the translated target signal in the time domain is determined based on the initial spreading code and several segments of target signal, specifically including:

[0128] A two-dimensional parallel time-frequency search is performed on each segment of the target signal for different translational target signals to determine the correlation value between the initial spreading code and the translational target signal in the time domain.

[0129] In practice, a time-frequency two-dimensional fully parallel search is performed on each target signal segment under different frequency offsets, that is, each translation target signal. That is, the convolution of the initial spreading code and each translation target signal in the time domain is transformed into multiplication in the frequency domain by FFT to obtain the correlation value of the initial spreading code and each translation target signal in the frequency domain. Then, the correlation value in the frequency domain is transformed by inverse Fourier transform to obtain its correlation value in the time domain.

[0130] In one implementation, the correlation value between the initial spreading code and the translation target signal in the time domain is determined by the following formula:

[0131]

[0132]

[0133]

[0134] Where y(m) is the m-th element in the sequence, c(mn) is the initial spreading code shifted n bits to the right based on the m-th element, N is the number of points in the time-domain discrete signal, and k is the number of the frequency-domain signal, with a value range of 0 ≤ k ≤ N-1, e -2πjkn / N e -2πjkm / N and e 2πjk(m-n) / N Let z(n) be an orthogonal basis in N-dimensional complex space, z(n) be the result of the convolution operation between the initial spreading code and the target signal in the time domain, Z(k) be the correlation value in the frequency domain, Y(k) be the received signal in the frequency domain, and C(k) be the initial spreading code signal in the frequency domain.

[0135] Step 4: Perform differential coherent accumulation on the correlation values ​​between the initial spreading code and the translation target signal in the time domain to obtain the positive and negative correlation peaks of the first target signal under each translation mode.

[0136] Coherent accumulation accumulates correlation values ​​over a certain time period, specifically the correlation values ​​between the initial spreading code and the translated target signal within each short, preset time segment. However, coherent accumulation has limitations, potentially leading to the failure to capture weak signals and the influence of residual Doppler. Therefore, differential coherent accumulation is employed for the correlation values ​​between the initial spreading code and each translated target signal obtained in the previous step. This differential coherent accumulation coherently accumulates the correlation values ​​of several segments of target signals with the same frequency offset, yielding the positive and negative correlation peaks of the first target signal under each translation mode. The aforementioned differential coherent accumulation multiplies the conjugate of the current segment's coherent accumulation result with the previous segment's coherent accumulation result.

[0137] In one implementation, differential coherent accumulation is performed on the correlation values ​​between the initial spreading code and the translation target signal in the time domain to obtain the positive and negative correlation peaks of the first target signal under each translation mode, specifically including:

[0138] Step 1: For each translation mode, accumulate the correlation values ​​between the initial spreading code in the time domain and the corresponding translated target signal in each segment of the target signal. Determine the positive and negative accumulation results of the first target signal for each translation mode using the following formula:

[0139]

[0140]

[0141] Step 2: Based on the positive and negative cumulative results of the first target signal under each translation mode, determine the positive and negative correlation peaks of the first target signal under each translation mode using the following formula:

[0142]

[0143] in, This indicates the positive accumulation of the correlation value in differential coherent demodulation. This indicates the negative accumulation of the correlation value in differential coherent demodulation, y k This represents the k-th coherent cumulative result. Let represent the conjugate of the (k+1)th coherent accumulation result, L represent the number of coherent accumulations, CB represent the correlation peak, V represent the differential coherent demodulation correlation accumulation, and E(V) represent the expectation of the differential coherent demodulation correlation accumulation.

[0144] Specifically, when the communication system frame format contains a synchronization sequence, a general acquisition algorithm can successfully complete the acquisition. However, without a dedicated synchronization sequence, the biggest impact on acquisition is the inability to directly derive the correlation peak through coherent accumulation, leading to acquisition failure. Therefore, the correlation values ​​between the initial spreading code and the corresponding shifted target signals of each segment of the target signal at the same frequency offset are first coherently accumulated in the time domain. For example, assuming the total time length of the first target signal is L, it is segmented according to the process described in step one of the coarse acquisition steps, that is, the first target signal with a total time length of L is divided into N small segments. If there are M different frequency offsets in the first preset shift method, each segment of the target signal is shifted according to the first preset shift method. After shifting, each segment of the target signal can obtain M shifted target signals. The correlation value between each shifted target signal and the spreading code is calculated. The correlation values ​​of the N shifted target signals shifted at the same frequency offset are accumulated and moduloed, and then calculated using the formula... and The positive and negative cumulative correlation values ​​of differential coherent demodulation under M different frequency offsets are obtained, and then the formula is used to obtain the correlation values. Positive and negative correlation peaks at different frequency offsets were obtained.

[0145] Step 5: Determine the final correlation peak based on the positive and negative correlation peaks of the first target signal under each translation mode.

[0146] In practice, the correlation values ​​of several target signals shifted by the same frequency offset are coherently accumulated. Each accumulation will yield two results: positive accumulation and negative accumulation. The peak values ​​of the positive and negative correlation peaks are compared, and the larger correlation peak is determined as the correlation peak of that frequency offset. Then, the peak values ​​of the correlation peaks of different frequency offsets are compared, and the one with the largest correlation peak is determined as the final correlation peak of the coarse acquisition process.

[0147] Specifically, based on the correlation peaks of different frequency offsets in the first preset translation method, the final correlation peak is determined using the following formula:

[0148]

[0149] Wherein, V is the correlation peak of each frequency offset in the first preset translation mode.

[0150] In this embodiment, the success of coarse acquisition is determined according to the following process:

[0151] Determine whether the peak value of the final correlation peak is greater than the coarse capture decision threshold;

[0152] If so, then the coarse capture was successful;

[0153] If not, then coarse capture has failed.

[0154] Specifically, using the correlation values ​​of the initial spreading code and the target signal in the time domain, the peak-to-average power ratio (PAPR) is calculated after coherent accumulation. This PAPR is then compared with a threshold value to determine whether the signal has been captured. The peak value of the final correlation peak is compared with a coarse capture decision threshold. If the correlation peak value is greater than the threshold value, the capture is successful; otherwise, the capture fails.

[0155] It should be noted that if the coarse acquisition fails, the initial target signal is sampled again to obtain another target signal, and coarse acquisition is performed on the other target signal. The above steps are repeated until coarse acquisition is successful.

[0156] Therefore, if the first coarse capture fails, sampling and coarse capture are repeated until the first coarse capture succeeds.

[0157] S14. When the first coarse acquisition is successful, the initial target signal is sampled to obtain the second target signal.

[0158] S15. Perform a second coarse acquisition on the second target signal.

[0159] Specifically, when the first coarse acquisition is successful, the received signal is sampled again to obtain the second target signal, and the second coarse acquisition is performed on the second target signal. If the second coarse acquisition is determined to be unsuccessful, the sampling and coarse acquisition are repeated in the same way as the first coarse acquisition until the second coarse acquisition is successful.

[0160] It should be noted that the process of performing a second coarse acquisition for the second target signal is the same as the process of performing a first coarse acquisition for the first target in step S13 above. The implementation of step S15 can refer to the implementation of step S13 above, and will not be repeated here.

[0161] S16. When it is determined that the second coarse acquisition is successful, the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition are determined according to the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively.

[0162] If the second coarse acquisition is successful, the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition are determined based on the final correlation peaks obtained from the two coarse acquisitions.

[0163] S17. Determine the chip offset difference based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition.

[0164] S18. If the chip offset difference is less than a preset threshold, the second coarse acquisition ends; if the chip offset difference is not less than the preset threshold, the second coarse acquisition is performed again.

[0165] The second coarse acquisition ends when the difference in chip offset between the two acquisitions is less than a preset threshold; if the difference in chip offset between the two acquisitions is not less than the preset threshold, the second coarse acquisition is repeated. The preset threshold can be determined based on experience, actual scenario requirements, etc.

[0166] After the second coarse acquisition, signal frequency offset and code phase can be acquired even without an all-zero or all-one synchronization sequence. Based on this, the synchronization sequence estimated by coarse acquisition is used for fine acquisition judgment, and the frequency offset and code phase of the signal can be further corrected through fine acquisition processing.

[0167] In one implementation, after the second coarse capture is completed, the process further includes:

[0168] Step 1: Determine the carrier Doppler compensation and synchronization head variation based on the final correlation peak in the coarse acquisition.

[0169] Based on the final correlation peak in the second coarse acquisition, the frequency offset of the signal can be obtained, which is the carrier Doppler compensation amount. If the final correlation peak is a positive correlation peak, the synchronization head change is determined to be positive; if the final correlation peak is a negative correlation peak, the synchronization head change is determined to be negative. For example, if the positive correlation peak is relatively large in the Kth coherent accumulation result, the synchronization head is determined to be 1; if the negative correlation peak is relatively large, the synchronization head is determined to be -1.

[0170] Step 2: Compensate the first target signal and the second target signal according to the carrier Doppler compensation amount to obtain the input signal;

[0171] In practice, the target signal that is finally acquired for the first coarse acquisition and the target signal that is finally acquired for the second coarse acquisition are demodulated into the input signal according to the carrier Doppler compensation amount.

[0172] Step 3: Based on the chip offset of the second coarse acquisition and the second preset translation method, the input signal is translated to obtain the first translation signal, the second translation signal, and the third translation signal respectively;

[0173] Based on different second preset translation methods, the input signal is translated using different second preset translation methods on the basis of the chip offset obtained from the second coarse acquisition, resulting in a first translation signal, a second translation signal, and a third translation signal. The optimal solution for each second preset translation method can be determined through multiple experiments, or it can be determined based on empirical values, actual needs, etc. For example, if the second preset translation method is determined to be a one-bit leading translation, an in-situ translation, and a one-bit lagging translation, then the input signal is translated according to the three different preset translation methods, namely, a one-bit leading translation compared to the chip offset obtained from the coarse acquisition, a one-bit lagging translation compared to the chip offset obtained from the coarse acquisition, and a translation of the code offset number of bits obtained from the coarse acquisition.

[0174] Step 4: Determine the first and second synchronization heads based on the changes in the synchronization heads;

[0175] In practice, since the first or second coarse capture decision of the synchronization header is uncertain when performing differential operation, it is divided into two cases: the first bit is 1 and the first bit is -1. The operation is performed on them respectively to obtain two types of synchronization headers.

[0176] Step 5: Based on the initial spreading code, determine the first spreading code and the second spreading code according to the first synchronization header and the second synchronization header, respectively.

[0177] Specifically, after differential operation of the synchronization header obtained through coarse acquisition decision, it is Kronecker product with the known spreading code. That is, the two synchronization headers obtained in step four above are spread with the initial spreading code to obtain the first spreading code and the second spreading code for fine acquisition.

[0178] Step 6: Multiply the first translation signal, the second translation signal, and the third translation signal by the first spreading code and the second spreading code respectively, and then coherently accumulate them to obtain the corresponding spreading sequence.

[0179] The processed three input data are multiplied by two fine acquisition spreading codes and then coherently accumulated to obtain six sequences.

[0180] Step 7: Perform a Fast Fourier Transform (FFT) on each spread spectrum sequence;

[0181] Step 8: Take the square of the modulus of each sequence after FFT;

[0182] Step 9: Determine the maximum value among the squares of the moduli of all sequences;

[0183] Step 10: Determine if the maximum value is greater than the decision threshold;

[0184] If so, then the capture was successful;

[0185] If not, the fine capture fails.

[0186] In practice, an FFT is performed on the six sequences obtained from the above steps, the square of the modulus is taken, the maximum value is found, and compared with the fine acquisition decision threshold, thus completing the fine acquisition process. Subsequent processing such as tracking, demodulation, frame synchronization, and decoding is then performed on the acquired signal to obtain the demodulated signal.

[0187] This invention provides a Doppler acquisition method. By down-converting the received signal to baseband and performing low-pass filtering on the baseband waveform to remove noise and high-frequency components, the processed digital baseband signal undergoes coarse acquisition processing, achieving acquisition of frequency offset and code phase even without an all-zero or all-one synchronization sequence. Further, using the correlation value between the spreading code and the target signal, the peak-to-average power ratio (PAPR) is calculated after coherent accumulation and compared with a threshold value to determine whether the signal has been acquired. Based on this, the synchronization sequence estimated by coarse acquisition is used for fine acquisition judgment, further correcting the signal's frequency offset and code phase. The acquired signal is then subjected to subsequent processing such as tracking, demodulation, frame synchronization, and decoding to demodulate the signal. Thus, through the above processing, acquisition can be successfully completed even without a synchronization sequence in the data link frame format, obtaining data with a very small residual frequency offset, thereby providing a data foundation for the communication system and helping the receiver to perform correct demodulation subsequently.

[0188] Example 2

[0189] Based on Embodiment 1, this embodiment is also provided to facilitate a better understanding by those skilled in the art.

[0190] Assume a spreading ratio of 1022, a local pseudo-code spreading sequence, QPSK modulation, a capture accuracy of 600Hz, a chip rate of 10.24MHz, and a Doppler frequency offset range of -200kHz to 200kHz.

[0191] Suppose that the received signal after down-conversion can be expressed as:

[0192] y(t)=Ad(t)c(t-τ)cos(ω0+ω d )t+n(t)

[0193] Where A is the signal amplitude; d(t) is the QPSK modulation data; c(t-τ) is the local pseudocode; ω0 is the carrier frequency; ω d is the Doppler shift; n(t) is additive white Gaussian noise.

[0194] The received signal is downsampled by a factor of two to obtain y(n). y(n) is then low-pass filtered to remove high-frequency components and out-of-band noise.

[0195] like Figure 2 The flowchart of a coarse acquisition process in a Doppler acquisition method according to an embodiment of the present invention is shown. The received signal, after the above processing, undergoes coarse acquisition processing. First, a two-dimensional parallel time-frequency search is performed. That is, the convolution of the local pseudocode and the received data in the time domain is transformed into a frequency domain multiplication by FFT to obtain the correlation value of the local pseudocode and the received data in the frequency domain. Then, the frequency domain correlation value is subjected to an inverse Fourier transform to obtain its correlation value in the time domain. The relevant formula is as follows:

[0196]

[0197]

[0198]

[0199] Where y(m) is the m-th element in the sequence, c(mn) is the local pseudocode shifted n bits to the right based on the m-th element, N is the number of points in the time-domain discrete signal, k is the number of the frequency-domain signal, and its value range is 0≤k≤N-1, e -2πjkn / N e -2πjkm / N and e 2πjk(m-n) / N Let z(n) be an orthogonal basis in N-dimensional complex space, z(n) be the result of the convolution operation between the local pseudocode and the target signal in the time domain, Z(k) be the correlation value in the frequency domain, Y(k) be the received signal in the frequency domain, and C(k) be the local pseudocode signal in the frequency domain.

[0200] The correlation values ​​of the two sequences are obtained using the above steps. After coherent accumulation, the peak-to-average power ratio (PAPR) of the obtained results is calculated and compared with the threshold value to determine whether the signal has been captured.

[0201] Specifically, the correlation values ​​over a certain time period are accumulated using differential coherent accumulation. Differential coherent accumulation multiplies the conjugate of the current coherent accumulation result by the previous coherent accumulation result; its expression is:

[0202]

[0203] Where V+ represents the positive accumulation of differential coherent demodulation correlation values, L represents the differential correlation value in each segment, and yk represents the k-th coherent accumulation result. It represents the conjugate of the (k+1)th coherent cumulative result.

[0204] When the data link frame format contains a synchronization sequence, a general acquisition algorithm can successfully complete the acquisition. However, when there is no synchronization sequence of all zeros or all ones, the biggest impact on acquisition is that the correlation peak cannot be directly accumulated through coherent accumulation, leading to acquisition failure. Therefore, the positive and negative correlation peaks are calculated using the formulas for positive and negative accumulation of differential coherent demodulation correlation values ​​and correlation peaks. The magnitudes of the positive and negative correlation peaks are compared, and the one with the larger correlation peak is taken as the final correlation peak in the coarse acquisition process. That is, if the positive correlation peak is larger in the Kth coherent accumulation result, the synchronization header is determined to be 1; if the negative correlation peak is larger, the synchronization header is determined to be -1. This is compared with the decision threshold (the coarse acquisition decision threshold is 20). If the correlation peak is greater than the threshold value, the first acquisition is successful, and a second acquisition is performed. If the chip offset difference between the two acquisitions is less than 2, the coarse acquisition is successful; if the first acquisition fails, the acquisition is re-performed.

[0205] The expression for the negative coherent accumulation of differential coherent demodulation is:

[0206]

[0207] The formula for calculating the relevant peak is:

[0208] CB = max|V| 2 / E(V)

[0209] Where V_ represents the negative cumulative correlation value of differential coherent demodulation, and y k This represents the k-th coherent cumulative result. Let represent the conjugate of the (k+1)th coherent accumulation result, L represent the number of coherent accumulations, CB represent the correlation peak, V represent the differential coherent demodulation correlation accumulation, and E(V) represent the expectation of the differential coherent demodulation correlation accumulation.

[0210] After being captured by the coarse capture module described above, the signal can be captured more accurately. However, coarse capture may result in capture errors. Therefore, a fine capture process can be added to refine the capture.

[0211] like Figure 3The flowchart of a fine acquisition process in a Doppler acquisition method according to an embodiment of the present invention is shown. The fine acquisition steps are as follows: demodulating the input signal according to the carrier Doppler compensation amount captured by the coarse acquisition module; shifting the input signal in three ways: shifting by three bits lag compared to the chip offset obtained from coarse acquisition, shifting by two bits lag compared to the chip offset obtained from coarse acquisition, and shifting by one bit lag compared to the chip offset obtained from coarse acquisition; and performing spread spectrum operations on the three processed data streams with the local pseudocode. The local pseudocode at this time is obtained by differential operation of the synchronization header obtained from the coarse acquisition decision and then performing Kronenstein calculation with the known local pseudocode. The result obtained from the coarse acquisition decision has two cases: the first bit is 1 and the first bit is -1. The coarse acquisition decision's synchronization header is divided into two cases during differential operation. The coarse acquisition decision's synchronization header is divided into two cases: the first bit is 1 and the first bit is -1. The coarse acquisition decision's synchronization header is divided into two cases. The coarse acquisition decision's synchronization header is then spread with the local pseudo-code to obtain the local pseudo-code for fine acquisition. Then, the three processed input data are multiplied by the two local pseudo-codes for fine acquisition and coherently accumulated. Then, FFT is performed on these six sequences, the square of the modulus is taken, the maximum value is found, and it is compared with the decision threshold (the fine acquisition decision threshold is 100) to complete the fine acquisition process.

[0212] Example 3

[0213] Based on the same inventive concept, this embodiment of the invention also provides a Doppler capture device. Since the principle of the above-mentioned device and equipment in solving the problem is similar to the Doppler capture method provided by this invention, the implementation of the above-mentioned device and equipment can refer to the implementation of the method, and the repeated parts will not be described again.

[0214] like Figure 4 A schematic diagram of a Doppler capture device according to an embodiment of the present invention is shown, the device comprising:

[0215] Preprocessing module 21 preprocesses the received signal to obtain the initial target signal;

[0216] The sampling module 22 is used to sample the initial target signal to obtain the first target signal; when the first coarse acquisition is successful, the initial target signal is sampled to obtain the second target signal.

[0217] The coarse acquisition module 23 is used to perform a first coarse acquisition process on the first target signal and a second coarse acquisition on the second target signal; when the chip offset difference is not less than a preset threshold, the second coarse acquisition is performed again.

[0218] The first determining module 24 is used to determine the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively; and to determine the chip offset difference based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition.

[0219] The first judgment module 25 is used to determine whether the chip offset difference is less than a preset threshold.

[0220] The termination module 26 is used to terminate the second coarse capture when the chip offset difference is less than a preset threshold.

[0221] In one embodiment, the coarse capture module includes:

[0222] The duration segmentation submodule is used to segment the total duration of the first target signal into several segments of the target signal with a preset duration based on a preset duration.

[0223] The translation submodule is used to translate each target signal of a preset duration according to a first preset translation method to obtain a preset number of translated target signals corresponding to each target signal segment;

[0224] The first determining submodule is used to determine the correlation value between the initial spreading code and the translated target signal in the time domain based on the initial spreading code and the translated target signal of several segments of target signal;

[0225] The coherent accumulation submodule is used to perform differential coherent accumulation on the correlation values ​​between the initial spreading code and the translation target signal in the time domain, so as to obtain the positive correlation peak and negative correlation peak of the first target signal under each translation mode.

[0226] The second determining submodule is used to determine the final correlation peak based on the positive and negative correlation peaks of the first target signal under each translation mode;

[0227] The judgment submodule is used to determine whether the peak value of the final correlation peak is greater than the coarse capture decision threshold; if yes, the coarse capture is determined to be successful; otherwise, the coarse capture is determined to be unsuccessful; and,

[0228] The coarse acquisition module is specifically used to perform a first coarse acquisition process on the first target signal and a second coarse acquisition on the second target signal through each sub-module; when the chip offset difference is not less than a preset threshold, the second coarse acquisition is performed again.

[0229] In one embodiment, the device further includes:

[0230] The second determining module is used to determine the carrier Doppler compensation amount and synchronization header change based on the final correlation peak in the coarse acquisition.

[0231] The compensation module is used to compensate the first target signal and the second target signal according to the carrier Doppler compensation amount to obtain the input signal;

[0232] The translation module is used to translate the input signal based on the chip offset of the second coarse capture and the preset translation mode, to obtain the first translation signal, the second translation signal, and the third translation signal, respectively.

[0233] The third determining module is used to determine the first synchronization head and the second synchronization head based on the change of the synchronization head;

[0234] The fourth determining module is used to determine the first spreading code and the second spreading code based on the initial spreading code and according to the first synchronization header and the second synchronization header, respectively.

[0235] The arithmetic module is used to coherently accumulate the first translation signal, the second translation signal, and the third translation signal after multiplying them with the first spreading code and the second spreading code, respectively, to obtain the corresponding spreading sequence; perform a Fast Fourier Transform (FFT) on each spreading sequence; take the square of the modulus of each sequence after FFT; and determine the maximum value among the squares of the moduli of all sequences.

[0236] The second judgment module is used to determine whether the maximum value is greater than the decision threshold; if so, the fine capture is successful; otherwise, the fine capture fails.

[0237] In one embodiment, the preprocessing module includes:

[0238] The frequency conversion submodule is used to down-convert the received signal. The baseband signal obtained after down-conversion is expressed by the following expression: y(t)=Ad(t)c(t-τ)cos(ω0+ω d )t+n(t);

[0239] The sampling submodule is used to sample the baseband signal to obtain the sampled signal;

[0240] The filtering submodule is used to perform low-pass filtering on the sampled signal to obtain the initial target signal;

[0241] Where y(t) is the baseband signal, A is the signal amplitude, d(t) is the modulation data information, c(t-τ) is the initial spreading code, ω0 is the carrier frequency, and ω d denoted as Doppler shift, and n(t) as additive white Gaussian noise.

[0242] In one implementation, the first determining submodule is specifically used to perform a time-frequency two-dimensional fully parallel search on different translation target signals of each segment of target signal to determine the correlation value between the initial spreading code and the translation target signal in the time domain.

[0243] In one implementation, the first determining submodule is specifically used to determine the correlation value between the initial spreading code and the translation target signal in the time domain using the following formula:

[0244]

[0245]

[0246] Where y(m) is the m-th element in the sequence, c(mn) is the initial spreading code shifted n bits to the right based on the m-th element, N is the number of points in the time-domain discrete signal, and k is the number of the frequency-domain signal, with a value range of 0 ≤ k ≤ N-1, e -2πjkn / N e -2πjkm / N and e 2πjk(m-n) / N Let z(n) be an orthogonal basis in N-dimensional complex space, z(n) be the result of the convolution operation between the initial spreading code and the target signal in the time domain, Z(k) be the correlation value in the frequency domain, Y(k) be the received signal in the frequency domain, and C(k) be the initial spreading code signal in the frequency domain.

[0247] In one implementation, the coherent accumulation submodule includes:

[0248] The arithmetic unit is used to perform an accumulation operation on the correlation value between the initial spreading code in the time domain and the corresponding translated target signal in each segment of the target signal under each translation mode. The positive accumulation result and negative accumulation result of the first target signal under each translation mode are determined by the following formula:

[0249]

[0250]

[0251] Furthermore, based on the positive and negative cumulative results of the first target signal under each translation mode, the positive and negative correlation peaks of the first target signal under each translation mode are determined using the following formula:

[0252]

[0253] in, This indicates the positive accumulation of the correlation value in differential coherent demodulation. This indicates the negative accumulation of the correlation value in differential coherent demodulation, y k This represents the k-th coherent cumulative result. Let represent the conjugate of the (k+1)th coherent accumulation result, L represent the number of coherent accumulations, CB represent the correlation peak, y represent the differential coherent demodulation correlation accumulation, and E(V) represent the expectation of the differential coherent demodulation correlation accumulation.

[0254] For ease of description, the above sections are divided into modules (or units) according to their functions and described separately. Of course, in implementing this invention, the functions of each module (or unit) can be implemented in one or more software or hardware components.

[0255] Having introduced a Doppler capture method and apparatus according to an exemplary embodiment of the present invention, a computing device according to another exemplary embodiment of the present invention will now be described.

[0256] Those skilled in the art will understand that various aspects of the present invention can be implemented as systems, methods, or program products. Therefore, various aspects of the present invention can be specifically implemented in the following forms: entirely hardware implementations, entirely software implementations (including firmware, microcode, etc.), or implementations combining hardware and software aspects, collectively referred to herein as “circuits,” “modules,” or “systems.”

[0257] In some possible implementations, the computing device according to the invention may include at least one processor and at least one memory. The memory stores program code that, when executed by the processor, causes the processor to perform the steps of a Doppler capture method according to various exemplary embodiments of the invention described above. For example, the processor may perform actions such as... Figure 1 The steps shown are as follows: S11, preprocessing the received signal to obtain an initial target signal; S12, sampling the initial target signal to obtain a first target signal; S13, performing a first coarse acquisition on the first target signal; S14, when the first coarse acquisition is successful, sampling the initial target signal to obtain a second target signal; S15, performing a second coarse acquisition on the second target signal; S16, when the second coarse acquisition is successful, determining the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively; S17, determining the chip offset difference based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition; S18, if the chip offset difference is less than a preset threshold, ending the second coarse acquisition; if the chip offset difference is not less than the preset threshold, re-performing the second coarse acquisition.

[0258] In some possible implementations, various aspects of the Doppler capture method provided by the present invention can also be implemented as a program product comprising program code that, when run on a computer device, causes the computer device to perform the steps of the Doppler capture method according to various exemplary embodiments of the present invention described above. For example, the computer device may perform actions such as... Figure 1 The steps shown are as follows: S11, preprocessing the received signal to obtain an initial target signal; S12, sampling the initial target signal to obtain a first target signal; S13, performing a first coarse acquisition on the first target signal; S14, when the first coarse acquisition is successful, sampling the initial target signal to obtain a second target signal; S15, performing a second coarse acquisition on the second target signal; S16, when the second coarse acquisition is successful, determining the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively; S17, determining the chip offset difference based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition; S18, if the chip offset difference is less than a preset threshold, ending the second coarse acquisition; if the chip offset difference is not less than the preset threshold, re-performing the second coarse acquisition.

[0259] The program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0260] The program product for Doppler capture according to embodiments of the present invention can be a portable compact disc read-only memory (CD-ROM) and include program code, and can run on a computing device. However, the program product of the present invention is not limited thereto. In this document, the readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0261] A readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying readable program code. This propagated data signal may take many forms, including—but not limited to—electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0262] The program code contained on the readable medium may be transmitted using any suitable medium, including—but not limited to—wireless, wired, fiber optic, RF, etc., or any suitable combination thereof.

[0263] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0264] It should be noted that although several units or sub-units of the device have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more units described above can be embodied in one unit. Conversely, the features and functions of one unit described above can be further divided and embodied by multiple units.

[0265] Furthermore, although the operations of the method of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0266] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0267] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0268] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0269] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0270] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0271] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A Doppler capture method, characterized in that, include: The received signal is preprocessed to obtain the initial target signal; The initial target signal is sampled to obtain the first target signal; The first coarse acquisition is performed on the first target signal, following the procedure below: Based on a preset duration, the total duration of the first target signal is segmented to obtain several segments of target signal with preset durations; Each target signal of a preset duration is translated according to the first preset translation method to obtain a preset number of translated target signals corresponding to each target signal segment; Based on the initial spreading code and the translation target signal of several target signals, determine the correlation value between the initial spreading code and the translation target signal in the time domain; Differential coherent accumulation is performed on the correlation values ​​between the initial spreading code and the translation target signal in the time domain to obtain the positive and negative correlation peaks of the first target signal under each translation mode; The final correlation peak is determined based on the positive and negative correlation peaks of the first target signal under each translation mode; and the success of coarse acquisition is determined according to the following procedure: Determine whether the peak value of the final correlation peak is greater than the coarse capture decision threshold; If so, then the coarse capture was successful; If not, then coarse capture has failed; When the first coarse acquisition is confirmed to be successful, the initial target signal is sampled to obtain the second target signal; A second coarse acquisition is performed on the second target signal; When the second coarse acquisition is confirmed to be successful, the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition are determined based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively. The chip offset difference is determined based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition. If the chip offset difference is less than a preset threshold, the second coarse acquisition ends; if the chip offset difference is not less than the preset threshold, the second coarse acquisition is performed again.

2. The method according to claim 1, characterized in that, After the second coarse capture is completed, it also includes: The carrier Doppler compensation and synchronization head variation are determined based on the final correlation peak in the coarse acquisition. The first target signal and the second target signal are compensated according to the carrier Doppler compensation amount to obtain the input signal; Based on the chip offset of the second coarse acquisition and the second preset translation method, the input signal is translated to obtain the first translation signal, the second translation signal, and the third translation signal respectively; Based on the changes in the synchronization header, determine the first synchronization header and the second synchronization header; Based on the initial spreading code, the first spreading code and the second spreading code are determined according to the first synchronization header and the second synchronization header, respectively. The first translation signal, the second translation signal, and the third translation signal are multiplied by the first spreading code and the second spreading code respectively, and then coherently accumulated to obtain the corresponding spreading sequence; Perform a Fast Fourier Transform (FFT) on each spread spectrum sequence; Take the square of the modulus of each sequence after FFT; Determine the maximum value among the squares of the moduli of all sequences; Determine if the maximum value is greater than the decision threshold; If so, then the capture was successful; If not, the fine capture fails.

3. The method according to claim 1, characterized in that, The received signal is preprocessed to obtain the initial target signal, specifically including: The received signal is down-converted, and the resulting baseband signal is expressed by the following expression: ; The baseband signal is sampled to obtain the sampled signal; The sampled signal is low-pass filtered to obtain the initial target signal; in, For baseband signals, For signal amplitude, To modulate data information, For the initial spreading code, For carrier frequency, For Doppler shift, It is additive white Gaussian noise.

4. The method according to claim 3, characterized in that, Based on the initial spreading code and the translational target signal from several segments of target signal, the correlation value between the initial spreading code and the translational target signal in the time domain is determined, specifically including: A two-dimensional parallel time-frequency search is performed on each segment of the target signal for different translational target signals to determine the correlation value between the initial spreading code and the translational target signal in the time domain.

5. The method according to claim 4, characterized in that, The correlation value between the initial spreading code and the translation target signal in the time domain is determined by the following formula: in, Let m be the m-th element in the sequence. The initial spreading code is based on the m-th element, shifted n bits to the right. Let be the number of points in the time-domain discrete signal, and k be the number of the frequency-domain signal, with a value range of . , , and Let it be an orthogonal basis over N-dimensional complex space. This is the result of the convolution operation between the initial spreading code and the target signal in the time domain. The correlation value in the frequency domain. The received signal in the frequency domain. This is the initial spreading code signal in the frequency domain.

6. The method according to any one of claims 1-5, characterized in that, Differential coherent accumulation is performed on the correlation values ​​between the initial spreading code and the translation target signal in the time domain to obtain the positive and negative correlation peaks of the first target signal under each translation mode, specifically including: For each translation mode, the correlation values ​​between the initial spreading code in the time domain and the corresponding translated target signal in each segment of the target signal are accumulated. The positive and negative accumulation results of the first target signal under each translation mode are determined by the following formula: Based on the positive and negative cumulative results of the first target signal under each translation mode, the positive and negative correlation peaks of the first target signal under each translation mode are determined by the following formula: in, This indicates the positive accumulation of the correlation value in differential coherent demodulation. This indicates the negative accumulation of the correlation value in differential coherent demodulation. Indicates the first A coherent cumulative result, Indicates the first The conjugate of a coherent cumulative result, Indicates the cumulative number of coherent events. Indicates the relevant peak, This represents the cumulative correlation value of differential coherent demodulation. This represents the expected cumulative correlation value of differential coherent demodulation.

7. A Doppler capture device applying the method of claim 1, characterized in that, include: The preprocessing module preprocesses the received signal to obtain the initial target signal; The sampling module is used to sample the initial target signal to obtain the first target signal; when the first coarse acquisition is successful, the initial target signal is sampled to obtain the second target signal. The coarse acquisition module is used to perform a first coarse acquisition process on the first target signal and a second coarse acquisition process on the second target signal; when the chip offset difference is not less than a preset threshold, the second coarse acquisition is performed again. The first determining module is used to determine the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition based on the final correlation peak in the first coarse acquisition and the final correlation peak in the second coarse acquisition, respectively. And determine the chip offset difference based on the chip offset of the first coarse acquisition and the chip offset of the second coarse acquisition; The first judgment module is used to determine whether the chip offset difference is less than a preset threshold. The termination module is used to end the second coarse capture when the chip offset difference is less than a preset threshold.

8. A computing device, characterized in that, It includes at least one processor and at least one memory, wherein the memory stores a computer program that, when executed by the processor, causes the processor to perform the steps of the method according to any one of claims 1-6.

9. A computer-readable medium, characterized in that, It stores a computer program executable by a terminal device, which, when run on the terminal device, causes the terminal device to perform the steps of the method according to any one of claims 1-6.

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