TACAN distance digital measurement method and module based on dynamic accumulation

Abstract

The invention discloses a TACAN distance digital measurement method and module based on dynamic accumulation, relates to the technical field of TACAN system distance measurement, and breaks through the limitation of fixed gate width by globally searching response signals in a distance measurement range after transmitting inquiry pulses, and remarkably improves the pulse extraction efficiency under different speeds and environments. And meanwhile, a dynamic accumulation threshold mechanism is introduced, and when the response pulse is accumulated to a preset value in a fixed distance, the tracking state is automatically switched, so that the search duration is shortened, and the calculation efficiency and the distance measurement timeliness are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of Tacan ranging, and particularly to a digital measurement method for Tacan distance based on dynamic accumulation.

[0002] The present invention also relates to a digital measurement module for Tacan distance based on dynamic accumulation. Background Art

[0003] As an air navigation system, the Tacan system is a traditional land-based radio navigation system that can achieve point source positioning and has reliable performance. It plays an important role in formation, route navigation, and homing guidance. The Tacan system is based on the principle of secondary radar ranging. By transmitting interrogation pulses with an airborne device and receiving reply pulses from a ground station, the distance is calculated using the time difference between the two. Its core process is divided into two states: search and tracking. The processes within each state of the traditional ranging algorithm are as follows:

[0004] 1. Search state: The system transmits interrogation pulses at a fixed frequency of 80 - 120 Hz, scans the ranging range through a dynamically moving gate window, and detects reply signals. When a valid reply pulse is captured multiple times within the gate, the state switch is triggered;

[0005] 2. Tracking state: The system reduces the interrogation frequency to 20 - 30 Hz, adopts a double-gate closed-loop control, generates an error signal by comparing the pulse occurrence frequencies within the front and rear gates, and adjusts the counter in real time to lock the target distance to ensure measurement accuracy.

[0006] "Research on Digital Tacan Ranging Technology" published in "Modern Navigation" discloses a method for implementing digital Tacan ranging. Through the comprehensive application of signal recognition, signal search, and filtering technologies, especially the correlation processing method and α-β filtering adopted, the rapid capture and processing of signals are achieved and successfully applied in actual projects. However, it uses a soft jump gate to implement the tracking state, and its width setting is limited by the target speed, resulting in limited algorithm robustness.

[0007] "Design of DME Airborne Receiver Based on FPGA" discloses a mechanism to accelerate the transition of TACAN ranging from the search state to the tracking state. This mechanism establishes a register with sufficient depth to ensure recording the reception time of each group of reply pulses. The system records the time of all received reply signals after the first interrogation and the interval between the reply time and the interrogation time. Subsequently, subsequent interrogations are captured according to the time interval of each group of reply signals recorded for the first time, and this process is repeated 15 times for searching. When signals corresponding to 8 or more valid times are captured, it can be determined as the reply pulse of the local machine, thereby locking the time window where the local reply signal is located and ending the search mode. This method improves the recognition efficiency of reply signals and significantly reduces the locking time. However, this algorithm overly relies on the first capture result, and subsequent pulse captures are only performed at specific times, resulting in fluctuating distance data that requires further smoothing processing.

[0008] The TACAN ranging algorithm realizes distance measurement by transmitting interrogation pulses and receiving reply pulses. However, existing algorithms use a fixed gate width to extract signals, making it difficult to adapt to signal delays caused by different flight speeds or environmental changes, resulting in low extraction efficiency of reply pulses. In addition, the algorithm takes a long time to transition from the search state to the tracking state and is prone to losing pulses in high-speed moving scenarios, affecting the real-time performance and accuracy of ranging. Summary of the Invention

[0009] The purpose of the present invention is to provide a digital TACAN distance measurement method based on dynamic accumulation to address the above problems. By globally searching for reply signals within the ranging range after transmitting interrogation pulses, it breaks through the limitation of the fixed gate width and significantly improves the pulse extraction efficiency under different speeds and environments. At the same time, a dynamic accumulation threshold mechanism is introduced. When the reply pulses accumulate to a preset value at a fixed distance, it automatically switches to the tracking state, shortening the search duration and enhancing the calculation efficiency and ranging timeliness.

[0010] The technical solution adopted by the present invention is as follows:

[0011] A digital TACAN distance measurement method based on dynamic accumulation, which is applied to a TACAN ranging system. The method includes:

[0012] Transmitting interrogation pulses, determining whether the current system is in the search state / tracking state, and flashing and transmitting interrogation pulse signals according to the frequency range corresponding to each state;

[0013] Single-shot ranging reply statistics, performing pulse recognition and pulse decoding on the received interrogation pulse signals to obtain a continuous decoded data stream;

[0014] Response pulse weight calculation and update. Determine the response pulse signal based on the acquired decoded data stream. After each interrogation pulse signal is transmitted, dynamically update the response pulse weight according to the decoded data stream obtained within a fixed interrogation period.

[0015] Judge the current state of the system, preset the response pulse weight threshold. After each update of the response pulse weight, judge the current state of the system by comparing the maximum response pulse weight with the response pulse weight threshold, and output the distance value.

[0016] Furthermore, the flash emission is to generate random numbers with an equal probability distribution within a preset range through a pseudo-random number generator, and determine whether to transmit an interrogation pulse according to the value of the random number.

[0017] Furthermore, set the trigger threshold, compare the generated random number with the trigger threshold. When the generated random number is less than or equal to the trigger threshold, the system triggers and transmits an interrogation pulse signal; otherwise, the system skips the transmission and enters the next cycle to continue the judgment.

[0018] Furthermore, the pulse recognition is specifically to perform pulse recognition on the received signal through the delay comparison method. Specifically: generate two rectangular pulses from the received interrogation pulse signal through the delay comparison method, perform an AND operation on the two rectangular pulses to obtain a new rectangular pulse, and use the new rectangular pulse as the timing reference to identify the Gaussian pulse through the timing reference.

[0019] Furthermore, the pulse decoding is specifically as follows:

[0020] Interval check: Divide the rectangular pulse obtained by pulse recognition into two paths. One path of signal A remains in the original position, and the other path of signal is delayed to obtain signal B. Generate signal C by performing an AND operation on signal A and signal B, and detect whether the pulse width and pulse pair interval of signal C meet the standard of the Gaussian pulse pair to determine whether the current pulse is a Gaussian pulse.

[0021] Center position capture: Delay signal A to obtain D, perform an AND operation on C and D to generate a narrow pulse E, and the rising edge of it corresponds to the maximum value of the first pulse in A, completing the first pulse decoding function.

[0022] Perform Gaussian pulse recognition and decoding on the Gaussian pulse group obtained through pulse recognition to obtain a continuous decoded data stream.

[0023] Furthermore, the update of the response pulse weight is specifically as follows:

[0024] Based on the pulse decoding value in a fixed time period within the interrogation cycle, determine whether a response pulse appears in this time period. If a response pulse appears, increase the response weight of this time period; if not, and a certain response weight has been previously accumulated, then decrease the response weight of this time period; then continuously update the response weight dynamically according to the decoding result in each interrogation cycle.

[0025] Further, after each update of the response pulse weight, determine the current state of the system by the maximum response pulse weight within the effective observation time:

[0026] Set a response pulse weight threshold. When the maximum response pulse weight is greater than the response pulse weight threshold, it indicates that the ranging system has found a response pulse, and the system switches to the tracking state, sends an interrogation pulse signal at a lower frequency, and converts the time point corresponding to the current maximum response weight into a distance and sends it to the host computer for display.

[0027] The present invention also provides a TACAN distance digital measurement system based on dynamic accumulation, adopting the above-mentioned TACAN distance digital measurement method based on dynamic accumulation. The system includes:

[0028] A flash frequency emission module, which sends interrogation pulses in different frequency ranges according to the current state of the system, outputs a trigger signal while transmitting each time, and triggers the subsequent module to perform a dynamic accumulation algorithm;

[0029] A pulse recognition and decoding module, which performs recognition and decoding operations on the TACAN baseband Gaussian pulse group each time it receives a trigger signal, and outputs all decoded data;

[0030] A response pulse weight calculation module, which updates and outputs the response weight according to the currently received decoded data and the previously accumulated response weight;

[0031] A response detection and state switching module, which determines and changes the state of the ranging system according to the current maximum response pulse weight, and at the same time outputs the time point corresponding to the maximum response pulse weight that reaches the response pulse weight threshold, that is, the time difference between the response pulse and the interrogation pulse;

[0032] A data output module, which is used to convert the time difference into a corresponding distance, and send the distance and the current state of the system to the host computer for display.

[0033] To sum up, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0034] The present invention proposes a digital measurement method and system for Tacan distance based on dynamic accumulation, which can lock the response pulse within 0.5 seconds, significantly shorten the search time, and improve the ranging accuracy to the order of ten meters. By comprehensively recording and updating the weights of the decoded data after each interrogation pulse is transmitted, this method realizes the dynamic adjustment of the response weight, overcomes the dependence on a fixed time window in traditional methods, and ensures the stable performance of the system under different environmental conditions. At the same time, the flashing emission mechanism of the interrogation pulse triggered by pseudo-random numbers provides better randomness, and all signal processing is carried out inside the FPGA. Using a relatively high clock frequency makes the triggering time of the interrogation pulse emission and the accumulation moment of the response pulse more accurate, thus improving the ranging accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 FIG. is a schematic flow chart of a digital measurement method for Tacan distance based on dynamic accumulation according to the present invention;

[0036] Figure 2 FIG. is a schematic diagram of the principle of the delay comparison method in the digital measurement method for Tacan distance based on dynamic accumulation according to the present invention;

[0037] Figure 3 FIG. is a schematic diagram of the principle of pulse decoding in the digital measurement method for Tacan distance based on dynamic accumulation according to the present invention;

[0038] Figure 4 FIG. is a process diagram of the dynamic accumulation of the response pulse weight in the digital measurement method for Tacan distance based on dynamic accumulation according to the present invention;

[0039] Figure 5 FIG. is a schematic structural diagram of a digital measurement system for Tacan distance based on dynamic accumulation according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in detail below with reference to the accompanying drawings.

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] Embodiment

[0043] This embodiment proposes a digital measurement method for Tacan distance based on dynamic accumulation. A register with a recording duration of 4.05 ms is established, and the corresponding register depth is 4.05 ms / T clk , where T clkis the clock period of the register, covering the 600km ranging range of the TACAN system; after each interrogation pulse is transmitted, each T in 4.05ms is recorded clk Whether the pulse is received, including the response pulse, random filling pulse, identification balance pulse and main and auxiliary reference pulse group, and immediately sent to the accumulation module for processing; in the accumulation module, the T clk The answering weight of the time period is dynamically accumulated in combination with the current pulse value until the answering weight of a certain time period reaches the threshold value, indicating that the system has captured the answering pulse, switches the ranging circuit to the tracking state, and converts the measured time point into the distance and sends it to the host computer for display. This embodiment significantly improves the answering pulse search efficiency of the TACAN ranging system, shortens the search time, and improves its ranging accuracy.

[0044] like Figure 1 As shown in the figure, after the ranging algorithm starts, it first transmits interrogation pulses at irregular intervals of 80 to 120 Hz, collects signal data through single ranging response statistics, and updates the target locking condition based on the response pulse weight calculation; if the response pulse weight does not reach the preset response pulse threshold, the search state is maintained and high-frequency scanning is continued; once the weight meets the requirements, it immediately switches to the tracking state, reduces the interrogation frequency to 20 to 30 Hz, and outputs the current distance in real time, completing the state switch from search to tracking to ensure the real-time and reliability of ranging. The specific process is as follows:

[0045] (1) According to the current system status, the interrogation pulse is emitted in the corresponding frequency range.

[0046] The system is initially in a search state, and then determines the current state based on the processing results after the last inquiry pulse was transmitted; if it is in a search state, inquiry pulses are transmitted at irregular intervals at a frequency of 80 to 120 Hz; if it is in a response state, inquiry pulses are transmitted at irregular intervals at a frequency of 20 to 30 Hz.

[0047] Flash frequency recognition technology is used to solve the signal interference problem when multiple aircraft use the ranging system at the same time. Since the baseband signal used for secondary radar ranging does not carry identity information, it is impossible to accurately match each set of interrogation and reply signals to a specific aircraft. If multiple aircraft send interrogation signals simultaneously, two types of problems will occur: first, the aircraft cannot identify whether the ground station reply signal is a response to itself; second, after receiving a set of valid interrogation signals, the ground station will enter a closed period of about 50μs, during which no new interrogation signals can be received, which will cause the interrogation of one of the aircraft to be unable to be responded to; if the transmission frequency of the two aircraft is the same, one of them will continue to be interfered by the signal of the other aircraft and will not receive a response; the flash frequency recognition technology effectively avoids such conflicts by randomizing the transmission interval of the interrogation signal, so that each aircraft can obtain its own reply signal without interference.

[0048] In this embodiment, a pseudo-random number generator generates random numbers with an equal probability distribution within a preset range, and determines whether to transmit an interrogation pulse according to the value of the pseudo-random number to implement the flash frequency mechanism. The specific implementation method is as follows:

[0049] Pseudo-random number generation: The FPGA has a built-in pseudo-random number generator, which is set to generate random numbers within a fixed range at the rising edge of the clock with a set period T clk to ensure that the generated numerical values are evenly distributed and appear with equal probability. Let the random number be R, and the generation range is [0, R max .

[0050] Trigger threshold setting: Define a trigger threshold R threshold , and compare the random number generated in each clock cycle T clk with this threshold. When the generated random number is less than or equal to the trigger threshold, the system triggers and transmits an interrogation pulse; otherwise, the system skips the transmission and enters the next cycle for continued judgment. Define the transmission state as TX st , where 1 represents transmission and 0 represents non-transmission. Then this process can be expressed as:

[0051]

[0052] Transmission frequency regulation: By adjusting the trigger threshold R threshold , the transmission frequency f of the interrogation pulse can be controlled:

[0053]

[0054] A lower trigger threshold will reduce the probability that the random number meets the condition and lower the transmission frequency to 20 - 30 Hz, that is, enter the tracking state; correspondingly, increasing the trigger threshold will increase the transmission frequency to 80 - 120 Hz, that is, enter the search state. This mechanism effectively avoids the signal conflict problem of a fixed frequency and ensures the ranging accuracy in a multi-device environment.

[0055] (2) Single ranging response statistics

[0056] Use the delay comparison method to identify the received interrogation pulse signal, and then perform the first pulse decoding to generate a decoded data stream;

[0057] Such as Figure 2As shown in the figure, the delay comparison method is an adaptive pulse measurement technique. By dividing the input signal into two paths, one for delay and the other for attenuation, a comparator is used to detect the reference pulse generated at the moment when the amplitudes of the two signals are equal. This method does not require a fixed threshold level and can effectively cancel the influence of amplitude changes caused by multipath reflection and noise, ensuring that the generated reference pulse depends only on the set delay and attenuation conditions and is not disturbed by the fluctuations of the signal amplitude or rise time. When detecting a single Gaussian pulse, the intersection point of the delayed signal and the attenuated signal forms a pair of rectangular pulses, and a timing reference pulse for pulse identification is obtained through logical operations.

[0058] The specific implementation steps of pulse identification by the delay comparison method provided in this embodiment are as follows: First, divide the input signal into two paths: one path is delayed by 1.75 μs, and the other path is attenuated to 50% of the original amplitude. The intersection point of these two signals appears at 50% of the pulse rising edge, generating a rectangular pulse as a reference; in the same way, divide the signal into two paths again, one path is delayed by 1.75 μs, and the other path is first attenuated by 50% and then delayed by 3.5 μs. The intersection point appears at 50% of the pulse falling edge, generating a second rectangular pulse; after ANDing the two rectangular pulses, a rectangular pulse with a width of 3.5 μs is obtained as the timing reference for identifying the Gaussian pulse.

[0059] As Figure 3 shown, the specific implementation steps of the first pulse decoding in this embodiment are as follows:

[0060] Interval check: Divide the pair of rectangular pulses obtained by pulse identification into two paths. One path, signal A, remains in its original position, and the other path is delayed by 12 μs to obtain signal B; generate signal C by ANDing signal A and signal B, and detect whether the pulse width of signal C is within the range of 3 - 4 μs to check whether the standard interval of 12 μs between the pulse pairs meets the requirements of Gaussian pulse pairs and whether it is affected by noise beyond the allowable error range of ±0.5 μs; if the pulse width of signal C meets the requirements, determine that the current pulse is a Gaussian pulse.

[0061] Center position capture: Delay signal A by 13.75 μs to obtain signal D. Since the interval of Gaussian pulse pairs is 12 μs and the pulse width is 3.5 μs, this delay aligns the rising edge of signal D with the center position of the second pulse of signal A. Generate a narrow pulse signal E by ANDing signal C and signal D, and the rising edge of it corresponds to the maximum value of the first pulse in signal A, completing the first pulse decoding function.

[0062] Through the above process, the sampled Gaussian pulse group is identified and decoded to generate a continuous decoded data stream. Each time the airborne device transmits an interrogation pulse, a FLAG signal will be output to inform the ranging circuit to start the ranging response statistics for this time; because the ranging range R of the Tacan system maxThe distance is 600 km and the fixed delay τ of the tower is 50 μs. Therefore, according to the ranging principle of secondary radar, the effective observation time T for each ranging response statistic is as follows:

[0063]

[0064] A register with a depth of 40500 is established. During the effective observation time T after each airborne device emits an interrogation pulse pair, the decoded data stream is statistically counted in units of 0.1 μs, and all decoded data measured within 4.05 ms after the emission of the interrogation pulse is written when each FLAG signal arrives. If there is a Gaussian pulse in the j-th 0.1 μs time period after the i-th interrogation pulse is emitted, the pulse decoding value r i,j is 1; otherwise, the pulse decoding value r i,j is 0.

[0065] This decoded data includes all pulse decoding values of the main and auxiliary reference pulse groups, ranging response pulses, random filling pulses, and identification pulses received within 4.05 ms, and is sent to the response pulse weight calculation module for dynamic accumulation and weight update to screen out the true ranging response pulses.

[0066] (3) Response pulse weight calculation and update

[0067] When the response pulse weight calculation module is initialized, the response pulse weight for each 0.1 μs time period within 4.05 ms is 0. After each interrogation pulse is emitted, the response weight is dynamically updated according to the decoded data stream within 4.05 ms. Specifically as follows:

[0068] If the pulse decoding value within a certain 0.1 μs time period within 4.05 ms after this interrogation is 1, it indicates that a response pulse may appear in this time period, and the calculation module increases the response weight of this time period; if there is no pulse decoding and a certain response weight has been previously accumulated, it indicates that it is more likely to be other pulses, and the calculation module decreases the response weight of this time period to avoid misidentification; in other cases, the response weight of this time period remains unchanged. Let the growth coefficient and decay coefficient of the response weight be α and β respectively, and the response weight accumulated in the j-th 0.1 μs time period after the i-th interrogation pulse is emitted be w i,j , the pulse decoding value is r i,j , then the response weight w i+1,j accumulated for the i + 1-th time is

[0069]

[0070] The ranging system continuously adjusts the response weight dynamically according to the decoding result within each interrogation period. According to the ranging principle of secondary radar, the response pulse and the interrogation pulse always have a fixed time interval. Therefore, within a certain time period after the interrogation pulse, relevant response pulses will always appear. As a result, the response weight in the corresponding time period will continuously increase; the time intervals between other pulses such as the main and auxiliary reference pulse groups, random filling pulses, and identification pulses and the interrogation pulse are completely random. Therefore, if other pulses appear at a certain time point during an accidental interrogation, the response weight in that time period will rise briefly. However, other pulses cannot appear in the same time period after each interrogation. Therefore, their response weights will quickly decrease and cannot accumulate. By accumulating multiple times and finding that the response weight in a certain time period reaches the threshold, the appearance time of the response pulse can be determined. The schematic diagram of the dynamic accumulation process of the response weight is as shown in Figure 4 shown.

[0071] (4) Judge the current state of the system

[0072] After each update of the response pulse weight, through the maximum response pulse weight w within the effective observation time T max Judge the current state of the system:

[0073] Set a response weight threshold w threshold , when w max ≥w threshold , it indicates that the ranging system has found the response pulse, and the system switches to the tracking state, sending interrogation pulses at a lower frequency (20 - 30 Hz), and converting the time point t corresponding to the current maximum response weight w max into distance and sending it to the host computer for display. According to the ranging principle of secondary radar, the conversion relationship is as follows:

[0074]

[0075] When w max <w threshold , it indicates that the current system has not tracked the response pulse, and it will switch to the search state and continue to send interrogation pulses at a high frequency of 80 - 120 Hz.

[0076] After the above TACAN ranging algorithm is implemented through FPGA modularization, by using the dynamic real-time accumulation of the response weight, this method effectively avoids the interference of other pulses, can quickly identify the real response pulse, and through the TACAN simulation source and field actual tests, the search time can be significantly shortened to 0.5 s, and the ranging accuracy can be improved to the ten-meter level.

[0077] This embodiment also provides a TACAN distance digital measurement module based on dynamic accumulation based on the above method, as shown in Figure 5 shown, specifically including:

[0078] The flash frequency emission module sends interrogation pulses in different frequency ranges according to the current state of the system, outputs a trigger signal during each emission, and triggers the subsequent module to perform a dynamic accumulation algorithm; the pulse recognition and decoding module recognizes and decodes the TACAN baseband Gaussian pulse group each time it receives a trigger signal, and outputs all the decoded data within 4.05 ms after interrogation in units of 0.1 μs; the reply pulse weight calculation module updates and outputs the reply weight according to the decoded data received this time and the previously accumulated reply weight; the reply detection and state switching module judges and changes the system state according to the current maximum reply weight, and at the same time outputs the time point corresponding to the maximum reply weight that reaches the threshold, that is, the time difference between the reply pulse and the interrogation pulse; the data output module converts the time difference into the corresponding distance, and sends the distance and the current state of the system to the upper computer for display.

[0079] In this article, specific embodiments are used to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A digital measurement method for Tacan distance based on dynamic accumulation, characterized in that, The method is applied to a Tacan ranging system, and the method includes: Transmitting interrogation pulses. Determine whether the current system is in the search state / reply state, and flash and transmit interrogation pulse signals according to the frequency ranges corresponding to each state. Single ranging reply statistics. Perform pulse identification and pulse decoding on the received interrogation pulse signals to obtain a continuous decoded data stream. Calculating and updating the reply pulse weight. Determine the reply pulse signal through the obtained decoded data stream. After each transmission of the interrogation pulse signal, dynamically update the reply pulse weight according to the decoded data stream obtained within a fixed interrogation period. Judging the current state of the system. Preset a reply pulse weight threshold. After each update of the reply pulse weight, judge the current state of the system by comparing the maximum reply pulse weight with the reply pulse weight threshold, and output the distance value.

2. The digital measurement method of Tacan distance based on dynamic accumulation according to claim 1, wherein The flash transmission is to generate random numbers with an equal probability distribution within a preset range through a pseudo-random number generator, and determine whether to transmit interrogation pulses according to the values of the random numbers.

3. A method for digital measurement of Tacan distance based on dynamic accumulation according to claim 2, characterized in that, Set a trigger threshold, compare the generated random numbers with the trigger threshold. When the generated random number is less than or equal to the trigger threshold, the system triggers and transmits an interrogation pulse signal. Otherwise, the system skips the transmission and enters the next cycle for continuous judgment.

4. A digital measurement method for Tacan distance based on dynamic accumulation according to claim 1, characterized in that, The specific pulse identification is to identify the received signal through the delay comparison method, specifically: generate two rectangular pulses from the received interrogation pulse signal through the delay comparison method, perform an AND operation on the two rectangular pulses to obtain a new rectangular pulse, and use the new rectangular pulse as the timing reference to identify Gaussian pulses through the timing reference.

5. A digital measurement method for Tacan distance based on dynamic accumulation according to claim 4, characterized in that The specific pulse decoding is as follows: Interval check: Divide the rectangular pulse obtained by pulse identification into two paths. One path of signal A remains in the original position, and the other path of signal is delayed to obtain signal B. Generate signal C by performing an AND operation on signal A and signal B, and detect whether the pulse width and pulse pair interval of signal C meet the standards of Gaussian pulse pairs to determine whether the current pulse is a Gaussian pulse. Center position capture: Delay signal A to obtain D, perform an AND operation on C and D to generate a narrow pulse E, and the rising edge of which corresponds to the maximum value of the first pulse in A, completing the first pulse decoding function. Perform Gaussian pulse identification and decoding on the Gaussian pulse group obtained through pulse identification to obtain a continuous decoded data stream.

6. A method for digital measurement of Tacan distance based on dynamic accumulation according to claim 1, characterized in that The specific update of the reply pulse weight is as follows: Judge whether a reply pulse appears in this time period according to the pulse decoding value in a fixed time period within the interrogation period. If a reply pulse appears, increase the reply weight of this time period; if not, and there is a certain accumulated reply weight previously, reduce the reply weight of this time period. Then continuously update the reply weight dynamically according to the decoding results in each interrogation period.

7. A digital measurement method for Tacan distance based on dynamic accumulation according to claim 6, characterized in that After each update of the reply pulse weight, judge the current state of the system by the maximum reply pulse weight within the effective observation time: Set a reply pulse weight threshold. When the maximum reply pulse weight is greater than the reply pulse weight threshold, it indicates that the ranging system has found a reply pulse. The system switches to the reply state, sends interrogation pulse signals at a lower frequency, and converts the time point corresponding to the current maximum reply weight into a distance and sends it to the upper computer for display.

8. A TACAN distance digital measurement system based on dynamic accumulation, which adopts any one of the TACAN distance digital measurement methods described in claims 1 to 7, is characterized in that, The system includes: The flash frequency emission module sends interrogation pulses in different frequency ranges according to the current state of the system, and outputs a trigger signal while transmitting each time, triggering the subsequent module to perform a dynamic accumulation algorithm; The pulse recognition and decoding module performs recognition and decoding operations on the Tacan baseband Gaussian pulse group each time it receives a trigger signal, and outputs all decoded data; The reply pulse weight calculation module updates and outputs the reply weight according to the currently received decoded data and the previously accumulated reply weight; The reply detection and state switching module judges and changes the state of the ranging system according to the current maximum reply pulse weight, and at the same time outputs the time point corresponding to the maximum reply pulse weight that reaches the reply pulse weight threshold, that is, the time difference between the reply pulse and the interrogation pulse; The data output module is used to convert the time difference into the corresponding distance, and send the distance and the current state of the system to the upper computer for display.

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