UWB radar based on TDM-MIMO and angle measurement method thereof

Abstract

The invention discloses a UWB radar angle measurement method and device based on TDM-MIMO, and belongs to the technical field of radar signal processing. The method comprises the following steps: controlling the radar system to work according to a preset time sequence, switching and controlling the connection and working states of at least two bidirectional channels and at least four physical antennas in different time slices through a switch, and performing time-sharing configuration into a transmitting or receiving mode to obtain echo data; wherein the switching time of the radio frequency switch is less than the difference value between the minimum flight time of the signal and the emission duration time, so as to ensure that the switching does not influence normal transceiving. And recombining the data based on the equivalent spatial positions of the physical antennas in different time slices to form a virtual antenna array, and then estimating the direction of arrival. The device comprises a radar chip, an antenna array, a switching network and a control processing unit. According to the invention, through the optimized TDM-MIMO time sequence and strict time sequence constraint, a large-scale virtual array is formed by using a small amount of hardware resources, and high-precision angle measurement is realized with relatively low system complexity.

Description

Technical Field

[0001] This invention relates to the field of radar signal processing technology, and in particular to a UWB radar based on TDM-MIMO and its angle measurement method. Background Technology

[0002] Ultra-wideband (UMB) radar has been widely used in automotive sensing, indoor positioning, and gesture recognition due to its advantages such as high resolution and strong anti-jamming capabilities. To achieve higher angular resolution and more accurate angle measurement, the physical aperture of the antenna needs to be increased, which usually means increasing the number of antennas. However, directly increasing the number of physical antennas significantly increases the system's hardware complexity, cost, and power consumption.

[0003] MIMO (Multiple-Input Multiple-Output) technology combines multiple transmit and receive antennas to form a virtual antenna array with a number far exceeding that of physical antennas. This effectively increases the array aperture and improves angle measurement accuracy without significantly increasing hardware costs. TDM-MIMO (Time Division Multiplexing Multiple-Input Multiple-Output) is a common implementation method, which constructs a virtual array by switching the operating states of different antennas at different time slices. However, designing an efficient and reliable TDM-MIMO timing and control scheme for UMB radar to optimally form the virtual array and perform accurate angle estimation remains a pressing technical challenge in this field. Summary of the Invention

[0004] (a) Purpose of the invention The purpose of this invention is to provide a TDM-MIMO-based UWB radar angle measurement method to solve the problems of system complexity and high cost in existing technologies for achieving high-precision angle measurement. This invention aims to achieve high-precision angle measurement by optimizing TDM-MIMO timing and control logic to form a large-scale virtual antenna array using a small number of physical antennas.

[0005] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a UWB radar angle measurement method based on TDM-MIMO is provided, comprising the following steps: S1. The control radar system operates according to a preset TDM-MIMO timing sequence. In multiple different time slices, the connection relationship and working status between at least two transmission channels and at least four physical antennas are controlled sequentially, so that the at least two transmission channels transmit signals in a time-division manner and the at least two receiving channels receive the echo signals reflected by the target in a time-division manner to obtain multiple sets of received data. Among them, the reserved switching time between the time slots where radio frequency switching is required satisfies the following condition: the switching time of the radio frequency switch is less than the minimum round-trip flight time of the radar signal to the nearest detection target minus the duration of signal transmission. S2. Based on the equivalent spatial positions of multiple physical antennas in different time slots, the multiple sets of received data are reorganized into a virtual antenna array with more array elements. S3. Based on the received data from the virtual antenna array, the direction of arrival is estimated to achieve angle measurement.

[0006] Preferably, the preset TDM-MIMO timing in step S1 specifically includes the following steps executed in sequence: a. At the first moment (t1), configure the first switch to connect the first bidirectional channel to the first antenna, and configure the first bidirectional channel to be in signal transmission state, while the second bidirectional channel is turned off; execute one signal transmission cycle; b. At the second time (t2), configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle; c. At the third moment (t3), configure the first bidirectional channel to signal transmission state and the second bidirectional channel to be closed; execute one signal transmission cycle; d. At the fourth time (t4), configure the first switch to connect the first bidirectional channel to the second antenna, configure the second switch to connect the second bidirectional channel to the fourth antenna, and configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle; e. At the fifth moment (t5), configure the second bidirectional channel to signal transmission state, and shut down the first bidirectional channel; execute one signal transmission cycle; f. At the sixth time (t6), configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle; g. At the seventh moment (t7), configure the second bidirectional channel to signal transmission state, and shut down the first bidirectional channel; execute one signal transmission cycle; h. At the eighth moment (t8), configure the first switch to connect the first bidirectional channel to the first antenna, configure the second switch to connect the second bidirectional channel to the third antenna, and configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle.

[0007] The preset timing sequence mentioned in step S1 specifically includes the sequential operation of eight time points (t1 to t8). By precisely controlling the connection and switching of the two transmission channels and four physical antennas (Ant1, Ant2, Ant3, Ant4), and in conjunction with the changes in the transmission and reception status, a complete signal transmission and reception cycle is completed in eight steps.

[0008] Preferably, the implementation of step S1 depends on a switch switching network; In steps a), d), and h), the first switch is configured to switch the connection between the first bidirectional channel and the first antenna or the second antenna; In steps d) and h), the second switch is configured to switch the connection between the second bidirectional channel and the third or fourth antenna.

[0009] Preferably, the data structure reorganization in step S2 is based on the final equivalent position χ formed in space by the combination of each transceiver channel and antenna in the TDM-MIMO working mode.

[0010] Preferably, the direction of arrival estimation in step S3 is performed using a beamforming algorithm based on a virtual antenna array or a super-resolution angle measurement algorithm.

[0011] Secondly, a TDM-MIMO-based UWB radar is provided, including: The radar chip integrates at least a first bidirectional channel and a second bidirectional channel; The antenna array includes at least a first antenna, a second antenna, a third antenna, and a fourth antenna; A switching network is connected between the radar chip and the antenna array; Control and processing unit; The control and processing unit is configured as follows: The switching network and the radar chip are controlled to change the connection relationship and working status of the first bidirectional channel, the second bidirectional channel and each antenna in the antenna array in multiple time slots according to a preset TDM-MIMO timing sequence, so as to obtain multiple sets of echo data in a time-division manner; wherein, between the time slots where radio frequency switching is required, the reserved switching time satisfies the following: the switching time of the radio frequency switch is less than the minimum round-trip flight time of the radar signal to the nearest detection target minus the duration of signal transmission; Based on the equivalent spatial positions of each physical antenna in different time slots, the multiple sets of echo data are reorganized into a virtual antenna array. Direction of arrival (DOA) estimation is performed based on the data from the virtual antenna array to achieve angle measurement.

[0012] Preferably, the switching network includes: The first switch has its moving end connected to the first bidirectional channel and its two stationary ends connected to the first antenna and the second antenna, respectively. The second switch has its moving end connected to the second bidirectional channel and its two stationary ends connected to the third and fourth antennas, respectively.

[0013] The preset TDM-MIMO timing allows the control and processing unit to be further configured to perform the following operations sequentially: a. At the first moment, control the first switch to connect the first bidirectional channel to the first antenna and configure it to signal transmission state, while simultaneously shutting down the second bidirectional channel; b. At the second moment, configure the first bidirectional channel and the second bidirectional channel to signal receiving mode; c. At the third moment, configure the first bidirectional channel to signal transmission mode, and simultaneously shut down the second bidirectional channel; d. At the fourth moment, control the first switch to connect the first bidirectional channel to the second antenna, control the second switch to connect the second bidirectional channel to the fourth antenna, and configure the first and second bidirectional channels to signal receiving mode; e. At the fifth moment, configure the second bidirectional channel to signal transmission mode, and simultaneously shut down the first bidirectional channel; f. At the sixth moment, configure the first bidirectional channel and the second bidirectional channel to signal receiving mode; g. At the seventh moment, configure the second bidirectional channel to signal transmission mode, and simultaneously shut down the first bidirectional channel; h. At the eighth moment, control the first switch to connect the first bidirectional channel to the first antenna, control the second switch to connect the second bidirectional channel to the third antenna, and configure the first and second bidirectional channels to signal receiving state.

[0014] Preferably, the control and processing unit is a microcontroller, a digital signal processor, or a system-on-a-chip.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention has the following significant advantages: 1. Achieving a significant leap in angular resolution with high cost-effectiveness: This invention, through meticulously designed TDM-MIMO timing and control logic, successfully forms an equivalent virtual uniform linear array with a larger number of array elements and a larger aperture using only two bidirectional RF channels, four physical antennas, and a simple switching network. This achieves an order-of-magnitude improvement in angular resolution without significantly increasing hardware cost, complexity, or power consumption, perfectly resolving the contradiction between high-precision angle measurement and system cost.

[0016] 2. Introduced critical timing constraints to ensure system reliability: The present invention clearly puts forward the core timing constraint condition of switchTime < flyTime - transTime. This design ensures that the RF switch has sufficient switching and stable time, completely avoiding the interference of the switch switching transient process on the weak echo signal, thus guaranteeing the integrity and consistency of all data snapshot acquisitions and laying a reliable data foundation for subsequent high-precision angle measurement. This is a key design criterion that has not been clearly revealed and systematically applied in the prior art.

[0017] 3. Provided an optimized eight-step timing implementation scheme: The proposed eight-step timing scheme (t1 - t8) has clear logic and high execution efficiency. It maximally utilizes the limited hardware resources. Through precise switch switching and channel state control, it ensures that the aperture of the virtual array is fully utilized, and the positions of each virtual array element are evenly and reasonably distributed without redundant operations, and the data acquisition efficiency is high. This scheme provides an optimal TDM-MIMO waveform design example that can be directly implemented in the industry.

[0018] 4. The system has strong robustness and applicability: Since the core algorithm is based on the finally formed virtual array, this method has a certain tolerance for hardware imperfections (such as inter-channel mismatch). At the same time, this scheme has a simple hardware implementation, small volume and low power consumption, and is very suitable for embedded radar application scenarios that are extremely sensitive to cost, volume and power consumption, such as vehicle-mounted radar, smart home sensing, robot navigation and consumer electronics gesture recognition, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the system hardware structure of the UMB radar based on TDM-MIMO of the present invention; Figure 2 is the overall flowchart of the UWB radar angle measurement method based on TDM-MIMO provided by an embodiment of the present invention; Figure 3 is the detailed step diagram of the preset timing described in step S1 in an embodiment of the present invention; Figure 4 is the schematic diagram of the constraint conditions of the preset timing described in step S1 in an embodiment of the present invention; Figure 5 is the schematic diagram of the equivalent positions of the finally formed virtual antenna array after timing control in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0021] As Figure 1As shown, the hardware of the TDM-MIMO based UWB radar system of the present invention mainly includes: Radar chip 30: An UWB chip with at least two bidirectional radio frequency channels (Channel 1, Channel 2) is adopted, and each channel can be configured as a transmitting or receiving mode through software.

[0022] Antenna array 10: At least includes four physical antennas, namely Antenna 1 (Ant1), Antenna 2 (Ant2), Antenna 3 (Ant3) and Antenna 4 (Ant4).

[0023] Switching network 20: At least includes a first switch (Switch1) and a second switch (Switch2). The moving end of Switch1 is connected to Channel 1, and its two static ends are respectively connected to Ant1 and Ant2. The moving end of Switch2 is connected to Channel2, and its two static ends are respectively connected to Ant3 and Ant4.

[0024] Control and processing unit 40: Usually a microcontroller (MCU) or a system on chip (SoC), which is used to control the timing, signal processing and algorithm execution of the whole system.

[0025] Reference Figure 2 , Figure 3 , the implementation process of this method is as follows: First, execute step S1: Data acquisition and timing control.

[0026] One of the cores of the present invention lies in its carefully designed eight-step TDM-MIMO timing and strict constraints on the radio frequency switch switching time. The control and processing unit executes the following steps in a preset order, and ensures that during the step intervals where switch switching is required, the timing constraint condition of switchTime < flyTime - transTime is satisfied, where switchTime is the switch switching time; flyTime is the minimum distance flying time; transTime is the transmission duration. As Figure 4 shown.

[0027] At time t1: Configure Switch1 to connect Channel 1 to Ant1. At the same time, configure the radar chip to make Channel 1 in the signal transmitting state and Channel 2 in the off state. Execute one signal transmission cycle. In this stage, the signal is transmitted by Ant1.

[0028] At time t2: Maintain the connection between Channel 1 and Ant1, and between Channel 2 and Ant3. Configure the radar chip so that both Channel 1 and Channel 2 are in signal receiving mode. Perform one signal receiving cycle. In this phase, it is equivalent to Ant1 transmitting (the signal originating from time t1) and Ant1 (through Channel 1) and Ant3 (through Channel 2) jointly receiving it.

[0029] At time t3: Maintain the connection between Channel 1 and Ant1, and between Channel 2 and Ant3. Configure the radar chip so that Channel 1 is in signal transmission mode and Channel 2 is in the off state. Perform one signal transmission cycle. During this phase, Ant1 transmits a signal again.

[0030] At time t4: Configure Switch1 to connect Channel 1 to Ant2, and simultaneously configure Switch2 to connect Channel 2 to Ant4. Configure the radar chip so that both Channel 1 and Channel 2 are in signal receiving mode. Perform one signal receiving cycle. In this phase, it is equivalent to Ant1 transmitting (the signal originating from time t3), which is jointly received by Ant2 (through Channel 1) and Ant4 (through Channel 2).

[0031] At time t5: Maintain connections between Channel 1 and Ant2, and between Channel 2 and Ant4. Configure the radar chip to enable signal transmission for Channel 2 and disable Channel 1. Perform one signal transmission cycle. During this phase, Ant4 transmits the signal.

[0032] At time t6: Maintain the connection between Channel 1 and Ant2, and between Channel 2 and Ant4. Configure the radar chip so that both Channel 1 and Channel 2 are in signal receiving mode. Perform one signal receiving cycle. In this stage, it is equivalent to Ant4 transmitting (the signal originating from time t5) and Ant2 (through Channel 1) and Ant4 (through Channel 2) jointly receiving it.

[0033] At time t7: Maintain connections between Channel 1 and Ant2, and between Channel 2 and Ant4. Configure the radar chip to enable signal transmission for Channel 2 and disable Channel 1. Perform one signal transmission cycle. During this phase, Ant4 transmits a signal again.

[0034] At time t8: Configure Switch1 to connect Channel 1 to Ant1, and simultaneously configure Switch2 to connect Channel 2 to Ant3. Configure the radar chip so that both Channel 1 and Channel 2 are in signal receiving mode. Perform one signal receiving cycle. This stage is equivalent to Ant4 transmitting (the signal originating from time t7), which is jointly received by Ant1 (through Channel 1) and Ant3 (through Channel 2).

[0035] At this point, a complete TDM-MIMO signal transmission and reception cycle has ended, and the system has acquired 8 data snapshots.

[0036] Next, proceed to step S2: virtual array reconfiguration.

[0037] The control and processing unit calculates the equivalent virtual antenna phase center position χ for each of the eight transmit / receive combinations mentioned above. For example... Figure 5 As shown, all these equivalent phase centers together form a virtual uniform linear array with a larger number of array elements and an enlarged aperture. Subsequently, the stored 8 sets of received data are rearranged and organized according to the structure of this virtual array.

[0038] Finally, perform step S3: Direction of arrival estimation.

[0039] The reconstructed virtual array data is then input into an angle measurement algorithm, such as the Capon beamformer or a super-resolution algorithm like MUSIC, to calculate the target's precise azimuth.

[0040] 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 variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A UWB radar angle measurement method based on TDM-MIMO, characterized in that, Includes the following steps: S1. The control radar system operates according to a preset TDM-MIMO timing sequence. In multiple different time slices, the connection relationship and working status between at least two bidirectional radio frequency channels and at least four physical antennas are controlled sequentially, so that the bidirectional radio frequency channels are configured to transmit or receive modes in a time-division manner to transmit signals and receive echo signals reflected by the target, thereby obtaining multiple sets of received data. Among them, the reserved switching time between the time slots where radio frequency switching is required satisfies the following condition: the switching time of the radio frequency switch is less than the minimum round-trip flight time of the radar signal to the nearest detection target minus the duration of signal transmission. S2. Based on the equivalent spatial positions of multiple physical antennas in different time slots, the multiple sets of received data are reorganized into a virtual antenna array with more array elements. S3. Based on the received data from the virtual antenna array, the direction of arrival is estimated to achieve angle measurement.

2. The UWB radar angle measurement method based on TDM-MIMO according to claim 1, characterized in that, The preset TDM-MIMO timing mentioned in step S1 specifically includes the following steps executed in sequence: a. At the first moment (t1), configure the first switch to connect the first bidirectional channel to the first antenna, and configure the first bidirectional channel to be in signal transmission state, while the second bidirectional channel is turned off; execute one signal transmission cycle; b. At the second time (t2), configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle; c. At the third moment (t3), configure the first bidirectional channel to signal transmission mode and the second bidirectional channel to be turned off; execute one signal transmission cycle; d. At the fourth time (t4), configure the first switch to connect the first bidirectional channel to the second antenna, configure the second switch to connect the second bidirectional channel to the fourth antenna, and configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle; e. At the fifth moment (t5), configure the second bidirectional channel to signal transmission state, and shut down the first bidirectional channel; execute one signal transmission cycle; f. At the sixth time (t6), configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle; g. At the seventh moment (t7), configure the second bidirectional channel to signal transmission state, and shut down the first bidirectional channel; execute one signal transmission cycle; h. At the eighth moment (t8), configure the first switch to connect the first bidirectional channel to the first antenna, configure the second switch to connect the second bidirectional channel to the third antenna, and configure the first bidirectional channel and the second bidirectional channel to signal receiving state; execute one signal receiving cycle.

3. The UWB radar angle measurement method based on TDM-MIMO according to claim 2, characterized in that, The implementation of step S1 depends on the switch switching network; In steps a), d), and h), the first switch is configured to switch the connection between the first bidirectional channel and the first antenna or the second antenna; In steps d) and h), the second switch is configured to switch the connection between the second bidirectional channel and the third or fourth antenna.

4. The UWB radar angle measurement method based on TDM-MIMO according to claim 1, characterized in that, The data structure reassembly described in step S2 is based on the final equivalent position χ formed in space by the combination of each transceiver channel and antenna in the TDM-MIMO working mode.

5. The UWB radar angle measurement method based on TDM-MIMO according to claim 1, characterized in that, The direction of arrival estimation described in step S3 is performed using a beamforming algorithm based on a virtual antenna array or a super-resolution angle measurement algorithm.

6. A UWB radar based on TDM-MIMO, characterized in that, include: The radar chip integrates at least a first bidirectional channel and a second bidirectional channel; The antenna array includes at least a first antenna, a second antenna, a third antenna, and a fourth antenna; A switching network is connected between the radar chip and the antenna array; Control and processing unit; The control and processing unit is configured as follows: The switching network and the radar chip are controlled to change the connection relationship and working status of the first bidirectional channel, the second bidirectional channel and each antenna in the antenna array in multiple time slots according to a preset TDM-MIMO timing sequence, so as to obtain multiple sets of echo data in a time-division manner; wherein, between the time slots where radio frequency switching is required, the reserved switching time satisfies the following: the switching time of the radio frequency switch is less than the minimum round-trip flight time of the radar signal to the nearest detection target minus the duration of signal transmission; Based on the equivalent spatial positions of each physical antenna in different time slots, the multiple sets of echo data are reorganized into a virtual antenna array. Direction of arrival (DOA) estimation is performed based on the data from the virtual antenna array to achieve angle measurement.

7. The UWB radar based on TDM-MIMO according to claim 6, characterized in that, The switching network includes: The first switch has its moving end connected to the first bidirectional channel and its two stationary ends connected to the first antenna and the second antenna, respectively. The second switch has its moving end connected to the second bidirectional channel and its two stationary ends connected to the third and fourth antennas, respectively.

8. The UWB radar based on TDM-MIMO according to claim 6, characterized in that, The preset TDM-MIMO timing allows the control and processing unit to be further configured to perform the following operations sequentially: a. At the first moment, control the first switch to connect the first bidirectional channel to the first antenna and configure it to signal transmission state, while simultaneously shutting down the second bidirectional channel; b. At the second moment, configure the first bidirectional channel and the second bidirectional channel to signal receiving mode; c. At the third moment, configure the first bidirectional channel to signal transmission mode, and simultaneously shut down the second bidirectional channel; d. At the fourth moment, control the first switch to connect the first bidirectional channel to the second antenna, control the second switch to connect the second bidirectional channel to the fourth antenna, and configure the first and second bidirectional channels to signal receiving mode; e. At the fifth moment, configure the second bidirectional channel to signal transmission mode, and simultaneously shut down the first bidirectional channel; f. At the sixth moment, configure the first bidirectional channel and the second bidirectional channel to signal receiving mode; g. At the seventh moment, configure the second bidirectional channel to signal transmission mode, and simultaneously shut down the first bidirectional channel; h. At the eighth moment, control the first switch to connect the first bidirectional channel to the first antenna, control the second switch to connect the second bidirectional channel to the third antenna, and configure the first and second bidirectional channels to signal receiving state.

9. The UWB radar based on TDM-MIMO according to claim 6, characterized in that, The control and processing unit is a microcontroller, a digital signal processor, or a system-on-a-chip.

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