System and method for measuring ground angle of aircraft

Abstract

The invention provides an aircraft ground angle measuring system and method. The system comprises a data processing unit, a transmit-receive unit and an antenna unit which are installed on an aircraft and connected in sequence. The transceiving unit comprises a transmitter and a receiver; the antenna unit comprises a transmitting antenna connected with the transmitter, and a first receiving antenna and a second receiving antenna which are connected with the receiver; the transmitting antenna radiates a transmitting signal outwards under the driving of the transmitter; the first receiving antenna and the second receiving antenna respectively receive echo signals reflected by the ground, and the two paths of echo signals are sent to the data processing unit after being subjected to frequency mixing conversion by the receiver; and the data processing unit converts the two paths of difference frequency signals subjected to frequency mixing conversion into digital signals, and calculates the ground angle of the aircraft by calculating the phase difference of the two paths of difference frequency signals. The method has the advantages of high angle measurement precision, good real-time performance and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio angle measurement, and in particular relates to a system and method for measuring the angle of an aircraft to the ground. Background Art

[0002] In the practical application of radio-controlled aircraft (such as drones), real-time measurement of the aircraft's ground angle (the angle between its axis and the ground) is crucial for improving flight stability, navigation accuracy, and mission execution. During flight, an aircraft's attitude and position can change due to external factors such as wind speed, air pressure, and obstacles. Real-time, accurate ground angle information allows the flight control system to quickly adjust the aircraft's attitude, ensuring smooth flight and accurate path.

[0003] Existing radio angle measurement technology generally uses the amplitude method. This method relies on the amplitude change of the antenna echo signal, but it has low accuracy and requires a complex antenna scanning system, which is expensive and unsuitable for small aircraft systems.

[0004] In view of this, the present invention proposes a system and method for measuring the angle of an aircraft to the ground, which can obtain stable and accurate aircraft angles to the ground in real time in complex and changing environments, providing real-time and reliable data support for the aircraft's attitude control, path planning and mission execution. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a system and method for measuring the angle of an aircraft to the ground.

[0006] In order to achieve the above objectives, the present invention adopts the following technical solutions.

[0007] In a first aspect, the present invention provides an aircraft angle-to-ground measurement system, comprising: a data processing unit, a transceiver unit, and an antenna unit connected in sequence and installed on the aircraft; the transceiver unit comprises a transmitter and a receiver; the antenna unit comprises a transmitting antenna connected to the transmitter and a first receiving antenna and a second receiving antenna connected to the receiver, wherein the axial directions of the transmitting antenna and the first receiving antenna are consistent with the axial direction of the aircraft, and the axial direction of the second receiving antenna deviates from the axial direction of the aircraft by an angle; the transmitting antenna radiates a transmission signal outward under the drive of the transmitter; the first receiving antenna and the second receiving antenna respectively receive echo signals reflected by the ground, and the two echo signals are sent to the data processing unit after mixing and conversion by the receiver; the data processing unit converts the two difference frequency signals after mixing and conversion into digital signals, and calculates the aircraft's angle-to-ground by solving the phase difference between the two difference frequency signals.

[0008] Furthermore, the transmitter includes: a frequency modulator whose output end is connected to the transmitting antenna, a modulation signal generator and a local oscillator whose output ends are both connected to the input end of the frequency modulator; the modulation signal generator is used to output a triangular wave signal, the local oscillator is used to output a high-frequency oscillation signal, and the frequency modulator is used to output a high-frequency transmitting signal whose frequency is modulated by the triangular wave.

[0009] Furthermore, the receiver includes: a first mixer and a second mixer whose input ends are respectively connected to the first receiving antenna and the second receiving antenna, a first filter amplifier and a second filter amplifier whose output ends are both connected to the data processing unit and whose input ends are respectively connected to the output ends of the first mixer and the second mixer, and the other input ends of the first mixer and the second mixer are both connected to the output end of the local oscillator; the intermediate frequency difference frequency signals output by the first mixer and the second mixer are output to the data processing unit after passing through the first filter amplifier and the second filter amplifier respectively.

[0010] Furthermore, the method for calculating the phase difference between the two difference frequency signals includes:

[0011] Convert the analog signals output by the first filter amplifier and the second filter amplifier into digital signals x1(n) and x2(n);

[0012] Perform full phase preprocessing on x1(n) and x2(n), including: adding double windows, delaying and weighted summing on x1(n) and x2(n);

[0013] Perform FFT transformation on the two signals after full phase preprocessing to obtain X1(k) and X2(k);

[0014] Perform spectrum peak search on X1(k) and X2(k) to obtain the peak spectrum line X1(k m1 )、X2(k m2 ));

[0015] Based on X1(k m1 )、X2(k m2 ))Calculate the initial phase of the two difference frequency signals The formula is:

[0016]

[0017] Where R e (), I m () represent the real part and imaginary part respectively;

[0018] Calculate the phase difference between the two difference frequency signals:

[0019] Furthermore, the formula for calculating the aircraft's angle to the ground is:

[0020]

[0021] Where β is the angle of the aircraft to the ground, α is the angle at which the axis of the second receiving antenna deviates from the axis of the aircraft, R2 is the slant distance between the second receiving antenna and the ground, and λ is the signal wavelength.

[0022] In a second aspect, the present invention provides a method for measuring an aircraft's angle to the ground using the system, comprising the following steps:

[0023] The transmitting antenna radiates the transmission signal outward under the drive of the transmitter;

[0024] The first receiving antenna and the second receiving antenna respectively receive the echo signals reflected by the ground, and send the two echo signals to the receiver for mixing and amplification conversion;

[0025] The data processing unit converts the two difference frequency signals after mixing conversion into digital signals, and calculates the angle of the aircraft to the ground by solving the phase difference between the two difference frequency signals.

[0026] Furthermore, the transmitter includes: a frequency modulator whose output end is connected to the transmitting antenna, a modulation signal generator and a local oscillator whose output ends are both connected to the input end of the frequency modulator; the modulation signal generator is used to output a triangular wave signal, the local oscillator is used to output a high-frequency oscillation signal, and the frequency modulator is used to output a high-frequency transmitting signal whose frequency is modulated by the triangular wave.

[0027] Furthermore, the receiver includes: a first mixer and a second mixer whose input ends are respectively connected to the first receiving antenna and the second receiving antenna, a first filter amplifier and a second filter amplifier whose output ends are both connected to the data processing unit and whose input ends are respectively connected to the output ends of the first mixer and the second mixer, and the other input ends of the first mixer and the second mixer are both connected to the output end of the local oscillator; the intermediate frequency difference frequency signals output by the first mixer and the second mixer are output to the data processing unit after passing through the first filter amplifier and the second filter amplifier respectively.

[0028] Furthermore, the method for calculating the phase difference between the two echo signals includes:

[0029] Convert the analog signals output by the first filter amplifier and the second filter amplifier into digital signals x1(n) and x2(n);

[0030] Perform full phase preprocessing on x1(n) and x2(n), including: adding double windows, delaying and weighted summing on x1(n) and x2(n);

[0031] Perform FFT transformation on the two signals after full phase preprocessing to obtain X1(k) and X2(k);

[0032] Perform spectrum peak search on X1(k) and X2(k) to obtain the peak spectrum line X1(k m1 )、X2(k m2 ));

[0033] Based on X1(k m1 )、X2(k m2 ))Calculate the initial phase of the two difference frequency signals The formula is:

[0034]

[0035] Where R e (), I m () represent the real part and imaginary part respectively;

[0036] Calculate the phase difference between the two difference frequency signals:

[0037] Furthermore, the formula for calculating the aircraft's angle to the ground is:

[0038]

[0039] Where β is the angle of the aircraft to the ground, α is the angle at which the axis of the second receiving antenna deviates from the axis of the aircraft, R2 is the slant distance between the second receiving antenna and the ground, and λ is the signal wavelength.

[0040] Compared with the prior art, the present invention has the following beneficial effects.

[0041] The present invention comprises a data processing unit, a transceiver unit, and an antenna unit, which are sequentially connected and installed on an aircraft. The transceiver unit includes a transmitter and a receiver, and the antenna unit includes a transmitting antenna connected to the transmitter and a first receiving antenna and a second receiving antenna connected to the receiver. The axial directions of the transmitting antenna and the first receiving antenna are both aligned with the axial direction of the aircraft, while the axial direction of the second receiving antenna deviates from the axial direction of the aircraft by an angle. Driven by the transmitter, the transmitting antenna radiates a transmission signal outward, while the first receiving antenna and the second receiving antenna respectively receive echo signals reflected from the ground. The data processing unit calculates the aircraft's angle to the ground by solving the phase difference between the two difference frequency signals, thereby achieving real-time measurement of the aircraft's angle to the ground. The present invention has the advantages of high angle measurement accuracy and good real-time performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1This is a block diagram of a system for measuring an aircraft's angle to the ground, according to an embodiment of the present invention. In the diagram: 1 - data processing unit, 2 - transceiver unit, 21 - transmitter, 22 - receiver, 3 - antenna unit, 30 - transmitting antenna, 31 - first receiving antenna, 32 - second receiving antenna.

[0043] Figure 2 This is a hardware structure block diagram of another embodiment of the present invention.

[0044] Figure 3 Schematic diagram of the data processing flow for solving the aircraft's angle to the ground based on full-phase FFT.

[0045] Figure 4 Schematic diagram of full-phase FFT transformation (N=4).

[0046] Figure 5 This is a schematic diagram of the aircraft-to-ground angle measurement system configuration.

[0047] Figure 6 The present invention is a flowchart of a method for measuring an aircraft's angle to the ground using the system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the present invention is further described below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] Figure 1 This is a block diagram of the composition of an aircraft-to-ground angle measurement system according to an embodiment of the present invention, comprising: a data processing unit 1, a transceiver unit 2, and an antenna unit 3, which are connected in sequence and installed on the aircraft; the transceiver unit 2 includes a transmitter 21 and a receiver 22; the antenna unit 3 includes a transmitting antenna 30 connected to the transmitter 21 and a first receiving antenna 31 and a second receiving antenna 32 connected to the receiver 22, wherein the axial directions of the transmitting antenna 30 and the first receiving antenna 31 are both consistent with the axial direction of the aircraft, and the axial direction of the second receiving antenna 32 deviates from the axial direction of the aircraft by an angle; the transmitting antenna 30 radiates a transmission signal outward under the drive of the transmitter 21; the first receiving antenna 31 and the second receiving antenna 32 respectively receive echo signals reflected by the ground, and the two echo signals are mixed and converted by the receiver 22 and sent to the data processing unit 1; the data processing unit 1 converts the two difference frequency signals after the mixing and conversion into digital signals, and calculates the aircraft's angle to the ground by solving the phase difference between the two difference frequency signals.

[0050] In this embodiment, the system mainly consists of three parts installed on the aircraft: a data processing unit 1, a transceiver unit 2, and an antenna unit 3. The functional principles of each part are described below.

[0051] The transceiver unit 2 includes a transmitter 21 and a receiver 22. Transmitter 21 generates a transmission signal of a certain power. Generally, higher power results in a longer range. Receiver 22 performs frequency mixing, signal filtering, and signal amplification on the target echo signal output by the receiving antenna. Since this embodiment measures the ground angle of the aircraft (the angle between its flight direction and the ground), the target echo signal is reflected from the ground.

[0052] The antenna unit 3 is mainly used to transmit and receive radio signals. The antenna unit 3 includes a transmitting antenna 30 and two receiving antennas. The transmitting antenna 30 is connected to the transmitter 21, and is used to radiate the transmission signal output by the transmitter 21 outward (in the air or on the ground). The axial direction of the transmitting antenna 30 is consistent with the axial direction of the aircraft. The receiving antenna is used to receive the echo signal reflected from the ground. The two receiving antennas use the same structural parameters, the difference is that the axial direction of the first receiving antenna 31 is consistent with the axial direction of the aircraft, while the axial direction of the second receiving antenna 32 deviates from the axial direction of the aircraft by an angle α. Figure 5 As shown in the figure, the three triangles from front to back represent the transmitting antenna 30, the first receiving antenna 31, and the second receiving antenna 32, respectively. Because the axes of the two receiving antennas are aligned in different directions, the echo signals received by each antenna have different round-trip distances. This means that the echo signals have different delays relative to the transmitted signal, which in turn means that the two echo signals have different phases, resulting in a phase difference. The magnitude of this phase difference is related to the aircraft's angle above the ground. Therefore, by calculating this phase difference, the aircraft's angle above the ground can be calculated.

[0053] Data processing unit 1 is primarily used to perform necessary data processing tasks. It generally consists of a microprocessor and an A / D converter. The A / D converter is used to convert the difference frequency signal generated by mixing and converting the echo signal into a digital signal that can be processed by the microprocessor. The microprocessor is used to perform data processing tasks according to a specific algorithm. For example, it can calculate the phase difference between the two difference frequency signals and calculate the aircraft's angle relative to the ground based on the relationship between the phase difference and the aircraft's angle relative to the ground. This embodiment calculates the phase difference in the frequency domain by performing FFT transforms on the two difference frequency digital signals.

[0054] This embodiment uses the phase method to calculate the aircraft's angle to the ground. Compared with the traditional algorithm that uses the amplitude method to measure angles, it can solve the problems of low accuracy and high cost caused by the traditional algorithm's reliance on the amplitude change of the antenna echo signal and the need for a complex antenna scanning system.

[0055] As an optional embodiment, the transmitter 21 includes: a frequency modulator whose output end is connected to the transmitting antenna 30, a modulation signal generator and a local oscillator whose output ends are both connected to the input end of the frequency modulator; the modulation signal generator is used to output a triangular wave signal, the local oscillator is used to output a high-frequency oscillation signal, and the frequency modulator is used to output a high-frequency transmission signal whose frequency is modulated by the triangular wave.

[0056] This embodiment provides a technical solution for the transmitter 21. The transmitter 21 of this embodiment is mainly composed of a frequency modulator, a modulation signal generator and a local oscillator. The connection relationship between the components is as follows: Figure 2 As shown. Since the higher the operating frequency, the more conducive it is to antenna miniaturization, in order to reduce the size of the antenna, the frequency of the transmission signal generated by the transmitter 21 is generally higher. Therefore, in this embodiment, a local oscillator is set to output a stable high-frequency oscillation signal to the frequency modulator. In order to facilitate the calculation of the time delay of the echo signal, the transmission signal generally adopts a high-frequency modulation signal. A low-frequency modulation signal, such as a triangular wave or a rectangular pulse signal, can be generated by a modulation signal generator to modulate the high-frequency oscillation signal output by the local oscillator, thereby obtaining a high-frequency modulation signal. There are two signal modulation methods, namely amplitude modulation and frequency modulation. Frequency modulation has stronger anti-interference performance than amplitude modulation. Therefore, this embodiment adopts a frequency modulation method, and outputs a frequency modulation signal to the transmitting antenna 30 by setting a frequency modulator.

[0057] As an optional embodiment, the receiver 22 includes: a first mixer and a second mixer whose input ends are respectively connected to the first receiving antenna 31 and the second receiving antenna 32; a first filter amplifier and a second filter amplifier whose output ends are both connected to the data processing unit 1 and whose input ends are respectively connected to the output ends of the first mixer and the second mixer; the other input ends of the first mixer and the second mixer are both connected to the output end of the local oscillator; the intermediate frequency difference frequency signals output by the first mixer and the second mixer are respectively output to the data processing unit 1 after passing through the first filter amplifier and the second filter amplifier.

[0058] This embodiment provides a technical solution for the receiver 22. Since the receiving antenna includes a first receiving antenna 31 and a second receiving antenna 32, the receiver 22 includes two identical receiving channels for performing mixing conversion on the echo signals output by the two receiving antennas. Both receiving channels are composed of a mixer and a filter amplifier, such as Figure 2As shown. Since the antenna received signal is a high-frequency echo signal, if data acquisition (A / D conversion) is performed directly on the high-frequency signal, a very high data acquisition frequency is required, which will increase the amount of calculation for data processing and is not conducive to real-time processing. To this end, this embodiment provides a mixer in each receiving channel, and the mixer outputs an intermediate frequency difference signal obtained by mixing the received signal with the local oscillation signal, thereby greatly reducing the data acquisition frequency, alleviating the data processing burden, and realizing real-time angle measurement. Since the power of the difference frequency signal is generally weak, a first-stage filter amplifier is provided in each receiving channel to amplify the difference frequency signal to a certain amplitude before sending it to the data processing unit 1.

[0059] As an optional embodiment, a method for calculating the phase difference between two difference frequency signals includes:

[0060] Convert the analog signals output by the first filter amplifier and the second filter amplifier into digital signals x1(n) and x2(n);

[0061] Perform full phase preprocessing on x1(n) and x2(n), including: adding double windows, delaying and weighted summing on x1(n) and x2(n);

[0062] Perform FFT transformation on the two signals after full phase preprocessing to obtain X1(k) and X2(k);

[0063] Perform spectrum peak search on X1(k) and X2(k) to obtain the peak spectrum line X1(k m1 )、X2(k m2 ));

[0064] Based on X1(k m1 )、X2(k m2 ))Calculate the initial phase of the two echo signals The formula is:

[0065]

[0066] Where R e (), I m () represent the real part and imaginary part respectively;

[0067] Calculate the phase difference between the two difference frequency signals:

[0068] This embodiment provides a technical solution for calculating the phase difference between two echo signals. The basic principle of calculating the phase difference in this embodiment is (see Figure 3 ): By performing FFT transformation on the two-way difference frequency digital signal, the spectrum containing phase information is obtained, and the initial phase of the two-way difference frequency signal is calculated by solving the peak frequency points of the two-way spectrum signal in the frequency domain. Thus, the phase difference of the two difference frequency signals is obtained FFT is a fast algorithm for the Discrete Fourier Transform (DFT). Using FFT can significantly improve DFT computation speed. Traditional FFT truncation of the original signal manifests itself in the time domain as large amplitude variations at the ends of the sequence, and in the frequency domain as signal spectrum leakage. Spectral leakage can severely impact the performance of spectral analysis. Using traditional FFT to calculate phase difference can compromise accuracy due to spectrum leakage and asynchronous sampling of the two echoes, thereby increasing angle measurement errors. Therefore, this embodiment uses full-phase FFT instead of traditional FFT to calculate phase difference.

[0069] The difference between full-phase FFT and traditional FFT is the way they handle truncated data. Full-phase FFT improves the problem caused by truncation by adding preprocessing steps and using overlapping method. The full-phase preprocessing steps include: adding double window, delay and weighted summation to the input x1(n) and x2(n), respectively. Figure 4 shown.

[0070] Double window processing is an effective measure to prevent spectrum leakage. Hanning window is widely used because it can make the energy of the main lobe more concentrated and can cancel out the side lobes, thereby effectively reducing the side lobe amplitude. To improve the performance of spectrum analysis, the traditional FFT directly introduces a Hanning window sequence of length N. The full-phase FFT introduces a convolution window, which is the convolution of two Hanning window sequences of length N, f1(n) and f2(n). c (n)=f1(n)*f2(n), a c The length of is 2N-1, which is expressed as:

[0071] a c =[a c (-N+1),a c (-N+2),...,a c (-1),a c (0),a c (1),...,a c (N-1)]

[0072] Next, a c (n) is normalized to obtain the weighted series w c (n). Use w c Each term of (n) is multiplied (weighted) by the 2N-1 terms of the input x(n) (obtained by delay) to form a windowed sequence. Each N-1 term of the windowed sequence is then added (summed) to the 2N-1 terms to form a sequence of length N, expressed as: [x(0), x(1)+x(N+1), x(2)+x(N+2), ..., x(N-1)+x(2N-1)].

[0073] After the full-phase preprocessing is completed, FFT is performed, which is the full-phase FFT.

[0074] After performing full-phase FFT, we get X1(k) and X2(k), and then perform spectrum peak search on X1(k) and X2(k) respectively, that is, we use the bubble algorithm to find the spectrum line X1(k) with the largest amplitude. m1 )、X2(k m2 )). Then, according to the real part, imaginary part and phase angle of the FFT transformation result The phase angle is obtained by taking the inverse tangent of the imaginary part / real part.

[0075] As an optional embodiment, the formula for calculating the aircraft's angle to the ground is:

[0076]

[0077] Wherein, β is the angle of the aircraft to the ground, α is the angle at which the axis direction of the second receiving antenna 32 deviates from the axis direction of the aircraft, R2 is the oblique distance between the second receiving antenna 32 and the ground, and λ is the signal wavelength.

[0078] This embodiment provides a technical solution for calculating the angle of the aircraft to the ground based on the phase difference. The principle of calculating the angle of the aircraft to the ground is as follows: Figure 5 As shown, the three triangles from front to back in the figure represent the transmitting antenna 30, the first receiving antenna 31, and the second receiving antenna 32, respectively. The axial directions of the transmitting antenna 30 and the first receiving antenna 31 are consistent with the axial direction of the aircraft, and the axial direction of the second receiving antenna 32 deviates from the axial direction of the aircraft by an angle α. R1 and R2 in the figure are the oblique distances between the first receiving antenna 31 and the second receiving antenna 32 and the ground, respectively. Since R1 and R2 are much larger than the spacing between the antennas, the round-trip distance difference corresponding to the two echo signals is approximately ΔR = 2(R1-R2). Since R2 is approximately equal to BD (the length), ΔR is approximately equal to 2AB; and since AB = BC × tanβ and BC = R2 × sinα, the expression for ΔR is:

[0079]

[0080] According to the relationship between the distance difference ΔR and the phase difference, the expression of the phase difference is:

[0081]

[0082] Where λ is the signal wavelength, λ = c / f, c is the speed of light, and f is the signal frequency.

[0083] According to the phase difference The expression of β can be used to calculate the aircraft's angle to the ground.

[0084] Figure 6 This is a flow chart of a method for measuring an aircraft's angle to the ground using the system according to an embodiment of the present invention, comprising the following steps:

[0085] Step 101: The transmitting antenna 30 radiates a signal outward under the drive of the transmitter 21;

[0086] Step 102: The first receiving antenna 31 and the second receiving antenna 32 respectively receive the echo signals reflected by the ground, and send the two echo signals to the receiver 22 for frequency mixing conversion;

[0087] Step 103: The data processing unit 1 converts the two difference frequency signals after the mixing conversion into digital signals, and calculates the angle of the aircraft to the ground by solving the phase difference between the two difference frequency signals.

[0088] The method of this embodiment, Figure 1 Compared with the technical solution of the system embodiment shown in FIG, its implementation principle and technical effect are similar, which will not be described in detail here. The same is true for the following embodiments, which will not be described in detail.

[0089] As an optional embodiment, the transmitter 21 includes: a frequency modulator whose output end is connected to the transmitting antenna 30, a modulation signal generator and a local oscillator whose output ends are both connected to the input end of the frequency modulator; the modulation signal generator is used to output a triangular wave signal, the local oscillator is used to output a high-frequency oscillation signal, and the frequency modulator is used to output a high-frequency transmission signal whose frequency is modulated by the triangular wave.

[0090] As an optional embodiment, the receiver 22 includes: a first mixer and a second mixer whose input ends are respectively connected to the first receiving antenna 31 and the second receiving antenna 32; a first filter amplifier and a second filter amplifier whose output ends are both connected to the data processing unit 1 and whose input ends are respectively connected to the output ends of the first mixer and the second mixer; the other input ends of the first mixer and the second mixer are both connected to the output end of the local oscillator; the intermediate frequency difference frequency signals output by the first mixer and the second mixer are respectively output to the data processing unit 1 after passing through the first filter amplifier and the second filter amplifier.

[0091] As an optional embodiment, a method for calculating the phase difference between two echo signals includes:

[0092] Convert the analog signals output by the first filter amplifier and the second filter amplifier into digital signals x1(n) and x2(n);

[0093] Perform full phase preprocessing on x1(n) and x2(n), including: adding double windows, delaying and weighted summing on x1(n) and x2(n);

[0094] Perform FFT transformation on the two signals after full phase preprocessing to obtain X1(k) and X2(k);

[0095] Perform spectrum peak search on X1(k) and X2(k) to obtain the peak spectrum line X1(k m1 )、X2(k m2 ));

[0096] Based on X1(k m1 )、X2(k m2 ))Calculate the initial phase of the two difference frequency signals The formula is:

[0097]

[0098] Where R e (), I m () represent the real part and imaginary part respectively;

[0099] Calculate the phase difference between the two difference frequency signals:

[0100] As an optional embodiment, the formula for calculating the aircraft's angle to the ground is:

[0101]

[0102] Wherein, β is the angle of the aircraft to the ground, α is the angle at which the axis direction of the second receiving antenna 32 deviates from the axis direction of the aircraft, R2 is the oblique distance between the second receiving antenna 32 and the ground, and λ is the signal wavelength.

[0103] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An aircraft-to-ground angle measurement system, characterized in that: include: A data processing unit, a transceiver unit and an antenna unit installed on the aircraft and connected in sequence; The transceiver unit includes a transmitter and a receiver; The antenna unit includes a transmitting antenna connected to the transmitter and a first receiving antenna and a second receiving antenna connected to the receiver. The axial directions of the transmitting antenna and the first receiving antenna are both consistent with the axial direction of the aircraft, and the axial direction of the second receiving antenna deviates from the axial direction of the aircraft by an angle. The transmitting antenna radiates the transmission signal outward under the drive of the transmitter. The first receiving antenna and the second receiving antenna respectively receive the echo signal reflected by the ground. The two echo signals are mixed and converted by the receiver and then sent to the data processing unit. The data processing unit converts the two difference frequency signals after mixing conversion into digital signals, and calculates the angle of the aircraft to the ground by solving the phase difference between the two difference frequency signals.

2. The aircraft-to-ground angle measurement system according to claim 1, characterized in that: The transmitter includes: a frequency modulator whose output end is connected to a transmitting antenna, a modulation signal generator and a local oscillator whose output ends are both connected to an input end of the frequency modulator; the modulation signal generator is used to output a triangular wave signal, the local oscillator is used to output a high-frequency oscillation signal, and the frequency modulator is used to output a high-frequency transmission signal whose frequency is modulated by a triangular wave.

3. The aircraft-to-ground angle measurement system according to claim 2, characterized in that: The receiver includes: a first mixer and a second mixer whose input ends are respectively connected to a first receiving antenna and a second receiving antenna; a first filter amplifier and a second filter amplifier whose output ends are both connected to a data processing unit and whose input ends are respectively connected to the output ends of the first mixer and the second mixer; the other input ends of the first mixer and the second mixer are both connected to the output end of a local oscillator; the intermediate frequency difference frequency signals output by the first mixer and the second mixer are output to the data processing unit after passing through the first filter amplifier and the second filter amplifier respectively.

4. The aircraft-to-ground angle measurement system according to claim 1, wherein: The method for calculating the phase difference between the two difference frequency signals includes: Convert the analog signals output by the first filter amplifier and the second filter amplifier into digital signals x1(n) and x2(n); Perform full phase preprocessing on x1(n) and x2(n), including: adding double windows, delaying and weighted summing on x1(n) and x2(n); Perform FFT transformation on the two signals after full phase preprocessing to obtain X1(k) and X2(k); Perform spectrum peak search on X1(k) and X2(k) to obtain the peak spectrum line X1(k m1 )、X2(k m2 )); Based on X1(k m1 )、X2(k m2 ))Calculate the initial phase of the two difference frequency signals The formula is: Where R e (), I m () represent the real part and imaginary part respectively; Calculate the phase difference between the two difference frequency signals:

5. The aircraft-to-ground angle measurement system according to claim 4, characterized in that: The formula for calculating the aircraft's angle to the ground is: Where β is the angle of the aircraft to the ground, α is the angle at which the axis of the second receiving antenna deviates from the axis of the aircraft, R2 is the slant distance between the second receiving antenna and the ground, and λ is the signal wavelength.

6. A method for measuring an aircraft's angle to the ground using the system of claim 1, characterized in that: The following steps are involved: The transmitting antenna radiates the transmission signal outward under the drive of the transmitter; The first receiving antenna and the second receiving antenna respectively receive the echo signals reflected by the ground, and send the two echo signals to the receiver for mixing, filtering, amplification and conversion; The data processing unit converts the two difference frequency signals after mixing conversion into digital signals, and calculates the angle of the aircraft to the ground by solving the phase difference between the two difference frequency signals.

7. The method according to claim 6, characterized in that The transmitter includes: a frequency modulator whose output end is connected to a transmitting antenna, a modulation signal generator and a local oscillator whose output ends are both connected to an input end of the frequency modulator; the modulation signal generator is used to output a triangular wave signal, the local oscillator is used to output a high-frequency oscillation signal, and the frequency modulator is used to output a high-frequency transmission signal whose frequency is modulated by a triangular wave.

8. The method according to claim 7, characterized in that The receiver includes: a first mixer and a second mixer whose input ends are respectively connected to a first receiving antenna and a second receiving antenna; a first filter amplifier and a second filter amplifier whose output ends are both connected to a data processing unit and whose input ends are respectively connected to the output ends of the first mixer and the second mixer; the other input ends of the first mixer and the second mixer are both connected to the output end of a local oscillator; the intermediate frequency difference frequency signals output by the first mixer and the second mixer are output to the data processing unit after passing through the first filter amplifier and the second filter amplifier respectively.

9. The method according to claim 6, characterized in that The method for calculating the phase difference between the two difference frequency signals includes: Convert the analog signals output by the first filter amplifier and the second filter amplifier into digital signals x1(n) and x2(n); Perform full phase preprocessing on x1(n) and x2(n), including: adding double windows, delaying and weighted summing on x1(n) and x2(n); Perform FFT transformation on the two signals after full phase preprocessing to obtain X1(k) and X2(k); Perform spectrum peak search on X1(k) and X2(k) to obtain the peak spectrum line X1(k m1 )、X2(k m2 )); Based on X1(k m1 )、X2(k m2 ))Calculate the initial phase of the two difference frequency signals The formula is: Where R e (), I m () represent the real part and imaginary part respectively; Calculate the phase difference between the two difference frequency signals:

10. The method according to claim 9, characterized in that The formula for calculating the aircraft's angle to the ground is: Where β is the angle of the aircraft to the ground, α is the angle at which the axis of the second receiving antenna deviates from the axis of the aircraft, R2 is the slant distance between the second receiving antenna and the ground, and λ is the signal wavelength.

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