A TT&C transponder system and device for fast and reliable acquisition of mixed spread spectrum signals
By combining digital down-conversion, direct spread spectrum acquisition, frequency hopping interval division, and matched filter modules, the shortcomings of telemetry and control transponder systems in terms of synchronization accuracy and reliability are solved, achieving fast and reliable acquisition of hybrid spread spectrum signals, which is suitable for the high dynamic and radiation environments of spacecraft.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING MICROELECTRONICS TECH INST
- Filing Date
- 2023-07-21
- Publication Date
- 2026-07-24
AI Technical Summary
Existing telemetry and control transponder systems are inadequate in terms of synchronization accuracy, reliability, and response speed, especially in environments with rapid spacecraft movement and high-energy particle radiation, where it is difficult to achieve fast and reliable acquisition of hybrid spread spectrum signals.
The system employs a digital down-conversion module, a direct-reading code acquisition module, a frequency hopping interval division module, a matched filter module, and an acquisition decision module, combined with a synchronous refresh module, to achieve fast and reliable acquisition of hybrid spread spectrum signals through Doppler frequency shift correction and pseudo-code phase modulation.
It improves the acquisition speed and synchronization accuracy, enhances the system's anti-interference capability and reliability, and meets the requirements of spacecraft's rapid movement and radiation environment.
Smart Images
Figure CN117118478B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of communication measurement and control, and specifically relates to a measurement and control transponder system and equipment for rapidly and reliably capturing hybrid spread spectrum signals. Background Technology
[0002] The most important onboard equipment in aerospace telemetry, tracking, and command (TT&C) systems is the TT&C transponder, which is crucial for realizing system functions. It requires high levels of secure communication, anti-interception and anti-jamming capabilities, as well as emergency communication and TT&C capabilities. Hybrid frequency hopping technology possesses excellent anti-jamming properties, high security, multi-access networking performance, and high system security, making it one of the most effective means of anti-jamming communication for TT&C transponders and widely used in the satellite TT&C field.
[0003] Hybrid hopping spread spectrum technology combines the advantages of direct sequence spread spectrum and frequency hopping techniques to achieve greater spread spectrum, further reducing the signal's spectral density. By continuously changing the frequency band occupied by the signal, it avoids malicious interference, greatly enhancing the system's anti-interference capability and survivability. However, it also presents significant challenges to system implementation, including the following difficulties:
[0004] Spacecraft fly at high speeds, resulting in large dynamics between spacecraft and the ground, large Doppler frequency deviation of signals, and high Doppler rate of change.
[0005] With limited onboard resources, the telemetry, tracking, and command (TT&C) transponder must synchronize with the signal as quickly as possible.
[0006] The measurement function of the telemetry and control transponder requires the system to have a very high synchronization accuracy;
[0007] Compared to ground-based equipment, telemetry and control transponders are exposed to high-energy particle radiation in the space environment. In addition to ensuring that the components used meet aerospace radiation resistance standards, the system also needs to be reliable. Summary of the Invention
[0008] To address the aforementioned problems in the existing technology, namely the insufficient synchronization accuracy, reliability, and response speed of existing telemetry and control transponder systems, this invention provides a telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals. The telemetry and control transponder system includes: a digital down-conversion module, a direct spread code acquisition module, a frequency hopping interval division module, a matched filter module, an acquisition decision module, and a synchronization refresh module.
[0009] The digital downconversion module is used to receive the local carrier signal fed back by the capture decision module and the intermediate frequency signal input from the outside, and to perform digital downconversion processing on the intermediate frequency signal according to the local carrier signal to downconvert the intermediate frequency signal to a zero intermediate frequency signal; the local carrier signal is obtained based on the Doppler frequency shift of the previous round according to the set rules;
[0010] The direct spread spectrum code acquisition module is used to capture the zero intermediate frequency signal and modulate it according to the phase of the spreading code to obtain the spread spectrum signal;
[0011] The frequency hopping interval division module is used to divide the bandwidth of the spread spectrum signal into N parallel frequency hopping intervals according to the frequency hopping pattern, thereby obtaining a frequency hopping signal divided into N frequency hopping intervals; the frequency hopping pattern is obtained by the frequency hopping code phase of the previous round through a frequency hopping pattern generator.
[0012] The matched filter module is used to filter the frequency hopping signal divided into N intervals through the matched filter and then perform N-point Fourier operation to obtain the final correlation result, pseudocode phase and Doppler frequency shift of the current round;
[0013] The acquisition decision module compares the code phase with a threshold value. If the threshold value is not exceeded, it outputs the frequency hopping code phase, the spreading code phase, and the Doppler shift, and proceeds to the next round to execute the functions of the digital down-conversion module, the direct-spread code acquisition module, the frequency hopping interval division module, and the matched filter module to obtain the code phase and the Doppler shift of the current round. This process continues until the obtained code phase exceeds the threshold value, at which point the acquisition is considered successful, and the final code phase and the final Doppler shift are obtained.
[0014] The synchronous refresh module generates a synchronous refresh signal through a synchronous refresh algorithm. The digital downconversion module, direct-reading code acquisition module, frequency hopping interval division module, matched filter module, and acquisition decision module dynamically refresh according to the synchronous refresh signal.
[0015] In some preferred embodiments, the zero intermediate frequency signal is obtained by:
[0016] The Doppler frequency shift of the previous round is captured by a carrier and code digitally controlled oscillator set in the digital downconversion module, and a local carrier signal is generated by the carrier NCO unit based on the Doppler frequency shift of the previous round.
[0017] The intermediate frequency signal is used to obtain an in-phase intermediate frequency signal and a quadrature intermediate frequency signal. The in-phase frequency conversion signal and the quadrature frequency conversion signal are combined into a complex signal. The complex signal is multiplied by the local carrier signal to obtain a zero intermediate frequency signal.
[0018] In some preferred embodiments, the spread spectrum signal is acquired by a method comprising:
[0019] Based on the spreading code phase, a local pseudo code is generated by the spreading code generator. The local pseudo code is then subjected to a Fourier transform to obtain the Fourier transform result of the local pseudo code. The complex conjugate of the Fourier transform result of the local pseudo code is multiplied and then subjected to an inverse Fourier transform to obtain the modulus value, thus obtaining the one-dimensional modulus value of the spreading pseudo code.
[0020] Perform a Fourier transform on the zero intermediate frequency data to obtain the zero intermediate frequency data in the frequency domain;
[0021] The spread spectrum signal is obtained by cross-correlating the one-dimensional modulus value of the spread spectrum pseudocode with the zero intermediate frequency data in the frequency domain.
[0022] In some preferred embodiments, the frequency hopping interval division module specifically includes:
[0023] Based on the phase of the frequency hopping code from the previous round, a frequency hopping pattern is generated by a frequency hopping pattern generator.
[0024] Based on the frequency hopping pattern, the spread spectrum signal is discretely hopped under pseudo-random sequence control to obtain the spectrum-spread signal.
[0025] The frequency-hopping signal is divided into N frequency-hopping intervals according to the frequency-hopping pattern, thus obtaining a frequency-hopping signal divided into N frequency-hopping intervals.
[0026] In some preferred embodiments, the matched filter module is specifically used for:
[0027] For a frequency-hopping signal divided into N intervals, correlation values are calculated by passing it through the corresponding matched filters to obtain N partial correlation values. The output x(n) of the nth segmented matched filter is calculated as follows:
[0028]
[0029] In the above formula, M is the data length processed by each matched filter, fd is the frequency offset, Ts is the sampling time interval, and c(i)e j(2πfd nTs) Here, c(i+r)) is the frequency hopping signal received by the current matched filter, c(i+r)) is the local spreading code, and r is the phase difference between the frequency hopping signal received by the current matched filter and the local spreading code;
[0030] The local spreading code is generated by direct sequence modulation of the spreading signal. Acquisition is successful only when the phase of the received frequency hopping signal matches that of the local spreading code.
[0031] Performing a Fourier operation on the N partial correlation values, the correlation result X(k) at point k is:
[0032]
[0033] The final correlation result |X(k)| is obtained based on the correlation result X(k) at point k. Based on the final correlation result |X(k)|, the Doppler frequency shift and pseudocode phase of the current round are obtained by searching for the position of the maximum value.
[0034] In some preferred embodiments, if the local spreading code is aligned with the received frequency hopping signal, i.e., the phase difference r between the frequency hopping signal received by the current matched filter and the local spreading code is 0, the output x(n) of the matched filter in the aligned case is:
[0035]
[0036] Where M is the data length processed by each matched filter, fd is the frequency offset, and Ts is the sampling time interval.
[0037] In some preferred embodiments, the Doppler frequency shift of the current round is calculated as follows:
[0038] If the relevant result X(k) is in Taking the maximum value at point , the Doppler frequency shift fd for the current round is:
[0039]
[0040] Where M is the data length processed by each matched filter, fd is the frequency offset, Ts is the sampling time interval, and k1 is the k value corresponding to the maximum correlation result X(k).
[0041] In some preferred embodiments, the synchronous refresh module specifically includes:
[0042] The synchronous refresh algorithm generates a synchronous refresh signal through calculation and decoding. The digital downconversion module, direct-sequence code acquisition module, frequency hopping interval division module, matched filter module, and acquisition decision module dynamically refresh according to the synchronous refresh signal.
[0043] A second aspect of the present invention provides an electronic device comprising:
[0044] At least one processor; and
[0045] A memory communicatively connected to at least one of the processors; wherein,
[0046] The memory stores instructions that can be executed by the processor to implement the aforementioned telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals.
[0047] In a third aspect, the present invention provides a computer-readable storage medium storing computer instructions for execution by the computer to implement the above-described telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals.
[0048] The beneficial effects of this invention are:
[0049] (1) The present invention combines a matched filter and FFT operation in the acquisition algorithm, which has a fast acquisition speed and can capture a large Doppler frequency shift;
[0050] (2) This invention transforms the two-dimensional search of pseudocode phase and carrier frequency into a one-dimensional search of frequency, thereby improving the acquisition speed;
[0051] (3) The present invention divides the broadband signal into N frequency intervals, which satisfies the requirement of high search accuracy for each interval, and the parallel operation improves the search speed;
[0052] (4) The present invention has carried out system-level reliability design, and the dynamic refresh module ensures that the system recovers from the abnormal state to normal, thereby improving the reliability of the system. Attached Figure Description
[0053] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0054] Figure 1 This is a structural block diagram of a telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals according to an embodiment of the present invention;
[0055] Figure 2 This is a schematic diagram of the telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals in an embodiment of the present invention;
[0056] Figure 3 This is a block diagram illustrating the principle of the matched filter in a telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals, as described in this embodiment of the invention. Detailed Implementation
[0057] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.
[0058] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.
[0059] To more clearly explain the telemetry and control transponder system for rapidly and reliably capturing hybrid spread spectrum signals according to the present invention, the following description is in conjunction with... Figure 1 The functional modules in the embodiments of the present invention will be described in detail below.
[0060] Specifically, the digital down-conversion module receives the local carrier signal fed back from the acquisition decision module and the intermediate frequency (IF) signal input from an external source. It performs digital down-conversion processing on the IF signal based on the local carrier signal, down-converting the IF signal to a zero IF signal. The local carrier signal is obtained based on the Doppler frequency shift of the previous round according to a set rule. The direct-reading code acquisition module captures the zero IF signal and modulates it according to the spreading code phase to obtain the spread spectrum signal. The frequency hopping interval division module divides the bandwidth of the spread spectrum signal into N parallel frequency hopping intervals according to the frequency hopping pattern, obtaining the frequency hopping signal divided into N frequency hopping intervals. The frequency hopping pattern is obtained from the frequency hopping code phase of the previous round through a frequency hopping pattern generator. The matched filter module filters the frequency hopping signals divided into N intervals using a matched filter. After the wave, an N-point Fourier operation is performed to obtain the final correlation result, pseudo-code phase, and Doppler shift of the current round. The acquisition decision module compares the code phase with a threshold value. If the threshold value is not exceeded, the frequency hopping code phase, spreading code phase, and Doppler shift are output, and the process proceeds to the next round to execute the functions of the digital down-conversion module, direct-spread code acquisition module, frequency hopping interval division module, and matched filter module to obtain the code phase and Doppler shift of the current round. This process continues until the obtained code phase exceeds the threshold value, at which point the acquisition is considered successful, and the final code phase and final Doppler shift are obtained. The synchronization refresh module generates a synchronization refresh signal through a synchronization refresh algorithm. The digital down-conversion module, direct-spread code acquisition module, frequency hopping interval division module, matched filter module, and acquisition decision module dynamically refresh according to the synchronization refresh signal.
[0061] This invention analyzes the key technical problems of hybrid hopping spread spectrum transponders and proposes a highly reliable method for rapid acquisition of hybrid spread spectrum signals from the aspects of overall architecture, principle, and system scheme design, thereby solving the problems in hybrid hopping spread spectrum transponder systems.
[0062] The first embodiment of the present invention provides a telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals. The telemetry and control transponder system includes: a digital down-conversion module, a direct-reading code acquisition module, a frequency hopping interval division module, a matched filter module, an acquisition decision module, and a synchronization refresh module. Detailed descriptions of each functional module are as follows:
[0063] The digital downconversion module is used to receive the local carrier signal fed back by the capture decision module and the intermediate frequency signal input from the outside. It performs digital downconversion processing on the intermediate frequency signal according to the local carrier signal, and downconverts the intermediate frequency signal to a zero intermediate frequency signal. The local carrier signal is obtained based on the Doppler frequency shift of the previous round according to the set rules.
[0064] In this embodiment, the zero intermediate frequency signal is obtained as follows:
[0065] The Doppler frequency shift of the previous round is captured by the carrier and code digitally controlled oscillator set in the digital downconversion module, and a local carrier signal is generated by the carrier NCO unit based on the Doppler frequency shift of the previous round.
[0066] The intermediate frequency signal is converted into an in-phase intermediate frequency signal and a quadrature intermediate frequency signal. The in-phase and quadrature frequency signals are combined into a complex signal. The complex signal is multiplied with the local carrier signal to obtain a zero intermediate frequency signal.
[0067] The direct spread spectrum code acquisition module is used to capture the zero intermediate frequency signal and modulate it according to the phase of the spreading code to obtain the spread spectrum signal.
[0068] In this embodiment, the method for acquiring the spread spectrum signal includes:
[0069] Based on the phase of the spreading code, a local pseudo code is generated by the spreading code generator. The local pseudo code is then subjected to a Fourier transform to obtain the Fourier transform result of the local pseudo code. The complex conjugate of the Fourier transform result of the local pseudo code is multiplied and then subjected to an inverse Fourier transform to obtain the modulus value, thus obtaining the one-dimensional modulus value of the spreading pseudo code.
[0070] The specific formula for performing a Fourier transform on the local pseudocode is as follows:
[0071]
[0072] Perform a Fourier transform on the zero-IF data to obtain the zero-IF data in the frequency domain; the calculation formula is as follows:
[0073]
[0074] The spread spectrum signal is obtained by cross-correlating the one-dimensional modulus value of the spread spectrum pseudocode with the zero intermediate frequency data in the frequency domain. The calculation formula is as follows:
[0075]
[0076] Transforming z(n) into the frequency domain yields the one-dimensional modulus value Z(k) of the spreading pseudocode:
[0077]
[0078]
[0079] Based on the frequency domain expression of cross-correlation, we know that we can first transform the two sequences to the frequency domain, perform conjugate multiplication, and then perform inverse Fourier transform to obtain the time domain expression.
[0080] The frequency hopping interval division module is used to divide the bandwidth of the spread spectrum signal into N parallel frequency hopping intervals according to the frequency hopping pattern, and obtain the frequency hopping signal divided into N frequency hopping intervals; the frequency hopping pattern is obtained by the frequency hopping code phase of the previous round through the frequency hopping pattern generator.
[0081] In this embodiment, the frequency hopping interval division module specifically includes:
[0082] Based on the phase of the frequency hopping code from the previous round, a frequency hopping pattern is generated using a frequency hopping pattern generator.
[0083] Based on the frequency hopping pattern, the spread spectrum signal is discretely hopped under the control of a pseudo-random sequence to obtain the spectrally spread signal.
[0084] The frequency-hopping signal is divided into N frequency-hopping intervals based on the frequency-hopping pattern, thus obtaining the frequency-hopping signal divided into N frequency-hopping intervals.
[0085] Matched filter module, such as Figure 2 As shown, the signal is used to filter the frequency hopping signal divided into N intervals through a matched filter and then perform an N-point Fourier operation to obtain the final correlation result, pseudocode phase, and Doppler shift of the current round.
[0086] In this embodiment, the matched filter module is specifically used for:
[0087] For a frequency-hopping signal divided into N intervals, correlation values are calculated by passing it through the corresponding matched filters to obtain N partial correlation values. The output x(n) of the nth segmented matched filter is calculated as follows:
[0088]
[0089] In the above formula, M is the data length processed by each matched filter, fd is the frequency offset, Ts is the sampling time interval, and c(i)e j(2πfd nTs) Here, c(i+r) is the frequency hopping signal received by the current matched filter, and c(i+r) is the local spreading code. r is the phase difference between the frequency hopping signal received by the current matched filter and the local spreading code. The local spreading code is generated by direct sequence modulation of the spreading signal. Acquisition is successful only when the phase of the received frequency hopping signal matches that of the local spreading code.
[0090] Performing a Fourier operation on the N partial correlation values, the correlation result X(k) at point k is:
[0091]
[0092] The final correlation result |X(k)| is obtained from the correlation result X(k) at point k. Based on the final correlation result |X(k)|, the Doppler frequency shift and pseudocode phase of the current round are obtained by searching for the position of the maximum value.
[0093] In this embodiment, the Doppler frequency shift of the current round is calculated as follows:
[0094] If the relevant result X(k) is in Taking the maximum value, the Doppler frequency shift fd for the current round is:
[0095]
[0096] Where M is the data length processed by each matched filter, fd is the frequency offset, Ts is the sampling time interval, and k1 is the k value corresponding to the maximum correlation result X(k).
[0097] In this embodiment, if the local spreading code is aligned with the received frequency hopping signal, i.e., the phase difference r between the frequency hopping signal received by the current matched filter and the local spreading code is 0, the output x(n) of the matched filter in the aligned case is:
[0098]
[0099] Where M is the data length processed by each matched filter, fd is the frequency offset, and Ts is the sampling time interval. Under aligned conditions, the product of the spreading code of the received frequency-hopping signal and the spreading code of the local signal is 1. This is because the spreading code is an encrypted sequence composed of 1s and -1s; if aligned, 1*1 = 1; -1*(-1) = 1. The correlation value is maximized in this case.
[0100] The capture decision module compares the code phase with a threshold value. If the threshold value is not exceeded, it outputs the frequency hopping code phase, spread spectrum code phase, and Doppler shift, and proceeds to the next round to execute the functions of the digital down-conversion module, direct-spread code capture module, frequency hopping interval division module, and matched filter module to obtain the code phase and the Doppler shift of the current round. This process continues until the obtained code phase exceeds the threshold value, at which point the capture is considered successful, and the final code phase and final Doppler shift are obtained.
[0101] In this embodiment, the Doppler frequency shift of the current round is calculated as follows:
[0102] If the relevant result X(k) is in Taking the maximum value at point , the Doppler frequency shift fd for the current round is:
[0103]
[0104] Where M is the data length processed by each matched filter, fd is the frequency offset, Ts is the sampling time interval, and k is the k value corresponding to the maximum correlation result X(k).
[0105] The synchronous refresh module generates a synchronous refresh signal using a synchronous refresh algorithm. The digital down-conversion module, direct-reading code acquisition module, frequency hopping interval division module, matched filter module, and acquisition decision module dynamically refresh based on the synchronous refresh signal. The synchronous refresh signal is generated through calculation and decoding.
[0106] like Figure 3 As shown, a specific description is given for a telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals. The digital down-conversion module receives the local carrier signal fed back by the acquisition decision module and the intermediate frequency (IF) signal input from an external source. It performs digital down-conversion processing on the IF signal based on the local carrier signal, down-converting the IF signal to a zero IF signal. The local carrier signal is obtained based on the Doppler frequency shift of the previous round according to a set rule. Then, the zero IF acquisition signal is sent to the direct-spread code acquisition module. The direct-spread code acquisition module receives the zero IF signal, acquires it, and modulates it according to the spreading code phase to obtain a spread spectrum signal. It then sends the spread spectrum signal to the frequency modulation interval division module. The frequency modulation interval division module receives the spread spectrum signal and divides the bandwidth of the spread spectrum signal into N parallel frequency hopping intervals, obtaining a frequency hopping signal divided into N frequency hopping intervals. The frequency hopping pattern is determined by the frequency hopping code phase of the previous round. The frequency hopping signal, divided into N frequency hopping intervals, is obtained through a frequency hopping pattern generator. The frequency interval division module sends the frequency hopping signal to the matched filter module. After receiving the frequency hopping signal, the matched filter module filters the frequency hopping signal divided into N intervals and performs an N-point Fourier operation to obtain the final correlation result, pseudo-code phase, and Doppler frequency shift of the current round. The final correlation result, pseudo-code phase, and Doppler frequency shift of the current round are then sent to the acquisition decision module. The acquisition decision module compares the code phase with a threshold value. If the threshold value is not exceeded, the module outputs the frequency hopping code phase, spreading code phase, and Doppler frequency shift and proceeds to the next round to execute the functions of the digital down-conversion module, direct-spread code acquisition module, frequency hopping interval division module, and matched filter module to obtain the code phase and Doppler frequency shift of the current round. This process continues until the obtained code phase exceeds the threshold value, at which point the acquisition is considered successful, and the final code phase and final Doppler frequency shift are obtained.
[0107] Although the steps in the above embodiments are described in the above order, those skilled in the art will understand that in order to achieve the effect of this embodiment, different steps do not need to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple variations are all within the protection scope of this invention.
[0108] It should be noted that the telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiments can be merged into one module, or further divided into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only for distinguishing the various modules or steps and are not considered as an improper limitation of the present invention.
[0109] An electronic device according to a second embodiment of the present invention includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the processor, the instructions being executed by the processor to realize the above-described telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals.
[0110] A computer-readable storage medium according to a third embodiment of the present invention stores computer instructions for execution by a computer to implement the above-described telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals.
[0111] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process and related descriptions of the storage device and processing device described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.
[0112] Those skilled in the art will recognize that the modules and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. The programs corresponding to the software modules and method steps can be placed in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. To clearly illustrate the interchangeability of electronic hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in electronic hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the invention.
[0113] The terms “first”, “second”, etc., are used to distinguish similar objects, not to describe or indicate a specific order or sequence.
[0114] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus / device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent in such process, method, article, or apparatus / device.
[0115] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.
Claims
1. A telemetry and control transponder system for rapidly and reliably acquiring hybrid spread spectrum signals, characterized in that, The telemetry and control transponder system includes: a digital down-conversion module, a direct-sequence code acquisition module, a frequency hopping interval division module, a matched filter module, an acquisition decision module, and a synchronous refresh module; The digital downconversion module is used to receive the local carrier signal fed back by the capture decision module and the intermediate frequency signal input from the outside, and to perform digital downconversion processing on the intermediate frequency signal according to the local carrier signal to downconvert the intermediate frequency signal to a zero intermediate frequency signal; the local carrier signal is obtained based on the Doppler frequency shift of the previous round according to the set rules; The direct spread spectrum code acquisition module is used to capture the zero intermediate frequency signal and modulate it according to the phase of the spreading code to obtain the spread spectrum signal; The frequency hopping interval division module is used to divide the bandwidth of the spread spectrum signal into N parallel frequency hopping intervals according to the frequency hopping pattern, thereby obtaining a frequency hopping signal divided into N frequency hopping intervals; the frequency hopping pattern is obtained by the frequency hopping code phase of the previous round through a frequency hopping pattern generator. The matched filter module is used to filter the frequency hopping signal divided into N intervals through the matched filter and then perform N-point Fourier operation to obtain the final correlation result, pseudocode phase and Doppler frequency shift of the current round; The acquisition decision module compares the code phase with a threshold value. If the threshold value is not exceeded, it outputs the frequency hopping code phase, the spreading code phase, and the Doppler shift, and proceeds to the next round to execute the functions of the digital down-conversion module, the direct-spread code acquisition module, the frequency hopping interval division module, and the matched filter module to obtain the code phase and the Doppler shift of the current round. This process continues until the obtained code phase exceeds the threshold value, at which point the acquisition is considered successful, and the final code phase and the final Doppler shift are obtained. The synchronous refresh module generates a synchronous refresh signal through a synchronous refresh algorithm. The digital downconversion module, direct-reading code acquisition module, frequency hopping interval division module, matched filter module, and acquisition decision module dynamically refresh according to the synchronous refresh signal. The matched filter module is specifically used for: For a frequency-hopping signal divided into N intervals, correlation values are calculated by passing it through the corresponding matched filters to obtain N partial correlation values. The output x(n) of the nth segmented matched filter is calculated as follows: ； In the above formula, M is the data length processed by each matched filter, fd is the frequency offset, and Ts is the sampling time interval. For the frequency hopping signal received by the current matched filter, c( r) is the local spreading code, where r is the phase difference between the frequency hopping signal received by the matched filter and the local spreading code. The local spreading code is generated by direct sequence modulation of the spreading signal. Acquisition is successful only when the phase of the received frequency hopping signal matches that of the local spreading code. Performing a Fourier operation on the N partial correlation values, the correlation result X(k) at point k is: ； The final correlation result |X(k)| is obtained based on the correlation result X(k) at point k. Based on the final correlation result |X(k)|, the Doppler frequency shift and pseudocode phase of the current round are obtained by searching for the position of the maximum value. If the local spreading code is aligned with the received frequency hopping signal, i.e., the phase difference r between the frequency hopping signal received by the current matched filter and the local spreading code is 0, the output x(n) of the nth matched filter in the aligned case is: ； Where M is the data length processed by each matched filter, fd is the frequency offset, and Ts is the sampling time interval.
2. The telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals according to claim 1, characterized in that, The zero intermediate frequency signal is obtained by the following method: The Doppler frequency shift of the previous round is captured by a carrier and code digitally controlled oscillator set in the digital downconversion module, and a local carrier signal is generated by the carrier NCO unit based on the Doppler frequency shift of the previous round. The intermediate frequency signal is used to obtain an in-phase intermediate frequency signal and a quadrature intermediate frequency signal. The in-phase and quadrature frequency signals are combined into a complex signal. The complex signal is multiplied by the local carrier signal to obtain a zero intermediate frequency signal.
3. The telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals according to claim 1, characterized in that, The spread spectrum signal is acquired using the following method: Based on the spreading code phase, a local pseudo code is generated by the spreading code generator. The local pseudo code is then subjected to a Fourier transform to obtain the Fourier transform result of the local pseudo code. The complex conjugate of the Fourier transform result of the local pseudo code is multiplied and then subjected to an inverse Fourier transform to obtain the modulus value, thus obtaining the one-dimensional modulus value of the spreading pseudo code. Perform a Fourier transform on the zero intermediate frequency data to obtain the zero intermediate frequency data in the frequency domain; The spread spectrum signal is obtained by cross-correlating the one-dimensional modulus value of the spread spectrum pseudocode with the zero intermediate frequency data in the frequency domain.
4. The telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals according to claim 1, characterized in that, The frequency hopping interval division module specifically includes: Based on the phase of the frequency hopping code from the previous round, a frequency hopping pattern is generated by a frequency hopping pattern generator. Based on the frequency hopping pattern, the spread spectrum signal is discretely hopped under pseudo-random sequence control to obtain the spectrum-spread signal. The frequency-hopping signal is divided into N frequency-hopping intervals according to the frequency-hopping pattern, thus obtaining a frequency-hopping signal divided into N frequency-hopping intervals.
5. The telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals according to claim 1, characterized in that, The Doppler frequency shift of the current round is calculated as follows: If the relevant result X(k) is in Taking the maximum value at point , the Doppler frequency shift fd for the current round is: ； Where M is the data length processed by each matched filter, fd is the frequency offset, Ts is the sampling time interval, and k is the k value corresponding to the maximum correlation result X(k).
6. The telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals according to claim 1, characterized in that, The synchronous refresh module specifically includes: The synchronous refresh algorithm calculates and decodes the acquisition period generated by the acquisition decision module to generate a synchronous refresh signal. Based on the synchronous refresh signal, the digital downconversion module, direct-sequence code acquisition module, frequency hopping interval division module, matched filter module, and acquisition decision module dynamically refresh the signal.
7. An electronic device, characterized in that, include: At least one processor; And a memory communicatively connected to at least one of the processors; wherein the memory stores instructions executable by the processor to implement the telemetry and control transponder system for fast and reliable acquisition of hybrid spread spectrum signals as described in any one of claims 1-6.
8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that are executed by the computer to implement the telemetry and control transponder system for rapid and reliable acquisition of hybrid spread spectrum signals as described in any one of claims 1-6.