Automatically calibrating height-finding radar system and method of measuring

Abstract

This invention provides an automatic calibration radar system and its measurement method. The radar system, mounted on a moving object, includes a transmitting phased-array antenna, a receiving phased-array antenna, a radio frequency module, a signal processing unit, a triaxial accelerometer, and a control unit. Because the control unit controls the transmitting and receiving phased-array antennas to sequentially adjust their beam angles to a vertical angle and a random angle during each measurement, the height above the ground can be calculated from measurements taken at two different beam angles. Comparing these two measurements allows for calibration of the measured height above the ground of the moving object. This method is suitable for situations where the moving object is in continuous motion and the radar system's measurement capabilities are limited. The triaxial accelerometer allows for calibration of the moving object's speed based on the measured acceleration information. In summary, the radar system and measurement method of this invention can accurately measure the moving speed and height above the ground of a moving object.

Description

Technical Field

[0001] This invention belongs to the field of millimeter-wave radar technology, specifically relating to an automatic calibration altimeter radar system and its measurement method. Background Technology

[0002] Millimeter-wave frequency-modulated continuous wave (FM-CW) radar has gained widespread application in recent years, attracting increasing attention due to its combination of the advantages of both millimeter-wave and FM-CW radars. Compared to microwave radar, millimeter-wave FM-CW radar can achieve a wider frequency modulation bandwidth and obtain higher range resolution. Compared to optical systems such as lasers and infrared systems, millimeter-wave systems are less affected by weather conditions and can operate in all weather conditions.

[0003] Since its civilian application, millimeter-wave radar has been increasingly used in various industries, primarily in intelligent transportation, high-end security, drones, automotive radar, and smart lighting. In intelligent transportation, millimeter-wave radar can trigger cameras to capture images of vehicles passing through lanes, identifying and detecting violations. In security, it can monitor sensitive areas; combined with PTZ cameras, the radar uploads target distance and angle information, which is then processed by backend algorithms to control the PTZ camera to track the target in real time. In smart lighting, millimeter-wave radar can turn lights on when people are present and off when they leave, saving energy. While infrared technology is currently used, it has significant drawbacks, including temperature sensitivity, a small detection angle, and short detection range. Millimeter-wave radar completely eliminates these problems and can be a viable alternative, especially for urban streetlights where long detection distances and wide angles are required. In the drone field, millimeter-wave radar's ranging capabilities enable functions such as altitude hold and collision avoidance. In recent years, the rise of smart agriculture has led to a surge in demand for drones. Drones use millimeter-wave radar to accurately position themselves at a specified distance above crops and spray pesticides, greatly improving work efficiency and reducing manpower. In the automotive sector, the booming development of autonomous driving has led to even more applications of millimeter-wave radar. Currently, automotive driver assistance functions include: Blind Spot Detection (BSD), Lane Change Assist (LCA), and Collision Early Warning System (CWBS).

[0004] However, existing height measurement radar systems are susceptible to electromagnetic interference, which can cause errors in the measured speed and altitude. Furthermore, individual objects on the ground can also affect the height measurement, thus impacting its practical application. Summary of the Invention

[0005] This invention addresses the aforementioned problems by providing an altimeter radar system capable of automatic calibration and ensuring measurement accuracy, thus suitable for measuring the speed and height above the ground of moving objects. It also includes a corresponding measurement method using this radar system. The invention employs the following technical solution:

[0006] This invention provides an automatic calibration altimeter radar system for measuring the moving speed and altitude of a moving object. It is characterized by comprising: a transmitting phased-array antenna for transmitting a signal from the moving object to the ground; a receiving phased-array antenna for receiving the echo signal of the transmitted signal; a radio frequency module connected to both the transmitting and receiving phased-array antennas for generating the transmitted signal and processing the transmitted signal and the echo signal to obtain a beat signal; and a signal processing unit connected to the radio frequency module for acquiring the beat signal and performing signal detection processing to obtain the altitude and speed of the moving object. A triaxial accelerometer is used to acquire acceleration information of the moving object, which is used to calibrate the measured velocity. A control unit is connected to the transmitting phased antenna, the receiving phased antenna, the radio frequency module, the signal processing unit, and the triaxial accelerometer, respectively, and is used to control them. In each measurement, the control unit controls the transmitting and receiving phased antennas to adjust their beam angles sequentially to a vertical angle and a random angle for measurement, and compares and calculates the first height measured at the vertical angle and the second height measured at the random angle to obtain the height of the moving object above the ground.

[0007] The automatic calibration altimeter radar system provided by this invention may also have the following technical features, wherein the radio frequency module includes: a radio frequency source for generating a modulation signal; a transmission link connected to the radio frequency source and the transmission phased antenna respectively, for processing the modulation signal to obtain the transmission signal and providing it to the transmission phased antenna; a receiving link connected to the receiving phased antenna for receiving the echo signal and processing it; and a mixing unit connected to the radio frequency source and the receiving link respectively, for mixing the processed echo signal and the modulation signal to obtain the beat signal.

[0008] The automatic calibration altimeter radar system provided by the present invention may also have the following technical features: the radio frequency source includes a high-frequency local oscillator and a frequency multiplier amplifier; the transmitting link includes a filter circuit, a power amplifier circuit and a matching circuit; and the receiving link includes a low-noise amplifier circuit.

[0009] The automatic calibration altimeter radar system provided by the present invention may also have the following technical features, wherein the signal processing unit includes: an ADC for sampling the beat signal; and a DSP core for performing windowing, FFT, and CFAR detection processing on the sampled beat signal to obtain the altitude above the ground.

[0010] The automatic calibration altimeter radar system provided by the present invention may also have the following technical feature: the triaxial accelerometer is a MEMS triaxial accelerometer.

[0011] The automatic calibration altimeter radar system provided by the present invention may also have the following technical features: a housing mounted on the moving object, wherein the transmitting phased antenna, the receiving phased antenna, the radio frequency module, the signal processing unit, the triaxial accelerometer, and the control unit are all disposed within the housing.

[0012] The automatic calibration altimeter radar system provided by the present invention may also include the following technical features: a host computer connected to the control unit, which acquires and displays the measured speed and altitude from the ground from the control unit.

[0013] This invention provides a method for measuring and calibrating the speed and height above the ground of a moving object using the aforementioned automatic calibration altimeter radar system, characterized in that the method includes the following steps:

[0014] Step S1: Adjust the beam angles of both the transmitting phased antenna and the receiving phased antenna to be perpendicular to the ground;

[0015] Step S2: The transmitting phased antenna transmits a transmission signal, and the receiving phased antenna receives the corresponding echo signal. The first altitude is calculated based on the transmission signal and the echo signal.

[0016] Step S3: Adjust the beam angles of both the transmitting phased antenna and the receiving phased antenna to random angles;

[0017] Step S4: The transmitting phased antenna transmits a transmission signal, and the receiving phased antenna receives the corresponding echo signal. Based on the transmission signal and the echo signal, a first distance and a first velocity are calculated, and a second height is calculated based on the random angle and the first distance.

[0018] Step S5: Determine whether the difference between the first height and the second height of the group is within a predetermined difference range;

[0019] Step S6: If the determination in step S5 is negative, discard the first height and the second height of that group;

[0020] Step S7: If the determination in step S5 is yes, calculate the weighted average of the first height and the second height of the group, and use it as the height of the moving object above the ground;

[0021] Step S8: The first velocity is calibrated based on the acceleration information measured by the triaxial accelerometer.

[0022] The method provided by this invention may also have the following feature: in step S4, the formula for calculating the second height based on the random angle and the first distance is:

[0023] h1 = h * cos(θ)

[0024] In the formula, h is the first distance, and θ is the random angle.

[0025] Invention Function and Effect

[0026] According to the automatic calibration radar system and measurement method of the present invention, the radar system is mounted on a moving object and includes a transmitting phased-array antenna, a receiving phased-array antenna, a radio frequency module, a signal processing unit, a triaxial accelerometer, and a control unit. Since the control unit controls the transmitting and receiving phased-array antennas to sequentially adjust their beam angles to a vertical angle and a random angle during each measurement, the height above the ground can be calculated from two measurements at two different beam angles. Comparing the two measurements allows for calibration of the measured height above the ground of the moving object, eliminating the influence of electromagnetic interference and individual ground objects. This measurement method is suitable for situations where the moving object is in continuous motion and the radar system's measurement calculations are limited. Because of the triaxial accelerometer, the moving speed of the object measured by the radar system can be calibrated based on the acceleration information measured by the accelerometer.

[0027] In summary, the radar system and measurement method of the present invention can accurately measure the moving speed and height of a moving object from the ground. Attached Figure Description

[0028] Figure 1 This is a structural block diagram of the automatic calibration altimeter radar system in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the automatic calibration altimeter radar system performing altimeter measurement and calibration in an embodiment of the present invention;

[0030] Figure 3 This is a flowchart illustrating how an automatic calibration altimeter radar system is used to measure and calibrate the speed and height above the ground of a moving object in an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the software implementation of calibration and measurement in an embodiment of the present invention.

[0032] Figure label:

[0033] Automatic calibration altimeter radar system 10; transmitting phased antenna 11; receiving phased antenna 12; radio frequency module 13; radio frequency source 131; transmitting link 132; receiving link 133; mixing unit 134; signal processing unit 14; triaxial accelerometer 15; control unit 16; power supply module 17; host computer 18. Detailed Implementation

[0034] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the automatic calibration altimeter radar system of the present invention will be specifically described below in conjunction with embodiments and accompanying drawings.

[0035] <Example>

[0036] Figure 1 This is a block diagram of the automatic calibration altimeter radar system in this embodiment;

[0037] like Figure 1 As shown, the automatic calibration altimeter radar system 10 of this embodiment includes a transmitting phased antenna 11, a receiving phased antenna 12, a radio frequency module 13, a signal processing unit 14, a triaxial accelerometer 15, a control unit 16, a power module 17, a host computer 18, and a housing (not shown in the figure). Except for the host computer 18, all other structural units are housed in the housing and mounted on a moving object. In this embodiment, the housing containing the above units is mounted on a drone.

[0038] The transmitting phased antenna 11 is used to transmit a signal (antenna beam), and the receiving phased antenna 12 is used to receive the echo signal of the antenna beam it transmits.

[0039] The radio frequency (RF) module 13 includes an RF source 131, a transmit link 132, a receive link 133, and a mixer unit 134. The RF source 131 is connected to the transmit link 132, the mixer unit 134, and the control unit 16, and includes a high-frequency local oscillator and a frequency multiplier amplifier. The transmit link 132 is connected to the transmit phased array antenna 11, the RF source 131, and the control unit 16, and includes a filter circuit, a power amplifier circuit, and a matching circuit. The receive link 133 is connected to the receive phased array antenna 12, the mixer unit 134, and the control unit 16, and includes a low-noise amplifier circuit. The mixer unit 134 is connected to the receive link 133, the RF source 131, the signal processing unit 14, and the control unit 16, and is used to generate a modulated signal.

[0040] The signal processing unit 14 is connected to the mixing unit 134 and the control unit 16 respectively. The signal processing unit 14 includes an ADC and a DSP core. The ADC is used to sample the beat signal (mixing signal), and the DSP core is used to perform windowing, FFT, CFAR detection and other processing on the beat signal sampled by the ADC to obtain the height above the ground and report it to the control unit 16.

[0041] The triaxial accelerometer 15 is connected to the control unit 16 and is used to measure the acceleration information of a moving object in real time. In this embodiment, the triaxial accelerometer 15 is a MEMS triaxial accelerometer.

[0042] The control unit 16 is used to control the transmitted waveform, receive preset parameters, control the calibration and measurement of the altitude above the ground, send the altitude result information, and communicate with external data.

[0043] The power module 17 is electrically connected to each of the above units and is used to supply power to them. To avoid making the structural block diagram too complicated, the connection relationship between the power module 17 and the above units is not shown in the figure.

[0044] The host computer 18 is connected to the control unit 16 and is used by the operator to set parameters, perform related controls, and receive and display the measured speed information and ground height results from the control unit 16.

[0045] When measuring altitude from the ground, the modulation signal generated by the radio frequency source 131 is amplified by the transmission link 132 and transmitted as a transmission signal by the transmitting phased antenna 11. Subsequently, the receiving phased antenna 12 receives the echo signal. The mixing unit 134 mixes the target echo (processed echo signal) and the modulation signal generated by the radio frequency source 131 to obtain the beat signal. The signal processing unit 14 performs AD acquisition and signal detection processing on the mixed beat signal to obtain the altitude information from the ground.

[0046] Figure 2 This is a schematic diagram of the automatic calibration altimeter radar system performing altimeter measurement and calibration in this embodiment.

[0047] like Figure 2As shown, taking advantage of the fact that the ground is roughly flat, the height of the moving object above the ground (i.e., the vertical height of the moving object relative to the ground) is denoted as h1. When the angle between the antenna beam and the perpendicular line to the ground is θ, and the measured distance is h, then h1 = h * cos(θ). Then, by controlling the phased array antenna to change different beam angles, different distances h can be measured, corresponding to multiple heights h1. A weighted average of these multiple h1 values ​​can eliminate the influence of ground objects, thus obtaining a relatively accurate height above the ground. The more measurement points (using different beam angles), the more accurate the measured height above the ground. Since the system's processing speed is limited due to the continuous movement of the moving object, it cannot measure too many points in a short time. Therefore, in this embodiment, a vertical angle and a random angle are used for measurement and calculation. When the deviation between the two measured heights above the ground is small, the weighted average of the two is calculated as the height above the ground; when the deviation is large, the data set is discarded to achieve a calibration effect. By performing multiple measurements during the movement of the moving object, an accurate instantaneous height above the ground can be calculated. When the path of a moving object roughly covers a ground area, a ground data point cloud map of that ground area can be compiled.

[0048] In addition, the control unit 16 calculates the moving speed of the radar system 10 relative to the ground target based on the frequency difference between the transmitted signal and the echo signal, that is, the instantaneous speed of the moving object, and calibrates the measured moving speed according to the acceleration information of the moving object measured by the triaxial accelerometer 15.

[0049] Figure 3 This is a flowchart illustrating the use of an automatic calibration altimeter radar system in this embodiment to measure and calibrate the speed and height above the ground of a moving object.

[0050] Figure 4 This is a schematic diagram of the software implementation of measurement and calibration in this embodiment.

[0051] like Figure 3-4 As shown, the method for calibrating and measuring the height of a moving object above the ground using the aforementioned automatic calibration altimeter radar system 10 specifically includes the following steps:

[0052] Step S1: Adjust the beam angles of both the transmitting phased antenna and the receiving phased antenna to be perpendicular to the ground;

[0053] Step S2: The transmitting phased antenna transmits a transmission signal, and the receiving phased antenna receives the corresponding echo signal. The first altitude is calculated based on the transmission signal and the echo signal.

[0054] Step S3: Adjust the beam angles of both the transmitting phased antenna and the receiving phased antenna to random angles;

[0055] Step S4: The transmitting phased antenna transmits a transmission signal, and the receiving phased antenna receives the corresponding echo signal. Based on the transmission signal and the echo signal, the first distance and the first velocity are calculated, and the second height is calculated based on the random angle and the first distance.

[0056] Step S5: Determine whether the difference between the first height and the second height is within a predetermined range.

[0057] Step S6: If the determination in step S5 is negative, discard the first and second heights of that group;

[0058] Step S7: If the determination in step S5 is yes, calculate the weighted average of the first height and the second height of the group, and use it as the height of the moving object above the ground;

[0059] Step S8: The measured first velocity is calibrated based on the acceleration information measured by the triaxial accelerometer 15;

[0060] Step S9: The calibrated altitude and speed are displayed on the host computer 18.

[0061] By repeating the above steps during the motion of the object, the instantaneous height and speed can be accurately measured.

[0062] Functions and effects of the embodiments

[0063] According to the automatic calibration altimeter radar system 10 and measurement method provided in this embodiment, the radar system 10 is mounted on a moving object and includes a transmitting phased-array antenna 11, a receiving phased-array antenna 12, a radio frequency module 13, a signal processing unit 14, a triaxial accelerometer 15, and a control unit 16. Since the control unit 16 controls the transmitting and receiving phased-array antennas 11 and 12 to sequentially adjust their beam angles to a vertical angle and a random angle during each measurement, the ground clearance can be calculated from two measurements at two different beam angles. Comparing the two measurements allows for calibration of the measured ground clearance of the moving object, eliminating the influence of electromagnetic interference and individual ground objects. This measurement method is suitable for situations where the moving object is in continuous motion and the radar system's measurement calculations are limited. Because of the triaxial accelerometer 15, the moving speed of the moving object measured by the radar system 10 can be calibrated based on the acceleration information measured by the accelerometer. In summary, the radar system 10 and measurement method of this embodiment can accurately measure the moving speed and ground clearance of a moving object.

[0064] In this embodiment, the triaxial accelerometer is a MEMS triaxial accelerometer, which has the advantages of small size, light weight, easy integration, and low cost.

[0065] The above embodiments are only used to illustrate specific implementations of the present invention, and the present invention is not limited to the scope of the description of the above embodiments.

Claims

1. An automatic calibration altimeter radar system for measuring the height and speed of a moving object above the ground, characterized in that, include: A phased array antenna is used to transmit signals from the moving object to the ground; A receiving phased antenna is used to receive the echo signal of the transmitted signal; The radio frequency module is connected to the transmitting phased antenna and the receiving phased antenna respectively, and is used to generate the transmitted signal and to perform signal processing on the transmitted signal and the echo signal to obtain the beat signal; A signal processing unit, connected to the radio frequency module, is used to acquire the beat signal and perform signal detection processing to obtain the height and speed of the moving object above the ground; MEMS triaxial accelerometer is used to acquire acceleration information of the moving object, and the acceleration information is used to calibrate the measured velocity; as well as The control unit is connected to the transmitting phased antenna, the receiving phased antenna, the radio frequency module, the signal processing unit, and the MEMS triaxial accelerometer, respectively, and is used to control them. In each measurement, the control unit controls the transmitting phased antenna and the receiving phased antenna to sequentially adjust their beam angles to a vertical angle and a random angle to transmit signals and receive corresponding echo signals for measurement. A first altitude is calculated based on the transmitted signal and echo signal at the vertical angle, a first distance is calculated based on the transmitted signal and echo signal at the random angle, and a second altitude is calculated based on the random angle and the first distance. When the difference between the first height and the second height is within a predetermined range, the weighted average of the first height and the second height is calculated as the height of the moving object above the ground; otherwise, the first height and the second height are discarded.

2. The automatic calibration altimeter radar system according to claim 1, Its features are: The radio frequency module includes: Radio frequency (RF) source, used to generate modulated signals; The transmission link is connected to the radio frequency source and the transmission phased antenna respectively, and is used to process the modulation signal to obtain the transmission signal and provide it to the transmission phased antenna; A receiving link, connected to the receiving phased antenna, is used to receive the echo signal and perform signal processing; and A mixing unit, connected to the radio frequency source and the receiving link respectively, is used to mix the processed echo signal and the modulation signal to obtain the beat signal.

3. The automatic calibration altimeter radar system according to claim 2, characterized in that: in, The radio frequency source includes a high-frequency local oscillator and a frequency multiplier amplifier. The transmission link includes a filter circuit, a power amplifier circuit, and a matching circuit. The receiving link includes a low-noise amplifier circuit.

4. The automatic calibration altimeter radar system according to claim 1, Its features are: The signal processing unit includes: ADC, used to sample the beat signal; and The system includes a DSP core, which performs windowing, FFT, and CFAR detection processing on the sampled beat signal to obtain the ground clearance.

5. The automatic calibration altimeter radar system according to claim 1, characterized in that, Also includes: The housing is mounted on the moving object, and the transmitting phased antenna, the receiving phased antenna, the radio frequency module, the signal processing unit, the triaxial accelerometer, and the control unit are all disposed within the housing.

6. The automatic calibration altimeter radar system according to claim 1, characterized in that, Also includes: The host computer is connected to the control unit, and obtains and displays the measured speed and height above the ground from the control unit.

7. A measurement method for measuring and calibrating the velocity and height above ground of a moving object using an automatic calibration altimeter radar system as described in any one of claims 1-6, characterized in that, Includes the following steps: Step S1: Adjust the beam angles of both the transmitting phased antenna and the receiving phased antenna to be perpendicular to the ground; Step S2: The transmitting phased antenna transmits a transmission signal, and the receiving phased antenna receives the corresponding echo signal. The first altitude is calculated based on the transmission signal and the echo signal. Step S3: Adjust the beam angles of both the transmitting phased antenna and the receiving phased antenna to random angles; Step S4: The transmitting phased antenna transmits a transmission signal, and the receiving phased antenna receives the corresponding echo signal. Based on the transmission signal and the echo signal, a first distance and a first velocity are calculated, and a second height is calculated based on the random angle and the first distance. Step S5: Determine whether the difference between the first height and the second height of the group is within a predetermined difference range; Step S6: If the determination in step S5 is negative, discard the first height and the second height of that group; Step S7: If the determination in step S5 is yes, calculate the weighted average of the first height and the second height of the group, and use it as the height of the moving object above the ground; Step S8: The first velocity is calibrated based on the acceleration information measured by the triaxial accelerometer.

8. The measurement method according to claim 7, characterized in that: in, In step S4, the formula for calculating the second height based on the random angle and the first distance is as follows: h1 = h*cos(θ) In the formula, h is the first distance, and θ is the random angle.

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