CN108363043A - Continuous wave Doppler radar sensor and multiple mobile object detection method are placed in distribution - Google Patents

Abstract

The invention discloses a distributed continuous wave Doppler radar sensor and a multi-moving target detection method. It includes a plurality of radio frequency transceivers, control modules and clock synchronization distribution modules. The radio frequency transceivers are connected to the clock synchronization distribution modules, and the control module is connected to the clock synchronization distribution modules and radio frequency transceivers. The radio frequency transceivers include radio frequency transceiver chips, analog-to-digital conversion device, power amplifier, low-noise amplifier and filter; the clock synchronization distribution module controls the radio frequency transceiver to generate a single-frequency continuous wave radio frequency signal, and the radio frequency transceiver receives the baseband echo signal transmission control module; low-pass filters the baseband echo signal, using The detection algorithm obtains the independent motion signal, and then obtains the relative displacement to recover the motion trajectory. The invention overcomes the problems of low resolution and signal aliasing, accurately reconstructs the motion trajectories of multiple objects to be measured, and can be widely used in systems such as motion speed measurement, tracking and positioning of multiple objects to be measured, and realizes multiple physical quantities in different occasions non-contact measurement.

Description

Distributed placement of continuous wave Doppler radar sensors and multi-moving target detection method

technical field

The invention relates to a radar and a detection method thereof, in particular to a distributed continuous wave Doppler radar sensor and a multi-moving target detection method.

Background technique

Pulse Doppler radar has been widely used in aerospace, civil navigation and multi-target ranging due to its advantages of high detection accuracy, strong anti-interference ability, and many tracking targets. The continuous wave Doppler radar is easy to distinguish moving targets and is suitable for detecting a single moving target. The design cost is low and there is no complex signal processing equipment necessary for pulse Doppler radar. Therefore, the present invention considers the design of a distributed continuous wave Doppler radar sensor, combines the advantages of the traditional continuous wave Doppler radar sensor structure, and uses the motion detection method to obtain the motion information of multiple objects to be measured.

Contents of the invention

In order to simplify the Doppler radar detection system, reduce the system cost, and improve the system stability, the present invention provides a distributed continuous wave Doppler radar sensor and a multi-moving target detection method, which can be widely used in the motion velocity measurement and tracking of multiple objects Positioning and other systems to realize non-contact measurement of multiple physical quantities in different occasions.

The technical scheme adopted in the present invention is:

1. A distributed Doppler radar sensor:

The radar sensor includes distributed multiple RF transceivers, control modules and clock synchronization distribution modules. Each RF transceiver is connected to the clock synchronization distribution module. The control module is connected to the clock synchronization distribution module and each RF transceiver. Each RF The transceiver has independent transmitting and receiving functions.

Described radio frequency transceiver comprises radio frequency transceiver chip, analog-to-digital converter, power amplifier, low-noise amplifier and filter, and radio frequency transceiver chip is connected with transmitting antenna through power amplifier, and radio frequency transceiver chip passes through filter, low noise successively. The amplifier is connected to the receiving antenna, the radio frequency transceiver chip is connected to the control module through the analog-to-digital converter, and the radio frequency transceiver chip is connected to the clock synchronization distribution module.

A plurality of radio frequency transceivers in the present invention are arranged in a distributed manner, and each transceiver can be arranged near the object to be measured, so that the emitted electromagnetic wave can reach the object to be measured.

The type and working performance of the transmitting antenna and receiving antenna are adjusted and replaced according to the size and motion range of the object to be measured.

Each radio frequency transceiver described above works independently, and is controlled by the control module to select an operating frequency according to the motion range of the object to be measured and the measurement environment.

The analog-to-digital converter uses a sampling frequency much lower than the Nyquist frequency for under-sampling, preferably a sine wave active crystal oscillator whose frequency is less than one percent of the carrier frequency.

The number of the radio frequency transceivers is greater than or equal to the number of objects to be tested, and the specific number increases or decreases according to the number of objects to be tested.

The clock synchronization distribution module controls each radio frequency transceiver to generate a single frequency continuous wave radio frequency signal with the same frequency and the same initial phase.

The control module is respectively connected with each radio frequency transceiver, independently adjusts the power and sensitivity of each radio frequency transceiver, and controls the analog-to-digital converter to collect signals, display them in real time or transmit them to other terminals such as personal computers.

Two, a multi-target motion detection method is characterized in that comprising the following specific steps:

The low-frequency sinusoidal clock signal is generated by the crystal oscillator in the clock synchronization distribution module. After clock synchronization, it is distributed into two channels. One channel is transmitted to each RF transceiver chip to generate a single-frequency continuous wave RF signal with the same frequency and initial phase, and the other channel is transmitted to the control panel. The module performs digital down-conversion;

The RF detection signal sent by the RF transceiver chip is amplified by the power amplifier, and then transmits a single-frequency continuous wave RF signal to the object to be measured through the transmitting antenna for target detection, and the receiving antenna receives the baseband echo signal reflected by the object to be measured, and then After passing through the low-noise amplifier and filter in turn, it enters the radio frequency transceiver chip, after down-conversion, it is under-sampled by the analog-to-digital converter, and the under-sampled baseband echo signal is transmitted to the control module;

The control module receives the under-sampled baseband echo signal, first performs low-pass filtering on the baseband echo signal after analog-to-digital conversion in the digital domain, then uses the detection algorithm to calculate and obtain the independent motion signal, and uses the independent motion signal to obtain the The relative displacement of the object, and then restore the trajectory of each object to be measured.

The use of the detection algorithm to obtain the independent motion signal, and the use of the independent motion signal to obtain the relative displacement of each object to be measured, the specific steps are as follows:

In the first step, the baseband echo signals of each radio frequency receiver after analog-to-digital conversion are formed into an echo matrix according to the order of the radio frequency receiver, and the moving average of the echo matrix is calculated by the following formula as the moving average matrix

In the formula, p is the moving average step size, x(nj) is the njth discrete time value of the echo signal, is the moving average, j represents the integer count value, and n represents the ordinal number of the discrete time value;

In the second step, the moving average matrix minus the echo matrix is used as a difference matrix, and then the difference matrix is multiplied with its own complex conjugate matrix;

In the third step, the moving average matrix is multiplied by its complex conjugate matrix, and divided by the operation result of the second step to obtain the eigenvector;

The fourth step is to dot-multiply the complex conjugate of the eigenvector and the echo matrix to obtain a matrix composed of multi-target independent motion signals, and each element of the matrix is used as an independent motion signal of the object to be measured detected by each radio frequency receiver;

In the fifth step, the independent motion signal contains a phase quantity used to characterize the relative displacement of each object to be measured. For each independent motion signal, the relative displacement of the object to be measured is calculated using the following formula:

Among them, m _k (t) is the relative displacement of each object to be measured relative to the initial position, the initial position is the position of the object to be measured at the initial moment of detection, t represents time, λ is the wavelength corresponding to the frequency of the electromagnetic wave emitted by the radio frequency receiver, φ _k (t) represents the phase quantity of the kth independent motion signal, k represents the ordinal number of the object to be measured, and N represents the total number of objects to be measured.

The under-sampling is performed with a sampling frequency much lower than the Nyquist frequency, preferably with a sine wave active crystal oscillator whose frequency is less than one percent of the carrier frequency.

Through the specific detection algorithm of the present invention, various radio frequency receivers can be arranged in a distributed manner, arranged in different places, and detect objects to be measured in different places in a distributed manner, without centralized arrangement of various radio frequency receivers.

The beneficial effects that the present invention has are:

The present invention innovatively designs a continuous wave Doppler radar sensor and its detection method, which can detect the motion of multiple objects, uses a low-speed analog-to-digital converter (ADC) and a low-speed computing center to control the adjustment process, and simplifies the process in a modular manner. The design structure is improved, which theoretically overcomes the problems of low resolution and signal aliasing when the single-frequency continuous wave radar detects the movement of multiple objects to be measured, and accurately reconstructs the trajectory of multiple targets.

The continuous wave Doppler radar and detection method of the present invention can independently change the operating frequency and receiving and transmitting antenna of each radio frequency transceiver according to the detection distance, overcome the shortcoming that the traditional continuous wave Doppler radar can only detect a single object, and does not need Complicated signal processing like Leradar, saves design cost and improves system stability.

The invention can be widely applied to systems such as multi-object motion speed measurement, tracking and positioning, etc., and realizes non-contact measurement of multiple physical quantities in different occasions.

Description of drawings

Fig. 1 is a structural block diagram of the transceiver system of the present invention.

Fig. 2 is a comparison diagram of the experimental results measured in the embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, the radar sensor includes distributed multiple radio frequency transceivers, control modules and clock synchronization distribution modules, each radio frequency transceiver is connected to the clock synchronization distribution module, and the control module is respectively connected to the clock synchronization distribution Machine connection, each radio frequency transceiver has independent transmitting and receiving functions.

The radio frequency transceiver includes a radio frequency transceiver chip, an analog-to-digital converter, a power amplifier, a low-noise amplifier and a filter. The antenna is connected, the radio frequency transceiver chip is connected to the control module through the analog-to-digital converter, and the radio frequency transceiver chip is connected to the clock synchronization distribution module.

The working principle process of the radar sensor of the present invention is: the crystal oscillator in the clock synchronization distribution module generates a low-frequency sinusoidal clock signal, which is distributed into two channels after clock synchronization, and is transmitted to each radio frequency transceiver chip to generate a single frequency with the same frequency and initial phase. The continuous wave radio frequency signal is sent to the control module for digital down-conversion; the radio frequency detection signal sent by the radio frequency transceiver chip is amplified by the power amplifier, and then the single frequency continuous wave radio frequency signal is transmitted to the object to be tested through the transmitting antenna for target detection , the receiving antenna receives the baseband echo signal reflected by the object to be measured, and then enters the RF transceiver chip through the low-noise amplifier and filter in turn, after down-conversion and then under-sampled by the analog-to-digital converter and the under-sampled baseband The echo signal is transmitted to the control module; the control module receives the under-sampled baseband echo signal, first performs low-pass filtering on the baseband echo signal after analog-to-digital conversion in the digital domain, and then uses the detection algorithm to calculate and obtain the independent motion signal, using The independent motion signal obtains the relative displacement of each object to be measured, and then restores the motion track of each object to be measured.

Embodiments of the present invention are as follows:

As shown in FIG. 1 , the embodiment takes a distribution-based continuous wave Doppler radar sensor applied in the 802.11a/g frequency band (covering the entire band range of 2.4GHz to 2.5GHz and 4.9GHz to 5.875GHz) as an example. Embodiment Using the radar sensor, the displacement tracks of multiple objects to be measured can be measured. In the embodiment, all systems share a 6MHz sinusoidal clock to realize phase synchronization, and the generation and distribution of control signals are realized by the control module MCU.

The transceiver chip selects Maxim's single-chip RF transceiver chip Max2829, which realizes all circuits such as RF signal source, receiver and mixer required for the RF transceiver function, and provides a fully integrated receiving channel, transmitting channel, VCO, frequency synthesizer and The baseband/control interface realizes a substantial cost reduction and saves space. The transmission link uses PLL phase-locked loop technology to multiply the frequency of the 6MHz sinusoidal clock signal to 5.86GHz and transmit it through the power amplifier. The power amplifier uses the AWL6951 chip of ANADIGICS Company. This chip is a dual-band InGaP HBT power amplifier that supports 2.4GHz and 5.8GHz dual-band. It occupies a small area and only needs two external capacitors. The input and output have achieved 50 ohm matching. No external matching is required, greatly simplifying the design. After the receiving link receives the echo signal, the RF filter selects the BFCN-5750+ filter of Mini-Circuits Company to filter out the clutter, amplifies it through the low-noise amplifier HMC320 and enters the Max2829 chip for down-conversion demodulation, and uses the Analog Devices company's The AD7357 analog-to-digital converter is undersampled.

The control module adopts the STM32F103 low-speed micro-control unit of STMicroelectronics, which can accurately and effectively control the power of the radio frequency signal and the sampling rate of the analog-to-digital converter.

The principle process of the subcarrier signal transmission and reception demodulation is further elaborated below for the embodiment: Consider an amplitude normalized single-frequency continuous wave radio frequency signal T (t)=cos(2πft+φ ₀ (t)), where t is the time, π is the circular ratio, f is the operating frequency of the transceiver chip, t is the time, and φ ₀ (t) is the initial phase. It can be expressed as:

The radio frequency signal is transmitted from the antenna to detect the motion of the two objects to be measured, and the objects to be measured do a round-trip sinusoidal motion and a round-trip uniform linear motion. At this time, the echo signals received by the two transceivers are:

Among them, m ₁ (t), m ₂ (t) are the motion trajectories of the two objects to be measured, and A ₁₁ , A ₁₂ , A ₂₁ , and A ₂₂ are the corresponding echo signals received by the receiver after electromagnetic wave transmission attenuation. The amplitude of the independent motion signal.

It can be seen from the above formula that the object’s motion track information m ₁ (t), m ₂ (t) is included in the phase of the independent motion signal cos() corresponding to the echo signal, and due to the superposition relationship of the cos() function, if there is no If each function is separated, it is impossible to extract the motion trajectory information in the phase of the cos() function.

Use the same local oscillator signal as the working frequency f to perform down-conversion and demodulation to obtain a baseband signal with a frequency of 0, perform undersampling and low-pass filter to remove the noise part, and obtain the baseband echo signal of the receiver as follows:

Using the detection algorithm, the independent motion signal of the object to be measured is obtained in the following ways:

In the first step, the baseband echo signals after the analog-to-digital conversion of each radio frequency receiver are formed into an echo matrix according to the order of the radio frequency receiver, and the sliding average value of the echo matrix is calculated as the sliding average matrix by the following formula;

In the formula, p is the moving average step size, x(nj) is the njth discrete time value of the echo signal, is the moving average, j represents the integer count value, and n represents the ordinal number of the discrete time value;

In the second step, the moving average matrix minus the echo matrix is used as a difference matrix, and then the difference matrix is multiplied with its own complex conjugate matrix;

In the third step, the moving average matrix is multiplied by its complex conjugate matrix, and divided by the operation result of the second step to obtain the eigenvector;

The fourth step is to dot-multiply the complex conjugate of the eigenvector and the echo matrix to obtain a matrix composed of multi-target independent motion signals, and each element of the matrix is used as an independent motion signal of the object to be measured detected by each radio frequency receiver;

After normalization, the independent motion signal can be written in the following format:

In the fifth step, after the phase quantity of each independent motion signal is obtained by inverting the trigonometric function, the motion trajectories of multiple objects to be measured are calculated and described by the following formula:

Among them, m _k (t) is the relative displacement of each object to be measured relative to the initial position, the initial position is the position of the object to be measured at the initial moment of detection, λ is the wavelength corresponding to the frequency of the electromagnetic wave emitted by the radio frequency receiver, φ _k (t ) represents the phase quantity of the kth independent motion signal, and k represents the ordinal number of the object to be measured.

According to the above method, the measured experimental results and the comparison of the known positions are shown in Figure 2, where the dotted line is the actual trajectory of the object to be measured, and the solid line is the experimentally measured and calculated according to the above method. motion track.

It can be seen from the above implementation that the method and sensor of the present invention can detect the motion of multiple objects to be measured, overcome the problems of low resolution and signal aliasing, and accurately reconstruct the motion trajectories of multiple objects to be measured. technical effect.

Claims (10)

1. A distributed placement Doppler radar sensor is characterized in that: a plurality of radio frequency transceivers, a control module and a clock synchronization distribution module are included, each radio frequency transceiver is connected with a clock synchronization distribution module, and the control module is respectively distributed with a clock synchronization distribution The module and each radio frequency transceiver are connected, and each radio frequency transceiver has independent transmitting and receiving functions. 2. a kind of distributed placement Doppler radar sensor according to claim 1, is characterized in that: described radio frequency transceiver comprises radio frequency transceiver chip, analog-to-digital converter, power amplifier, low noise amplifier and filter, The RF transceiver chip is connected to the transmitting antenna through the power amplifier, the RF transceiver chip is connected to the receiving antenna through the filter, the low noise amplifier in turn, the RF transceiver chip is connected to the control module through the analog-to-digital converter, and the RF transceiver chip is connected to the clock synchronization Assign modules. 3. a kind of distributed placement Doppler radar sensor according to claim 1, is characterized in that: each radio frequency transceiver described works independently, and is controlled by control module and selects operating frequency according to the range of motion of object to be measured and the measurement environment . 4. A distributed Doppler radar sensor according to claim 2, characterized in that: the analog-to-digital converter uses a sampling frequency lower than the Nyquist frequency for under-sampling. 5. A distributed Doppler radar sensor according to claim 1, characterized in that: the number of said radio frequency transceivers is greater than or equal to the number of objects to be measured. 6. A distributed Doppler radar sensor according to claim 1, characterized in that: the clock synchronization distribution module controls each radio frequency transceiver to generate a single frequency continuous wave radio frequency signal with the same frequency and the same initial phase. 7. a kind of distributed placement Doppler radar sensor according to claim 1, is characterized in that: described control module is connected with each radio frequency transceiver respectively, independently regulates the power and the sensitivity of each radio frequency transceiver, and control module The signal is collected by a digital converter, displayed in real time or transmitted to other terminals such as a personal computer. 8. be applied to a kind of multi-target motion detection method that the arbitrary described distribution of claim 1～7 places Doppler radar sensor, it is characterized in that comprising the following specific steps: The low-frequency sinusoidal clock signal is generated by the crystal oscillator in the clock synchronization distribution module. After clock synchronization, it is distributed into two channels. One channel is transmitted to each RF transceiver chip to generate a single-frequency continuous wave RF signal with the same frequency and initial phase, and the other channel is transmitted to the control panel. The module performs digital down-conversion; The RF detection signal sent by the RF transceiver chip is amplified by the power amplifier, and then transmits a single-frequency continuous wave RF signal to the object to be measured through the transmitting antenna, and the receiving antenna receives the baseband echo signal reflected by the object to be measured, and then passes through the low-noise After the amplifier and filter enter the RF transceiver chip, after down-conversion, the analog-to-digital converter is under-sampled and the under-sampled baseband echo signal is transmitted to the control module; The control module receives the under-sampled baseband echo signal, first performs low-pass filtering on the baseband echo signal after analog-to-digital conversion in the digital domain, then uses the detection algorithm to calculate and obtain the independent motion signal, and uses the independent motion signal to obtain the The relative displacement of the object, and then restore the trajectory of each object to be measured. 9. A kind of multi-target motion detection method according to claim 8, is characterized in that: The use of the detection algorithm to obtain the independent motion signal, and the use of the independent motion signal to obtain the relative displacement of each object to be measured, the specific steps are as follows: In the first step, the baseband echo signals after the analog-to-digital conversion of each radio frequency receiver are formed into an echo matrix, and the sliding average value of the echo matrix is calculated by the following formula as the sliding average matrix x%(n); In the formula, p is the moving average step size, x(n-j) is the n-j discrete time value of the echo signal, x%(n) is the moving average value, j represents the integer count value, and n represents the ordinal number of the discrete time value; In the second step, the moving average matrix minus the echo matrix is used as a difference matrix, and then the difference matrix is multiplied with its own complex conjugate matrix; In the third step, the moving average matrix is multiplied by its complex conjugate matrix, and divided by the operation result of the second step to obtain the eigenvector; The fourth step is to dot-multiply the complex conjugate of the eigenvector and the echo matrix to obtain a matrix composed of multi-target independent motion signals, and each element of the matrix is used as an independent motion signal of the object to be measured detected by each radio frequency receiver; In the fifth step, for each independent motion signal, the following formula is used to calculate the relative displacement of the object to be measured: Among them, m _k (t) is the relative displacement of each object to be measured relative to the initial position, the initial position is the position of the object to be measured at the initial moment of detection, t represents time, λ is the wavelength corresponding to the frequency of the electromagnetic wave emitted by the radio frequency receiver, φ _k (t) represents the phase quantity of the kth independent motion signal, k represents the ordinal number of the object to be measured, and N represents the total number of objects to be measured. 10. A kind of multi-target motion detection method according to claim 8, is characterized in that: The under-sampling is performed with a sampling frequency lower than the Nyquist frequency, preferably with a sine wave active crystal oscillator whose frequency is less than one percent of the carrier frequency.