Doppler radio altimeter based on pulse coding

Abstract

The utility model discloses a Doppler radio altimeter based on pulse coding. The Doppler radio altimeter mainly solves the problems that a traditional radio altimeter is low in detection precision and poor in stability. The device comprises a transceiver, an indicator, a transmitting antenna and a receiving antenna, the transceiver comprises a signal processing board, a microwave transmitting assembly, a microwave receiving assembly, an interface board, a power supply board and a mother board, and plug boards and assemblies are connected through the mother board; the signal processing board comprises a high-speed analog-to-digital converter, an FPGA module, an ARM module, a DDR3 memory and an external interface, and is used for completing generation of inter-pulse coded pulse signals, acquisition and preprocessing of echo signals, height tracking calculation and original data storage. The transceiver transmits pulse signals to the transmitting antenna to radiate the pulse signals to the ground, and the receiving antenna receives echo signals and then transmits the echo signals to the transceiver to complete data processing and then transmits height information to the indicator. According to the utility model, the accuracy and stability of output height information are improved, and the device can be used for aerospace aircrafts.

Description

Technical Field

[0001] The utility model belongs to the technical field of radio distance measurement, and particularly relates to a Doppler radio altimeter which can be used for testing a flying object in aerospace and aviation. Background Art

[0002] A radio altimeter is a range-finding radar that is mainly used to ensure the safety of aircraft takeoff, route navigation, descent approach, and landing phases. It can also provide accurate relative altitude information for airborne systems such as ground proximity warning and collision avoidance or airborne weapons. Currently, radio altimeters have a variety of working systems, including pulse system, frequency modulation system, and pseudo-code height measurement system. Among them:

[0003] A pulse radio altimeter is an instrument used to measure the height of an aircraft from the ground. It sends radio pulse signals through a transmitting antenna and receives the signals reflected by the ground at a receiving antenna to measure the distance.

[0004] When an aircraft is flying, the pulse radio altimeter periodically sends short pulse signals. These pulse signals propagate toward the ground at the speed of light and are reflected when they come into contact with the ground.

[0005] The reflected signal is received back to the aircraft after a certain time delay and is received by the pulse radio altimeter. By measuring the time delay from the pulse being sent to being received, the distance difference between the aircraft and the ground can be calculated, thereby measuring the height of the aircraft relative to the ground.

[0006] Pulse radio altimeters usually send multiple pulse signals and calculate their average value to improve measurement accuracy and stability. In addition, since there may be obstacles or different types of ground surfaces on the ground, the pulse radio altimeter will also make appropriate compensation and corrections to make the measurement results more accurate. The pulse radio altimeter uses the delay in sending and receiving radio pulse signals to measure the height of the aircraft relative to the ground to provide the aircraft's altitude information.

[0007] Patent document No. 201810564185.7 discloses a method based on a pulse radio altimeter, which transmits a random pulse signal, processes the echo signal, and outputs two signals. The first signal accumulates multiple range gate pulses. When the number of pulses exceeds the threshold value, a stop signal is generated, and the height value is calculated using mathematical statistics. The second signal controls the sensitivity of the receiver so that the amplitude of the first signal is greater than the sampling threshold and maintains a stable output. Due to the limitations of signal transmission and reception, the measurement height and measurement accuracy are low.

[0008] Patent document No. 201810564291.5 discloses a radio altimeter with a digital pulse system, which generates two pulse signals with different amplitudes through FPGA, one signal is used for internal signal detection and tracking, and the other is used for internal AGC control logic, wherein the second pulse is sampled using a binary method. Although this radio altimeter can solve the problems of co-channel interference and external radio frequency interference between multiple radio altimeters, the pulse front edge detected and tracked by this pulse system radio altimeter is the front point within the beam range, and the front point within the beam range is output as height information, which has a relatively large error. Therefore, for complex and undulating ground, there are problems of low measurement accuracy and poor stability. Utility Model Content

[0009] The utility model aims to address the deficiencies of the prior art and to propose a Doppler radio altimeter based on pulse coding to adapt to different undulating ground environments and improve the detection accuracy of the aircraft to the ground and the stability of the detection results.

[0010] To achieve the above-mentioned purpose, the utility model is a Doppler radio altimeter based on pulse coding, comprising: a transceiver, an indicator, a transmitting antenna, a receiving antenna, and two high-frequency cables. The transceiver comprises an interface board, a power board, a microwave transmitting component, a microwave receiving component, a signal processing board and a motherboard. Each plug-in board and component are interconnected through the motherboard. The utility model is characterized in that the signal processing board comprises: a high-speed analog-to-digital converter, an FPGA module, an ARM module, a DDR3 memory and a system external interface;

[0011] The high-speed analog-to-digital converter is used to collect the echo signal received by the microwave receiving component at high speed and transmit it to the FPGA module;

[0012] The FPGA module is used to pre-process the echo signal collected by the high-speed analog-to-digital converter and transmit the processed result to the ARM module, generate an inter-pulse coded pulse signal to the microwave transmitting component,

[0013] The ARM module is used to detect and track the echo signal after FPAG preprocessing and calculate the altitude value;

[0014] The DDR3 memory is used to expand the external storage space of the FPGA module;

[0015] The system's external interface is used to provide clock signals to the signal processing board and exchange information with other external devices.

[0016] Further, the FPGA module includes:

[0017] A range gate submodule, used for generating a plurality of range gates within a range segment centered on the search distance to the preprocessing submodule;

[0018] A reference phase code submodule, used to generate a reference phase code based on a code period signal to the preprocessing submodule;

[0019] The preprocessing submodule is used to divide the intermediate frequency signal sampled and input by the high-speed analog-to-digital converter and the range gate gating generated by the range gate submodule into multiple parallel wave gate channels. Each channel uses the reference code generated by the reference phase code submodule to perform phase demodulation, correlation filtering, down-conversion, and detection, and output the results to the ARM module;

[0020] The output phase code submodule is used to generate a phase code with a code width of 10us and a code period of 130us to the phase pulse modulation submodule;

[0021] The pulse submodule is used to generate a pulse signal with a pulse frequency of 100KHz and a code width of 10us to the phase pulse modulation submodule;

[0022] The phase pulse modulation submodule is used to modulate the phase code generated by the output phase code submodule and the pulse signal generated by the pulse submodule into an inter-pulse coded pulse signal and output it to the microwave transmitting component.

[0023] Further, the ARM module includes:

[0024] Initialize submodules to initialize other modules;

[0025] The interface control submodule is used to receive speed and attitude angle data information transmitted by external devices and send altitude data to the indicator.

[0026] The target signal detection submodule is used to perform target detection on the result of the FPGA preprocessing submodule, determine whether the target is detected, and output the result to the altitude solution and tracking submodule;

[0027] The height calculation and tracking submodule is used to calculate the data and track the target based on the output of the target signal detection submodule, and transmit the calculated height data to the interface control submodule;

[0028] The parameter setting submodule is used to complete the parameter setting of the transmission signal, wave gate and filter according to the speed, attitude angle data output by the interface control submodule and the wave gate data output by the height solution and tracking submodule, and send the set parameters to the FPGA module.

[0029] Furthermore, the system external interface includes:

[0030] A receiving interface, used to receive an intermediate frequency echo signal and transmit it to a high-speed analog-to-digital converter;

[0031] The transmitting interface is used to transmit the pulse code pulse signal of the FPGA module to the microwave transmitting component;

[0032] Clock interface, used for inputting sampling clock;

[0033] External control signal interface, used to output the transmission control signal to the interface board;

[0034] Four ARINC429 interfaces are used for inertial navigation signal input, navigation computer signal input and two outputs of altitude value signal;

[0035] Two Gigabit network ports, one for monitoring and debugging the system and the other for reading stored data;

[0036] SATA interface, used for storage data output of FPGA module;

[0037] UART interface: used to transmit the transmission gain control signal to the microwave transmission component and transmit the reception gain control signal to the microwave reception component.

[0038] Furthermore, the microwave receiving component includes: a bandpass filter, a low-noise amplifier, a receiving voltage-controlled oscillator VCO, a receiving mixer, an intermediate frequency amplifier and a receiving phase-locked loop. The bandpass filter filters the radio frequency echo pulse input by the receiving antenna, removes the interference signal and then outputs it to the low-noise amplifier for pre-amplification; the receiving mixer mixes the echo signal output by the low-noise amplifier with the local oscillator signal generated by the receiving voltage-controlled oscillator VCO to obtain an intermediate frequency echo signal; the intermediate frequency amplifier amplifies the intermediate frequency echo signal output by the mixer and receives the receiving gain control signal sent by the signal processing board to keep the pulse amplitude stable; the receiving phase-locked loop uses the clock signal input by the signal processing board to tune the frequency and phase of the local oscillator signal generated by the receiving voltage-controlled oscillator VCO.

[0039] Furthermore, the microwave transmitting component includes: a digital up-converter, a transmitting voltage-controlled oscillator VCO, a transmitting mixer, a power amplifier and a transmitting phase-locked loop. The digital up-converter converts the pulse coded signal output by the signal processing board into an intermediate frequency signal after up-converting it; the transmitting mixer mixes the intermediate frequency signal output by the digital up-converter with the local oscillator signal generated by the transmitting voltage-controlled oscillator VCO, and outputs the converted radio frequency pulse coded signal to the power amplifier for amplification. The power amplifier simultaneously receives the gain control signal sent by the signal processing board to keep the pulse amplitude stable; the transmitting phase-locked loop uses the clock signal input by the signal processing board to tune the frequency and phase of the local oscillator signal generated by the transmitting voltage-controlled oscillator VCO.

[0040] Furthermore, the interface board includes: a main controller, a logic controller and a DA converter. The main controller receives control instructions issued by the overall system and uploads relevant data to the overall system; the logic controller performs SPI communication with the signal processing board according to the control instructions issued by the main controller; the DA converter converts the height value digital signal output by the signal processing board into an analog signal and outputs it.

[0041] Furthermore, the power board includes: an EMI filter module and a DC-DC power supply module. The EMI filter module filters the 28v voltage signal on the switchboard to reduce electromagnetic interference, and then outputs it to the DC-DC power supply module. The filtered 28v voltage signal of the DC-DC power supply module is converted into 12v, 5v and 3.3v fixed voltage signals respectively, and provides power to other devices through the motherboard.

[0042] Furthermore, the height calculation and tracking submodule calculates the height data by the following formula:

[0043]

[0044] Where H represents the measured height, t 2 -t 1 Represents in t 1 Detect rectangular echo at every moment and t 2 The time difference of detecting the rectangular echo at each moment, c represents the speed of light.

[0045] Compared with the prior art, the utility model has the following advantages:

[0046] 1. The utility model adopts an inter-pulse coded pulse signal system, which encodes the pulses to expand the signal repetition period, thereby increasing the height measurement range, and the coding system can bring signal processing gain and reduce the transmission power.

[0047] 2. Improved the accuracy of output height information.

[0048] Traditional altimeters output the leading point within the beam range as altitude information, resulting in large measurement errors;

[0049] The utility model adopts the pulse Doppler filtering processing technology according to the law that the scattering points corresponding to the same Doppler frequency are distributed in stripes on the ground, and performs pulse front capture and tracking on the echo after Doppler strip filtering, thereby effectively improving the accuracy of the output height information.

[0050] 3. Improved the stability of output height information.

[0051] Traditional altimeters use front and rear gates to track the pulse front edge. Due to the large fluctuations in the ground, the echo front edge can easily jump out of the front and rear tracking gates, resulting in a loss of lock and inability to output altitude information stably.

[0052] The utility model finds the center of gravity of each return waveform based on statistical laws, fits the irregular echo in the tracking window into a regular rectangular echo, and adopts a wider tracking window, so that the loss of lock phenomenon will not occur, and thus stable height information can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The overall structural block diagram of the Doppler radio altimeter of the utility model is shown in FIG.

[0054] Figure 2 This is a structural block diagram of the signal processing board of the utility model;

[0055] Figure 3 This is the structural block diagram of the FPAG module of the utility model;

[0056] Figure 4 This is the structural block diagram of the ARM module of the utility model.

[0057] Figure 5 This is a structural block diagram of the microwave transmitting component of the utility model;

[0058] Figure 6 This is a structural block diagram of the microwave receiving component of the utility model;

[0059] Figure 7 This is the structure diagram of the interface board of the utility model;

[0060] Figure 8 This is a structural block diagram of the power board of the utility model. DETAILED DESCRIPTION

[0061] The embodiments of the present utility model are described below in conjunction with the accompanying drawings.

[0062] Reference Figure 1 The pulse coded Doppler radio altimeter in the utility model includes a transceiver, an indicator, a transmitting antenna, and a receiving antenna; the transceiver includes a signal processing board 1, a microwave transmitting component 2, a microwave receiving component 3, an interface board 4, a power board 5 and a motherboard 6, and each plug-in board and component are interconnected through the motherboard 6.

[0063] The signal processing board generates an inter-pulse coded pulse signal and transmits it to the microwave transmitting component 2. The microwave transmitting component 2 up-converts, mixes and amplifies the inter-pulse coded pulse signal and transmits it to the transmitting antenna through a high-frequency cable and radiates it to the ground; the receiving antenna transmits the received echo signal to the receiving microwave component 3 through a high-frequency cable. The microwave receiving component 3 filters, low-noise amplifies, mixes and amplifies the echo signal and then sends it to the signal processing board. The signal processing board completes the altitude search, altitude tracking, altitude data calculation after high-speed acquisition and preprocessing of the echo signal and transmits the results to the overall and indicator. The power supply board 5 converts the 28V power supply on the switchboard into fixed voltages of 12v, 5v and 3.3v, and sends it to each plug-in through the motherboard 6.

[0064] refer to Figure 2 The signal processing board 1 includes: a high-speed analog-to-digital converter 11, an FPGA module 12, an ARM module 13, a DDR3 memory 14 and a system external interface 15. The high-speed analog-to-digital converter 11 adopts but is not limited to the LTC2153 model.

[0065] The high-speed analog-to-digital converter 11 collects the echo signal of the microwave receiving component 3 at high speed and transmits it to the FPGA module 12; the FPGA module 12 preprocesses the echo signal collected by the high-speed analog-to-digital converter 11 and transmits the processed result to the ARM module 13, generates an inter-pulse coded pulse signal and transmits it to the microwave transmitting component 2; the ARM module 13 detects and tracks the echo signal preprocessed by the FPAG module 12 and calculates the height value; the DDR3 memory 14 expands the external storage space of the FPGA module 12; the system external interface 15 provides a clock signal to the signal processing board and exchanges information with other external devices.

[0066] refer to Figure 3 The FPGA module 12 includes: a range gate submodule 121, a reference phase code submodule 122, a preprocessing submodule 123, a phase code submodule 124, a pulse submodule 125 and a phase pulse modulation submodule 126, wherein the functions of each submodule are as follows:

[0067] The range gate submodule 121 is used to generate a plurality of range gates within a range segment centered on the search distance to the preprocessing submodule 123;

[0068] A reference phase code submodule 122, used to generate a reference phase code based on a code period signal to a preprocessing submodule 123;

[0069] The preprocessing submodule 123 is used to divide the intermediate frequency signal sampled and input by the high-speed analog-to-digital converter 1 and the range gate gating generated by the range gate submodule 121 into multiple parallel wave gate channels, and each channel uses the reference code generated by the reference phase code submodule 122 to perform phase demodulation, correlation filtering, down-conversion, and detection, and output the result to the ARM module 13;

[0070] The phase code submodule 124 is used to generate a phase code with a code width of 10us and a code period of 130us to the phase pulse modulation submodule 126;

[0071] The pulse submodule 125 is used to generate a pulse signal with a pulse frequency of 100KHz and a code width of 10us to the phase pulse modulation submodule 126;

[0072] The phase pulse modulation submodule 126 is used to modulate the phase code generated by the phase code submodule 124 and the pulse signal generated by the pulse submodule 125 into an inter-pulse coded pulse signal and output it to the microwave transmitting component 2.

[0073] refer to Figure 4 The module ARM module 13 includes an initialization submodule 131, an interface control submodule 132, a target signal detection submodule 133, a height calculation and tracking submodule 134 and a parameter setting submodule 135. The functions of each submodule are as follows:

[0074] Initialization submodule 131, used to initialize other modules;

[0075] The interface control submodule 132 is used to receive speed and attitude angle data information transmitted by external equipment and send altitude data to the indicator.

[0076] The target signal detection submodule 133 is used to perform target detection on the result of the preprocessing submodule 123, determine whether the target is detected, and output the result to the altitude solution and tracking submodule 134;

[0077] The altitude calculation and tracking submodule 134 is used to perform data calculation and target tracking on the result output by the target signal detection submodule 133, and transmit the calculated altitude data to the interface control submodule 132;

[0078] The parameter setting submodule 135 is used to complete the parameter setting of the transmission signal, wave gate and filter according to the speed, attitude angle data output by the interface control submodule 132 and the wave gate data output by the altitude solution and tracking submodule 134, and send the set parameters to the FPGA module 12.

[0079] refer to Figure 5The microwave transmitting component 2 includes: a digital up-converter 21, a transmitting mixer 22, a transmitting voltage-controlled oscillator VCO23, a power amplifier 24 and a transmitting phase-locked loop 25. The digital up-converter 21 converts the pulse coded signal output by the signal processing board into an intermediate frequency signal after up-converting; the transmitting mixer 22 mixes the intermediate frequency signal output by the digital up-converter 21 with the local oscillator signal generated by the transmitting voltage-controlled oscillator VCO23, and outputs the mixed RF pulse coded signal to the power amplifier 24 for amplification. The power amplifier 24 simultaneously receives the gain control signal sent by the signal processing board to keep the pulse amplitude stable; the transmitting phase-locked loop 25 uses the clock signal input by the signal processing board to tune the frequency and phase of the local oscillator signal generated by the transmitting voltage-controlled oscillator VCO23.

[0080] refer to Figure 6 The microwave receiving component 3 includes: a bandpass filter 31, a low noise amplifier 32, a receiving mixer 33, a receiving voltage controlled oscillator VCO34, an intermediate frequency amplifier 35 and a receiving phase-locked loop 36. The bandpass filter 31 filters the RF echo pulse input by the receiving antenna, removes the interference signal and outputs it to the low noise amplifier 32 for pre-amplification; the receiving mixer 33 mixes the echo signal output by the low noise amplifier 32 with the local oscillator signal generated by the receiving voltage controlled oscillator VCO34 to obtain an intermediate frequency echo signal; the intermediate frequency amplifier 35 amplifies the intermediate frequency echo signal output by the receiving mixer 31, and receives the receiving gain control signal sent by the signal processing board to keep the pulse amplitude stable; the receiving phase-locked loop 36 uses the clock signal input by the signal processing board to tune the frequency and phase of the local oscillator signal generated by the receiving voltage controlled oscillator VCO34.

[0081] refer to Figure 7 The interface board 4 includes: a main controller 41, a logic controller 42 and a DA converter 43. The main controller 41 receives the control instructions issued by the overall system, and uploads the relevant data of the signal processing board to the overall system; the logic controller 42 receives the SPI data sent by the signal processing board, and sends it to the signal processing board through the communication protocol SPI according to the relevant content of the overall control instructions; the DA converter 43 converts the height value digital signal output by the signal processing board into an analog signal.

[0082] refer to Figure 8 The power board 5 includes: an EMI filter module 51 and a DC-DC power supply module 52. The EMI filter module 51 filters the 28V voltage signal on the switchboard to reduce electromagnetic interference, and then outputs it to the DC-DC power supply module 52. The 28V voltage signal filtered by the DC-DC power supply module 52 is converted into 12V, 5V and 3.3V fixed voltage signals respectively, and provides power to other devices through the motherboard 6.

[0083] The working process of the utility model is as follows:

[0084] The signal processing board starts working, the ARM module 13 first enters the search mode, the parameter setting submodule 135 completes the parameter setting of the transmission signal, the wave gate and the filter according to the speed and attitude angle data output by the interface control submodule 132 and the wave gate data output by the height solution and tracking submodule 134, and sends the set parameters to the FPGA module 12;

[0085] The phase code submodule 124 in the FPGA module 12 generates a phase code according to the parameter setting information, the pulse submodule 125 generates a pulse signal according to the parameter setting information, and the phase pulse modulation submodule 126 modulates the above phase code and pulse signal into an inter-pulse coded pulse signal and transmits it to the microwave transmitting component 2; the microwave transmitting component 2 transmits the processed inter-pulse coded pulse signal to the transmitting antenna through a high-frequency cable and radiates it to the ground;

[0086] After receiving the echo signal, the receiving antenna transmits it to the microwave receiving component 3 through a high-frequency cable. The microwave receiving component 3 performs low-noise amplification and mixing on the echo signal, and after amplification by an intermediate frequency amplifier whose gain is controlled by AGC, it is sent to the high-speed analog-to-digital converter 11 of the signal processing board.

[0087] The high-speed analog-to-digital converter 11 transmits the sampled input intermediate frequency signal to the preprocessing submodule 123; the preprocessing submodule 123 divides the received intermediate frequency signal and the range gate selection generated by the range gate submodule 121 into multiple parallel wave gate channels, each channel performs phase demodulation, correlation filtering, mixing, strip filtering and detection on the reference code generated by the reference phase code submodule 122, and transmits the multi-path strip filtering and detection values ​​to the target signal detection submodule 133.

[0088] The target signal detection submodule 133 compares the multi-channel detection results of the preprocessing submodule 123 with the predetermined capture threshold. If all wave gates do not pass the threshold, the search continues until all wave gates pass the threshold. When the preprocessing results of multiple channels all pass the threshold, the closest one is selected as the pulse front edge, and the ARM module 13 switches to the tracking mode, and re-initializes the configuration and parameter settings, and transmits the parameter information to the FPGA module 12; at the same time, the target signal detection submodule 133 transmits the multi-channel strip filtering and detection values ​​to the height resolution and tracking submodule 134, and the height resolution and tracking submodule 134 calculates the center of gravity and width of the fitting rectangle according to the detection value of the tracking channel, and substitutes the time difference of the received rectangular echo into the following formula:

[0089]

[0090] The height value H is calculated, and the calculated height data is transmitted to the interface control submodule 132 and output to the external device. Due to the use of Doppler strip filtering and the selection of a wider tracking window, the height information measured by the altimeter is more accurate and stable.

[0091] The effect of the utility model can be further proved by the following experiments:

[0092] 1. High-precision flight test verification:

[0093] The UAV is within the height measurement range of 6000m of the Doppler radio altimeter, and different altitude layers such as 10m, 20m, 100m, 200m, 500m, 1000m, 1500m, 3000m and 6000m are selected for test flight. The test flight site includes water surface, grassland and hillside. The real height of the UAV is obtained by differential GPS. The real height of the UAV is compared with the height tested by the altimeter of the utility model to obtain the height measurement accuracy error statistics of the utility model, as shown in Table 1.

[0094] Table 1 Statistics of high precision errors of altimeter measurement

[0095]

[0096] It can be seen from Table 1 that the error value of the Doppler radio altimeter of the utility model is controlled within a relatively small range when the inertial navigation is not cross-linked, and the height measurement accuracy meets the error of 1m or 2%H specified in the index.

[0097] 2. Flight test for height stability verification

[0098] The Doppler radio altimeter of the utility model is installed on a UAV and tested on water surface, grassland and hillside for flight verification, and the altimeter output is stable.

[0099] In summary, the test flights on water, grass and hillsides show that the utility model can adapt to different undulating ground environments and improve the detection accuracy of the aircraft to the ground and the stability of the detection results.

[0100] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principle of the present invention, they may make various modifications and changes in form and details without departing from the principle and structure of the present invention. However, these modifications and changes based on the idea of ​​the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A pulse coding based Doppler radio altimeter comprising: A transceiver, an indicator, a transmitting antenna, and a receiving antenna. The transceiver comprises a signal processing board (1), a microwave transmitting component (2), a microwave receiving component (3), an interface board (4), a power board (5), and a motherboard (6). Each plug-in board and component are interconnected via the motherboard (6). The signal processing board (1) comprises: a high-speed analog-to-digital converter (11), an FPGA module (12), an ARM module (13), a DDR3 memory (14), and a system external interface (15); The high-speed analog-to-digital converter (11) is used to collect the echo signal received by the microwave receiving component at high speed and transmit it to the FPGA module (12); The FPGA module (12) is used to pre-process the echo signal collected by the high-speed analog-to-digital converter (11) and transmit the processed result to the ARM module (13), and generate an inter-pulse coded pulse signal to transmit to the microwave transmitting component (2); The ARM module (13) is used to detect and track the echo signal after FPAG preprocessing and calculate the altitude value; The DDR3 memory (14) is used to expand the external storage space of the FPGA module (12); The system external interface (15) is used to provide a clock signal to the signal processing board and to exchange information with other external devices.

2. The altimeter according to claim 1, characterized in that: The system external interface (15) includes: A receiving interface (151), used for receiving an intermediate frequency echo signal and transmitting it to a high-speed analog-to-digital converter (11); A transmitting interface (152) for transmitting the inter-pulse coded pulse signal of the FPGA module (12) to the microwave transmitting component (2); A clock interface (153), used for inputting a sampling clock; An external control signal interface (154) for outputting a transmission control signal to an interface board (4); Four ARINC429 interfaces (155, 156, 157, 158) are respectively used for input of inertial navigation signals, input of navigation computer signals and two outputs of altitude value signals; Two Gigabit network ports (159, 1510), used for monitoring and debugging one system and reading the other stored data; R-SATA interface (1511), used for outputting storage data of FPGA module (12); UART interface (1512): used to transmit the transmission gain control signal to the microwave transmission component (2) and to transmit the reception gain control signal to the microwave reception component (3).

3. The altimeter according to claim 1, characterized in that The microwave transmitting component (2) comprises: a digital up-converter (21), a transmitting mixer (22), a transmitting voltage-controlled oscillator VCO (23), a power amplifier (24) and a transmitting phase-locked loop (25); The digital up-converter (21) up-converts the pulse coded signal output by the signal processing board into an intermediate frequency signal; The transmitting mixer (22) mixes the intermediate frequency signal output by the digital up-converter (21) with the local oscillator signal generated by the transmitting voltage-controlled oscillator VCO (23), and outputs a post-converted radio frequency pulse coded signal to the power amplifier (24) for amplification. The power amplifier (24) simultaneously receives a gain control signal sent by the signal processing board to keep the pulse amplitude stable. The transmitting phase-locked loop (25) uses the clock signal input from the signal processing board to tune the frequency and phase of the local oscillation signal generated by the transmitting voltage-controlled oscillator VCO (23).

4. The altimeter according to claim 1, characterized in that: The microwave receiving component (3) comprises: a bandpass filter (31), a low noise amplifier (32), a receiving mixer (33), a receiving voltage-controlled oscillator VCO (34), an intermediate frequency amplifier (35) and a receiving phase-locked loop (36); The bandpass filter (31) filters the radio frequency echo pulse input by the receiving antenna, removes the interference signal and then outputs it to the low noise amplifier (32) for pre-amplification; The receiving mixer (33) mixes the echo signal output by the low noise amplifier (32) with the local oscillation signal generated by the receiving voltage controlled oscillator VCO (34) to obtain an intermediate frequency echo signal; The intermediate frequency amplifier (35) amplifies the intermediate frequency echo signal output by the mixer and receives a receiving gain control signal sent by the signal processing board to keep the pulse amplitude stable; The receiving phase-locked loop (36) uses the clock signal input from the signal processing board to tune the frequency and phase of the local oscillation signal generated by the receiving voltage-controlled oscillator VCO (34).

5. The altimeter according to claim 1, characterized in that The interface board (4) comprises: a main controller (41), a logic controller (42) and a DA converter (43); The main controller (41) receives control instructions issued by the overall system and uploads relevant data of the signal processing board to the overall system; The logic controller (42) performs SPI communication with the signal processing board according to the control instruction issued by the main controller (41); The DA converter (43) converts the height value digital signal output by the signal processing board into an analog signal and outputs the analog signal.

6. The altimeter according to claim 1, characterized in that: The power board (5) comprises: an EMI filter module (51) and a DC-DC power supply module (52); The EMI filter module (51) filters the 28V voltage signal on the switchboard to reduce electromagnetic interference, and then outputs it to the DC-DC power supply module (52); The 28V voltage signal after filtering by the DC-DC power supply module (52) is converted into 12V, 5V and 3.3V fixed voltage signals respectively, and provides power to other devices through the motherboard (6).

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