Fmcw millimeter wave radar communication modulation waveform, modulation method, and radar system

Abstract

The application discloses a FMCW millimeter wave radar communication modulation waveform, a modulation method and a radar system, and belongs to the technical field of radar communication waveform modulation. The modulation waveform comprises a preamble field and a payload field; the preamble field comprises an acquisition field and a synchronization field after the acquisition field; the acquisition field comprises a single-tone waveform used for acquisition and frequency synchronization of a receiving end; the synchronization field comprises a linear sweep waveform used for accurate timing synchronization; and the payload field comprises M-FSK symbols used for carrying data, wherein M is greater than or equal to 2 and is a power of 2. The modulation method is realized by controlling the output frequency of an RF PLL of the FMCW millimeter wave radar. The radar system comprises a plurality of FMCW millimeter wave radars for modulating and demodulating the modulation waveform. The application can enable the FMCW millimeter wave radar device to have the ability of transmitting and receiving data packets without significantly increasing the circuit cost, and facilitates the realization of the communication networking of the FMCW millimeter wave radar.

Description

Technical Field

[0001] This invention belongs to the field of radar communication waveform modulation technology, specifically relating to an FMCW millimeter-wave radar communication modulation waveform, modulation method, and radar system. Background Technology

[0002] In smart home and other multi-radar coexistence application scenarios, FMCW millimeter-wave radar has a strong demand for networking, not only for interactive sensing information, but also to solve the problem of mutual interference among multiple FMCW millimeter-wave radars and the interference between FMCW millimeter-wave radar and co-frequency communication equipment (for example, a common method to resist co-frequency interference is to set time and frequency resource blocks for each FMCW millimeter-wave radar device and co-frequency communication device to be exclusively used).

[0003] Network deployment requires the FMCW millimeter-wave radar's ability to send and receive data packets. However, the FMCW millimeter-wave radar has two fatal limitations when sending data packets:

[0004] 1) The waveform modulator of FMCW millimeter-wave radar usually uses a simple voltage-controlled VCO to achieve linear frequency modulation, which means that when it sends data packets, it can only select frequency-modulated waveforms.

[0005] 2) The intrinsic phase noise of millimeter-wave band circuits is usually tens of dB worse than that of common low-frequency bands (such as 2.4G ISM frequency). In order to optimize phase noise, filters with very narrow passbands are usually built into the RFPLL (radio frequency phase-locked loop) to suppress phase noise. These filters will severely slow down the frequency switching response speed and introduce severe inter-symbol interference (ISI), making it difficult to support high symbol rates. This will cause FMCW radar to spend too much time transmitting and receiving data packets.

[0006] Furthermore, overly complex waveforms, such as OFDM and massive MIMO, significantly increase the circuit cost of millimeter-wave radar. Therefore, designing a modulation waveform that is highly compatible with FMCW millimeter-wave radar has become a real challenge for FMCW millimeter-wave radar networking. Summary of the Invention

[0007] This invention provides an FMCW millimeter-wave radar communication modulation waveform, modulation method, and radar system, optimizing the data packet transmission and reception capabilities of FMCW millimeter-wave radar equipment. This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides an FMCW millimeter-wave radar communication modulation waveform, comprising a preamble field and a payload field; the preamble field comprises an acquisition field and a synchronization field following the acquisition field; the acquisition field comprises a single-tone waveform for acquisition and frequency synchronization at the receiving end; the synchronization field comprises a linear sweep waveform for precise timing synchronization; the payload field comprises M-FSK symbols for carrying data, where M≥2 and M is a power of 2.

[0009] As a preferred technical solution, for multi-receiver FMCW millimeter-wave radar, the single-tone waveform of the acquisition field is also used for DOA measurement at the receiver.

[0010] As a preferred technical solution, the synchronization field is a linear sweep waveform whose frequency increases or decreases linearly with time.

[0011] As a preferred technical solution, the center frequency of the M-FSK symbol in the load field increases or decreases linearly with time.

[0012] As a preferred technical solution, a switching interval field of preset length is configured between two adjacent M-FSK symbols and before the first M-FSK symbol in the load field.

[0013] As a preferred technical solution, the preamble field further includes a protection interval field, which is configured between the synchronization field and the load field.

[0014] A second aspect of the present invention provides a modulation method for the above-mentioned FMCW millimeter-wave radar communication modulation waveform, wherein the FMCW millimeter-wave radar achieves the above-mentioned modulation waveform by controlling the output frequency of the RFPLL; comprising the following steps:

[0015] S100. During the capture field duration, the modulator inputs a constant to the division ratio port, causing the RFPLL to output a single-tone waveform.

[0016] S200. During the duration of the synchronization field, the modulator inputs linearly increasing or decreasing data to the frequency division ratio port, causing the RFPLL to output a linear sweep waveform.

[0017] S300. During the duration of the payload field, the modulator continues to send the frequency point information of the M-FSK symbol mapped according to the bit data to be transmitted to the frequency division ratio port one by one.

[0018] As a preferred technical solution, when the preamble field also includes a guard interval field configured between the synchronization field and the load field, a step S250 is set between steps S200 and S300: during the duration of the guard interval field, the modulator continues to input linearly increasing, decreasing or constant data to the frequency division ratio port, so that the RFPLL outputs the corresponding linear sweep waveform or single-tone waveform.

[0019] As a preferred technical solution, for multi-transmitter FMCW millimeter-wave radar, the transmitted data packets traverse all beamforming combinations.

[0020] A third aspect of the present invention provides a radar system comprising multiple FMCW millimeter-wave radars, wherein the multiple FMCW millimeter-wave radars modulate and demodulate the FMCW millimeter-wave radar communication modulation waveform described above.

[0021] The modulation waveform and radar system for inter-FMCW millimeter-wave radar communication provided by this invention have the following advantages: without significantly increasing circuit costs, it enables FMCW millimeter-wave radar equipment to transmit and receive data packets, thereby facilitating the networking of FMCW millimeter-wave radars. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a diagram illustrating the structure of the FMCW millimeter-wave radar communication modulation waveform provided in an embodiment of the present invention.

[0024] Figure 2 This is an optimized configuration diagram of the modulation waveform for FMCW millimeter-wave radar communication provided in an embodiment of the present invention.

[0025] Figure 3 This is a flowchart of the modulation method for FMCW millimeter-wave radar communication modulation waveform provided in an embodiment of the present invention.

[0026] Figure 4 This is a configuration diagram of the radar system provided in an embodiment of the present invention. Detailed Implementation

[0027] To make the technical solution of the present invention clearer and its technical advantages more apparent, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of the present invention.

[0028] It should be noted that, in this document, the terms "comprising," "including," "configuration," "setting," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which needs to be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.

[0029] It should be understood that although the steps in the flowcharts of this application's embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] like Figure 1As shown, as a basic implementation, this embodiment provides an FMCW millimeter-wave radar communication modulation waveform for communication between FMCW millimeter-wave radars. The structure of the modulation waveform includes a preamble field and a payload field. The preamble field includes an acquisition field and a synchronization field following the acquisition field. The acquisition field includes a single-tone waveform used by the receiver for acquisition and frequency synchronization. The synchronization field includes a linear sweep waveform used for precise timing synchronization. For example, the synchronization field is a linear sweep waveform whose frequency increases or decreases linearly with time. The payload field includes M-FSK symbols used to carry data, i.e., several M-FSK symbols connected end to end, where M represents M-ary frequency shift keying, M≥2, and M is a power of 2.

[0032] The advantages of using a single tone as the acquisition field are as follows: for the transmitter, the single-tone waveform is easy to generate; for the receiver, the multiplexed FFT circuit of the FMCW radar can easily acquire data packets and perform frequency offset and DOA measurements. The former is used for frequency synchronization, and the latter is used by multi-Rx FMCW millimeter-wave radar for Rx beamforming to improve receiver sensitivity. The advantages of using a linear sweep waveform as the synchronization field are as follows: for the transmitter, the linear sweep waveform is the waveform used by FMCW radar, so it is easy to generate; for the receiver, after frequency synchronization through the acquisition field, the frequencies of the transmitter and receiver are precisely aligned. At this point, the receiver can achieve precise time synchronization by performing matched filtering on the synchronization field. The advantages of using M-FSK symbols as the payload field are as follows: When symbol rates are limited, this invention selects high-order M-FSK symbols, allowing the receiver to reuse the FFT circuitry of the FMCW millimeter-wave radar for M-FSK demodulation, avoiding the cost of additional demodulation circuitry. Furthermore, each M-FSK symbol contains a single-tone waveform, which is easy for the transmitter to generate. For multi-receiver (i.e., multi-Rx) FMCW millimeter-wave radars, the single-tone waveform of the acquisition field is also used by the receiver for DOA (Direction of Arrival) measurement.

[0033] As an optional optimized implementation, the center frequency of the M-FSK symbol in the payload field increases or decreases linearly with time. In this optimized implementation, allowing the center frequency of the M-FSK symbol in the payload field to change linearly and promptly leave the basic channel (referring to the channel where the capture field is located) can prevent the transmitted waveform from occupying the basic channel for a long time, thereby improving network capacity.

[0034] Combination Figure 2As shown, as an optional optimized implementation, a switching interval field of preset length is configured between two adjacent M-FSK symbols and before the first M-FSK symbol in the payload field. As yet another optional optimized implementation, the preamble field further includes a guard interval field, configured between the synchronization field and the payload field.

[0035] Combination Figure 3 As shown, embodiments of the present invention also provide a modulation method for the above-mentioned FMCW millimeter-wave radar communication modulation waveform. The principle is to adjust the frequency division ratio in real time according to a predetermined method to achieve the desired frequency modulation waveform. Mainly, the FMCW millimeter-wave radar controls the frequency division ratio port of the RFPLL to make the output frequency of the RFPLL achieve the above-mentioned modulation waveform. This waveform is then transmitted into the environment via a PA (Power Amplifier) ​​and an antenna, forming a signal transmission. The specific modulation method is as follows:

[0036] S100. During the capture field duration, the modulator inputs a constant to the division ratio port, causing the RFPLL to output a single-tone waveform.

[0037] S200. During the duration of the synchronization field, the modulator inputs linearly increasing or decreasing data to the frequency division ratio port, causing the RFPLL to output a linear sweep waveform.

[0038] S300. During the duration of the payload field, the modulator continues to send the frequency point information of the M-FSK symbol mapped according to the bit data to be transmitted to the frequency division ratio port one by one; the transmission duration is the symbol period of the M-FSK symbol. If there is an optional switching interval field, the transmission duration is equal to the switching interval + symbol period; the switching interval and symbol period are preset durations. The switching interval is used to accommodate the unstable waveform during the establishment process of the RFPLL output when the frequency division ratio is switched.

[0039] When the leading field also includes an optional guard interval field, a step S250 is set between steps S200 and S300: during the duration of the guard interval field, the modulator continues to input linearly increasing, decreasing or constant data to the frequency division ratio port, so that the RFPLL outputs the corresponding linear sweep waveform or single-tone waveform.

[0040] As a preferred implementation, for multi-transmitter (multi-Tx) FMCW millimeter-wave radars, the transmitted data packets traverse all beamforming combinations. Specifically, multi-Tx FMCW millimeter-wave radars are a common configuration for mid-to-high-end radars. Beamforming formed by multiple Txes can improve eIRP (Electronic Irp) and thus increase the coverage range of the data packets. For example, for an N-Tx FMCW millimeter-wave radar, each Tx has an independent phase adjustment function, with phase adjustments of 0°, 90°, 180°, and 270° (i.e., a four-phase adjustment example). The 2nd to Nth Txes are encoded, and the 1st Tx is always set to 0°, resulting in a total of 4... N-1 There are several phase sequence combinations; at the transmitting end, each data packet is transmitted using all of these combinations, so for the receiving end, all 4... N-1 In each repeated reception, at least one data packet achieves a beamforming gain of N times. For example, in an FMCW millimeter-wave radar with N Tx values, each Tx has an independent phase adjustment function, with phase adjustments of 0° and 180° (i.e., a two-phase adjustment example). Encoding is performed on the 2nd to Nth Tx values, while the 1st Tx is always set to 0°, resulting in a total of 2... N -1 There are several phase sequence combinations. At the transmitting end, each data packet is transmitted using all of these combinations. Therefore, for the receiving end, all 2... N-1 In each repeated reception, at least one data packet receives N times the beam forming gain.

[0041] Below is a specific example of a transceiver:

[0042] The transceiver agrees on a carrier frequency of fc = 60GHz, and the following items are preset:

[0043] 1. Capture field: Frequency point is 60GHz, duration is 10us;

[0044] 2. Synchronization field: Frequency sweep from 60GHz to 60.005GHz, duration 5µs;

[0045] 3. Payload field: M-FSK symbol period is 4µs, switching interval is 1µs, and the M-FSK symbol space is {60GHz, 60.001GHz, 60.002GHz, 60.003GHz, 60.004GHz, 60.005GHz, 60.006GHz, 60.007GHz}, containing a total of M=8 symbols, each symbol containing 3 bits of information.

[0046] Assuming the transmitter needs to transmit 6 bits of data ({1,0,0,1,1,1}), and the reference frequency of the transmitter's RFPLL is 1GHz, the control flow for the division ratio input to the RFPLL is as follows: A fixed division ratio of 60 is input and held for 10µs to complete the acquisition field transmission. Then, a control word is input to the division ratio, incrementing by 0.000001 per reference frequency cycle, based on 60. After 5µs, when the control word input to the division ratio reaches 60.005, the synchronization field ends. Next, a division ratio of 60.001 is input and held for 5µs to complete the transmission of the first M-FSK symbol. Then, a division ratio of 60.007 is input and held for 5µs to complete the transmission of the second M-FSK symbol. This completes the entire transmission process.

[0047] The receiver remains powered on and its local oscillator (LO) frequency is configured to 59.999 GHz to downconvert the RF signal transmitted by the transmitter to an intermediate frequency (IF), which is then sampled by the ADC and fed into the digital circuit. In the digital circuit, the capture module performs a sliding FFT calculation on the ADC output data stream. When the amplitude of a frequency point after the FFT exceeds a threshold, a data packet is considered captured. At this point, the frequency Δf at this point is precisely measured and compared to 1 MHz. If Δf is higher than 1 MHz, it indicates that the local carrier frequency is too low, and the LO frequency needs to be increased by Δf-1 MHz. If Δf is lower than 1 MHz, it indicates that the local carrier frequency is too high, and the LO frequency needs to be decreased by Δf-1 MHz. After adjustment, the LO frequency and the transmitter's carrier frequency are aligned, achieving frequency synchronization. Then, the time synchronization module uses a locally pre-stored timing waveform to perform matched filtering on the ADC output data stream. According to matched filtering theory, when a signal appears in the ADC output data stream... When the waveform is the same as the locally stored timing waveform, a spike appears in the matching result. Based on this feature, the starting point of the payload field of the data packet can be identified. Then, starting from the starting point of the payload field, two 5µs data segments are extracted from the data stream output by the ADC. The first 1µs of each data segment is discarded, and only the last 4µs is retained as symbol data. These two symbol data are sent to the FFT module to be converted to the frequency domain. The strongest peak is found in the frequency domain, and the frequency of the strongest peak is accurately measured to obtain 2MHz and 8MHz. After adding the frequency of the local oscillator (LO), the radio frequency is obtained as 60.001GHz and 60.007GHz. Based on these two frequencies and the M-FSK symbol space, the bit sequence sent by the transmitter is {1,0,0,1,1,1}.

[0048] Finally, see Figure 4As shown, this embodiment of the invention also provides a radar system, including multiple FMCW millimeter-wave radars, such as radar device A, radar device B, and radar device C; the multiple FMCW millimeter-wave radars modulate and demodulate the FMCW millimeter-wave radar communication modulation waveform described above. Of course, the radar system may also include other devices capable of modulating and demodulating the modulation waveform. That is, if a standard communication device has a built-in module for modulating and demodulating the modulation waveform, it can connect to the cloud and can also be considered a system node participating in the network and acting as a gateway. For example, in a home, several FMCW millimeter-wave radars and a millimeter-wave band router participate in the network. After the router acts as a gateway, this network can connect to a cloud server, allowing consumers to access relevant information about their home devices on their mobile phones.

[0049] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A modulation method of a FMCW millimeter wave radar communication modulation waveform, characterized by, The modulation waveform for FMCW millimeter-wave radar communication includes a preamble field and a payload field. The preamble field includes an acquisition field and a synchronization field following the acquisition field. The acquisition field includes a single-tone waveform for acquisition and frequency synchronization at the receiver. The synchronization field includes a linear sweep waveform for precise timing synchronization. The payload field includes M-FSK symbols for carrying data, where M ≥ 2 and M is a power of 2. The modulation method includes the following steps: S100. During the capture field duration, the modulator inputs a constant to the division ratio port, causing the RFPLL to output a single-tone waveform. S200. During the duration of the synchronization field, the modulator inputs linearly increasing or decreasing data to the frequency division ratio port, causing the RFPLL to output a linear sweep waveform. S300. During the duration of the payload field, the modulator continues to send the frequency point information of the M-FSK symbol mapped according to the bit data to be transmitted to the frequency division ratio port one by one.

2. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: For multi-receiver FMCW millimeter-wave radar, the single-tone waveform of the acquisition field is also used for DOA measurement at the receiver.

3. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: The synchronization field is a linear sweep waveform whose frequency increases or decreases linearly with time.

4. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: The center frequency of the M-FSK symbol in the payload field increases or decreases linearly with time.

5. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: The payload field is configured with a preset length of switching interval field between two adjacent M-FSK symbols and before the first M-FSK symbol.

6. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: The leading field also includes a protection interval field, which is configured between the synchronization field and the load field.

7. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: When the preamble field also includes a guard interval field configured between the synchronization field and the load field, a step S250 is set between steps S200 and S300: During the duration of the guard interval field, the modulator continues to input linearly increasing, decreasing or constant data to the frequency division ratio port, so that the RFPLL outputs the corresponding linear sweep waveform or single-tone waveform.

8. The modulation method for the FMCW millimeter-wave radar communication modulation waveform according to claim 1, characterized in that: For multi-transmitter FMCW millimeter-wave radars, the transmitted data packets traverse all beamforming combinations.

9. An FMCW millimeter-wave radar communication modulation waveform, characterized in that: It includes a preamble field and a payload field; the preamble field includes an acquisition field and a synchronization field following the acquisition field; the acquisition field includes a single-tone waveform for acquisition and frequency synchronization at the receiving end; the synchronization field includes a linear sweep waveform for precise timing synchronization; the payload field includes M-FSK symbols for carrying data, where M≥2 and M is a power of 2; the FMCW millimeter-wave radar communication modulation waveform is modulated by the modulation method of the FMCW millimeter-wave radar communication modulation waveform according to any one of claims 1-8.

10. A radar system comprising multiple FMCW millimeter-wave radars, characterized in that: Multiple FMCW millimeter-wave radars perform the modulation method of the FMCW millimeter-wave radar communication modulation waveform as described in any one of claims 1-8.

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