Device for radar sensor, IC for radar sensor, and radar sensor

Abstract

Disclosed are an apparatus for a radar sensor, an IC for a radar sensor, and a radar sensor. Disclosed is an apparatus for a radar sensor, comprising: a transmission circuit configured to generate a transmission signal with linear frequency chirp modulation in a predetermined frequency band for output to a radar antenna; a receiving circuit configured to receive a reflection signal corresponding to reflections of the transmitted radar signal from one or more physical objects; and a control circuit configured to select a frequency range and / or a timing pattern within the predetermined frequency band for the transmission signal; wherein the apparatus is configured to: receive another signal from another radar sensor; determine from the other signal a frequency range and / or a timing pattern used by the other radar sensor for transmission of the other transmission signal; and select a frequency range and / or a timing pattern within the predetermined frequency band for the transmission signal that does not conflict with the frequency range and / or the timing pattern used for the other transmission signal.

Description

Technical Field

[0001] The present invention relates to a device for a radar sensor, an IC for a radar sensor, and a radar sensor. In particular, but not exclusively, it relates to a device for a radar sensor, an IC for a radar sensor, and a radar sensor configured to reduce or avoid interference between different radar sensors. Background Art

[0002] With the rapid increase in the adoption rate of radar sensors for ADAS (Advanced Driver Assistance System) functionality in automobiles such as emergency braking and the trend of using radar sensors as an essential part of autonomous driving systems, potential failure of these sensors due to mutual interference has become a matter of concern. The frequency regulation for the 77 GHz band commonly used by these sensors neither restricts the modulation scheme nor defines the process for cooperative operation of multiple applications in this band.

[0003] Interference between two similar radar sensors can be very strong because the "aggressor" sensor can radiate directly into the "victim" sensor. The direct radiation from the "aggressor" sensor interferes incoherently at the "victim" sensor, with a power reduction of 1 / R int 2 , where R int is the distance between the two sensors. Conversely, the reflected signal to be coherently detected by the “victim” sensor from a target at distance R is reduced to 1 / R 4 In addition, the power absorption of the target (i.e., the reflection cross section or RCS) further reduces the power of the reflected signal. In some cases, the reflected signal from the target may be undetectable due to the high jammer signal level. Due to the similarity of the waveform of the radar signal emitted by the sensor, and due to the high stability of the sensor's oscillator, the jammer can persist for a considerable time.

[0004] The effect of interference typically manifests itself as detected signal values ​​exceeding the normal signal range for target reflections. The resulting problems include saturation of the receiver module, signal range limitation resulting in additional harmonics (ghost targets), obscuration of weaker targets in the same range, and an increase in the overall noise floor before detection.

[0005] Many analyses have shown that the impact of interference on radar sensor functionality can be severe and ranges from reduced detection sensitivity due to the presence of additional noise to complete failure of the intended detection function. Different waveforms have been proposed to overcome this problem, such as PMCW (Phase Modulated Continuous Wave) and OFDM (Orthogonal Frequency Division Multiplexing) waveforms, which support additional coding to distinguish several transmitters in the same frequency band and minimize mutual interference through the orthogonal properties of such codes. The disadvantage of these proposals is that they require the design of new transceiver architectures with more challenging design requirements than the widely used FCM (Fast Chirp Modulation) waveform. The latter is widely used because of its simplicity of implementation and its high-resolution capabilities. The interaction of such new modulation schemes with existing FCM sensors is another source of concern in the industry. A further proposal is based on the use of another communication channel such as V2X. Summary of the invention

[0006] Various aspects of the disclosure are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate, and not just as set out in the claims.

[0007] According to one aspect of the present disclosure, there is provided an apparatus for a radar sensor, comprising:

[0008] a transmission circuit configured to generate a transmission signal with linear frequency chirp modulation in a predetermined frequency band for output to a radar antenna, and

[0009] receiving circuitry configured to receive reflection signals corresponding to reflections of the transmitted radar signal from one or more physical objects, and

[0010] a control circuit configured to select a frequency range and / or a timing pattern within the predetermined frequency band for the transmission signal;

[0011] The device is configured to:

[0012] receiving an additional signal from an additional radar sensor;

[0013] determining from the further signal a frequency range and / or a timing pattern used by the further radar sensor for transmission of a further transmission signal; and

[0014] A frequency range and / or timing pattern for the transmission signal within the predetermined frequency band is selected that does not conflict with a frequency range and / or timing pattern for the further transmission signal.

[0015] Thus, the apparatus may be useful in reducing or avoiding interference between different radar sensors. By being configured to determine a frequency range and / or timing pattern used by a further radar sensor for transmission of a further transmission signal, and selecting a frequency range and / or timing pattern within the predetermined frequency band for the transmission signal that does not conflict with the frequency range and / or timing pattern used for the further transmission signal, a plurality of such apparatuses operating in the same predetermined frequency band may select spectrum usage to minimize interference.

[0016] The timing pattern may be defined according to a scanning period, a scanning offset and / or a duty cycle of the transmission signal.The frequency range and / or the timing pattern selected for the transmission signal may not overlap with the frequency range and / or the timing pattern of the further transmission signal, respectively.

[0017] The receiving circuit may be configured to listen for the further signal from the further radar sensor before the transmitting circuit outputs the transmitting signal.

[0018] Thus, before outputting the transmission signal, the device can check whether the frequency range and / or timing pattern intended for use by the transmission signal conflicts with another radar sensor, thereby reducing the possibility of interference with another radar sensor.

[0019] The further signal received from the further radar sensor may be a beacon signal transmitted in the predetermined frequency band, the beacon signal including information indicating the frequency range and / or timing pattern of the further transmission signal. The information may include, for example, a start frequency and a frequency change (or a start frequency and a stop frequency), a scanning period and a duty cycle.

[0020] However, in some embodiments, the further signal may also or alternatively comprise a further transmission signal transmitted by the further sensor.

[0021] That is, the radar sensor can be configured to determine the frequency range and / or timing pattern used by the further radar sensor for the transmission of the further transmission signal based on the further transmission signal itself. This can be useful in the case where the further radar sensor does not operate according to the same protocol as the radar sensor and does not transmit a beacon signal including information indicating the frequency range and / or timing pattern of the further transmission signal. Nevertheless, the radar sensor can be configured to determine the frequency range and / or timing pattern used by the further radar sensor based on the further transmission signal itself, and then select a frequency range and / or timing pattern within the predetermined frequency band for its own transmission signal that does not conflict with the frequency range and / or timing pattern used for the further transmission signal.

[0022] The transmission circuit may be further configured to output a beacon signal including information indicative of a frequency range and / or a timing pattern of the transmission signal prior to outputting the transmission signal.

[0023] The apparatus may be configured to delay output of said beacon signal for a random period of time.

[0024] Delaying the output of the beacon signal by a random period of time may be useful in reducing the likelihood of two different radar signals transmitting a beacon signal simultaneously.

[0025] The beacon signal may be output within the predetermined frequency band.

[0026] Therefore, it is not necessary to provide a dedicated signaling channel for the transmission of information between devices.In some embodiments, the beacon signal is transmitted at a predetermined frequency, such as a center frequency of a predetermined frequency band.

[0027] The beacon signal may be output within said frequency range selected by the apparatus for transmission of said transmission signal.

[0028] For example, a beacon signal may be transmitted at the center of the selected frequency range.Outputting a beacon signal within the selected frequency range may be useful in simplifying operation of the device.

[0029] The beacon signal may have a constant carrier frequency.

[0030] Information can be encoded in the beacon signal using xPSK or xFSK modulation.

[0031] The first part of the beacon signal may comprise information for synchronizing the radar sensor with the further radar sensor and the second part of the beacon signal comprises said information indicative of a frequency range and / or a timing pattern of the transmission signal.

[0032] Synchronizing the radar sensor with the further radar sensor may include determining a difference frequency between an internal clock frequency of the radar sensor and an internal clock frequency of the further radar sensor. The internal clock frequencies of the radar sensor and the further radar sensor may correspond to respective carrier frequencies of the transmission signal and the further transmission signal. Synchronizing the radar sensor with the further radar sensor may include determining a symbol frequency of the beacon signal.

[0033] In some embodiments, the beacon signal includes a third portion including information indicative of one or more frequency ranges and / or timing patterns used by one or more corresponding other radar sensors.

[0034] The receiving circuit may additionally include decoding circuitry for decoding the information from the beacon signal, wherein a carrier frequency of the received beacon signal is not synchronized with an internal clock frequency used by the receiving circuitry.

[0035] The decoding circuitry may include a digital demodulator and / or a Goertzel frequency bank.

[0036] The radar sensor may be configured to, upon receiving the beacon signal from the further radar sensor, decode the first portion of the beacon signal to synchronize the radar sensor with the further radar sensor, and then decode the second portion of the beacon signal.

[0037] The apparatus may further comprise a memory configured to store information indicative of a frequency range and / or a timing pattern of the further transmission signal transmitted by the at least one further radar sensor.

[0038] The beacon signal output by the transmission circuit may further include the information indicating the frequency range and / or timing pattern of the further radar signal. The information may include, for example, a start frequency and a frequency change (or a start frequency and a stop frequency), a scanning period and a duty cycle.

[0039] The apparatus may be configured to delete the information relating to the further radar sensor after being stored for a predetermined period of time.

[0040] The timing pattern may be defined at least in part based on a scan period, a duty cycle, and / or a start time of the transmission signal.

[0041] According to another aspect of the present disclosure, there is provided a radar sensor, comprising:

[0042] Radar transmission antenna;

[0043] radar receiving antenna; and

[0044] An apparatus as hereinbefore defined.

[0045] Radar sensors may be installed in or on road vehicles.

[0046] According to another aspect of the invention, there is provided a road vehicle comprising a radar sensor as defined above.

[0047] According to another aspect of the present invention, there is provided an IC for a radar sensor, the IC including a transmission circuit configured to generate a transmission signal with linear frequency chirp modulation in a predetermined frequency band for output to a radar antenna, and further configured to output a beacon signal including information indicating a frequency range and / or a timing pattern of the transmission signal for output to the radar antenna before outputting the transmission signal.

[0048] According to another aspect of the present invention, there is provided an IC for a radar sensor, the IC comprising a receiving circuit, the receiving circuit being configured to:

[0049] receiving a reflection signal corresponding to reflections of a radar signal transmitted by the radar sensor in a predetermined frequency band from one or more physical objects, and

[0050] Before transmitting the transmission signal by the radar sensor, a further signal from a further radar sensor is listened for, the further signal being a beacon signal transmitted in the predetermined frequency band, the beacon signal including information indicating a frequency range and / or a timing pattern used by the further radar sensor for transmission of the further transmission signal.

[0051] The IC may additionally include decoding circuitry for decoding the information from the beacon signal, wherein a carrier frequency of the beacon signal is not synchronized with an internal clock frequency used by the IC.

[0052] The decoding circuit may include a digital demodulator and / or a Goertzel frequency bank.

[0053] Embodiments of the present disclosure may use radar frequencies typically in the 76 GHz to 81 GHz range, but are not necessarily limited thereto. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A frequency modulated continuous wave (FMCW) radar sensor 100 is shown according to an embodiment of the present disclosure;

[0055] Figure 2 The embodiment according to the present disclosure includes Figure 1 A road vehicle with a radar sensor of the type shown;

[0056] Figure 3 An example scheme for time and frequency division multiplexing operation of multiple radar sensors according to an embodiment of the present disclosure is shown;

[0057] Figure 4 shows a signaling scheme for use with an apparatus 10 of a radar sensor 100 according to an embodiment of the present disclosure;

[0058] Figure 5 It shows that multiple sensors are connected to Figure 4 Use of a signaling scheme similar to that shown in ;

[0059] Figure 6 is a schematic diagram of a device for a radar sensor according to an embodiment of the present disclosure; and

[0060] Figure 7 is a schematic diagram of a device for a radar sensor according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0061] Figure 1 A frequency modulated continuous wave (FMCW) radar sensor 100 according to an embodiment of the present disclosure is shown. The radar sensor 100 includes a device 10, a radar transmission antenna 120, and a radar reception antenna 130. The device 10 includes: a transmission circuit 20, 30, which is configured to generate a transmission signal with linear frequency chirp modulation in a predetermined frequency band for output to the radar transmission antenna 120; and a reception circuit 30, 40, which is configured to receive a reflection signal corresponding to the reflection of the transmitted radar signal from one or more physical objects via the radar reception antenna 130. The device 10 further includes a control circuit 50 in communication with the transmission circuit 20, 30 and the reception circuit 30, 40. The control circuit 50 is configured to select a frequency range and / or a timing pattern within a predetermined frequency band for the transmission signal.

[0062] Figure 2 The embodiment according to the present disclosure includes Figure 1 1. A road vehicle 150 with a radar sensor 100 of the type shown in FIG. 1. The road vehicle may be, for example, a car, a van, a truck, a lorry, a motorcycle or any other type of road vehicle. As is known in the art, FMCW radar sensors can be used to obtain information (e.g., distance information, speed information) about objects located in the vicinity of the road vehicle incorporating the radar sensor. Objects may also typically be other road vehicles. Other road vehicles may also themselves include one or more FMCW radar sensors.

[0063] Figure 3 An example scheme for time and frequency division multiplexing operation of multiple such radar sensors 100 transmitting in the 76 GHz to 81 GHz frequency band is shown. The spectrum usage of five different radar sensors S1, S2, S3, S4 and S5 is represented by blocks occupying regions of frequency and time. For each block, the vertical position and height of the block indicates the frequency range used by the corresponding radar sensor, while the horizontal position and width of the block indicates the frequency range used in a single scanning period t 扫描 The time and duration of active transmission by the respective radar sensor in this frequency range.

[0064] In this example, each of sensors S1, S2, S3, S4, and S5 has a scanning period t 扫描 The scanning cycle is typically about 50 ms. As will be described later, it is possible to align or synchronize the scanning cycles of the various sensors S1, S2, S3, S4 and S5.

[0065] Typically, for short-range scanning requiring relatively high range resolution, only up to 4 GHz of transmission bandwidth is required. For long-range to medium-range scanning, lower range resolution is acceptable and the required bandwidth is typically 0.5 to 1 GHz. As a result, the frequency band can be divided into sub-bands, allowing simultaneous use by multiple sensors. Multiple frequency sub-bands can be used by several sensors simultaneously without interference. By controlling the chirp modulation, small headroom between frequency sub-bands can be maintained.

[0066] At the same time, the radar sensor typically transmits only during a portion of the scanning period. That is, the transmission period or CPI (coherent processing interval) of the radar sensor is longer than the scanning period t 扫描 Short. The duty cycle is usually up to 50% for the highest resolution scans, and typically between 20% and 30% for lower resolution scans. Typically, due to the tradeoff between range resolution (which increases with bandwidth) and Doppler resolution (which increases with scan time), shorter scan times are used for higher bandwidth scans, and vice versa. As a result, it is often possible to time-division multiplex any sub-band of the frequency band. For example, a 50% duty cycle allows two sensors to share the same frequency band, while a 30% duty cycle allows three sensors to share the same frequency band. The allocation of frequency bands to sub-bands can be changed during the scan cycle.

[0067] Figure 3The sensors S1 to S5 shown in the figure are all multi-mode sensors, capable of performing scans with more than one bandwidth to achieve different resolutions required. At the beginning of the scanning cycle, sensor S1 uses the 77-81 GHz frequency range or a sub-band of the 76 to 81 GHz frequency band to operate a short-range 4 GHz bandwidth scan. At the same time, sensor S3 uses the 76.5-77 GHz frequency range or sub-band to start a long-range 0.5 GHz bandwidth scan. Once the first scan of sensor S1 has been completed, sensors S2, S4 and S5 jointly use the 77-81 GHz frequency range previously used by sensor S1, and each starts a scan with a corresponding bandwidth of 2 GHz (frequency range 79-81 GHz), 1 GHz (frequency range 78-79 GHz) and 1 GHz (frequency range 77-78 GHz). After the 1 GHz bandwidth scan is completed by sensor S4 in the 78-79 GHz sub-band, the 78-79 GHz sub-band is reused for the 1 GHz bandwidth scan by sensor S1 and subsequently by sensor S5. After completing a 2 GHz bandwidth scan in the 79-81 GHz sub-band by sensor S2, a portion of this sub-band is used by sensor 3 which performs a 1 GHz bandwidth scan using the 79-80 GHz sub-band. Similarly, a 1 GHz bandwidth scan using the 77-78 GHz range by sensor S5 is followed by a 0.5 GHz scan using the 77.5-78 GHz frequency range by sensor S4. After performing a long-range 0.5 GHz bandwidth scan in the 76.5-77 GHz sub-band by sensor S3, this sub-band is reused by sensor S2 for another 0.5 GHz bandwidth scan. The above scheme is merely an example, and those skilled in the art will appreciate that many other subdivisions and allocations of the band in time and frequency are possible to avoid interference between multiple radar sensors. In some embodiments, sensors with high bandwidth and long duty cycle may be given higher priority than sensors with low bandwidth and short duty cycle.

[0068] In order to enable multiple radar sensors 100 to cooperatively allocate available frequency bands, the device 10 is configured to receive a further signal from another radar sensor (not shown), to determine from the further signal a frequency range and / or timing pattern used by the further radar sensor for transmission of a further transmission signal, and to select a frequency range and / or timing pattern within a predetermined frequency band for its own transmission signal that does not conflict with the frequency range and / or timing pattern used for the further transmission signal. For example, the device 10 may select a frequency sub-band different from the frequency sub-band used by the further radar sensor so that it uses a frequency range that does not overlap with the frequency range of the further radar sensor. Alternatively (or additionally), the device 10 may select a timing pattern different from the timing pattern used by the further radar sensor, for example by shifting the start of its active transmission period so that it does not overlap with the start of the active transmission period of the further radar sensor. As a result, interference between the two radar sensors can be eliminated.

[0069] Figure 4 A signalling scheme 300 is shown for use by the arrangement 10 of the radar sensor 100 in order to achieve an interference-free allocation of a predetermined frequency band. In this embodiment, in-band signalling is used.

[0070] Each sensor 100 following the signaling scheme 300 initially "listens" in a predetermined frequency band before it starts talking. This can be accomplished by simple, uncorrelated radar measurements and spectrum analysis. The listening time can be limited to a duration of approximately 1-2 scan cycles (e.g., 100ms).

[0071] If the predetermined frequency band or a portion thereof is found to be available, the device 10 generates a beacon signal 310 which is transmitted by the transmission antenna 120 of the radar sensor 100 at a time interval t 信标The carrier frequency of the beacon signal is within a predetermined frequency band. In some embodiments, the beacon signal carrier frequency is located at a predetermined frequency, such as at the center of the predetermined frequency band, or in the middle of a subband currently in use or expected to be used by the transmitting radar sensor 100. The beacon signal 310 can be transmitted at a predefined output power (e.g., 3 dBm). The first part 311 of the beacon signal 310 is a code synchronization part 311 for synchronizing the clock of the potential interfering radar sensor 100 (also referred to as "clock run in"). The code synchronization part 311 includes several a priori known symbols decoded by the remote radar sensor receiving the beacon signal 310 in order to synchronize with the radar sensor 100 transmitting the beacon signal 310. The clocks of different radar sensors 100 are unrelated, and therefore it is necessary to establish a certain degree of time synchronization in order to perform time-multiplex division of the scanning cycle. For the synchronized clock, high accuracy is not required. The radar sensors 100 can be loosely synchronized with each other, for example, about 1 ms, which provides sufficient accuracy for timing the time slots of the scanning cycle of about 50 ms. The second part 312 of the beacon signal 310 includes information indicating the frequency range and / or timing mode expected for the radar sensor 100 to use for its transmission signal. For example, the frequency range can be defined by a frequency start value and a range value. For example, the timing mode can be defined according to scanning parameters such as a scanning period, a duty cycle, and / or an active transmission start time. Additional information such as chirp duration, the number of chirps, output power, and other waveform details (e.g., up / down scanning) may also be included. The third part 313 of the beacon signal 310 includes entries 1...N of a service allocation table (SAT). The SAT is stored locally by the radar sensor 100 and includes parameters of other scans and other sensors detected by the radar sensor 100. The SAT is continuously updated by the radar sensor 100, and the entries have a maximum lifespan. Although not required, it is useful to broadcast entries of the SAT stored locally by the radar sensor 100 because it makes the sensor more easily discoverable by other radar sensors.

[0072] After transmitting beacon signal 310 , radar sensor 100 continues to use frequency range Δf φ included in second portion 312 of transmitted beacon signal 310 . b and / or timing mode, at time interval t 帧 The chirp sequence 320 is transmitted internally. Figure 4 The chirp sequence shown in is a FCM (Fast Chirp Modulation) sequence. 扫描 After completion, radar sensor 100 transmits another beacon signal 310 before starting the next chirp sequence.

[0073] Figure 5 The diagram shows the detection of the sensor by multiple sensors S1, S2 and S3. Figure 4 A signaling scheme similar to that shown in FIG. 1 is used. Initially, the sensor S1 is in the first sub-band of the predetermined frequency band at a scanning period t 扫描,S1 and approximately 50% duty cycle, while sensors S2 and S3 search for unallocated bandwidth and / or time in the same predetermined frequency band. Sensor S1 initially completes a period of listening 405a and then transmits a frame length t in the first subband. 帧,S1 Before the chirp sequence 420a, at a duration t 信标,S1 The beacon signal 410a includes a subband indicating the subband used by the sensor S1, a scanning period t 扫描,S1 and frame length t 帧,S1 During the broadcast of the beacon signal 410a, the other two sensors S2 and S3 listen in a predetermined frequency band and detect and decode the beacon signal 410a broadcast by sensor S1. The two sensors S2 and S3 update their respective SATs (Service Allocation Tables) to include the information decoded from the beacon signal 410a, and select a frequency range and timing pattern for their own transmission signals that does not conflict with the frequency range and timing pattern of sensor S1. In this example, each of sensors S2 and S3 determines that the duty cycle of sensor S1 is less than 50%, and therefore it can use the same frequency sub-band as sensor S1. Sensors S2 and S3 continue to listen for the entire duration of the chirp sequence 420a of sensor S1, and once sensor S1 is silent and for another random time period t rnd After that, it is ready to start broadcasting beacon signals. This random time period t rnd Arbitration between the two sensors S2 and S3 is provided on a first-come, first-served basis. In this case, sensor S2 uses a shorter random time period than S3 and therefore starts broadcasting the beacon signal 510 while sensor S3 is still in listening mode. The beacon signal 510 is broadcast at time interval t 信标,S2 is transmitted during the period and includes an indication of the subband to be used by sensor S2, the scanning period t 扫描,S2 and frame length t 帧,S2 The sensor S2 then transmits a frame with a length of t in the first sub-band (ie the same sub-band as used by the sensor S1). 帧,S2Since the chirp sequence 520 transmitted by sensor S2 does not overlap in time with the chirp sequence 420a transmitted by sensor S1, there is no interference between sensors S1 and S2. The beacon signal 510 transmitted by sensor S2 is detected and decoded by each of sensors S1 and S3. Both sensors S1 and S3 update their respective SATs to include information decoded from the beacon signal 510. Upon discovering the presence of sensor S2 using the same frequency sub-band, sensor S1 may adjust its scanning period. For example, sensor S1 may increase its own scanning period to enable sensor S2 to transmit in the same frequency sub-band, particularly where only a small increase is required. As an example, if sensor S2 transmits a beacon signal indicating its intent to transmit a chirp sequence with a 20 ms frame length, and sensor S1 is currently transmitting for a 31 ms frame length within a 50 ms scanning period, sensor S1 may increase its scanning period to 51 ms to allow both sensors S1 and S2 to transmit in the same frequency sub-band. Sensor S1 listens for the entire duration of S2's chirp sequence 520 and then begins its next scanning period by transmitting another beacon signal 410 b and its next chirp sequence 420 b. Meanwhile, upon decoding the beacon signal 520 broadcast by sensor S2, sensor S3 determines that the first sub-band used by sensors S1 and S2 is now fully allocated to S1 and S2. Therefore, sensor S3 selects a second sub-band or frequency range and switches to this second sub-band during a time interval 602 before initiating a period of listening 605 in the selected second sub-band. At the end of this listening period 605, sensor S3 switches to this second sub-band during a time interval t 信标,S3 The beacon signal 610 is transmitted during the period. The beacon signal 610 includes an indication of the sub-band to be used by the sensor S3 (ie, the second sub-band), a scanning period t 信标,S3 and frame length t 帧,S3 After transmitting the beacon signal 610, sensor S3 will transmit a chirp sequence in the selected second sub-band. The second sub-band used by sensor S3 does not overlap with the first sub-band used by sensors S1 and S2 and therefore does not cause any interference between the sensors.

[0074] Sensors S1, S2 and S3 may also detect transmission signals transmitted by radar sensors that do not operate according to the above scheme and therefore do not switch frequency sub-bands or timing patterns to avoid interference. In such cases, sensors S1, S2 and S3 may determine the frequency range and / or timing pattern in use by another sensor by spectral analysis of the transmission signal and select different frequency sub-bands and / or timing patterns accordingly to avoid or reduce interference.

[0075] The skilled person will appreciate that various methods can be used to encode information in the beacon signal. The beacon modulation method can be selected with regard to minimization of interference and simplicity of information encoding and recovery.

[0076] For example, BPSK (Binary Phase Shift Keying) and QPSK / QAM-4 (Quadrature Phase Shift Keying / Quadrature Amplitude Keying) are well suited for this application. Both are easy to implement using phase rotators in the transmission circuits 20, 30 of the device 10 that use constant power for each symbol, can use simple decoding mechanisms, and exhibit low interference to FCM (Fast Chirp Modulation) due to non-coherent integration. However, due to the phase offset between the transmitting and receiving radar sensors and the lack of frequency synchronization between the transmitting and receiving radar sensors, non-coherent demodulation must be performed in order to decode the information encoded in the beacon signal.

[0077] FSK (Frequency Shift Keying) is another choice for encoding the beacon signal because it is compatible with most transceiver implementations and even simple decoders with non-coherent detection. Although FSK is considered less robust than the PSK (Phase Shift Keying) method due to a higher error rate, this error rate can be mitigated by additional error coding (e.g., Viterbi) or by using a reduced data rate.

[0078] Figure 6 7 is a schematic diagram of an apparatus 700 for a radar sensor 100 according to an embodiment of the present disclosure. The apparatus 700 takes the form of a transceiver 700 that implements xPSK modulation / demodulation for transmission / reception of beacon signals. The transceiver 700 includes transmission circuits 720, 730, reception circuits 730, 740, and control circuits 750. The transceiver 700 may be implemented as a single IC (integrated circuit) or a group of ICs.

[0079] The transmission circuits 720, 730 and the reception circuits 730, 740 share a local oscillator (LO) 730. The local oscillator 730 includes a linear ramp generator 731, a constant voltage source 732, a chirped PLL (phase locked loop) 733 for stabilizing the frequency, and a VCO (voltage controlled oscillator) 734. The VCO 734 has an input configured to receive the output of the chirped PLL 733. The chirped PLL 733 includes a first input and a second input, the first input being arranged to selectively receive the output of the ramp generator 731 or the output of the constant voltage source 732, and the second input being connected to the output of the VCO 734. The frequency division coefficient of the chirped PLL 733 is selectively controlled according to the output of the ramp generator 731 or the output of the constant voltage source 732, so that the output of the VCO 734 has a correspondingly increased / decreased frequency for use in generating a frequency chirp for radar measurement, or has a constant frequency for use in generating a beacon signal.

[0080] The transmission circuit 720, 730 comprises a transmitter (TX) 720 including a phase rotator 721 having a first input arranged to receive the output of the VCO 734, and an RF power amplifier 722 having an input connected to the output of the phase rotator 721 and arranged to output a transmission signal to the radar antenna. The transmitter 720 further comprises a beacon data buffer 723 arranged to receive data from a processor 751 of a control circuit 750, a symbol encoder 724 having an input connected to the output of the beacon data buffer 723, and a D / A (digital-to-analog) converter 725 having an input connected to the output of the symbol encoder 724. The phase rotator 721 has a second input arranged to receive the output of the D / A converter 725. The phase rotator 721 may be, for example, a 1-bit phase rotator for enabling BPSK, or a 4-bit phase rotator for enabling QPSK / 4-QAM. Although only one transmission channel is shown, the apparatus 10 may include multiple transmitters 720 to provide multiple transmission channels and may be used for power combining.

[0081] The control circuit 750 in the form of an MCU 750 comprises a processor 751 (which may comprise a plurality of processor cores) and a memory 752 in the form of a RAM for storing a SAT (Service Allocation Table) 753. The control circuit 750 also comprises a digital demodulator 754 which will be described in more detail below. The control circuit 750 may be integrated with the transceiver circuits 720, 730, 740, or provided as a separate device. The processor 751 is configured to convert entries of the SAT 753 into beacon data which is transmitted during a beacon transmission period t 信标 Transferred to beacon data buffer 723 before start.

[0082] During the beacon transmission period, the chirp PLL 733 receives a constant voltage input from the constant voltage source 732, so that the chirp PLL 733 and the VCO 734 generate a fixed frequency of approximately the intermediate frequency band. The symbols preloaded in the beacon data buffer 723 are read and encoded by the symbol encoder 724 according to the details of the modulation scheme (e.g., DPSK). The encoded symbols output by the symbol encoder 724 are D / A converted by the D / A converter 725 and provided to the phase rotator 721. The phase rotator 721 shifts the phase of the signal output by the VCO 734 and provides the phase-shifted signal to the power amplifier 722, which in turn drives the transmission antenna. During the chirp transmission period t 帧 During this time, the chirp PLL 733 receives the ramp voltage input from the voltage ramp generator 731, and the transmission circuits 720, 730 generate a chirp sequence as is well known in the art.

[0083] The receiving circuit 730, 740 includes a receiver (RX) 740, which includes: an input amplifier / impedance converter 741 having an input arranged to receive a signal from a radar antenna; an input mixer 742 having a first input connected to the output of the input amplifier / impedance converter 741 and a second input connected to the output of the VCO 734 of the local oscillator 730; a programmable gain amplifier 743 having an input connected to the output of the input mixer 742; a high pass / anti-aliasing filter 744 having an input connected to the output of the programmable gain amplifier 743; and an A / D (analog-to-digital) converter 745 having an input connected to the output of the high pass / anti-aliasing filter 744. The A / D converter 745 outputs a digital signal to a digital demodulator 754 of a control circuit or MCU 750. Although only one receive channel is shown, the device 700 may include multiple receivers 740 to provide multiple receive channels, and the combined signals from all receive channels may be used to improve sensitivity.

[0084] When beacon signals are received from different radar sensors, the detection is incoherent. This is because the frequency of the VCO output of the transmitting radar sensor is not synchronized with the frequency of the VCO 734 output of the receiving radar sensor 700. However, the frequencies of the two radar sensors are sufficiently stable over the duration of the beacon transmission period so that the difference between the frequency and phase is approximately constant. Typically, the frequency difference between the VCO frequencies of the two radar sensors is expected to be approximately a few MHz and approximately stable within a few milliseconds. This is ensured by the high performance requirements of the transceiver (high linearity, low phase noise) and the fact that the chirp PLL of each radar sensor implements an exact multiple of the local crystal oscillator (XTAL) frequency with a constant value during the chirp (typically accurate to better than + / -50ppm). In contrast to the strict requirements for the measurement signal (chirp sequence), the beacon signal can require only one stable frequency for PSK or several stable frequencies for FSK. Furthermore, the beacon period may be a few milliseconds (eg, 2 ms), which is only a fraction of the time required for measurement (eg, 20 ms), thus enforcing the frequency stability requirement on the beacon signal in a much shorter time.

[0085] Outside of its active transmission time, the device 700 switches to a listening mode and a constant frequency is generated by the chirp PLL 733 and VCO 734, with the chirp PLL 733 receiving a constant voltage at its first input from the constant voltage source 732. Since there is no simple way to synchronize the VCO frequencies of the transmitting and receiving radar sensors, the filtered baseband signal output by the high pass / anti-aliasing filter 744 of the receiver 740 will be a combination of the message signal (i.e., the content of the beacon signal) and the difference frequency signal, i.e., the filtered baseband signal will be scrambled by cos(2π·Δf·t+p0 -pm(t)), where Δf is the difference between the VCO frequencies of the local (receive) and remote (transmit) radar sensors, and p 0 Is a constant phase shift, and pm (t) is a phase shift that encodes the message symbol. That is, the xPSK reception constellation diagram rotates effectively at the rate of the difference frequency, and the symbol rate is not precisely known. Therefore, additional demodulation occurs in the digital domain. The decoded packet information output by the digital demodulator 754 can be processed by the processor 751 of the MCU 750. Complex (I / Q) demodulation is used to avoid phase ambiguity. Carrier recovery requires several a priori known symbols to synchronize the local carrier frequency. It is also required that these known symbols included in the first part 311 of the beacon signal 310 are used to extract symbol timing. Differential coding techniques (DBPSK, DQPSK) can be used. By encoding the symbol of the beacon signal as the difference between the current message symbol and the next message symbol, the need for phase synchronization between the local receiving radar sensor and the remote transmission radar sensor is eliminated. Carrier recovery requires several a priori known symbols to synchronize the local carrier frequency. It is also required that these known symbols included in the first part 311 of the beacon signal 310 are used to extract symbol timing.

[0086] Digital demodulator 754 determines the frequency offset Δf from clock operation 311 with known symbols and generates a sin / cos waveform for mixing with the filtered baseband signal, producing s dm = cos(pm(t)-p0)+j sin(pm(t)-p0), which directly gives for t = kT s The discrete pm(t) of the beacon signal includes a sequence of complex symbols, where 1 / T s is the symbol rate, or in calculating s dm,dk =s dm,k –s dm,k -1 is followed by differential encoding.

[0087] The digital demodulator 754 includes a CRI block 755 that receives the digital output from the A / D converter 745. The CRI block 755 detects the clock run with a known symbol (i.e., the first portion 311 of the beacon signal 310) and sends it to the carrier recovery block 756. The carrier recovery block 756 is trained by the clock run and determines the difference frequency Δf so that the symbol sequence best matches the symbol value from the symbol space. After this loop is locked, the symbol timing extraction block 757 determines the optimal symbol timing for low inter-symbol interference, and this optimal symbol timing is used by the symbol decoder block 758 to extract the symbol from the output of the CRI block 755. Typically, this can be simplified by oversampling with the A / D converter 745 to obtain several samples for the same symbol. Optimally, the sampling frequency A / D converter 745 is controlled to be an exact multiple of the symbol rate, such as 4*1 / T s The word packer block 759 packs the extracted symbols output by the symbol decoder block 758 into words, and the words are provided to the CPU 751 for evaluation. The CPU 751 updates the local SAT 753 with the received data. The digital demodulator 754 may be implemented on a DSP (digital signal processor).

[0088] Figure 7 8 is a schematic diagram of an apparatus 800 for a radar sensor 100 according to yet another embodiment of the present disclosure. The apparatus 800 takes the form of a transceiver 800 that implements xFSK modulation / demodulation for transmission / reception of a beacon signal. The transceiver 800 includes transmission circuits 820, 830, reception circuits 830, 840, and a control circuit 850. The transceiver 800 may be implemented as a single IC (integrated circuit) or a group of ICs.

[0089] The transmission circuits 820, 830 and the reception circuits 830, 840 share a local oscillator 830. The local oscillator 830 includes a linear ramp generator 831, a constant voltage source 832, a chirped PLL 833, a VCO 834 having an input arranged to receive the output of the chirped PLL 833, and a summing node 835 having one of its two inputs connected to the output of the constant voltage source 832. The chirped PLL 833 includes a first input arranged to selectively receive the output of the ramp generator 831 or the output of the summing node 835. The second input of the chirped PLL 833 is connected to the output of the VCO 834. The division factor of the chirp PLL 833 is selectively controlled according to the output of the ramp generator 831 or the output of the constant voltage source 832 so that the output of the VCO 834 has a correspondingly increasing / decreasing frequency for use in generating a frequency chirp for radar measurement, or has a constant frequency for use in generating a beacon signal.

[0090] The transmission circuits 820, 830 include a transmitter 820 (including a phase rotator 821 having an output arranged to receive a VCO 834) and an RF power amplifier 822 connected to the output of the phase rotator 821 and arranged to output a transmission signal to the radar antenna. The transmitter 820 further includes a beacon data buffer 823 arranged to receive beacon data from a processor 851 of the transmission circuit 850, a symbol encoder 824 having an input connected to the output of the beacon data buffer 823, and a D / A converter 825 having an input connected to the output of the symbol encoder 824, operating as discussed in conjunction with the corresponding elements of the previous embodiment. In this xFSK implementation, the phase rotator 821 is not used for beacon transmission. That is, a constant phase is used. Instead, the output of the D / A converter 825 is received at the second input of the summing node 835. In this way, the symbol of the beacon data is encoded into the beacon signal as a frequency step. The constant voltage source 832 controls the center frequency of the beacon signal. During the beacon transmission period t 信标 During this time, the chirped PLL 833 and VCO 834 thus generate a beacon signal centered at a fixed frequency determined by the constant voltage source 832 and encoding symbols as frequency shifts. The frequency shifted signal output by the VCO 834 receives a fixed phase shift from the phase rotator 821 and is amplified by the power amplifier 822, which in turn drives the transmit antenna.

[0091] The control circuit or MCU 850 includes a memory 852 in the form of a RAM for storing a SAT (Service Allocation Table) 853 and a CPU 851 configured to convert the entries of the SAT into beacon data, which is transmitted to the beacon data buffer 823 before the start of the beacon transmission period. The control circuit 850 also includes a digital demodulator 860, which will be described in more detail below. The MCU 850 can be integrated with the transceiver circuits 820, 830, 840, or provided as a separate device. Although only one transmission channel is shown, multiple transmission channels can be provided and can be used for power combining.

[0092] The receiving circuits 830, 840 include a receiver 840 including an input amplifier / impedance converter 841, an input mixer 842, a programmable gain amplifier 843, a high pass / anti-aliasing filter 844, and an A / D converter 845 arranged as corresponding elements for the previous embodiments. The A / D converter 845 outputs a digital signal to a digital demodulator 860 implemented in a control circuit or MCU 850. Although only one receive channel is shown, multiple receive channels may be provided and the combined signals from all receive channels may be used to increase sensitivity.

[0093] As above combined Figure 5As described in the embodiment shown in , the detection of beacon signals from different radar sensors is incoherent, the frequency difference between the VCO frequencies of the two radar sensors is typically in the order of a few MHz and is approximately stable within a few milliseconds.

[0094] Outside of its active transmission time, the device 800 switches to a listening mode and a chirp PLL 833 and VCO 834 generate a constant frequency, the chirp PLL 833 receiving a constant voltage from a constant voltage source 832 via a summing node 835 at its first input. The frequency steps in the received signal output by the A / D converter 845 are decoded into symbols by a Goertzel filter bank or by a related method. In the digital demodulator, the offset estimation block 861 uses the clock-running sequence of known symbols (i.e., the first part 311 of the received beacon signal) to determine the difference Δf between the VCO frequencies of the local (receiving) and remote (transmitting) radar sensors. This offset estimate is used to adjust the filter bank in the Goertzel filter bank block 862. The symbol timing extraction block 863 recovers the symbol timing from the clock-running portion of the beacon signal. The symbols encoded in the beacon signal are then captured from the filter bank block 862 and are packaged into words by the word packer block 864 using the symbol timing output by the symbol timing extraction block 863. The output of the word packer block 864 is provided to the CPU 851 for evaluation. The CPU 851 updates the local SAT 853 with the received data. The digital receiver 860 may be implemented on a DSP (Digital Signal Processor).

[0095] While specific embodiments of the present disclosure have been described, it will be appreciated that numerous modifications, additions and / or substitutions may be made within the scope of the claims.

Claims

1. A device for a radar sensor, characterized in that: include: a transmission circuit configured to generate a transmission signal with linear frequency chirp modulation in a predetermined frequency band for output to a radar antenna, and receiving circuitry configured to receive reflection signals corresponding to reflections of the transmitted radar signal from one or more physical objects, and a control circuit configured to select a frequency range and / or a timing pattern within the predetermined frequency band for the transmission signal; The device is configured to: receiving an additional signal from an additional radar sensor; determining from the further signal a frequency range and / or a timing pattern used by the further radar sensor for transmission of a further transmission signal; and selecting a frequency range and / or timing pattern for said transmission signal within said predetermined frequency band that does not conflict with a frequency range and / or timing pattern for said further transmission signal; wherein the transmission circuit is further configured to output a beacon signal before outputting the transmission signal, the beacon signal including information indicating a frequency range and / or a timing pattern of the transmission signal; wherein the apparatus further comprises: a memory configured to store information indicative of a frequency range and / or a timing pattern of the further transmission signal transmitted by the further radar sensor; The beacon signal output by the transmission circuit further comprises information indicative of a frequency range and / or a timing pattern of the further radar signal.

2. The device according to claim 1, characterized in that The receive circuit is configured to listen for the further signal from the further radar sensor before the transmit circuit outputs the transmit signal.

3. The device according to claim 1 or 2, characterized in that: The further signal received from the further radar sensor is a further beacon signal transmitted in the predetermined frequency band, the further beacon signal comprising information indicative of a frequency range and / or a timing pattern of the further transmission signal.

4. The device according to claim 1, characterized in that The apparatus is configured to delay output of the beacon signal for a random period of time.

5. The device according to claim 1, characterized in that The beacon signal is output within the predetermined frequency band.

6. The device according to claim 5, characterized in that The beacon signal is output within the frequency range selected by the device for transmission of the transmission signal.

7. A radar sensor, characterized in that: include: Radar transmission antenna; Radar receiving antenna; and A device according to any one of claims 1 to 6.

8. An IC for a radar sensor, characterized in that: The IC includes: a transmission circuit configured to generate a transmission signal with linear frequency chirp modulation in a predetermined frequency band for output to a radar antenna, and further configured to generate a beacon signal including information indicating a frequency range and / or a timing pattern of the transmission signal for output to the radar antenna before outputting the transmission signal; a memory configured to store information indicative of a frequency range and / or a timing pattern of an additional transmission signal transmitted by the additional radar sensor; and a control circuit configured to configure the beacon signal based on the information stored in the memory so that the beacon signal output by the transmission circuit additionally includes information indicative of a frequency range and / or a timing pattern of the additional radar signal; Wherein the transmission circuit is configured to generate the transmission signal having a frequency range and / or timing pattern within the predetermined frequency band selected not to conflict with a frequency range and / or timing pattern used for the further transmission signal.

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