Quantum key distribution satellite-ground synchronous transmission system based on microwaves

Abstract

The invention relates to the technical field of quantum communication, in particular to a microwave-based quantum key distribution satellite-ground synchronous transmission system, which comprises a microwave signal preprocessing module, a pulse time compression module, a dual-channel difference calibration module, a signal synchronization judgment module and a key sequence generation module. According to the method, the input pulse is kept stable before entering the comparison link by performing spectrum analysis on the satellite-ground transmission signal and extracting the unified time domain feature, and waveform distortion and judgment deviation caused by pulse trailing are avoided by matching with the reference template and compressing under the condition of abnormal extension. A fitting calculation mode is introduced into amplitude and phase double-path detection, background noise interference is reduced, accurate recognition of candidate signals is enhanced, time reference consistency is achieved through difference value screening and synchronous threshold value comparison, stable quantum signal flow can be formed in the transmission process, and the accuracy of quantum signal detection is improved. Therefore, the reliability and safety of the output sequence are kept in the key generation link.

Description

Technical Field

[0001] This invention relates to the field of quantum communication technology, and in particular to a microwave-based quantum key distribution satellite-to-ground synchronous transmission system. Background Technology

[0002] The field of quantum communication technology involves research and applications related to secure information transmission using the principles of quantum mechanics. Its core aspects include the generation and distribution of quantum entangled states, the maintenance and measurement of quantum states, the establishment and management of quantum channels, and the generation and transmission of quantum keys. This technology field as a whole covers quantum state manipulation, photon signal transmission, key generation mechanisms, and anti-eavesdropping detection, aiming to ensure information security during communication through the quantum no-cloning theorem and the principle of measurement collapse.

[0003] The traditional quantum key distribution satellite-ground synchronization transmission system refers to the method of transmitting quantum signals between a satellite and a ground station through a satellite-ground optical link to achieve key distribution. This system addresses the problems of severe attenuation of quantum signals and insufficient synchronization accuracy during long-distance transmission by using an optical telescope to establish a satellite-ground link, using laser pulses for clock synchronization, and using a single-photon detector to complete signal reception and measurement, thereby completing the quantum key distribution process between the satellite and the ground.

[0004] Traditional satellite-to-ground synchronization methods are insufficient in maintaining signal strength over long distances. Photon signals attenuate significantly during propagation, leading to frequent waveform distortion at the receiver and making it difficult to guarantee accuracy. Under conditions of satellite-to-ground motion and atmospheric interference, pulse-based clock synchronization suffers from time drift, causing deviations in the output signal stream during comparison and calibration. Some invalid signals are mixed into the valid data, resulting in insufficient sequence stability of the final quantum key and making it difficult to maintain security and continuity during communication. Summary of the Invention

[0005] To address the shortcomings of traditional satellite-to-ground synchronization methods in maintaining signal strength over long distances, the significant attenuation of photon signals during propagation leading to frequent waveform distortion at the receiver and difficulty in guaranteeing accuracy, and the time drift inherent in pulse-based clock synchronization under conditions of satellite-to-ground motion and atmospheric interference, causing deviations in the output signal stream during comparison and calibration, and the incorporation of invalid signals into valid data, resulting in insufficient sequence stability of the final quantum key and difficulties in maintaining security and continuity during communication, this invention provides a microwave-based quantum key distribution satellite-to-ground synchronization transmission system. The technical solution is as follows:

[0006] On the one hand, a microwave-based quantum key distribution satellite-to-ground synchronous transmission system is provided, which includes:

[0007] The microwave signal preprocessing module acquires the microwave signal transmitted via the satellite-to-ground link through the antenna array, performs spectrum analysis using the Fourier transform algorithm, generates a time-domain characteristic standardized microwave signal, and transmits it to the pulse time compression module.

[0008] The pulse time compression module constructs a reference pulse template based on the time-domain characteristic standardized microwave signal, compares the input pulse with the template, and performs a compression operation when the pulse duration exceeds the template threshold to generate a time-compressed optimized pulse, which is then transmitted to the dual-channel difference calibration module.

[0009] The dual-channel difference calibration module calls the time compression optimization pulse and filters candidate signals based on the background noise benchmark. The signals are input into the amplitude channel and phase channel for parallel detection, and the least squares method is used for fitting calculation to generate a dual-channel verification qualified signal, which is then transmitted to the signal synchronization judgment module.

[0010] The signal synchronization determination module calls the dual-channel verified qualified signal to perform amplitude and phase time point synchronization verification, calculates the time point difference between the two channels and compares it with a preset synchronization threshold, filters signals with a difference less than the threshold, generates a satellite-to-ground synchronization quantum signal stream, and transmits it to the key sequence generation module.

[0011] As a further aspect of the present invention, the time-domain characteristic standardized microwave signal includes frequency distribution, power spectral density and time-domain stability; the time-compression optimized pulse includes pulse width, peak power and waveform smoothness; the dual-channel verified qualified signal includes amplitude consistency, phase consistency and signal-to-noise ratio; and the satellite-to-ground synchronized quantum signal stream includes time synchronization accuracy, channel matching degree and quantum state fidelity.

[0012] As a further aspect of the present invention, the microwave signal preprocessing module includes:

[0013] The data stream receiving submodule acquires the microwave signal transmitted via the satellite-to-ground link through the antenna array, performs sampling synchronization correction on the channel timing points, aligns the amplitude difference values ​​of multiple channels according to the time reference, removes interference signal segments, and generates an array synchronization waveform sequence.

[0014] The frequency domain conversion submodule, based on the array synchronization waveform sequence, groups the continuous sampling points into fixed sampling segments, performs discrete frequency domain decomposition on the grouped signals using the Fourier transform algorithm, compares the frequency segment amplitude values ​​with the noise threshold, removes interference points with amplitude values ​​lower than the threshold, and obtains the spectrum amplitude sequence.

[0015] The feature standardization submodule calls the spectrum amplitude sequence, calculates the standardization coefficient of the frequency point amplitude value based on the energy mean, normalizes the amplitude value and reconstructs it into a time domain sequence according to the time index, and generates a time domain feature-standardized microwave signal.

[0016] As a further aspect of the present invention, the pulse time compression module includes:

[0017] The time-domain feature detection submodule collects a sequence of sampling points based on the time waveform of the microwave signal standardized by the time-domain features, calculates the time interval and amplitude values ​​between sampling points, extracts the amplitude distribution and maps it to a time index table, and generates a standardized time-domain vector group.

[0018] The threshold judgment and comparison submodule calls the standardized time-domain vector group, extracts the time interval boundary value according to the reference pulse template duration threshold, compares the duration interval of the microwave signal with the threshold point by point, marks and combines the pulse segments that exceed the threshold to obtain the set of pulse intervals exceeding the threshold.

[0019] The compressed pulse generation submodule calls the over-threshold pulse interval set, adjusts the interval between adjacent sampling points within the interval, performs weighted correction on the amplitude value, and recombines the corrected time and amplitude sequences to establish a time-compressed optimized pulse.

[0020] As a further aspect of the present invention, the amplitude distribution is the statistical distribution of the amplitude values ​​of the sampling points in the time-domain sampling sequence and their correspondence with the time index;

[0021] The pulse template duration threshold is a pulse duration limit range determined based on a reference pulse template.

[0022] As a further aspect of the present invention, the dual-channel difference calibration module includes:

[0023] The signal candidate filtering submodule calls the processed signal sequence of the time compression optimized pulse, compares the energy amplitude value with the background noise reference value, marks the signal exceeding the reference value as a candidate object, and calls the candidate object signals to recombine in time order to generate an effective signal set sequence.

[0024] The parallel channel detection submodule calls the effective signal set sequence, extracts the amplitude value vector based on the amplitude feature input amplitude channel, extracts the phase difference sequence based on the phase feature input phase channel, and compares the correspondence between the amplitude value vector and the phase difference sequence in the same time sequence to obtain the amplitude and phase channel feature sequence.

[0025] The least squares fitting submodule calls the amplitude vector and phase difference sequence based on the amplitude and phase channel feature sequence, compares it with the preset fitting reference sequence to calculate the difference value sequence, performs the least squares fitting operation and extracts the data group with the error value less than the preset error threshold to obtain the dual-channel verification qualified signal.

[0026] As a further aspect of the present invention, the signal synchronization determination module includes:

[0027] The amplitude determination submodule, based on the acquisition results of the dual-channel verification qualified signal, detects the amplitude value of each signal at continuous sampling points, extracts the difference between the amplitude values ​​of the two channels at the same sampling points, arranges the differences into a sequence, and generates an amplitude difference sequence.

[0028] The time difference calculation submodule calls the amplitude difference sequence, extracts the timestamps based on the positioning results of the two signals at the phase change point, performs difference calculations on the timestamps in sequence, and serializes and arranges the differences to obtain the channel output time difference sequence;

[0029] The threshold filtering submodule compares the time difference values ​​in the output time difference sequence of the channel with the preset synchronization threshold point by point, filters out the time difference values ​​less than the threshold, outputs a continuous signal stream, and obtains the star-ground synchronization quantum signal stream.

[0030] As a further aspect of the present invention, the preset synchronization threshold is a reference value for the dual-channel output time difference set based on the system clock accuracy and channel delay characteristics;

[0031] The continuous signal stream is a continuous sequence composed of time difference values ​​less than the threshold obtained from the time difference sequence based on the preset synchronization threshold.

[0032] As a further embodiment of the present invention, the key sequence generation module performs quantum key encoding conversion based on the satellite-ground synchronization quantum signal stream, maps the synchronization signal into a binary bit sequence according to the quantum state measurement results, inserts random bits to perform sequence balancing adjustment when the continuous length exceeds a set upper limit, and outputs the satellite-ground quantum key distribution transmission key.

[0033] The satellite-to-ground quantum key distribution transmission key includes bit randomness, sequence balance, and key security.

[0034] As a further aspect of the present invention, the key sequence generation module includes:

[0035] The quantum signal receiving submodule acquires the satellite-to-ground synchronous quantum signal stream, records the photon pulse detection results of different time segments in the signal stream, compares the photon arrival time based on a set time reference value, calculates the synchronization difference of photon pulses within the time segment based on the time difference value, and generates a synchronization difference sequence.

[0036] The quantum state mapping submodule, based on the synchronization difference sequence, compares the photon polarization state in each time segment with the set polarization reference value, and maps the photon polarization state to the corresponding binary bit value according to the comparison result, thereby generating a quantum bit sequence;

[0037] The sequence balancing submodule calls the quantum bit sequence, detects whether the length of consecutive bit segments exceeds the set sequence length threshold, collects random bits for bit segments that exceed the threshold, inserts them into the corresponding positions, and reassembles the adjusted bit segments into a complete sequence to obtain the satellite-to-ground quantum key distribution transmission key.

[0038] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0039] By performing spectral analysis on the satellite-to-ground transmission signal and extracting unified time-domain features, the input pulse remains stable before entering the comparison stage. By matching with the reference template and compressing it under abnormal extension conditions, waveform distortion and judgment bias caused by pulse tailing are avoided. By introducing a fitting calculation method in the dual-path detection of amplitude and phase, background noise interference is reduced and the accurate identification of candidate signals is enhanced. The consistency of the time base is achieved by difference screening and synchronization threshold comparison, so that a stable quantum signal flow can be formed during transmission, thereby maintaining the reliability and security of the output sequence in the key generation stage. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a system schematic diagram of the present invention;

[0042] Figure 2 This is a schematic diagram of the system framework of the present invention;

[0043] Figure 3 This is a flowchart of the microwave signal preprocessing module in this invention;

[0044] Figure 4 This is a flowchart of the pulse time compression module in this invention;

[0045] Figure 5 This is a flowchart of the dual-channel difference calibration module in this invention;

[0046] Figure 6 This is a flowchart of the signal synchronization determination module in this invention;

[0047] Figure 7 This is a flowchart of the key sequence generation module in this invention. Detailed Implementation

[0048] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0049] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0050] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0051] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0052] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0053] This invention provides a microwave-based quantum key distribution satellite-to-ground synchronous transmission system, such as... Figure 1-2 The diagram shown illustrates a microwave-based quantum key distribution satellite-to-ground synchronous transmission system, which includes:

[0054] The microwave signal preprocessing module acquires the microwave signal transmitted via the satellite-to-ground link through the antenna array, performs spectrum analysis using the Fourier transform algorithm, generates a time-domain characteristic standardized microwave signal, and transmits it to the pulse time compression module.

[0055] The pulse time compression module constructs a reference pulse template based on the time-domain characteristic standardized microwave signal, compares the input pulse with the template, and performs a compression operation when the pulse duration exceeds the template threshold to generate a time-compressed optimized pulse, which is then transmitted to the dual-channel difference calibration module.

[0056] The dual-channel difference calibration module calls time compression optimization pulses and filters candidate signals based on background noise benchmarks. The signals are input into the amplitude channel and phase channel for parallel detection, and the least squares method is used for fitting calculation to generate dual-channel verification qualified signals, which are then transmitted to the signal synchronization judgment module.

[0057] The signal synchronization determination module calls the dual-channel qualified signal to verify the synchronization of amplitude and phase time points, calculates the difference between the output time points of the two channels and compares it with the preset synchronization threshold, filters out signals with a difference less than the threshold, generates a satellite-to-ground synchronization quantum signal stream, and transmits it to the key sequence generation module.

[0058] The key sequence generation module performs quantum key encoding conversion based on the satellite-to-ground synchronization quantum signal stream, maps the synchronization signal into a binary bit sequence according to the quantum state measurement results, inserts random bits to balance the sequence when the continuous length exceeds the set upper limit, and outputs the satellite-to-ground quantum key distribution transmission key.

[0059] The time-domain characteristic normalized microwave signal includes frequency distribution, power spectral density, and time-domain stability; the time-compression optimized pulse includes pulse width, peak power, and waveform smoothness; the dual-channel verified qualified signal includes amplitude consistency, phase consistency, and signal-to-noise ratio; the satellite-to-ground synchronized quantum signal stream includes time synchronization accuracy, channel matching degree, and quantum state fidelity; and the satellite-to-ground quantum key distribution transmission key includes bit randomness, sequence balance, and key security.

[0060] Specifically, such as Figure 2 , 3 As shown, the microwave signal preprocessing module includes:

[0061] The data stream receiving submodule acquires the microwave signal transmitted via the satellite-to-ground link through the antenna array, performs sampling synchronization correction on the channel timing points, aligns the amplitude difference values ​​of multiple channels according to the time reference, removes interference signal segments, and generates an array synchronization waveform sequence.

[0062] The data stream receiving submodule retrieves the satellite-to-ground transmitted microwave signal obtained through an antenna array consisting of four antenna elements. The carrier frequency of this signal is... Sampling rate That is, sampling per second At each point, the initial data was stored in the form of voltage amplitude, as shown in Table 1. The table displays the initial values. Within a nanosecond (ns) time interval, discrete voltage values ​​acquired from four channels (channels 1 to 4) are used to obtain microwave signals transmitted via a satellite-to-ground link through an antenna array. First, sampling synchronization correction is performed at the channel timing points. This process uses channel 1 as the reference channel. The cross-correlation function between the signal sequences of channels 2, 3, and 4 and the signal sequence of channel 1 is calculated. The time delay of a channel relative to the reference channel is determined by finding the peak position of the cross-correlation function. For example, in actual calculations, the cross-correlation function between channel 2 and channel 1 at a delay of [value missing]... The peak value is reached at each sampling point, that is... The peak delay of channel 3 is Each sampling point, i.e. The peak delay of channel 4 is Each sampling point, i.e. The correction operation involves advancing the entire data sequence of channel 2 on the time axis. Each sampling point delays the data sequence of channel 3. Each sampling point advances the data sequence of channel 4. After sampling points are used to complete timing alignment, the amplitude difference values ​​of multiple channels are aligned according to the time base. This process also uses channel 1 as the base and calculates the value after synchronization. microseconds ( Within the time window (i.e.) The average power of the channel signal (each sampling point) is calculated as follows: The average power of channel 1 is calculated as... Channel 2 is Channel 3 is Channel 4 is Assuming the calculation yields , , , Then, calculate the amplitude adjustment coefficient for each channel. The coefficient is calculated by dividing the square root of the average power of the reference channel by the square root of the average power of the target channel. The coefficient for channel 2 is... The coefficient of channel 3 is The coefficient of channel 4 is Then, the amplitude value of each sampling point in channels 2, 3, and 4 is multiplied by its corresponding adjustment coefficient to align the average signal power of the channels with the reference channel. Next, interference signal segments are removed. This process sets a short-time energy threshold, which is determined by referencing the average energy of the signal during interference-free periods. Specifically, continuous... The average energy of the sampled points is calculated as follows: Assuming The lower limit of the energy determination interval is set to The upper limit is set to , with a containing A sliding window of sampling points traverses the entire signal sequence, calculating the signal energy within the window. If the energy value of a certain window is higher than... For example, the energy of a window is calculated as If the window energy is lower than a certain value, then the segment is determined to be high-intensity pulse interference. If the signal is lost or interrupted, the amplitude of the data point of the identified interference segment will be set to zero, and the final output channel data will be integrated into the array synchronization waveform sequence.

[0063] Table 1: Example of initial microwave signal sampling

[0064]

[0065] As shown in Table 1, this table lists the discrete voltage signal samples acquired by the four channels of the antenna array within the first 8 nanoseconds, demonstrating the small time and amplitude differences between the channels.

[0066] The frequency domain conversion submodule, based on the array synchronous waveform sequence, groups the continuous sampling points into fixed sampling segments, performs discrete frequency domain decomposition on the grouped signals using the Fourier transform algorithm, compares the amplitude values ​​of the frequency segments with the noise threshold, removes interference points with amplitude values ​​lower than the threshold, and obtains the spectrum amplitude sequence.

[0067] The frequency domain conversion submodule receives the array synchronization waveform sequence, for example, taking a continuous sequence from one of the channels. Each sampling point is used as a processing unit to process this... Each consecutive voltage sampling point is grouped into a fixed sampling segment. Discrete frequency domain decomposition is then performed on this grouped signal. This decomposition process transforms the time domain... Each amplitude value is converted into a frequency domain value by multiplying each point by a complex exponential function and summing the results. Each complex value corresponds to a specific frequency unit. Its real and imaginary parts together determine the amplitude and phase of that frequency component. The calculation yields the amplitude value for each frequency unit. For example, for a frequency point... Its magnitude It is actually part With the imaginary part The square root of the sum of squares, assuming in The amplitude value calculated at the frequency point is ,exist Frequency point is ,exist (At a noise frequency point) Next, the frequency band amplitude value is compared with a preset noise threshold. This noise threshold is set with reference to the background noise power spectral density measured by the communication system in a silent state (i.e., when there is no effective signal transmission). The specific setting process is as follows: a segment of... For a silent period signal of milliseconds (ms), perform the same discrete frequency domain decomposition and calculate... The average amplitude at each frequency point, assuming the calculated average noise amplitude is... Then the noise threshold is set to this average value. Multiples, i.e., threshold The amplitude value of each point in the obtained signal spectrum amplitude sequence is compared with the threshold. Comparison, for frequency points Its amplitude value Higher than Retain the frequency points. Its amplitude value Higher than The frequency points will be retained, while the frequency points will be... Its amplitude value Below the threshold Then the amplitude value at that point is set to This operation iterates through all groups. At each frequency point, eliminate those with amplitude values ​​lower than [a certain value]. The interference points or noise points are identified, thus obtaining a noise-suppressed spectral amplitude sequence.

[0068] The feature standardization submodule calls the spectrum amplitude sequence, calculates the standardization coefficient of the frequency point amplitude value based on the energy mean, normalizes the amplitude value and reconstructs it into a time domain sequence according to the time index, and generates a time domain feature-standardized microwave signal.

[0069] The feature normalization submodule calls the spectral amplitude sequence generated in the previous process. This sequence is a sequence containing... An array of frequency point amplitude values ​​that have undergone thresholding, for example, a sequence of... Some values ​​were set to zero because they were below a threshold. The frequency point amplitude values ​​were standardized using an energy mean. First, the total energy of the current sequence was calculated by taking the values ​​in the sequence as an example. Sum the squares of the amplitude values, assuming the total energy of the current sequence is calculated as follows:

[0070] ;

[0071] The reference content for the energy mean has been continuous in the past processing The arithmetic mean of the energy values ​​of each effective signal segment, assuming this The average calculation result of the original energy values ​​is: The standardized coefficient is calculated as the square root of the ratio of the energy mean to the current energy, i.e., the coefficient. Then, each amplitude value in the current spectral amplitude sequence is normalized. Specifically, each amplitude value in the sequence is normalized. Multiply by the standardized coefficient For example, an amplitude value in the original sequence The points, after normalization, become The other amplitude value is The point becomes This process iterates through the entire sequence, generating a new, energy-normalized spectral amplitude sequence. Then, this normalized spectral amplitude sequence is reconstructed into a time-domain sequence based on its time index. This reconstruction process requires incorporating the original phase information obtained during the frequency domain transformation, for each frequency point... The normalized new amplitude value Phase with the original point Combine to form a new complex number Then, regarding this A new complex number is used to perform the inverse discrete frequency domain decomposition operation, that is, the frequency domain complex values ​​are used as weighting coefficients to superimpose and sum a series of sine waves with different phases and frequencies from low to high, and finally synthesize a single complex number containing... The time series of each sampling point is the output of one processing cycle. The continuously processed periodic time-domain sequences are spliced ​​together in chronological order to generate the final time-domain characteristic standardized microwave signal.

[0072] Specifically, such as Figure 2 , 4 As shown, the pulse time compression module includes:

[0073] The time-domain feature detection submodule collects the sampling point sequence of the time waveform of the microwave signal based on the time-domain feature standardization, calculates the time interval and amplitude values ​​between sampling points, extracts the amplitude distribution and maps it to the time index table, and generates a standardized time-domain vector group.

[0074] The time-domain feature detection submodule retrieves the time waveform of the time-domain feature-normalized microwave signal, which is a series of... A nanosecond (ns) is a sequence of voltage amplitude sampling points at fixed time intervals, for example, a segment of it. Sequence data:

[0075] The unit is millivolt (mV);

[0076] Calculate the time interval and amplitude values ​​between adjacent sampling points for this sequence, where the time interval is constant. The amplitude value is the numerical value at a point in the sequence. Next, the amplitude distribution characteristics of the signal are extracted. This process is accomplished by identifying local peak points. Specifically, this involves traversing the sampling point sequence and selecting any sampling point... The amplitude value and its two adjacent sampling points and Compare the amplitude values, if At the same time greater than and Then this point Marked as a local peak point, in the example sequence above, it is located at the 6th time index point ( amplitude value Its previous value is The second value ,satisfy and The condition is met, therefore this point is identified as a peak. Similarly, the 15th time index point ( amplitude value The values ​​before and after are respectively and ,satisfy and The conditions were also identified as peaks. The amplitudes of the identified peaks and their corresponding time indices were mapped to create a time index table, as shown in Table 2. This table records the observed peak values. All local peak point information identified within the segment is ultimately structured into a set of vector pairs with [time, amplitude] as elements, generating a standardized time-domain vector group.

[0077] Table 2: Example of local peak point time index representation

[0078]

[0079] As shown in Table 2, this table lists the key feature points extracted from the example signal segment using the local peak detection algorithm, namely the position and intensity of the signal pulse peak.

[0080] The threshold judgment and comparison submodule calls the standardized time domain vector group, extracts the time interval boundary value according to the reference pulse template duration threshold, compares the duration interval of the microwave signal with the threshold point by point, marks and combines the pulse segments that exceed the threshold to obtain the set of pulse intervals exceeding the threshold;

[0081] The threshold comparison submodule calls the standardized time-domain vector group from the previous process. This vector group contains multiple peak point information in the format [time, amplitude], for example... and Subsequently, the time interval boundary values ​​of the pulse are extracted based on a duration threshold of a reference pulse template. This reference pulse template is pre-defined based on the physical characteristics of the effective quantum signal in the QKD system, and its nominal duration is... The duration threshold is set with reference to this nominal value and taking into account the broadening effect introduced by channel distortion. The specific setting process is as follows: with the nominal value as the center, set a positive and negative threshold. The fluctuation range, i.e., the lower threshold. Upper limit threshold This constitutes an effective duration interval. Before extracting boundary values, an amplitude reference value is first set to determine the start and end points of the pulse. This reference value is set with reference to the average amplitude of the signal in the pulse-free region. Times, assuming the average amplitude in the pulse-free region is The amplitude reference value is Then, in the original time-domain standardized microwave signal, a search is performed outwards from the peak point in the vector group, and the first amplitude value is lower than... The time points are defined as the start and end boundaries of the pulse, respectively, for the peak point. Search to the left to find the first The amplitude is Search to the right to find the first The amplitude is Then the boundary value of the pulse is Next, the duration range of the microwave signal is compared point by point with the threshold, and the calculated duration is... The duration With effective duration interval Comparison, because Less than the lower threshold This pulse segment was determined to be invalid interference, for another peak point Assuming its boundary values ​​are calculated as Its duration is ,because The duration of the pulse segment is within the threshold range, so it is marked as a valid pulse segment. The start and end time points of the pulse segments determined by this comparison are combined to finally obtain the set of pulse intervals exceeding the threshold.

[0082] The compressed pulse generation submodule calls the over-threshold pulse interval set, adjusts the interval between adjacent sampling points within the interval, performs weighted correction on the amplitude value, and recombines the corrected time and amplitude sequences to establish a time-compressed optimized pulse.

[0083] The compressed pulse generation submodule calls the output set of over-threshold pulse intervals, for example, a valid interval is... This interval corresponds to the original signal. For each sampling point, the interval between adjacent sampling points within the interval is first adjusted. This process normalizes effective pulses of different lengths in time, mapping them uniformly to a standard value. In a point time series, if the current pulse contains If there are 1 sampling point, then the time interval remains 1. If the other effective pulse interval remains unchanged, , length is If there are 10 sampling points, then they are compressed into 10 using linear interpolation. The point, the first point of the new sequence points ( from arrive The amplitude value is determined by the position in the original sequence. The amplitude value at the point is obtained by linear interpolation. Next, the normalized value is... Each amplitude value is weighted and corrected. The weighting coefficients are set with reference to a centrally symmetric Gaussian function, so that the amplitude at the center of the pulse has a higher weight and the two ends have a lower weight. The specific coefficients are calculated as follows: ,in For the sampling point index (from) arrive ), calculated The weight coefficient sequence of each point is approximately:

[0084] ;

[0085] interval corresponding An original amplitude value, for example:

[0086] (Unit: mV);

[0087] By multiplying each point in the above weighted coefficient sequence, we obtain the corrected magnitude sequence. For example, the corrected magnitude at the 4th point is... The correction magnitude for the first point is This yields a new amplitude sequence:

[0088] ;

[0089] This corrected amplitude sequence was then compared with a standard... The time series is recombined, that is, new amplitude values ​​are assigned from... arrive By using 10 consecutive time points, a time compression optimization pulse with standard duration and optimized amplitude shape is finally established.

[0090] Specifically, such as Figure 2 , 5 As shown, the dual-channel difference calibration module includes:

[0091] The signal candidate filtering submodule calls the processed signal sequence of time-compressed optimized pulses, compares the energy amplitude value with the background noise reference value, marks signals that exceed the reference value as candidate objects, and calls the candidate object signals to recombine them in time order to generate an effective signal set sequence.

[0092] The signal candidate filtering submodule calls a processed signal sequence consisting of multiple time-compressed optimized pulses, where each pulse is a sequence containing... A sequence of amplitude values ​​at sampling points, for example, receiving three pulse signals within a continuous time period, the sequence of pulse one is as follows: The sequence of pulse two is The sequence of pulse three is The units are all millivolts (mV). Next, the energy amplitude value of each pulse is compared with a background noise reference value. The pulse energy amplitude value is calculated as the energy amplitude of the pulse sequence. The sum of squares of several amplitude values, and the background noise reference value are set with reference to multiple data collected by the system during periods without signal. The average energy of a point noise segment is calculated, with an added statistical confidence factor. The specific calculation process involves randomly collecting... The average energy of the noise segments is calculated to be [value]. The standard deviation of energy is The benchmark value is then set as the average plus three times the standard deviation, i.e.:

[0093] ;

[0094] Then, the energy amplitude of the pulse is calculated; the energy of pulse one is... The energy of pulse two is The energy of pulse three is The calculated energy value is compared with the baseline value. Comparison, due to the energy of pulse one Greater than Energy of pulse three Also greater than Then pulse one and pulse three are marked as candidate objects, while the energy of pulse two is... Less than If the signal is not identified as noise, it will be removed. Finally, the signals marked as candidate objects, namely the sequences of pulse one and pulse three, are called and recombined according to their time order of appearance in the original signal stream. Zero values ​​are filled in the time periods of non-candidate objects to generate a valid signal set sequence.

[0095] The parallel channel detection submodule calls the effective signal set sequence, extracts the amplitude value vector based on the amplitude feature input amplitude channel, extracts the phase difference sequence based on the phase feature input phase channel, and compares the correspondence between the amplitude value vector and the phase difference sequence in the same time sequence to obtain the amplitude and phase channel feature sequence.

[0096] The parallel channel detection submodule calls the generated valid signal set sequence, which consists of multiple pulses that have passed energy screening. For example, it takes a sequence of pulses from this sequence for processing:

[0097] ;

[0098] The sequence is first input into the amplitude channel based on amplitude characteristics, and its amplitude values ​​are directly extracted to form an amplitude value vector. Simultaneously, this sequence is input into the phase channel based on its phase characteristics. Within the phase channel, an imaginary sequence is first obtained by performing operations on the real number sequence, forming a complex signal sequence. Then, the instantaneous phase at each sampling point is calculated. For example, the calculated... The phase sequence of points is The unit is radians (rad). Then, the difference between adjacent phase values ​​is extracted to obtain a value containing... Phase difference sequence at each point Calculations yielded Next, compare the amplitude value vectors. Phase difference sequence In the correspondence within the same time sequence, this comparison process sets a phase stability benchmark value, which is set with reference to the phase jitter upper limit of the channel model. For example, in the current... In the frequency band, the maximum allowable phase jump between adjacent sampling points becomes radians, then the reference value The comparison operation involves finding the amplitude value vector. The point with the highest amplitude, i.e., the 4th point. And check the phase difference value within the corresponding time window, i.e., the phase difference value sequence. The absolute values ​​of the 3rd and 4th values ​​(corresponding to the phase changes from the 3rd to the 4th point and from the 4th to the 5th point) are respectively and Since both of these values ​​are less than the phase stability reference value If the amplitude-to-pulse relationship is stable, then the amplitude vector corresponding to the pulse is determined. and phase difference sequence If the phase difference in the peak region is greater than a certain value, the data is retained as a pair. If a pulse is detected, it is identified as an unstable pulse and discarded. Finally, the amplitude and phase channel characteristic sequence is obtained by combining the identified data pairs.

[0099] The least squares fitting submodule calls the amplitude vector and phase difference sequence based on the amplitude and phase channel feature sequence, compares it with the preset fitting reference sequence to calculate the difference value sequence, performs the least squares fitting operation and extracts the data group with the error value less than the preset error threshold to obtain the dual-channel verification qualified signal.

[0100] The least squares fitting submodule, based on the amplitude and phase channel feature sequences generated by the aforementioned process, calls the amplitude vector of one set of candidate signals:

[0101] Phase difference sequence This is then compared with a pre-defined fitting reference sequence to calculate the difference value sequence. This pre-defined fitting reference sequence is a standard template generated based on the physical model of the ideal QKD signal, as shown in Table 3, where the reference amplitude sequence... For a standard Gaussian pulse shape, referencing a sequence of phase differences. For a sequence of all zeros, the difference sequence is calculated by subtracting the corresponding points of the candidate signal sequence from the reference sequence point by point to obtain the amplitude difference sequence. and phase difference sequence Next, a least-squares fitting operation is performed. This operation essentially calculates a weighted total error value. This total energy is obtained by weighting and summing the squares of the amplitude and phase components separately. The amplitude component has 10 difference terms, and the phase component has 9 difference terms, with weighting coefficients... and It is preset, and its setting refers to the contribution of amplitude information and phase information in key generation. This setting is configured here. , Substituting the example data, the sum of squared magnitude errors is The sum of squared phase errors is The total error value is Subsequently, data sets with error values ​​less than a preset error threshold are extracted. This error threshold is set based on the statistical distribution of errors calculated from a large number of known good and bad signal samples. The confidence interval is obtained and set as The calculated error value Compared with this threshold, since Less than If the calculated error value is greater than 1, then the current set of candidate signals is considered qualified. If the result is not satisfactory, it will be rejected. Finally, the data set obtained by comparing the error will be used to obtain the dual-channel verification qualified signal.

[0102] Table 3: Examples of Fitted Reference Sequence and Candidate Signal Data Representation

[0103]

[0104] As shown in Table 3, this table lists the point-to-point correspondence between the ideal reference template data used for final signal verification and a candidate signal data to be verified.

[0105] Specifically, such as Figure 2 , 6 As shown, the signal synchronization determination module includes:

[0106] The amplitude determination submodule, based on the acquisition results of the dual-channel verified qualified signal, detects the amplitude value of each signal at continuous sampling points, extracts the difference between the amplitude values ​​of the two channels at the same sampling points, arranges the differences into a sequence, and generates an amplitude difference sequence.

[0107] The amplitude determination submodule is based on the acquisition results of dual-channel verified qualified signals from two parallel receiving channels. For example, if channel one and channel two both capture a verified qualified pulse signal within the same time period, this submodule first detects and records the amplitude of these two signals in continuous... The amplitude values ​​at each sampling point are shown in Table 4. This table displays the amplitude values ​​at each sampling point. Within a nanosecond (ns) pulse duration, the voltage amplitude values ​​recorded by the two channels at each sampling time point are then extracted. The difference between the amplitude values ​​of the two channels at the same sampling point is then extracted. This process is accomplished by performing a subtraction operation on the data in each row of Table 4, i.e., at the [missing value] 1st [missing value]. sampling points ( Calculate the difference value from 1 to 10. ,in It is channel one in the first The amplitude of the point, It is channel two in the first The magnitude of the point, for example, at a time index of At that time, the amplitude of channel one is The amplitude of channel two is The difference in amplitude at that point is In the time index At that time, the difference was This calculation traversal Each sampling point will be used to calculate the... The difference values ​​are arranged in chronological order to form a sequence:

[0108] The unit is millivolt (mV).

[0109] This sequence is the generated amplitude difference sequence.

[0110] Table 4: Example of Dual-Channel Qualified Signal Amplitude Representation

[0111]

[0112] As shown in Table 4, this table details the amplitude data collected by the two parallel receiving channels in the same pulse event after front-end processing and verification, providing a basis for subsequent difference analysis.

[0113] The time difference calculation submodule calls the amplitude difference sequence, extracts the timestamps based on the positioning results of the two signals at the phase change point, performs difference calculations on the timestamps in sequence, and serializes and arranges the differences to obtain the channel output time difference sequence;

[0114] The time difference calculation submodule calls the generated amplitude difference sequence and simultaneously retrieves the original phase information associated with the signal pulse. It extracts the timestamp based on the location results of the phase change points of the two signals. Here, phase change location refers to identifying the key time points where significant phase transitions occur. This identification process sets a phase change rate threshold, which is set according to the minimum phase modulation unit defined in the communication protocol. For example, for a system using Differential Phase Shift Keying (DPSK), the minimum effective phase transition is... In radians, the threshold is set to that value. ,Right now In the phase data streams of the two channels, the phase change between adjacent sampling points is searched and divided by the time interval. The obtained phase change rate exceeded for the first time At a given time point, assuming that in a signal stream, the phase sequence of channel one is at time point... The phase value at that point is , and The phase value at that point is Its phase change rate is ,because Then This time point is marked as a valid timestamp for channel one. Through the same operation, in the phase sequence of channel two, in... arrive A phase jump was detected, and its rate of change was calculated as follows: If it is also greater than the threshold, then... The corresponding timestamp is marked as Channel 2. Next, we will analyze these two extracted timestamps. and Perform interpolation to calculate the time difference. If multiple pairs of such phase transition events are detected in the subsequent signal stream, for example, the timestamps of the second pair of events are respectively and The difference is The timestamps of the third pair of events are and The difference is The calculated differences are serialized and arranged to obtain a channel output time difference sequence containing multiple time differences.

[0115] The threshold filtering submodule compares the time difference values ​​in the channel output time difference sequence with the preset synchronization threshold point by point, filters out the time difference values ​​less than the threshold, outputs a continuous signal stream, and obtains the star-ground synchronization quantum signal stream.

[0116] The threshold filtering submodule is based on the generated The channel outputs a time difference sequence, and each time difference value in the sequence is compared point-by-point with a preset synchronization threshold. The specific setting of this synchronization threshold is based on the transmission delay jitter of the satellite-to-ground link and the time resolution of the receiving device. The specific calculation process is as follows: through long-term monitoring of the link, the standard deviation of the time delay jitter is statistically obtained. Picosecond (ps) time resolution of the receiving device Then the synchronization threshold is set to the sum of the two, plus an additional one. The tolerance factor is 10 times, that is This threshold defines the maximum acceptable time difference between the signals from two channels that are considered to arrive synchronously. The comparison process involves iterating through each element in the time difference sequence, calculating its absolute value, and comparing it with... Compare the first value of the sequence. Its absolute value is less than The first value is determined to be synchronized and is retained; for the second value... Its absolute value is less than The third value is retained. Its absolute value is greater than This value was determined to be out of sync and was discarded. As for the fourth value... Its absolute value is greater than The fifth value is discarded. Its absolute value is less than The selected events are retained. This screening process removes signal events whose time difference exceeds the synchronization tolerance range and only outputs the continuous signal stream corresponding to events whose time difference value is less than the threshold. The selected signal events are then spliced ​​together in their original time order to obtain the final satellite-to-ground synchronization quantum signal stream.

[0117] Specifically, such as Figure 2 , 7 As shown, the key sequence generation module includes:

[0118] The quantum signal receiving submodule acquires the satellite-to-ground synchronous quantum signal stream, records the photon pulse detection results of different time segments in the signal stream, compares the photon arrival time based on a set time reference value, calculates the synchronization difference of photon pulses within the time segment based on the time difference value, and generates a synchronization difference sequence.

[0119] The quantum signal receiving submodule acquires a satellite-to-ground synchronized quantum signal stream consisting of a series of pulse events that have passed synchronization screening. The photon detector array within this module records the photon pulse detection results at different time segments within the signal stream. The specific recording content is shown in Table 5, which details the detection results of four single-photon detectors (corresponding to...) within a series of continuous time segments. The module detects events in four polarization states, where "photon arrival time" is a high-precision timestamp and "detector number" is the detector that triggered the response. The module then compares the photon arrival time with a predefined time reference value, which is set according to the clock period defined in the space-to-ground quantum communication protocol. At the system clock frequency, the interval between each time reference point is Nanoseconds (ns) are time reference points in a sequence of time points. The comparison process involves taking the arrival time of the first photon event from Table 5. It is compared with the time base point sequence to determine its belonging to the time base point sequence. The time segment is used as the starting point, and then the synchronization difference of photon pulses within the time segment is calculated based on this time difference value. The calculation process is to subtract the starting reference point of the time segment to which the actual arrival time belongs from the actual arrival time to obtain the synchronization difference value. For the second photon event in Table 5, its arrival time is Belonging to For the time segment starting from the given point, calculate its synchronization difference value. For the third photon event, the arrival time is Belonging to The initial time segment, the synchronization difference value is For the fourth event, the arrival time is Belonging to The initial time segment, the synchronization difference value is The calculated synchronization difference values ​​are arranged and combined according to their chronological order of occurrence to finally generate a synchronization difference sequence.

[0120] Table 5: Examples of Photon Pulse Detection Results

[0121]

[0122] As shown in Table 5, this table records the key information of single-photon events captured by the receiver within a continuous time segment, which is the original data basis for subsequent quantum state mapping and key generation.

[0123] The quantum state mapping submodule, based on the synchronization difference sequence, compares the photon polarization state in each time segment with the set polarization reference value, and maps the photon polarization state to the corresponding binary bit value according to the comparison result, thereby generating a quantum bit sequence;

[0124] The quantum state mapping submodule compares the photon polarization state within each time segment with a predetermined polarization reference value based on the generated synchronization difference sequence and its associated photon detector information. This polarization reference value refers to the measurement basis independently and randomly selected by the receiver for each time segment. In typical BB84 protocol applications, the measurement basis is the "+" basis (composed of...). and (composed of detectors) or "X" base (made of and (Detector configuration), assuming that for the four time segments in Table 5 above, the receiver randomly selects the measurement basis sequence as ["+", "X", "+", "X" basis], and simultaneously, the transmitter (satellite) actually transmits the photon polarization state sequence as [ , , , The comparison process is as follows: In the first time segment, the measurement basis at the receiving end is the "+" basis, and the photon polarization state at the transmitting end is... Since both belong to the same basis, the measurement result is valid. Based on the comparison result, the polarization state of the photon is mapped to the corresponding binary bit value. The mapping rule is that in the "+" basis, The polarization state is mapped to the binary value "0". The polarization state is mapped to "1", so the photon in the first time segment is mapped to bit "1". In the second time segment, the measurement basis at the receiver is the "X" basis, while the polarization state of the photon at the transmitter is... Since the two bases belong to different groups, the measurement result was deemed invalid and discarded. In the third time segment, the receiver measured the "+" base, and the transmitter measured the polarization state. The basis set is matched, the measurement is valid, and according to the mapping rule, the photon is mapped to bit "0". In the fourth time segment, the receiver's measurement basis is "X" basis, and the transmitter's polarization state is... Basis set matching, measurement valid, mapping rule in basis "X" is, Mapped to "0", It is mapped to "1", so this photon is mapped to bit "1". After comparing and screening the time segments, the valid binary bit values are arranged in their original time order to generate a qubit sequence.

[0125] The sequence balancer sub-module calls the qubit sequence, detects whether the length of the continuous bit segment exceeds the set sequence length threshold, collects random bits for the bit segments that exceed the threshold, and inserts them into the corresponding positions. The adjusted bit segments are re-stitched into a complete sequence to obtain the satellite-ground quantum key distribution transmission key.

[0126] The sequence balancer sub-module calls the generated qubit sequence. For example, a sequence obtained after screening is "101100000000001011111111111101". This module first detects whether the length of the segment of consecutive identical bits in the sequence exceeds a set sequence length threshold. The setting of this threshold refers to the prevention standard for randomness weakening in the cryptographic protocol. The specific calculation process is that if it is required that the Hamming weight deviation of any consecutive bits does not exceed by more than For a bit block with a length of the maximum allowable length of consecutive identical bits is calculated as and rounded down to get and a safety margin is added to set the final sequence length threshold The detection process starts from the head of the sequence. It is found that there is a segment of consecutive "0"s starting from the 7th bit. Its length is less than the threshold and is judged to be qualified. Continue scanning. It is found that there is a segment of consecutive "1"s starting from the 20th bit. Its length is less than the threshold and is also judged to be qualified. Suppose another sequence is “…011111111111111110…”, which contains consecutive "1"s and its length exceeds the threshold Then a random bit is collected for this bit segment that exceeds the threshold. This random bit is generated by the quantum random number generator carried by the system to ensure its physical true randomness. Suppose the generated random bit is "0" and it is inserted into the corresponding position. The rule for the insertion position is after the bit that reaches the threshold length, that is, at the After inserting a "1" after the original bit segment "1111111111111111" is adjusted to "1111111111111101". Then, the adjusted bit segment and the unadjusted bit segment are reassembled according to their order in the original sequence to obtain the satellite-to-ground quantum key distribution transmission key.

[0127] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A microwave-based quantum key distribution satellite-to-ground synchronous transmission system, characterized in that, The system includes: The microwave signal preprocessing module acquires the microwave signal transmitted via the satellite-to-ground link through the antenna array, performs spectrum analysis using the Fourier transform algorithm, generates a time-domain characteristic standardized microwave signal, and transmits it to the pulse time compression module. The pulse time compression module constructs a reference pulse template based on the time-domain characteristic standardized microwave signal, compares the input pulse with the template, and performs a compression operation when the pulse duration exceeds the template threshold to generate a time-compressed optimized pulse, which is then transmitted to the dual-channel difference calibration module. The dual-channel difference calibration module calls the time compression optimization pulse and filters candidate signals based on the background noise benchmark. The signals are input into the amplitude channel and phase channel for parallel detection, and the least squares method is used for fitting calculation to generate a dual-channel verification qualified signal, which is then transmitted to the signal synchronization judgment module. The signal synchronization determination module calls the dual-channel verified qualified signal to perform amplitude and phase time point synchronization verification, calculates the time point difference between the two channels and compares it with a preset synchronization threshold, filters signals with a difference less than the threshold, generates a satellite-to-ground synchronization quantum signal stream, and transmits it to the key sequence generation module.

2. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 1, characterized in that, The time-domain characteristic standardized microwave signal includes frequency distribution, power spectral density, and time-domain stability; the time-compression optimized pulse includes pulse width, peak power, and waveform smoothness; the dual-channel verified qualified signal includes amplitude consistency, phase consistency, and signal-to-noise ratio; and the satellite-to-ground synchronized quantum signal stream includes time synchronization accuracy, channel matching degree, and quantum state fidelity.

3. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 1, characterized in that, The microwave signal preprocessing module includes: The data stream receiving submodule acquires the microwave signal transmitted via the satellite-to-ground link through the antenna array, performs sampling synchronization correction on the channel timing points, aligns the amplitude difference values ​​of multiple channels according to the time reference, removes interference signal segments, and generates an array synchronization waveform sequence. The frequency domain conversion submodule, based on the array synchronization waveform sequence, groups the continuous sampling points into fixed sampling segments, performs discrete frequency domain decomposition on the grouped signals using the Fourier transform algorithm, compares the frequency segment amplitude values ​​with the noise threshold, removes interference points with amplitude values ​​lower than the threshold, and obtains the spectrum amplitude sequence. The feature standardization submodule calls the spectrum amplitude sequence, calculates the standardization coefficient of the frequency point amplitude value based on the energy mean, normalizes the amplitude value and reconstructs it into a time domain sequence according to the time index, and generates a time domain feature-standardized microwave signal.

4. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 1, characterized in that, The pulse time compression module includes: The time-domain feature detection submodule collects a sequence of sampling points based on the time waveform of the microwave signal standardized by the time-domain features, calculates the time interval and amplitude values ​​between sampling points, extracts the amplitude distribution and maps it to a time index table, and generates a standardized time-domain vector group. The threshold judgment and comparison submodule calls the standardized time-domain vector group, extracts the time interval boundary value according to the reference pulse template duration threshold, compares the duration interval of the microwave signal with the threshold point by point, marks and combines the pulse segments that exceed the threshold to obtain the set of pulse intervals exceeding the threshold. The compressed pulse generation submodule calls the over-threshold pulse interval set, adjusts the interval between adjacent sampling points within the interval, performs weighted correction on the amplitude value, and recombines the corrected time and amplitude sequences to establish a time-compressed optimized pulse.

5. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 4, characterized in that, The amplitude distribution refers to the statistical distribution of the amplitude values ​​of the sampling points in the time-domain sampling sequence and their correspondence with the time index; The pulse template duration threshold is a pulse duration limit range determined based on a reference pulse template.

6. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 1, characterized in that, The dual-channel difference calibration module includes: The signal candidate filtering submodule calls the processed signal sequence of the time compression optimized pulse, compares the energy amplitude value with the background noise reference value, marks the signal exceeding the reference value as a candidate object, and calls the candidate object signals to recombine in time order to generate an effective signal set sequence. The parallel channel detection submodule calls the effective signal set sequence, extracts the amplitude value vector based on the amplitude feature input amplitude channel, extracts the phase difference sequence based on the phase feature input phase channel, and compares the correspondence between the amplitude value vector and the phase difference sequence in the same time sequence to obtain the amplitude and phase channel feature sequence. The least squares fitting submodule calls the amplitude vector and phase difference sequence based on the amplitude and phase channel feature sequence, compares it with the preset fitting reference sequence to calculate the difference value sequence, performs the least squares fitting operation and extracts the data group with the error value less than the preset error threshold to obtain the dual-channel verification qualified signal.

7. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 1, characterized in that, The signal synchronization determination module includes: The amplitude determination submodule, based on the acquisition results of the dual-channel verification qualified signal, detects the amplitude value of each signal at continuous sampling points, extracts the difference between the amplitude values ​​of the two channels at the same sampling points, arranges the differences into a sequence, and generates an amplitude difference sequence. The time difference calculation submodule calls the amplitude difference sequence, extracts the timestamps based on the positioning results of the two signals at the phase change point, performs difference calculations on the timestamps in sequence, and serializes and arranges the differences to obtain the channel output time difference sequence; The threshold filtering submodule compares the time difference values ​​in the output time difference sequence of the channel with the preset synchronization threshold point by point, filters out the time difference values ​​less than the threshold, outputs a continuous signal stream, and obtains the star-ground synchronization quantum signal stream.

8. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 7, characterized in that, The preset synchronization threshold is a reference value for the dual-channel output time difference set based on the system clock accuracy and channel delay characteristics; The continuous signal stream is a continuous sequence composed of time difference values ​​less than the threshold obtained from the time difference sequence based on the preset synchronization threshold.

9. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 1, characterized in that, The key sequence generation module performs quantum key encoding conversion based on the satellite-to-ground synchronization quantum signal stream, maps the synchronization signal into a binary bit sequence according to the quantum state measurement results, inserts random bits to adjust the sequence balance when the continuous length exceeds the set upper limit, and outputs the satellite-to-ground quantum key distribution transmission key. The satellite-to-ground quantum key distribution transmission key includes bit randomness, sequence balance, and key security.

10. The microwave-based quantum key distribution satellite-to-ground synchronous transmission system according to claim 9, characterized in that, The key sequence generation module includes: The quantum signal receiving submodule acquires the satellite-to-ground synchronous quantum signal stream, records the photon pulse detection results of different time segments in the signal stream, compares the photon arrival time based on a set time reference value, calculates the synchronization difference of photon pulses within the time segment based on the time difference value, and generates a synchronization difference sequence. The quantum state mapping submodule, based on the synchronization difference sequence, compares the photon polarization state in each time segment with the set polarization reference value, and maps the photon polarization state to the corresponding binary bit value according to the comparison result, thereby generating a quantum bit sequence; The sequence balancing submodule calls the quantum bit sequence, detects whether the length of consecutive bit segments exceeds the set sequence length threshold, collects random bits for bit segments that exceed the threshold, inserts them into the corresponding positions, and reassembles the adjusted bit segments into a complete sequence to obtain the satellite-to-ground quantum key distribution transmission key.

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