Distance ambiguity-based inter-pulse phase modulation radar height measurement method

Abstract

The invention belongs to the technical field of radar height measurement, and particularly discloses an inter-pulse phase modulation radar height measurement method based on range ambiguity. The method comprises the following steps: a transmitting branch of a pulse Doppler radar altimeter transmits a pulse signal; a receiving branch of the pulse Doppler radar altimeter receives the echo signal; obtaining an echo signal after the range gate is gated, and determining a demodulation code corresponding to the range gate; and carrying out decoding identification on the echo signal of the target distance received at the distance door according to the demodulation code. According to the scheme, the technical problem of fuzzy ranging of the pulse Doppler system radar altimeter is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radar height measurement, and particularly relates to a radar height measurement method based on distance ambiguity. BACKGROUND

[0002] As an essential device for detecting the relative height between an airplane or a missile and the ground or the sea surface, the altimeter plays a vital role in the field of aerospace.

[0003] According to the working system of the altimeter, the altimeter can be divided into a barometric altimeter, a laser altimeter and a radar altimeter. The barometric altimeter calculates the relative height by sensing the atmospheric pressure, but the measurement result of the barometric altimeter will have certain differences due to the influence of the differences in the region, temperature and humidity and other natural conditions. The laser altimeter has high ranging accuracy, but is easily disturbed by the atmospheric environment and aerosol particles, and the attitude of the airplane or the missile will have certain influence on the measurement result of the laser altimeter. At present, the radar altimeter is used more frequently. The radar altimeter adopts the radio detection system, is not affected by the region, the natural environment and other factors, and has relatively high ranging accuracy, and will not cause large system errors.

[0004] At present, the radar altimeter is divided into the pulse system and the continuous wave system according to the different height measurement methods. The continuous wave system altimeter detects by continuously emitting a continuous radio wave, has fast scanning speed, can capture the ground and sea surface information in fast movement, but the detection distance is relatively short. The pulse system altimeter emits a short high-intensity electromagnetic pulse, and calculates according to the time delay of the pulse returning from the ground and the sea surface, and has a long detection distance.

[0005] Generally, the pulse system radar altimeter adopts the pulse Doppler system, has the distance measurement and resolution ability of the ordinary pulse system radar altimeter, and has the speed measurement and resolution ability of the continuous wave system altimeter, and has strong clutter suppression ability. For the pulse system radar altimeter, the maximum unambiguous distance is the maximum single value ranging range that can be determined. The radar altimeter emits a pulse, and the reflected pulse returns after encountering the ground and the sea surface. If the received echo arrives after the second pulse is emitted, it is impossible to judge whether it is the echo signal of the first emitted pulse or the echo signal of the second emitted pulse. Therefore, the parameter selection of the pulse Doppler radar altimeter must consider avoiding the generation of distance ambiguity. The higher the pulse repetition frequency, the more likely the radar altimeter is to generate distance ambiguity.

[0006] Since a higher pulse repetition frequency is generally adopted, such as Figure 1 and Figure 2As shown, the echo generated by the first cycle of transmission pulses within the ambiguous distance and outside the ambiguous distance can be detected by the second cycle of transmission pulses corresponding to the distance gate, and the Doppler frequency can also be detected, which causes the ranging ambiguity and affects the ranging result of the altimeter. SUMMARY

[0007] The application aims to provide a ranging ambiguity based pulse-to-pulse phase modulation radar altimeter height measurement method to solve the technical problem of ranging ambiguity of the pulse Doppler radar altimeter.

[0008] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0009] A ranging ambiguity based pulse-to-pulse phase modulation radar altimeter height measurement method, comprising: a transmission branch of a pulse Doppler radar altimeter transmits a pulse signal; a receiving branch of the pulse Doppler radar altimeter receives an echo signal; an echo signal after distance gate gating is acquired, and a demodulation code corresponding to the distance gate is determined; and the echo signal of a target distance received at the distance gate is decoded and identified according to the demodulation code.

[0010] A ranging ambiguity based pulse-to-pulse phase modulation radar altimeter height measurement system, comprising: a transmission unit for transmitting a pulse signal by a transmission branch of a pulse Doppler radar altimeter; a receiving unit for receiving an echo signal by a receiving branch of the pulse Doppler radar altimeter; a demodulation code unit for acquiring an echo signal after distance gate gating and determining a demodulation code corresponding to the distance gate; and a decoding and identifying unit for decoding and identifying the echo signal of a target distance received at the distance gate according to the demodulation code.

[0011] A computer readable storage medium, which stores a computer program, wherein the computer program is configured to execute the ranging ambiguity based pulse-to-pulse phase modulation radar altimeter height measurement method when running.

[0012] An electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor is configured to execute the ranging ambiguity based pulse-to-pulse phase modulation radar altimeter height measurement method through the computer program.

[0013] In the application, the phase modulation is performed by a pseudo-random code in the transmission branch, the signal generated by the transmission branch forms an echo signal after the ground and sea surface, the receiving branch performs phase demodulation and decoding on the received echo signal, the echo signal of the ambiguous distance is processed by using the orthogonality of the pseudo-random code, the detection of the ambiguous distance is realized, and thus the ambiguous distance signal detected in the set distance gate is identified in the signal processing process, the detection distance of the pulse Doppler radar altimeter is improved, and the technical problem of ranging ambiguity of the pulse Doppler radar altimeter is solved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a schematic diagram of echo signals of an altimeter within the ambiguous distance without phase modulation of the transmitted pulse;

[0015] Figure 2 is a schematic diagram of echo signals of an altimeter outside the ambiguous distance without phase modulation of the transmitted pulse;

[0016] Figure 3 is a flowchart of a radar altimeter method based on inter-pulse phase modulation of the distance ambiguity in an embodiment of the present application;

[0017] Figure 4 is a schematic diagram of decoding signals outside the ambiguous distance by the altimeter using the current cycle decoding pulse to phase modulate the transmitted pulse;

[0018] Figure 5 is a schematic diagram of decoding signals outside the ambiguous distance by the altimeter using the previous cycle decoding pulse to phase modulate the transmitted pulse;

[0019] Figure 6 is a schematic diagram of decoding echo signals within the ambiguous distance by the altimeter using the current cycle decoding pulse to phase modulate the transmitted pulse;

[0020] Figure 7 is a structural diagram of a radar altimeter system based on inter-pulse phase modulation of the distance ambiguity in an embodiment of the present application. DETAILED DESCRIPTION

[0021] The present application will be further described below in conjunction with the drawings and specific embodiments, and the advantages and features of the present application will be more apparent according to the following description and claims. It should be noted that the drawings are very simplified and are not to scale, and are only used to facilitate and clarify the purpose of assisting in the description of the embodiments of the present application.

[0022] It should be noted that, in order to clearly illustrate the content of the present application, the present application is characterized by multiple embodiments to further illustrate different implementation manners of the present application, wherein the multiple embodiments are enumerated and not exhaustive. In addition, in order to facilitate the description, the content mentioned in the previous embodiments is often omitted in the later embodiments, therefore, the content not mentioned in the later embodiments can be correspondingly referred to the previous embodiments.

[0023] Embodiment 1

[0024] A radar altimeter method based on inter-pulse phase modulation of the distance ambiguity, as shown in FIG. 1, the method comprises: Figure 3

[0025] S102, the transmitting branch of the pulse Doppler radar altimeter transmits a pulse signal; ​

[0026] S104, the receiving branch of the pulse Doppler radar altimeter receives the echo signal;

[0027] S106, the echo signal after the range gate selection is obtained, and a demodulation code corresponding to the range gate is determined.

[0028] S108, the echo signal of the target distance received at the range gate is decoded and identified according to the demodulation code.

[0029] As an optional implementation, the transmitting branch of the pulse Doppler radar altimeter transmits the phase-modulated pulse signal, comprising: the transmitting branch of the pulse Doppler radar altimeter transmits the phase-modulated pulse signal to the ground or sea surface.

[0030] As an optional implementation, the transmitting branch of the pulse Doppler radar altimeter transmits the phase-modulated pulse signal to the ground or sea surface, comprising: the transmitting branch of the pulse Doppler radar altimeter transmits the phase-modulated pulse signal to the ground or sea surface, and the phase-modulated pulse signal has a repetition period and a preset transmission power.

[0031] As an optional implementation, the receiving branch of the pulse Doppler radar altimeter receives the echo signal, comprising: the transmitted pulse signal is reflected by the ground or sea surface, and the echo signal transmitted by the ground or sea surface is received by the receiving branch of the pulse Doppler radar.

[0032] As an optional implementation, the echo signal after the range gate selection is obtained, comprising: setting a range gate corresponding to different distances on the receiving branch of the pulse Doppler radar altimeter; and using a low-pass filter corresponding to the range gate to perform range gate selection on the echo signal to obtain the echo signal after the range gate selection.

[0033] As an optional implementation, the echo signal after the range gate selection is obtained, comprising: using a low-pass filter to perform range gate selection on the echo signal mixed with the transmitted signal.

[0034] As an optional implementation, the demodulation code corresponding to the range gate is determined, comprising: the pseudo code generated by the pseudo code generator passes through the delay device to generate a local fixed delay demodulation code at the range gate.

[0035] As an optional implementation, the demodulation code corresponding to the range gate is determined, comprising: the output signal of the low-pass filter and the pseudo code sequence output by the delay device are integrated in a pseudo code period in the correlator.

[0036] As an optional implementation, before the echo signal of the target distance received at the range gate is decoded and identified according to the demodulation code, the method further comprises: calculating the target distance according to the repetition period of the transmitted signal and the distance corresponding to the range gate.

[0037] Specifically, the above-mentioned height measurement method based on range ambiguity of pulse phase modulation radar is not limited to comprising the following steps:

[0038] Firstly, the transmitting branch of the pulse Doppler radar altimeter transmits a pulse signal with a repetition period and a certain transmission power after being phase-modulated by a pseudo-random code to the ground or sea surface. The transmitted signal is not limited to the following formula (1):

[0039]

[0040] In the formula:

[0041] τ is the pulse width of the transmitted pulse signal;

[0042] T r is the repetition period of the transmitted signal;

[0043] ω0 is the carrier angular frequency of the transmitted signal;

[0044] is the phase determined by the pseudo-random code sequence, which is 0 or π;

[0045] is a single rectangular pulse.

[0046] Secondly, after the signal is reflected by the ground or sea surface, the signal transmitted by the ground or sea surface is received by the receiving branch of the pulse Doppler radar at the distance R d The received signal at the distance R

[0047]

[0048] In the formula:

[0049] τ d is the time delay of the signal round trip between the altimeter at the distance R d and the ground or sea surface;

[0050] ω d is the Doppler shift;

[0051] is the pseudo-random code of the received signal at the distance R d

[0052] Thirdly, a range gate corresponding to the distance is set on the receiving branch of the altimeter for range gating. The range gate is used for range gating.​d The distance gate is not limited to the corresponding number After mixing with the transmitted signal and passing through a low-pass filter to filter out the high harmonic components, the echo signal after the selection of the distance gate is shown in equation (3):

[0053]

[0054] In the fourth step, the pseudo code generated by the pseudo code generator passes through the delay unit, and the distance R d The distance gate The demodulation code with a local fixed delay is generated, as shown in equation (4):

[0055] C j = C k (t-τ gate ) (4)

[0056] The low-pass filter output signal and the pseudo code sequence output by the delay unit are integrated for one pseudo code period in the correlator, and the correlator output signal is shown in equation (5):

[0057]

[0058] In the equation, R(τ d -τ gate ) is the autocorrelation function of the pseudo-random code. When τ d = τ gate , R(τ d -τ gate ) takes the maximum value, and at this time the amplitude of the decoded echo signal is maximum.

[0059] In the fifth step, since the radar transmitted signal has the distance ambiguity characteristic, at the distance gate Not only the echo signal of distance R d is received, but also the echo signal of distance R d +cT r / 2 is received, that is, the echo signal formed by the transmitted signal from the last period in the current period will be received, if not distinguished by the form of pseudo-random code encoding, the echo signal of distance R d +cT r / 2 will be considered as the echo signal of distance R d , resulting in inaccurate ranging, as shown in Figure 4 and Figure 5 .

[0060] By utilizing the distance ambiguity characteristic of the radar, the echo signal of distance R d +cT r / 2 received at the distance gate is decoded and identified, and the ranging range of the radar altimeter is improved, as shown in Figure 6 .

[0061] In the embodiment of the present application, the pulse signal transmitted by the pulse Doppler radar altimeter is phase-modulated by a pseudo-random code in the transmitting branch. After the signal generated by the transmitting branch forms an echo signal through the ground and the sea surface, the receiving branch performs phase demodulation and decoding on the received echo signal. The echo signal of the ambiguous distance is processed by using the orthogonality of the pseudo-random code, and the detection of the ambiguous distance is realized.

[0062] The pulse Doppler radar altimeter mainly sets a range gate to perform ranging. The number of the range gates set in the pulse Doppler radar altimeter is limited. Under the premise of fixed and limited hardware conditions, the ambiguous distance signals detected in the set range gate are identified in the signal processing process, and the detection distance of the pulse Doppler radar altimeter is improved.

[0063] In the embodiment of the present application, the ambiguous distance can be identified, and the problem of ranging ambiguity of the pulse Doppler radar altimeter is solved. In order to avoid the influence of the distance ambiguity on the detection of the altimeter, the ambiguous distance is phase-modulated by a pseudo-random code. When the pulse peak power is low, a larger average power can be obtained. Since the ground and the sea surface are large transmitting bodies, the reflected signals at a long distance are strong. Since the pseudo-random code has good autocorrelation characteristics, the echo signals of the distance ambiguity points corresponding to the pulse repetition period can be suppressed. Through algorithm processing, the ambiguous distance is identified, and the detection distance of the radar altimeter is increased to a certain extent.

[0064] Embodiment 2

[0065] A radar altimeter system based on distance ambiguity and inter-pulse phase modulation, as shown in Figure 7 The system comprises:

[0066] The transmitting unit 702 is configured to transmit a pulse signal by the transmitting branch of the pulse Doppler radar altimeter.

[0067] The receiving unit 704 is configured to receive an echo signal by the receiving branch of the pulse Doppler radar altimeter.

[0068] The demodulation and coding unit 706 is configured to obtain the echo signal after the range gate is gated, and determine the demodulation and coding corresponding to the range gate.

[0069] The decoding and identifying unit 708 is configured to decode and identify the echo signal of the target distance received at the range gate according to the demodulation and coding.

[0070] Optionally, the transmitting unit 702 transmits a pulse signal by the transmitting branch of the pulse Doppler radar altimeter, which comprises that the transmitting branch of the pulse Doppler radar altimeter transmits a transmitting pulse signal phase-modulated by a pseudo-random code to the ground or the sea surface.

[0071] Optionally, the transmitting branch of the pulse Doppler radar altimeter in the transmitting unit 702 transmits the phase-modulated transmitting pulse signal to the ground or sea surface, comprising: the transmitting branch of the pulse Doppler radar altimeter transmits the phase-modulated pulse signal with a repetition period and a preset transmitting power to the ground or sea surface.

[0072] Optionally, the receiving branch of the pulse Doppler radar altimeter in the receiving unit 704 receives the echo signal, comprising: the transmitted pulse signal is reflected by the ground or sea surface, and the receiving branch of the pulse Doppler radar receives the echo signal transmitted by the ground or sea surface.

[0073] Optionally, the demodulation and coding unit 706 acquires the range gate gated echo signal, comprising: setting different distance gates corresponding to different distances on the receiving branch of the pulse Doppler radar altimeter; and using a low-pass filter corresponding to the distance gate to gate the echo signal to obtain the range gate gated echo signal.

[0074] Optionally, the demodulation and coding unit 706 uses a low-pass filter corresponding to the distance gate to gate the echo signal, comprising: using a low-pass filter to gate the echo signal mixed with the transmitting signal.

[0075] Optionally, the demodulation and coding unit 706 determines the demodulation and coding corresponding to the distance gate, comprising: the pseudo code generated by the pseudo code generator passes through the delay unit to generate a local fixed delay demodulation and coding at the distance gate.

[0076] Optionally, the demodulation and coding unit 706 determines the demodulation and coding corresponding to the distance gate, comprising: integrating the output signal of the low-pass filter and the pseudo code sequence output by the delay unit in the correlator for one pseudo code period.

[0077] Optionally, before the decoding and identifying unit 708 decodes and identifies the echo signal of the target distance received at the distance gate according to the demodulation and coding, it further comprises: calculating the target distance according to the repetition period of the transmitting signal and the distance corresponding to the distance gate.

[0078] In the embodiments of the present application, the phase modulation is performed by the pseudo random code in the transmitting branch, the signal generated by the transmitting branch forms an echo signal after being reflected by the ground and sea surface, the receiving branch performs phase demodulation and decoding on the received echo signal, the echo signal of the ambiguous distance is processed by using the orthogonality of the pseudo random code, the detection of the ambiguous distance is realized, so that in the signal processing process, the ambiguous distance signal detected in the set distance gate is identified, the detection distance of the pulse Doppler radar altimeter is improved, and the technical problem of ambiguous distance detection of the pulse Doppler radar altimeter is solved.

[0079] Embodiment 3

[0080] In yet another aspect of the embodiments of the present application, an electronic device for implementing the above-mentioned distance ambiguity based pulse-to-pulse phase modulation radar height finding method is provided, which is not limited to be a terminal device or a server in the system. The electronic device is not limited to include a memory and a processor, the memory stores a computer program, and the processor is configured to execute the steps in any of the above-mentioned method embodiments by the computer program.

[0081] Embodiment 4

[0082] In yet another aspect of the embodiments of the present application, a computer program product or a computer program is provided, which includes computer instructions stored in a computer readable storage medium. A processor of a computer device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions to make the computer device execute the method provided in any of the above-mentioned various optional embodiments of the distance ambiguity based pulse-to-pulse phase modulation radar height finding method. Wherein, the computer program is configured to execute the steps in any of the above-mentioned method embodiments when running.

Claims

1. A pulse-to-pulse phase modulation radar altimetry method based on range ambiguity, characterized in that, include: The transmitting branch of the pulse Doppler radar altimeter transmits pulse signals; The receiving branch of the pulse Doppler radar altimeter receives the echo signal; Acquire the echo signal after the range gate is selected, and determine the demodulation code corresponding to the range gate; The echo signal of the target distance received at the distance gate is decoded and identified according to the demodulation code.

2. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 1, characterized in that, The pulse Doppler radar altimeter transmits pulse signals via its transmitting branch, including: The transmitting branch of the pulse Doppler radar altimeter transmits a pulse signal modulated by a pseudo-random code to the ground or sea surface.

3. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 2, characterized in that, The transmitting branch of the pulse Doppler radar altimeter transmits a pseudo-random code-modulated pulse signal towards the ground or sea surface, including: The transmitting branch of the pulse Doppler radar altimeter transmits pulse signals with a repetition period and preset transmission power to the ground or sea surface after being phase-modulated by a pseudo-random code.

4. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 1, characterized in that, The receiving branch of the pulse Doppler radar altimeter receives echo signals, including: The transmitted pulse signal is reflected by the ground or sea surface and then received by the pulse Doppler radar receiving branch as an echo signal transmitted from the ground or sea surface.

5. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 1, characterized in that, Acquire the echo signal after range-gated selection, including: Set range gates corresponding to different distances on the receiving branch of the pulse Doppler radar altimeter; The echo signal is gated by a low-pass filter corresponding to the range gate to obtain the range-gated echo signal.

6. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 5, characterized in that, Range-gated selection of the echo signal is performed using a low-pass filter corresponding to the range gate, including: The echo signal after mixing with the transmitted signal is gated using a low-pass filter.

7. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 1, characterized in that, Determine the demodulation code corresponding to the distance gate, including: The pseudocode generated by the pseudocode generator is passed through a delay unit and a local fixed-delay demodulation code is generated at the distance gate.

8. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 7, characterized in that, Determine the demodulation code corresponding to the distance gate, including: The output signal of the low-pass filter and the pseudo-code sequence output by the delay are integrated in the correlator for one pseudo-code cycle.

9. The pulse-to-pulse phase modulation radar altimeter method based on range ambiguity as described in claim 1, characterized in that, Before decoding and identifying the echo signal of the target distance received at the distance gate according to the demodulation code, the following steps are also included: The target distance is calculated based on the repetition period of the transmitted signal and the distance corresponding to the range gate.

10. A pulse-to-pulse phase-modulation radar altimeter system based on range ambiguity, characterized in that, include: The transmitting unit is used to transmit pulse signals through the transmitting branch of the pulse Doppler radar altimeter; The receiving unit is used to receive echo signals in the receiving branch of the pulse Doppler radar altimeter; The demodulation coding unit is used to acquire the echo signal after the range gate is selected and to determine the demodulation code corresponding to the range gate. The decoding and identification unit is used to decode and identify the echo signal of the target distance received at the distance gate according to the demodulation code.

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