A method, system and device for detecting gravitational waves

Abstract

This invention discloses a method, system, and device for gravitational wave detection, relating to the field of gravitational wave detection technology. The method includes: spreading communication data using a pseudo-random noise code sequence to generate a spread spectrum signal; using the spread spectrum signal as a first modulation signal to modulate a USO clock signal to obtain a sideband modulation signal, and using the sideband modulation signal as a second modulation signal to modulate a laser carrier to generate a laser modulation signal; transmitting the laser modulation signal to a receiver, so that the receiver can separate the main carrier signal component and the sideband signal component from the laser interference signal according to the Jacobi-Anger expansion, and extract the laser phase measurement result to achieve the extraction of the gravitational wave signal. This invention can suppress the interference of the spread spectrum signal on the laser phase measurement result without affecting the inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions, thus meeting the phase measurement accuracy requirements of space gravitational wave detection.

Description

Technical Field

[0001] This invention relates to the field of gravitational wave detection technology, and in particular to a gravitational wave detection method, system and device. Background Technology

[0002] Space-based gravitational wave detection projects (such as LISA, Tianqin, and Taiji) construct space-based long-baseline Michelson laser interferometers to measure minute distance changes between satellites caused by gravitational waves, providing a new observational window for studying major physical questions such as the merger of compact objects and the early evolution of the universe. This detection method can overcome the low-frequency limitations of ground-based interferometers, enabling direct observation of gravitational wave sources such as the merger of medium- and high-mass black holes in the millihertz frequency band, which is of great scientific significance for promoting the development of astronomy, cosmology, and fundamental physics.

[0003] In existing space-based gravitational wave detection systems, a carrier pseudocode ranging scheme is typically used to integrate laser phase measurement, inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions. This scheme directly modulates the spread spectrum signal used for ranging and communication, and the USO clock signal used for clock comparison, onto the phase of the laser carrier using low-depth phase modulation, according to certain modulation coefficients, thereby generating a complete transmitted signal. The receiver can simultaneously acquire the four types of measurement results by processing the interference signal. However, because the spread spectrum signal in the interference signal is directly modulated onto the main carrier phase, it generates significant components near the main carrier frequency, severely interfering with the laser phase measurement results used for gravitational wave detection. This results in the phase measurement accuracy in this millihertz band failing to meet the stringent requirements of gravitational wave detection. This deficiency has become one of the key technical bottlenecks restricting the improvement of space-based gravitational wave detection performance. Summary of the Invention

[0004] This invention provides a gravitational wave detection method, system, and device that can suppress the interference of spread spectrum signals on laser phase measurement results without affecting inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions, thereby meeting the phase measurement accuracy requirements of space gravitational wave detection.

[0005] In a first aspect, embodiments of the present invention provide a gravitational wave detection method, applicable to a transmitting end, comprising: The communication data to be transmitted is spread using a pseudo-random noise code sequence to generate a spread spectrum signal. Using the spread spectrum signal as the first modulation signal, a preset USO clock signal is phase-modulated to obtain a sideband modulation signal, and the sideband modulation signal is used as the second modulation signal to phase-modulate a preset laser carrier to generate a laser modulation signal. The laser modulation signal is transmitted to the receiving end so that the receiving end can extract the gravitational wave signal through the laser modulation signal.

[0006] This invention converts communication data into a spread spectrum signal with ranging capabilities, providing a time-shifting reference for subsequent gravitational wave extraction to ensure the purity of the extracted gravitational waves. By loading the spread spectrum signal (ranging / communication information) onto the USO clock signal, direct modulation onto the carrier wave is avoided, thus reducing interference with the main carrier phase measurement in the interferometric signal. Furthermore, through two-stage modulation, an transmittable laser signal is formed, maintaining the frequency structure of the main carrier and sidebands. The transmitted laser-modulated signal provides the signal source required for interferometric processing at the receiving end. Compared to existing methods that directly modulate the spread spectrum signal and USO clock signal onto the laser carrier, this invention can suppress the interference of the spread spectrum signal on the laser phase measurement results without affecting inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions, thereby meeting the phase measurement accuracy requirements for space gravitational wave detection.

[0007] Secondly, embodiments of the present invention provide a gravitational wave detection method, applicable to a receiving end, comprising: The laser modulation signal is received from the first transmitter and the second transmitter, and the laser modulation signal is subjected to interference processing to obtain a laser interference signal; According to the Jacobi-Ang expansion, the main carrier signal component and the sideband signal component are separated from the laser interference signal; wherein, the sideband signal component includes the upper sideband signal component and the lower sideband signal component. Laser phase data is obtained through the main carrier signal component; clock comparison results and inter-satellite absolute distance measurement results are obtained through the sideband signal component. Based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results, gravitational wave signals are extracted.

[0008] This invention mixes the laser signals from two satellites through interference to generate a composite signal containing gravitational wave information, clock difference, and distance information. By using mathematical expansion, the signals of different frequency components are separated, allowing the main carrier and sidebands to be processed independently, avoiding crosstalk. Laser phase data is acquired to extract core scientific data for gravitational wave detection (i.e., phase information modulated by gravitational waves), and auxiliary data—clock synchronization information and inter-satellite distance—is extracted from the sidebands carrying spread spectrum information. By comprehensively utilizing these three types of data and performing post-processing to eliminate laser frequency noise and clock noise, a pure gravitational wave signal is finally obtained. Compared to existing methods that directly modulate the spread spectrum signal and USO clock signal onto the laser carrier, this invention can suppress the interference of the spread spectrum signal on the laser phase measurement results without affecting inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions, thereby improving the performance of space gravitational wave detection.

[0009] In some preferred embodiments of the first aspect, laser phase data is obtained through the main carrier signal component, specifically as follows: The main carrier signal component is input into the first phase-locked loop so that the first phase-locked loop performs laser phase measurement and outputs laser phase data.

[0010] This invention employs a phase-locked loop (PLL) to precisely track the frequency and phase of the main carrier, achieving high-precision laser phase measurement and providing raw data for gravitational wave extraction.

[0011] In some preferred embodiments of the first aspect, the clock comparison results and inter-satellite absolute distances are obtained through the sideband signal components, specifically as follows: The upper sideband signal component and the lower sideband signal component are respectively input into the second phase-locked loop and the third phase-locked loop, so that the second phase-locked loop and the third phase-locked loop can perform sideband phase tracking and clock comparison, and separate the spread spectrum signal from the Q output signal of the second phase-locked loop and the third phase-locked loop; The inter-satellite absolute distance measurement results are obtained through the spread spectrum signal.

[0012] This invention uses a PLL to extract the phase change of the sideband signal, thereby obtaining the relative jitter of the clocks between two satellites and achieving high-precision clock comparison; the spread spectrum signal hidden in the sideband phase is extracted and used as the input signal for ranging.

[0013] In some preferred embodiments of the first aspect, the inter-satellite absolute distance measurement results are obtained through the spread spectrum signal, specifically as follows: The spread spectrum signal is input into a delay phase-locked loop (PLL) so that the PLL calculates the time delay of the spread spectrum signal relative to a local pseudo-random noise code sequence copy, thereby obtaining the inter-satellite absolute distance measurement result.

[0014] This invention employs a DLL to accurately measure the transmission delay of the spread spectrum signal, thereby calculating the absolute inter-satellite distance and providing a time-shifting reference for the TDI algorithm.

[0015] In some preferred embodiments of the first aspect, the gravitational wave signal is extracted based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results, specifically as follows: The laser phase data is corrected for clock noise using the clock comparison results to obtain the corrected laser phase data. Using a time-delay interferometry algorithm, with the interstellar absolute distance measurement results as the time-shift reference, the corrected laser phase data is time-shifted and linearly combined to extract gravitational wave signals.

[0016] This invention eliminates the influence of clock noise on laser phase measurement by comparing clock results; it uses a distance reference to time-shift align the signal, cancels laser frequency noise through linear combination, and finally extracts a pure gravitational wave signal.

[0017] Thirdly, embodiments of the present invention provide a gravitational wave detection system suitable for a transmitting end, comprising a spread spectrum signal acquisition module, a laser signal modulation module, and a laser signal transmission module, wherein... The spread spectrum signal acquisition module is used to spread the communication data to be transmitted using a pseudo-random noise code sequence to generate a spread spectrum signal. The laser signal modulation module is used to use the spread spectrum signal as the first modulation signal to perform phase modulation on a preset USO clock electrical signal to obtain a sideband modulation signal, and to use the sideband modulation signal as the second modulation signal to perform phase modulation on a preset laser carrier to generate a laser modulation signal. The laser signal transmitting module is used to transmit the laser modulation signal to the receiving end, so that the receiving end can extract the gravitational wave signal through the laser modulation signal.

[0018] In this embodiment of the invention, a spread spectrum signal acquisition module converts communication data into a spread spectrum signal with ranging capability, providing a time-shifting reference for subsequent gravitational wave extraction to ensure the purity of the extracted gravitational waves. A laser signal modulation module loads the spread spectrum signal (ranging / communication information) onto the USO clock signal, avoiding direct modulation on the main carrier and thus reducing interference with the main carrier phase measurement. Furthermore, through two-stage modulation, a transmittable laser signal is formed, maintaining the frequency structure of the main carrier and sidebands. A laser signal transmission module transmits the laser modulation signal to provide the signal source required for interference processing at the receiving end.

[0019] Fourthly, a gravitational wave detection system, suitable for a receiver, includes an interferometry processing module, a signal separation module, a data acquisition module, and a gravitational wave extraction module, wherein... The interference processing module is used to receive laser modulation signals emitted from the first transmitting end and the second transmitting end, and to perform interference processing on the laser modulation signals to obtain laser interference signals; The signal separation module is used to separate the main carrier signal component and the sideband signal component from the laser interference signal according to the Jacobi-Ang expansion; wherein the sideband signal component includes an upper sideband signal component and a lower sideband signal component. The data acquisition module is used to acquire laser phase data through the main carrier signal component; and to acquire clock comparison results and inter-satellite absolute distance measurement results through the sideband signal component. The gravitational wave extraction module is used to extract gravitational wave signals based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results.

[0020] This invention employs an interferometry processing module to mix the laser signals from two satellites using interference, generating a composite signal containing gravitational wave information, clock difference, and distance information. A signal separation module uses mathematical expansion to separate signals of different frequency components, allowing the main carrier and sidebands to be processed independently, avoiding crosstalk. A data acquisition module acquires laser phase data to extract core scientific data for gravitational wave detection (i.e., phase information modulated by gravitational waves), and extracts auxiliary data—clock synchronization information and inter-satellite distance—from the sidebands carrying spread spectrum information. Finally, a gravitational wave extraction module comprehensively utilizes these three types of data, post-processing to eliminate laser frequency noise and clock noise, ultimately obtaining a pure gravitational wave signal.

[0021] Fifthly, embodiments of the present invention provide a terminal device suitable for a transmitter, comprising: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform operations as described in the first aspect of the gravitational wave detection method.

[0022] Sixthly, embodiments of the present invention provide a terminal device suitable for a receiving end, comprising: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform operations as described in the second aspect of the gravitational wave detection method.

[0023] The above description is merely an overview of the technical solutions of the embodiments of the present invention. In order to better understand the technical means of the embodiments of the present invention and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0024] Figure 1 A schematic diagram of a gravitational wave detection method suitable for the transmitting end provided in an embodiment of the present invention; Figure 2 A schematic diagram of a gravitational wave detection method suitable for a receiving end provided by an embodiment of the present invention; Figure 3 A flowchart illustrating a laser phase measurement process, as exemplified by an embodiment of the present invention; Figure 4 A flowchart illustrating the measurement of absolute inter-satellite distances, as exemplified by an embodiment of the present invention; Figure 5 This is a flowchart illustrating an overall method for detecting gravitational waves provided in an embodiment of the present invention. Figure 6 This is a structural diagram illustrating the composition of a spread spectrum signal, as exemplified in an embodiment of the present invention. Figure 7 This is a normalized ASD image of the interference signal from a traditional method; Figure 8 The image is a normalized ASD image of the interference signal after applying this method; Figure 9 This is a schematic diagram of the normalized correlation function of the ranging signal after applying this method; Figure 10 A comparison of the effects of the spread spectrum signal on the laser phase measurement results after applying the original method and this method; Figure 11 A comparison diagram showing the impact of the spread spectrum signal on clock alignment after applying the original method and this method; Figure 12 A schematic diagram of a gravitational wave detection system suitable for the transmitting end is provided in an embodiment of the present invention; Figure 13 This is a schematic diagram of a gravitational wave detection system suitable for a receiving end, provided as an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: like Figure 1 The image shows a gravitational wave detection method provided by an embodiment of the present invention, applicable to the transmitting end, comprising the following steps: S101, using a pseudo-random noise code sequence, spread spectrum processing is performed on the communication data to be transmitted to generate a spread spectrum signal; In one specific embodiment, the communication data to be transmitted is spread spectrum processed using a pseudo-random noise code sequence to generate a spread spectrum signal. Specifically, the data generated in this step may include the PRN sequences of the remote spacecraft and the local spacecraft, the communication code, and the spread spectrum signal. The PRN sequence is generated by adding a "0" bit to the end of a 1023-bit m-sequence of order 10 (512 "1" bits and 511 "0" bits), with a total sequence length of 1024 bits. The number of "0" bits and "1" bits are equal, so that the PSD of the PRN sequence is 0 at the clock sideband carrier frequency after bipolarization processing, reducing interference to clock comparison performance. The communication code is a randomly generated sequence of 0 and 1 bits to simulate the communication data transmitted during communication.

[0027] Let the spreading factor be 16. Each spread spectrum signal is generated by modulo-2 addition of a 1024-bit PRN code and a 64-bit communication code. Taking a remote spacecraft launch system (represented by the superscript M) as an example, the form of the PRN sequence and communication code, and the process of generating the spread spectrum signal, can be represented as follows: in, For remote spacecraft PRN code sequences, For the communication code sequence of remote spacecraft, This is a spread spectrum sequence for remote spacecraft.

[0028] S102, using the spread spectrum signal as the first modulation signal, phase-modulate the preset USO clock signal to obtain a sideband modulation signal, and using the sideband modulation signal as the second modulation signal, phase-modulate the preset laser carrier to generate a laser modulation signal; In one specific embodiment, the spread spectrum signal is used as the first modulation signal to perform phase modulation on a preset USO clock signal to obtain a sideband modulation signal. Specifically, the spread spectrum signal generated by the remote spacecraft launch system is phase-modulated onto the phase of the USO clock signal through a modulator according to the pseudocode modulation coefficients to obtain the sideband modulation signal. The USO clock signal of the remote spacecraft and the modulation process can be represented as follows: in, For the USO clock signal of remote spacecraft, For the clock signal frequency of remote spacecraft, For pseudocode modulation coefficients, The symbol duration of the spread spectrum signal, The pulse waveform of the spread spectrum signal has a duration of T. This is the clock sideband modulation signal for remote spacecraft.

[0029] In one specific embodiment, the sideband modulation signal is used as the second modulation signal to perform phase modulation on a preset laser carrier to generate a laser modulation signal. Specifically, the sideband modulation signal output by the modulator is then phase-modulated onto the corresponding laser carrier phase through EOM low-depth phase modulation according to the sideband modulation coefficient to obtain the laser modulation signal. The laser carrier and modulation process of the remote spacecraft can be represented as follows: in, For laser carrier signals of remote spacecraft, For remote spacecraft laser frequencies, For sideband modulation coefficients, For laser modulation signals of remote spacecraft, This refers to the power of the laser modulation signal for the remote spacecraft.

[0030] It should be noted that the obtained laser modulation signal can be derived from the Jacobi-Anger expansion. To expand, among which Let z be the nth-order Bessel function, whose value decreases as n increases. This is because the sideband modulation coefficients in the sideband pseudocode ranging scheme based on the Jacobi-Anger expansion... The higher-order Bessel function is smaller than the first-order Bessel function (under the parameter settings of this invention). =0.258, and its first-order Bessel function is approximately 15 times that of its second-order Bessel function. Therefore, in this invention, when expanding the laser modulation signal according to the Jacobi-Anger expansion, the higher-order sideband signal components are omitted, and only the main carrier signal component and the first-order upper and lower sideband signal components are retained. (Because the sideband modulation depth is low under the sideband pseudocode ranging scheme based on the Jacobi-Anger expansion...) The higher-order Bessel functions are smaller than the first-order Bessel functions; therefore, this invention omits the higher-order sideband signal components when expanding the laser modulation signal according to the Jacobi-Anger expansion. S103, the laser modulation signal is transmitted to the receiving end so that the receiving end can extract the gravitational wave signal through the laser modulation signal.

[0031] It should be noted that, similarly, the laser modulation signal generated by the local spacecraft's (indicated by the superscript S) transmitting system can be expressed as: in, For the spread spectrum sequence of local spacecraft, For local spacecraft laser frequency, For the local spacecraft's clock signal frequency, For local spacecraft laser modulation signals, The power of the local spacecraft laser modulation signal.

[0032] This invention converts communication data into a spread spectrum signal with ranging capabilities, providing a time-shifting reference for subsequent gravitational wave extraction to ensure the purity of the extracted gravitational waves. By loading the spread spectrum signal (ranging / communication information) onto the USO clock signal, direct modulation onto the main carrier is avoided, thus reducing interference with the main carrier phase measurement. Furthermore, through two-stage modulation, a transmittable laser signal is formed, maintaining the frequency structure of the main carrier and sidebands. The transmitted laser-modulated signal provides the signal source required for interferometry processing at the receiver. Compared to existing methods that directly modulate the spread spectrum signal and USO clock signal onto the laser carrier, this invention can suppress the interference of the spread spectrum signal on the laser phase measurement results without affecting inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions, thereby meeting the phase measurement accuracy requirements for space gravitational wave detection.

[0033] Example 2: like Figure 2 The image shows a gravitational wave detection method provided by an embodiment of the present invention, applicable to a receiving end, comprising the following steps: S201, receive laser modulation signals emitted from the first transmitting end and the second transmitting end, and perform interference processing on the laser modulation signals to obtain laser interference signals; In one specific embodiment, laser modulation signals transmitted from a first transmitting end and a second transmitting end are received, and the laser modulation signals are subjected to interference processing to obtain a laser interference signal. Specifically, at the PD (photodetector), the laser modulation signal from the remote spacecraft interferes with the laser modulation signal from the local spacecraft. The interference signal received by the PD can be equivalent to the real part of the conjugate multiplication result of the two laser modulation signals. Simultaneously, due to the low-pass characteristic of the PD, the PD output signal is the result of low-pass filtering the input interference signal.

[0034] S202, according to the Jacobi-Anger expansion, the main carrier signal component and the sideband signal component are separated from the laser interference signal; wherein, the sideband signal component includes the upper sideband signal component and the lower sideband signal component; In one specific embodiment, the main carrier signal component and the sideband signal component are separated from the laser interference signal according to the Jacobi-Ang expansion, specifically as follows: Based on the parameters of a real-world space-based gravitational wave detection system, the PD output signal retains only the main carrier component and the first-order upper and lower sideband components of the interferometric signal. This process can be expressed as: in, The PD response rate, the signal obtained after the PD output signal is sampled by the ADC, can be expressed as: ,in, This is the ADC sampling frequency.

[0035] As can be seen from the expression for the interference signal, the interference signal contains one main carrier signal component and two first-order upper and lower sideband signal components whose frequencies are symmetrical about the main carrier signal frequency. The three signal components can be separated by a bandpass filter with a corresponding passband range. The three separated signal components can be expressed as follows: in, main carrier signal, For the upper sideband signal, This is the signal with the lower sideband.

[0036] It should be noted that, as can be seen from the expression for the interference signal, the frequency interval between the upper and lower sideband signal carriers is only 2. The power of the spread spectrum signal modulated in the sideband is distributed throughout the entire frequency domain. Therefore, the sideband signal output by the sideband BPF will contain a spread spectrum signal component modulated by another sideband. In the subsequent clock sideband phase measurement and ranging communication steps, the spread spectrum signal components from adjacent sidebands will affect the performance of the system function as interference signals.

[0037] To address this, this invention introduces a single-sided filtering technique: Utilizing the fact that the autocorrelation function of the spread spectrum signal is a real-valued symmetric function, the PSD (Power Spectral Density) function of the spread spectrum signal obtained by Fourier transforming the autocorrelation function is an even function. After being modulated onto the carrier, it is symmetric about the carrier frequency. Therefore, when setting the passband range of the BPF (band-pass filter), single-sided filtering can be used to retain only the frequency components of the spread spectrum signal that are far from the other sideband. This reduces the relative magnitude of interference components in the BPF output signal while ensuring the normal operation of subsequent inter-satellite ranging and communication functions, improves the SIR (Signal-to-Interference Ratio) of the input DLL (Delay-Locked Loop) signal, and enhances the system's inter-satellite ranging and communication performance.

[0038] S203, obtain laser phase data through the main carrier signal component; obtain clock comparison results and inter-satellite absolute distance measurement results through the sideband signal component; In this embodiment, laser phase data is obtained through the main carrier signal component. Specifically, the main carrier signal component is input into the first phase-locked loop so that the first phase-locked loop performs laser phase measurement and outputs laser phase data.

[0039] In one specific embodiment, laser phase data is obtained through the main carrier signal component. Specifically, among the three signal components separated by the bandpass filter, the main carrier signal component enters the carrier PLL at the corresponding center frequency for laser phase measurement, while the upper and lower sideband signal components enter the sideband PLL at the corresponding center frequency for clock comparison and spread spectrum signal separation, respectively.

[0040] In summary, the function of a PLL is to track the frequency and phase of the input signal, while simultaneously separating the phase-modulated spread spectrum signal from the carrier and performing the inverse operation of low-depth phase modulation. For example... Figure 3 As shown, Figure 3 The following is a flowchart illustrating a laser phase measurement process according to an embodiment of the present invention. The input modulated signal is first multiplied by the tracking signal of the PLL to obtain the difference between the input and tracking signals. This difference signal is then low-pass filtered to obtain the Q-terminal output. In this system, the Q-terminal output represents the difference between the remote and local spacecraft spread spectrum signals. In the phase measurement step, the filtered signal is processed by a PI controller to obtain a frequency correction. This correction is added to the inherent frequency offset of the PLL to obtain the PLL's frequency estimate of the input signal. Finally, a phase accumulator is used to obtain the signal phase measurement result.

[0041] Based on the principle and function of a PLL, the upper and lower sideband signals corresponding to the Q output signals of the PLL can be expressed as follows: in, For the Q output signal of the PLL above, This is the Q output signal of the PLL below.

[0042] In this embodiment, the clock comparison result and inter-satellite absolute distance are obtained through the sideband signal components. Specifically, the upper sideband signal component and the lower sideband signal component are input into the second phase-locked loop and the third phase-locked loop, respectively, so that the second phase-locked loop and the third phase-locked loop perform sideband phase tracking and clock comparison, and the spread spectrum signal is separated from the Q-terminal output signal of the second phase-locked loop and the third phase-locked loop; the inter-satellite absolute distance measurement result is obtained through the spread spectrum signal.

[0043] In this embodiment, the inter-satellite absolute distance measurement result is obtained through the spread spectrum signal. Specifically, the spread spectrum signal is input into a delay phase-locked loop (PLL) so that the PLL calculates the time delay of the spread spectrum signal relative to a local pseudo-random noise code sequence copy, thereby obtaining the inter-satellite absolute distance measurement result.

[0044] In one specific embodiment, the inter-satellite absolute distance measurement results and inter-satellite communication data are obtained through the spread spectrum signal. Specifically, the function of the DLL is to determine the delay time of the input spread spectrum signal by searching for the time shift corresponding to the peak value of the correlation value between the input spread spectrum signal and the local PRN sequence copy stored in the receiving system, thereby realizing the measurement of the inter-satellite absolute distance. After determining the delay corresponding to the relevant peak, the aligned spread spectrum signal is added modulo 2 to the PRN code copy, and the communication code from the remote spacecraft is obtained by despreading, thus realizing inter-satellite communication.

[0045] like Figure 4 As shown, Figure 4 This invention provides an example of an inter-satellite absolute distance measurement flowchart, where the ranging process is divided into two stages: acquisition and tracking. In the acquisition stage, the input spread spectrum signal is time-shifted in units of symbols and correlated sequentially with a local PRN sequence copy. The peak value of the obtained correlation is then searched for the number of symbol bits corresponding to it. In the tracking stage, the search is performed with the horizontal coordinate delay of the peak value from the acquisition stage as the center point, and the local PRN sequence copy is advanced and delayed accordingly. The early and late copies of the local PRN sequence are obtained by taking a symbol length of 1. Then, the difference between the correlation values ​​of the input spread spectrum signal and the early and late copies is calculated to obtain the error signal. The spread spectrum signal is time-shifted in units of sampling points to minimize the absolute value of the error signal. At this time, the time delay of the spread spectrum signal is the distance measurement result of the tracking stage.

[0046] The despreading process of the communication code from the remote spacecraft can be represented as follows: in, The number of sampling points corresponding to each symbol For the communication code demodulated by the receiving system, The delay of the composite code sequence measured by the receiving system DLL.

[0047] S204. Gravitational wave signals are extracted based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results.

[0048] In this embodiment, gravitational wave signals are extracted based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results. Specifically, the laser phase data is corrected for clock noise using the clock comparison results to obtain corrected laser phase data. Then, using a time-delay interferometry algorithm, the corrected laser phase data is time-shifted and linearly combined with the inter-satellite absolute distance measurement results as a time-shift reference to extract gravitational wave signals.

[0049] In one specific embodiment, after laser interferometry, the phase of the main carrier signal includes gravitational wave signals, laser frequency noise, and other noise. The expression for the main carrier signal component in a single-satellite received signal is as follows: in, For satellite i laser frequency noise, This refers to the interstellar travel time (absolute distance).

[0050] It should be noted that when the arm lengths are unequal, the laser frequency noise cannot be directly canceled out.

[0051] In one specific embodiment, a PRN code (low-depth BPSK modulation) is superimposed on the laser beam, and the receiver measures the code delay through a delay phase-locked loop (DLL) to obtain the pseudorange. in, For actual optical travel time, pseudorange includes absolute distance. and the clock difference between the two stars .

[0052] It should be noted that, through bidirectional measurements (mutual transmission and reception between the two satellites), the following can be determined: This provides the time-shift reference required for TDI (meter-level → nanosecond-level).

[0053] In one specific embodiment, the sideband phase measurement (clock comparison) process is as follows: the USO signal is frequency multiplied to... The laser is low-depth modulated using EOM. The receiver extracts the sideband-to-sideband beat frequency phase, including relative clock noise. in, Time jitter (seconds) for USO of satellite i This represents the phase of the main carrier of the interference signal.

[0054] Furthermore, the pure clock term can be extracted through combination or differential of the upper and lower sidebands: This provides the correction amount needed to eliminate clock noise in TDI.

[0055] In one specific embodiment, gravitational wave signals are extracted based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results. Specifically, three types of results are acquired simultaneously: the laser emitted by each satellite simultaneously contains carrier phase (scientific signal), PRN code (ranging), and GHz sideband (clock comparison); the receiver extracts the carrier phase through DPLL, extracts the PRN delay through DLL, and extracts the sideband phase through sideband PLL.

[0056] Furthermore, the two-way PRN ranging provides: in, Given the system's inherent delay (known calibration value), this Used for time translation in TDI.

[0057] Furthermore, the sideband phase gives rise to relative clock jitter: This amount is used to correct the laser phase measurement results: in, The main carrier beat frequency.

[0058] Furthermore, TDI combinations eliminate laser noise, taking X-type TDI as an example (simplified form): in, The distance is given by PRN ranging.

[0059] After this combination, the laser frequency noise is canceled out by common-mode, the clock noise is subtracted, and the gravitational wave signal is differentially preserved, resulting in the following output: For a better explanation of the implementation principle and workflow of this invention, please refer to [link / reference]. Figure 5 , Figure 5 This is a flowchart illustrating a gravitational wave detection method provided in an embodiment of the present invention.

[0060] To verify the practicality of this invention, the simulation experiment process of this gravity detection method is described below. In a single simulation, eight sets of spread spectrum signals are continuously transmitted. The PRN sequence generated by the system has a length of 1024 bits, a symbol rate of 1 MHz, a communication rate of 62.5 bps, and a spreading factor of 16, all consistent with the carrier pseudocode ranging scheme currently used by the system. Under these parameter settings, the structure of the spread spectrum signal used in the simulation is as follows: Figure 6 As shown.

[0061] Regarding the selection of laser frequency, the simulation uses a laser with a wavelength of 1064 nm as the local spacecraft laser carrier, and external modulation is used to make the far-end laser frequency 10 MHz higher than the local laser frequency. Regarding the selection of clock signal frequency, the simulation selects the far-end and local clock signal frequencies of 2.001 GHz and 2.000 GHz respectively, that is, keeping the difference between the clock sideband frequencies measured by the receiving system at 1 MHz, which is consistent with the original carrier pseudocode ranging scheme.

[0062] In the laser modulation signal output by the transmitting system, the simulation maintains the power ratio of the laser carrier, clock sideband, and spread spectrum signal consistent with the carrier pseudocode ranging scheme, i.e., laser carrier:clock sideband:composite code = 100:15:1. It can be deduced that one sideband accounts for 7.5% of the carrier power, and the pseudocode accounts for a certain percentage of the sideband power. The pseudocode modulation coefficient and sideband modulation coefficient of the sideband pseudocode ranging scheme based on the Jacobi-Anger expansion can be calculated using this power allocation ratio. The specific calculation process is as follows: Solving the above equations, we can obtain... , .

[0063] In summary, all parameters involved in the simulation are shown in Table 1.

[0064] Table 1. Schematic diagram of relevant parameters in the simulation experiment For comparison, a simulation of the carrier pseudocode ranging scheme currently used in gravitational wave detection systems is performed, yielding the normalized ASD image of the interference signal output by the ADC of the laser interferometer and analog-to-digital converter module, as shown below. Figure 7 As shown; After adopting a sideband pseudocode ranging scheme based on Jacobi-Anger expansion, the normalized ASD image of the interference signal output by the ADC of the laser interferometry and analog-to-digital conversion module is as follows: Figure 8 As shown; Depend on Figure 7 and Figure 8 The comparison shows that, compared to the carrier pseudocode ranging scheme, the sideband pseudocode ranging scheme based on Jacobi-Anger expansion has fewer components of the spread spectrum signal in the interferometric signal at the frequency of the main carrier signal used for laser phase measurement. This means that the spread spectrum signal has less impact on the accuracy of the laser phase measurement results.

[0065] Furthermore, taking the upper sideband BPF as an example, considering that the upper sideband signal carrier frequency is 11MHz, let the passband range of the upper sideband BPF be 10-12MHz and 11-12MHz respectively. The relevant function graphs for the upper sideband DLL capture stage are as follows: Figure 9 As shown, by Figure 9 It is evident that the correlation of the ranging signal output by the sideband PLL is significantly improved after applying the single-sided filtering technique.

[0066] Furthermore, since the influence of the spread spectrum signal on the laser phase measurement results is equivalent to the magnitude of the spread spectrum signal component in the interferometric signal in the frequency band of 0.1 mHz to 1 Hz near the main carrier frequency, the following simulation quantitative analysis is performed on the influence of the spread spectrum signal on the laser phase measurement results in the frequency band of 0.1 mHz to 1 Hz under the carrier pseudocode ranging scheme and the sideband pseudocode ranging scheme based on Jacobi-Anger expansion.

[0067] In the carrier pseudocode ranging scheme, since the phase of the spread spectrum signal in the interferometric signal is modulated on the phase of the main carrier, the influence of the spread spectrum signal on the laser phase measurement result is equivalent to the magnitude of the spread spectrum signal component in the 0.1 mHz to 1 Hz frequency band. In the sideband pseudocode ranging scheme based on the Jacobi-Anger expansion, since the phase of the spread spectrum signal is modulated on the upper and lower clock sideband phases that differ from the main carrier frequency by 1 MHz, the influence of the spread spectrum signal on the laser phase measurement result is equivalent to the magnitude of the spread spectrum signal component in the 1 MHz + 0.1 mHz to 1 MHz + 1 Hz frequency band. Considering that the main detection target of the space gravitational wave detection mission is the gravitational waves generated by the merger of two black holes with a mass of millions of solar masses, and that the ringing phase of the black hole merger lasts for tens of seconds and is a key stage for verifying the no-hair theorem for black holes, the number of periods of the PRN sequence contained in the spread spectrum signal is taken as 10^6 in the simulation. Under this parameter configuration, the influence of the spread spectrum signal on the laser phase measurement results in the 0.1 mHz to 1 Hz frequency band can be obtained under both the carrier pseudocode ranging scheme and the Jacobi-Anger expansion-based sideband pseudocode ranging scheme. Figure 10 As shown. By Figure 10It is evident that for carrier pseudocode ranging schemes, the influence of spread spectrum signals on laser phase measurement is insufficient to meet phase measurement accuracy requirements in the frequency band from 0.1 mHz to 1 Hz. In contrast, the sideband pseudocode ranging scheme based on Jacobi-Anger expansion has a smaller influence on laser carrier phase measurement and can meet the phase measurement accuracy requirements of space gravitational wave detection missions.

[0068] The analysis of the influence of the spread spectrum signal on the clock comparison results in the Jacobi-Anger expansion-based sideband pseudocode ranging scheme is similar to that of the influence of the spread spectrum signal on the laser phase measurement results. The magnitude of the influence is equivalent to the magnitude of the spread spectrum signal components in the 0.1 mHz to 1 Hz frequency band. The influence of the spread spectrum signal on the clock comparison results in the 0.1 mHz to 1 Hz frequency band in the Jacobi-Anger expansion-based sideband pseudocode ranging scheme is as follows: Figure 11 As shown, by Figure 11 It is evident that for the Jacobi-Anger expansion-based sideband pseudocode ranging scheme, the influence of the spread spectrum signal on clock comparison can meet the phase measurement accuracy requirements within the frequency band of 0.1mHz to 1Hz.

[0069] This invention mixes the laser signals from two satellites through interference to generate a composite signal containing gravitational wave information, clock difference, and distance information. By using mathematical expansion, the signals of different frequency components are separated, allowing the main carrier and sidebands to be processed independently, avoiding crosstalk. Laser phase data is acquired to extract core scientific data for gravitational wave detection (i.e., phase information modulated by gravitational waves), and auxiliary data—clock synchronization information and inter-satellite distance—is extracted from the sidebands carrying spread spectrum information. By comprehensively utilizing these three types of data and performing post-processing to eliminate laser frequency noise and clock noise, a pure gravitational wave signal is finally obtained. Compared to existing methods that directly modulate spread spectrum and sideband signals onto the laser carrier, this invention can suppress the interference of spread spectrum signals on laser phase measurement results without affecting inter-satellite absolute distance measurement, clock comparison, and inter-satellite communication functions, thereby improving the performance of space gravitational wave detection.

[0070] Example 3: like Figure 12 As shown, an embodiment of the present invention provides a gravitational wave detection system suitable for a transmitting end, including a spread spectrum signal acquisition module 301, a laser signal modulation module 302, and a laser signal transmission module 303, wherein... The spread spectrum signal acquisition module 301 is used to spread the communication data to be transmitted using a pseudo-random noise code sequence to generate a spread spectrum signal. The laser signal modulation module 302 is used to use the spread spectrum signal as the first modulation signal to perform phase modulation on a preset USO clock electrical signal to obtain a sideband modulation signal, and to use the sideband modulation signal as the second modulation signal to perform phase modulation on a preset laser carrier to generate a laser modulation signal. The laser signal transmitting module 303 is used to transmit the laser modulation signal to the receiving end, so that the receiving end can extract the gravitational wave signal through the laser modulation signal.

[0071] For a more detailed explanation of the working principle and procedures of this embodiment, please refer to the relevant description in Embodiment 1.

[0072] In this embodiment of the invention, the spread spectrum signal acquisition module 301 converts communication data into a spread spectrum signal with ranging capability, providing a time-shifting reference for subsequent gravitational wave extraction to ensure the purity of the extracted gravitational waves; the laser signal modulation module 302 loads the spread spectrum signal (ranging / communication information) onto the USO clock signal, avoiding direct modulation on the carrier wave, thereby reducing interference to the phase measurement of the main carrier in the interference signal, and through two-stage modulation, forms an emitting laser signal, maintaining the frequency structure of the main carrier and sidebands in the interference signal; the laser signal transmission module 303 transmits the laser modulation signal to provide the signal source required for the receiver to perform interference processing.

[0073] Example 4: like Figure 13 As shown, this is an embodiment of a gravitational wave detection method provided by the present invention, applicable to a receiving end, including an interference processing module 401, a signal separation module 402, a data acquisition module 403, and a gravitational wave extraction module 404, wherein... The interference processing module 401 is used to receive laser modulation signals emitted from the first transmitting end and the second transmitting end, and to perform interference processing on the laser modulation signals to obtain laser interference signals; The signal separation module 402 is used to separate the main carrier signal component and the sideband signal component from the laser interference signal according to the Jacobi-Ang expansion; wherein the sideband signal component includes an upper sideband signal component and a lower sideband signal component. The data acquisition module 403 is used to acquire laser phase data through the main carrier signal component; and to acquire clock comparison results and inter-satellite absolute distance measurement results through the sideband signal component. In this embodiment, the data acquisition module 403 acquires laser phase data through the main carrier signal component. Specifically, the data acquisition module 403 inputs the main carrier signal component into the first phase-locked loop so that the first phase-locked loop performs laser phase measurement and outputs laser phase data.

[0074] In this embodiment, the data acquisition module 403 acquires the clock comparison result and the inter-satellite absolute distance through the sideband signal components. Specifically, the upper sideband signal component and the lower sideband signal component are input into the second phase-locked loop and the third phase-locked loop respectively, so that the second phase-locked loop and the third phase-locked loop perform sideband phase tracking and clock comparison, and the spread spectrum signal is separated from the Q-terminal output signal of the second phase-locked loop and the third phase-locked loop. The inter-satellite absolute distance measurement results are obtained through the spread spectrum signal.

[0075] In this embodiment, the data acquisition module 403 obtains the inter-satellite absolute distance measurement result through the spread spectrum signal. Specifically, the data acquisition module 403 inputs the spread spectrum signal into a delay phase-locked loop (PLL) so that the PLL calculates the time delay of the spread spectrum signal relative to a local pseudo-random noise code sequence copy, thereby obtaining the inter-satellite absolute distance measurement result.

[0076] The gravitational wave extraction module 404 is used to extract gravitational wave signals based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results.

[0077] In this embodiment, the gravitational wave extraction module 404 extracts gravitational wave signals based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results. Specifically, the gravitational wave extraction module 404 corrects the clock noise of the laser phase data using the clock comparison results to obtain corrected laser phase data; and uses a time-delay interferometry algorithm, with the inter-satellite absolute distance measurement results as the time shift reference, performs time shifting and linear combination on the corrected laser phase data to extract gravitational wave signals.

[0078] For a more detailed explanation of the working principle and procedures of this embodiment, please refer to the relevant description in Embodiment 2.

[0079] In this embodiment of the invention, the interferometry processing module 401 mixes the laser signals of two satellites using interference to generate a composite signal containing gravitational wave information, clock difference, and distance information. The signal separation module 402 separates the signals of different frequency components using mathematical expansion, allowing the main carrier and sidebands to be processed independently and avoiding crosstalk. The data acquisition module 403 acquires laser phase data to extract the core scientific data for gravitational wave detection (i.e., phase information modulated by gravitational waves), and extracts auxiliary data from the sidebands carrying spread spectrum information: clock synchronization information and inter-satellite distance. The gravitational wave extraction module 404 comprehensively utilizes the three types of data, and after post-processing, eliminates laser frequency noise and clock noise, finally obtaining a pure gravitational wave signal.

[0080] Example 5: This embodiment provides a terminal device, including: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform the operation of the gravitational wave detection method as described in Embodiment 1.

[0081] Example 6: This embodiment provides a terminal device, including: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform the operation of the gravitational wave detection method as described in any of Embodiment 2.

[0082] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0083] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for detecting gravitational waves, characterized in that, Applicable to the sending end, including: The communication data to be transmitted is spread using a pseudo-random noise code sequence to generate a spread spectrum signal. Using the spread spectrum signal as the first modulation signal, a preset USO clock signal is phase-modulated to obtain a sideband modulation signal, and the sideband modulation signal is used as the second modulation signal to phase-modulate a preset laser carrier to generate a laser modulation signal. The laser modulation signal is transmitted to the receiving end so that the receiving end can extract the gravitational wave signal through the laser modulation signal.

2. A method for detecting gravitational waves, characterized in that, Applicable to the receiving end, including: The laser modulation signal is received from the first transmitter and the second transmitter, and the laser modulation signal is subjected to interference processing to obtain a laser interference signal; According to the Jacobi-Ang expansion, the main carrier signal component and the sideband signal component are separated from the laser interference signal; wherein, the sideband signal component includes the upper sideband signal component and the lower sideband signal component; Laser phase data is obtained through the main carrier signal component; clock comparison results and inter-satellite absolute distance measurement results are obtained through the sideband signal component. Based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results, gravitational wave signals are extracted.

3. The gravitational wave detection method as described in claim 2, characterized in that, Laser phase data is obtained through the main carrier signal component, specifically as follows: The main carrier signal component is input into the first phase-locked loop so that the first phase-locked loop performs laser phase measurement and outputs laser phase data.

4. The gravitational wave detection method as described in claim 3, characterized in that, The clock alignment results and inter-satellite absolute distances are obtained through the sideband signal components, specifically as follows: The upper sideband signal component and the lower sideband signal component are respectively input into the second phase-locked loop and the third phase-locked loop, so that the second phase-locked loop and the third phase-locked loop can perform sideband phase tracking and clock comparison, and separate the spread spectrum signal from the Q output signal of the second phase-locked loop and the third phase-locked loop; The inter-satellite absolute distance measurement results are obtained through the spread spectrum signal.

5. The gravitational wave detection method as described in claim 4, characterized in that, The inter-satellite absolute distance measurement results are obtained through the spread spectrum signal, specifically as follows: The spread spectrum signal is input into a delay phase-locked loop (PLL) so that the PLL calculates the time delay of the spread spectrum signal relative to a local pseudo-random noise code sequence copy, thereby obtaining the inter-satellite absolute distance measurement result.

6. The gravitational wave detection method as described in claim 5, characterized in that, Based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results, gravitational wave signals are extracted, specifically as follows: The laser phase data is corrected for clock noise using the clock comparison results to obtain the corrected laser phase data. Using a time-delay interferometry algorithm, with the interstellar absolute distance measurement results as the time-shift reference, the corrected laser phase data is time-shifted and linearly combined to extract gravitational wave signals.

7. A gravitational wave detection system, characterized in that, Applicable to the transmitting end, including a spread spectrum signal acquisition module, a laser signal modulation module, and a laser signal transmission module, wherein, The spread spectrum signal acquisition module is used to spread the communication data to be transmitted using a pseudo-random noise code sequence to generate a spread spectrum signal. The laser signal modulation module is used to use the spread spectrum signal as the first modulation signal to perform phase modulation on a preset USO clock electrical signal to obtain a sideband modulation signal, and to use the sideband modulation signal as the second modulation signal to perform phase modulation on a preset laser carrier to generate a laser modulation signal. The laser signal transmitting module is used to transmit the laser modulation signal to the receiving end, so that the receiving end can extract the gravitational wave signal through the laser modulation signal.

8. A gravitational wave detection system, characterized in that, Suitable for the receiving end, it includes an interference processing module, a signal separation module, a data acquisition module, and a gravitational wave extraction module, among which, The interference processing module is used to receive laser modulation signals emitted from the first transmitting end and the second transmitting end, and to perform interference processing on the laser modulation signals to obtain laser interference signals; The signal separation module is used to separate the main carrier signal component and the sideband signal component from the laser interference signal according to the Jacobi-Ang expansion; wherein the sideband signal component includes the upper sideband signal component and the lower sideband signal component. The data acquisition module is used to acquire laser phase data through the main carrier signal component; and to acquire clock comparison results and inter-satellite absolute distance measurement results through the sideband signal component. The gravitational wave extraction module is used to extract gravitational wave signals based on the laser phase data, clock comparison results, and inter-satellite absolute distance measurement results.

9. A terminal device, characterized in that, Applicable to the transmitting end, including: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform the operation of the gravitational wave detection method as described in claim 1.

10. A terminal device, characterized in that, Applicable to the receiving end, including: a processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction that causes the processor to perform the operation of the gravitational wave detection method as described in any one of claims 2 to 6.

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