EVALUATION DEVICE AND METHOD FOR EVALUATING AT LEAST ONE RADAR SENSOR

Description

[0001] The invention relates to an evaluation device for at least one radar sensor and a radar device. Furthermore, the invention relates to a method for evaluating at least one radar sensor. State of the art

[0002] The use of radar sensors for environmental detection is known from the prior art. For example, DE 10 2016 221 947 A1 describes a radar sensor for motor vehicles for detecting the respective vehicle surroundings. Techniques for evaluating the measurement signals of such a radar sensor are described, for example, in DE 10 2013 210 256 A1, EP 3 098 623 A1, DE 10 2014 212 281 A1, EP 3 173 812 A1, and DE 10 2016 202 112 A1. Disclosure of the invention

[0003] The invention provides an evaluation device for at least one radar sensor having the features of claim 1, a radar device having the features of claim 3 and a method for evaluating at least one radar sensor having the features of claim 5. Advantages of the invention

[0004] The present invention provides possibilities for evaluating at least one radar sensor whose measurement cycles are each interrupted by an intervening pause time. Despite adhering to the pause times, the present invention enables "uninterrupted observation" of the radar sensor's surroundings over at least two measurement cycles. This can also be described as increasing the "integration time" when evaluating the at least one radar sensor using the present invention. The present invention therefore results in improved Doppler resolution and a higher signal-to-noise ratio (SNR) when evaluating the at least one radar sensor. This also results in increased sensitivity and / or a greater range when evaluating the at least one radar sensor using the present invention.The advantages described here can be realized by means of the present invention without having to shorten the break times or reduce the degree of utilization.

[0005] In an advantageous embodiment of the evaluation device, the electronic device is designed to perform the Fourier transformation with respect to a Doppler effect-relevant quantity using the evaluation signals derived from the measurement signals from at least two different measurement cycles. As will become clear from the further description, the embodiment of the evaluation device described here therefore enables an improvement in the Doppler separation capability during the evaluation of the at least one radar sensor.

[0006] The advantages described above are also achieved in a radar device with such an evaluation device and the at least one radar sensor. For example, the at least one radar sensor can be an FMCW radar sensor and / or a JSFMCW radar sensor. Thus, these advantageous sensor types can also be used to implement the present invention.

[0007] Furthermore, implementing a corresponding method for electronically evaluating at least one radar sensor also provides the advantages already described above. The method for evaluating at least one radar sensor can easily be further developed to achieve the advantages of the above-described embodiments of evaluation devices and radar units. Short description of the drawings

[0008] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1a to 1c show functional diagrams for explaining an embodiment of the method for evaluating at least one radar sensor; and Fig. 2 shows a schematic representation of an embodiment of the evaluation device or the radar device formed therewith. Embodiments of the invention

[0009] Fig. 1a bis 1c show functional diagrams for explaining an embodiment of the method for evaluating at least one radar sensor.

[0010] The method described below can be implemented to evaluate a plurality of radar sensors. For example, only a single radar sensor is evaluated using the method described below. Preferably, the respective radar sensor is used to determine information relating to at least a partial environment of the radar sensor. The respective radar sensor can, for example, be part of a monitoring system and / or part of a vehicle guidance system.

[0011] In the method described here, the radar sensor is, for example, an FMCW radar sensor (Frequency Modulated Continuous Wave Radar Sensor), in particular a JSFMCW radar sensor (Joint Sampling Frequency Modulated Continuous Wave Radar Sensor). Such a radar sensor is very efficient in terms of its resources and allows good resolution of ambiguities. The advantages of FMCW radar sensors, or JSFMCW radar sensors, can thus be used together with the advantages of the method described below. However, the feasibility of the method described below is not limited to the use of one of these radar sensor types. For example, the radar sensor can also be an OFDM radar sensor (Orthogonal Frequency-Division Multiplexing Radar Sensor) or a PN radar sensor (Pseudo-random Noise Radar Sensor).

[0012] The radar sensor transmits radar signals 12 during its measuring cycles 10, each with a measuring cycle time / measuring cycle duration Δt m. Likewise, the radar sensor receives radar signals 14 reflected from its surroundings during its measuring cycles 10 and outputs signals corresponding to the received reflected radar signals 14 as measuring signals. In the functional diagram of the Fig. 1b and 1c the respective coordinate system has the time axis t as abscissa, while its ordinate represents time-dependent frequencies f(t) of the radar signals 12 emitted by the radar sensor and the radar signals 14 reflected by its surroundings.

[0013] The radar sensor is designed to execute chirp sequence modulation (Chirp Sequence Modulation) such that a plurality of chirps 16, preferably at least 100 chirps 16, are executed during a single measurement cycle 10 with the measurement cycle time Δt m . The measurement cycle time Δt m is between 1 ms (milliseconds) and 40 ms (milliseconds). The measurement cycle time Δt m can be, for example, 20 ms (milliseconds).

[0014] Between two subsequent measuring cycles 10, the radar sensor remains inactive for a specified pause time / pause duration Δt b. The pause time Δt b is preferably selected such that component heating of the radar sensor is prevented by the pause time Δt b observed between each two subsequent measuring cycles 10. The pause time Δt b is between 5 ms (milliseconds) and 100 ms (milliseconds). The sum of the measuring cycle time Δt m and the pause time Δt b results in a total cycle time / total cycle duration ΔT. A quotient of the measuring cycle time Δt m divided by the total cycle time ΔT is often referred to as a duty cycle.

[0015] The measurement signals output by the radar sensor preferably represent frequency differences between the radar signals 12 emitted by the radar sensor and the radar signals 14 reflected by its surroundings. These frequency differences are composed of a distance-dependent component and a relative speed-dependent / Doppler effect-induced component. The distance-dependent component indicates the respective distance from the radar sensor of at least one object in the surroundings reflecting the emitted radar signals 12. Accordingly, the relative speed-dependent component indicates the respective relative speed at which the at least one object is moving relative to the radar sensor.

[0016] Using the method described below, the radar sensor's measurement signals are evaluated, with a Fourier transformation being performed using evaluation signals derived from the measurement signals from at least two different measurement cycles 10. This is explained in more detail below: In the method described here, first, a Fourier transformation 18 is performed for each chirp 16 of at least two different measurement cycles 10 with respect to the baseband frequency f B . In this way, a plurality of Fourier series 20 are defined for each measurement cycle 10 of the at least two different measurement cycles 10. A total number of defined Fourier series 20 per measurement cycle 10 of the at least two different measurement cycles 10 thus corresponds to a total number of chirps 16 per measurement cycle 10.

[0017] The Fourier transforms 18 with respect to the baseband frequency f B can also be referred to as fast Fourier transforms 18 (Fast Fourier Transformations, FFT). The Fourier series 20 determined by means of the fast Fourier transforms 18 all have the same total number of bins. The Fourier transforms 18 with respect to the baseband frequency f B result in a "spanning of a first dimension f B " with respect to the respective distance of the at least one reflecting object in the vicinity of the radar sensor. The at least one reflecting object in the vicinity of the radar sensor each causes a peak P1 in the determined Fourier series 20, although peaks P1 of objects at the same distance from the radar sensor can overlap despite their different relative velocities.

[0018] In another in Fig. 1b In the method step shown schematically, for each measuring cycle 10 of the at least two different measuring cycles 10, a further Fourier transformation 22 is carried out with respect to a Doppler frequency f D using the plurality of Fourier series 20 defined for the respective measuring cycle 10. This further Fourier transformation 22 can also be described as a group of one Fourier transformation 22 for each bin of the plurality of Fourier series 20 of the respective measuring cycle 10. In this way, a two-dimensional Fourier array 24 is defined for the respective measuring cycle 10. The functional diagram of the Fig. 1b thus represents a two-dimensional fast Fourier transform, a so-called 2D FFT. A first dimension f B of the two-dimensional Fourier array 24 defined in this way is the respective distance of the at least one reflecting object in the vicinity of the radar sensor, while a second dimension f D of the two-dimensional Fourier array 24 represents the respective relative speed of the at least one reflecting object in the vicinity of the radar sensor. The two-dimensional Fourier array 24 defined for each measurement cycle 10 can also be referred to as a 2D spectrum of the respective measurement cycle 10. The at least one reflecting object in the vicinity of the radar sensor also causes a peak P2 in the two-dimensional Fourier array 24. Overlapping peaks P2 in the two-dimensional Fourier array 24 can be corrected using the method step described below:

[0019] The functional diagram of the Fig. 1c shows, as a further method step, the Fourier transformation 26, which is carried out using the two-dimensional Fourier arrays 24 derived from the measurement signals from at least two different measurement cycles 10. The Fourier transformation 26 is carried out with respect to a Doppler effect-relevant quantity f 3 , wherein a fast Fourier transformation (FFT) is preferably carried out for each bin of the two-dimensional Fourier arrays 24. In this way, a three-dimensional Fourier matrix 28, or a so-called 3D FFT, is obtained for a specific number of evaluated measurement cycles 10. The Fourier transformation 26 thus extends the previously defined two-dimensional Fourier arrays 24 by a third dimension with respect to the Doppler effect-relevant quantity f 3 . The third dimension can be calculated for any possible relative velocity.Depending on the dimensioning of the radar parameters, it may be advantageous to account for the changing range of the target across the measurements. Preferably, the third dimension is spanned for each bin of the two-dimensional Fourier arrays 24.

[0020] The number of measurement cycles 10 from whose two-dimensional Fourier arrays 24 the three-dimensional Fourier matrix 28 is determined can, for example, be between 2 and 15. Preferably, the number of measurement cycles 10 evaluated to determine the three-dimensional Fourier matrix 28 is between 5 and 10.

[0021] Since the data for creating the three-dimensional Fourier matrix 28 originates from at least two different measurement cycles 10, the three-dimensional Fourier matrix 28 enables observation of the at least one reflective object in the vicinity of the radar sensor over a so-called integration time T total , which extends from the beginning of the earliest of the at least two different measurement cycles 10 to the end of the last of the at least two different measurement cycles 10. The integration time T total is thus significantly longer than the measurement cycle time Δt m or the total cycle time ΔT. The method described here thus allows "uninterrupted observation" of the at least one reflective object in the vicinity of the radar sensor for a period of time equal to the integration time T total , without the radar sensor having to perform measurements for the entire integration time T total .This allows the radar sensor to be inactive at least once during the integration time T total for the pause time Δt b , while the three-dimensional Fourier matrix 28 still displays information about the at least one reflecting object in the vicinity of the radar sensor, as if the radar sensor were continuously measuring during the entire integration time T total . The integration time T total can easily be selected to be so long that an uninterrupted measurement cycle over such a long period would pose a high risk of overheating of the radar sensor.

[0022] The method described here thus allows for "uninterrupted observation" of the at least one reflecting object in the vicinity of the radar sensor, even for a long integration time T total , without the risk of overheating the radar sensor. Instead, a desired temperature of the radar sensor can be easily maintained by means of the at least one pause time Δt b during the integration time T total . At the same time, the "uninterrupted observation" for the relatively long integration time T total enables a good signal-to-noise ratio (SNR) and improved separation of the individual objects in the vicinity of the radar sensor compared to the state of the art, thus reliably avoiding ambiguities.In particular, the so-called third dimension with respect to the Doppler effect-relevant quantity f3 ensures improved separation of multiple targets based on their differences in the third dimension, and thus also increased Doppler separation capability. The at least one reflecting object in the vicinity of the radar sensor also causes a peak P3 in the three-dimensional Fourier matrix 28, whereby an overlap of peaks P3 of different objects cannot or hardly occurs.

[0023] It should be noted that the advantages described above are also guaranteed when maintaining a comparatively long pause time Δt b between two subsequent measurement cycles 10, or at a relatively low duty cycle. Therefore, using the method described here, the "uninterrupted observation" of the at least one reflecting object in the vicinity of the radar sensor can be extended while maintaining the pause time Δt b and the duty cycle. At the same time, the radar sensor can cool down sufficiently during the pause time Δt b maintained between the measurement cycles 10, so that overheating of the radar sensor is not a concern.

[0024] The three-dimensional Fourier matrix 28 can also be determined using a "sliding discrete Fourier transform" (sliding DFT). For this purpose, after each measurement cycle 10, the measured values ​​of the "oldest measurement cycle 10" from a previously defined three-dimensional Fourier matrix 28 can be replaced by the measured values ​​of the "most recent measurement cycle 10," possibly using a phase term for correction. In this way, the computing time for determining the three-dimensional Fourier matrix 28 can be significantly reduced. To reduce computational effort, the third dimension of the three-dimensional Fourier matrix 28 can also be determined only for relative velocities considered particularly relevant.

[0025] Fig. 2 shows a schematic representation of an embodiment of the evaluation device or the radar device formed therewith.

[0026] The Fig. 2 The schematically illustrated evaluation device 30 is designed to interact with at least one radar sensor 32. The respective radar sensor 32 is configured to emit radar signals 12 during its measuring cycles and to receive radar signals 14 reflected from an environment (not shown) of the radar sensor 32 and to output measurement signals 34 corresponding to the received reflected radar signals, while the radar sensor 32 remains inactive for a predetermined pause time between two subsequent measuring cycles. The at least one radar sensor 32 interacting with the evaluation device 30 can be, for example, an FMCW radar sensor (Frequency Modulated Continuous Wave Radar Sensor), a JSFMCW radar sensor (Joint Sampling Frequency Modulated Continuous Wave Radar Sensor), an OFDM radar sensor (Orthogonal Frequency-Division Multiplexing Radar Sensor) and / or a PN radar sensor (Pseudo-random Noise Radar Sensor).However, the applicability of the evaluation device 30 is not limited to these radar sensor types.

[0027] The evaluation device 30 has an electronic device 36 designed to evaluate measurement signals 34 from the radar sensor 32. In particular, the electronic device 36 is designed to perform a Fourier transformation using measurement signals 34 from at least two different measurement cycles and / or using evaluation signals derived from the measurement signals 34 from at least two different measurement cycles. Preferably, the electronic device 36 is designed to perform this Fourier transformation with respect to a Doppler effect-relevant quantity.

[0028] As is clear from the preceding description, the electronic device 36 can be designed, in particular, to perform a Fourier transform with respect to a baseband frequency for each chirp of the at least two different measurement cycles and, in this way, to define a plurality of Fourier series for each measurement cycle of the at least two different measurement cycles. Subsequently, the electronic device 36 can perform a further Fourier transform with respect to a Doppler frequency for each measurement cycle of the at least two different measurement cycles using the plurality of Fourier series defined for the respective measurement cycle and, in this way, to define a 2-dimensional Fourier array for each measurement cycle.The Fourier transformation performed using the evaluation signals derived from the measurement signals 34 from at least two different measurement cycles is then performed using the 2-dimensional Fourier arrays of the at least two different measurement cycles. Specifically, the method described above can be implemented using the electronic device 36.

[0029] In the embodiment of the Fig. 2 the evaluation device 30 is part of a radar device 38 formed with the at least one radar sensor 32. However, the evaluation device 30 can also interact (as a "separate device") with at least one radar sensor formed separately therefrom.

Claims

1. Evaluation device (30) for at least one radar sensor (32), wherein the radar sensor (32) is designed, during its measurement cycles (10), to emit radar signals (12) by emitting a plurality of chirps (16) during each individual measurement cycle (10) with a measurement cycle time (Δtm) of between 1 millisecond and 40 milliseconds and to receive radar signals (14) reflected from an environment of the radar sensor (32) and to output signals corresponding to the received reflected radar signals (14) as measurement signals (34), while the radar sensor (32) remains inactive between two subsequent measurement cycles (10) for a predefined pause time (Δtb), comprising: an electronic unit (36) designed to evaluate measurement signals (34) of the radar sensor (32); characterized in that the electronic unit (36) is designed: - for each chirp (16) of at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10), to carry out a respective first Fourier transformation (18) with respect to a baseband frequency (fB) and in this way to define in each case a plurality of Fourier series (20) for each measurement cycle (10) of the at least two different measurement cycles (10), - for each measurement cycle (10) of the at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10), to carry out a respective further, second Fourier transformation (22) with respect to a Doppler frequency (fD) using the plurality of Fourier series (20) defined for the respective measurement cycle (10), and in this way to define a respective 2-dimensional Fourier array (24) for the respective measurement cycle (10), and - to carry out a further, third Fourier transformation (26) using evaluation signals (24) derived from the measurement signals (34) from the at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10), wherein the derived evaluation signals (24) are the 2-dimensional Fourier arrays (24) of the at least two different measurement cycles (10).

2. Evaluation device (30) according to Claim 1, wherein the electronic unit (36) is designed to carry out the third Fourier transformation (26) with respect to a Doppler effect-relevant variable (f3) using the evaluation signals (24) derived from the measurement signals (34) from the at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10).

3. Radar instrument (38) comprising: an evaluation device (30) according to either of the preceding claims; and the at least one radar sensor (32).

4. Radar instrument (38) according to Claim 3, wherein the at least one radar sensor (32) is in each case an FMCW radar sensor and / or a JSFMCW radar sensor.

5. Method for the electronic evaluation of at least one radar sensor (32) which, during its measurement cycles (10), emits radar signals (12) by emitting a plurality of chirps (16) during each individual measurement cycle (10) with a measurement cycle time (Δtm) of between 1 millisecond and 40 milliseconds and receives radar signals (14) reflected from an environment of the radar sensor (32) and outputs signals corresponding to the received reflected radar signals (14) as measurement signals (34), but remains inactive between two subsequent measurement cycles (10) for a predefined pause time (Δtb), wherein measurement signals (34) of the radar sensor (32) are evaluated; characterized in that for each chirp (16) of at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10), a respective first Fourier transformation (18) with respect to a baseband frequency (fB) is carried out and in this way in each case a plurality of Fourier series (20) are defined for each measurement cycle (10) of the at least two different measurement cycles (10), for each measurement cycle (10) of the at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10), a respective further, second Fourier transformation (22) with respect to a Doppler frequency (fD) is carried out using the plurality of Fourier series (20) defined for the respective measurement cycle (10), and in this way a respective 2-dimensional Fourier array (24) is defined for the respective measurement cycle (10), and a further, third Fourier transformation (26) is carried out using evaluation signals (24) derived from the measurement signals (34) from the at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10), wherein the 2-dimensional Fourier arrays (24) of the at least two different measurement cycles (10) are used as derived evaluation signals (24) .

6. Method according to Claim 5, wherein the third Fourier transformation (26) is carried out with respect to a Doppler effect-relevant variable (f3) using the evaluation signals (24) derived from the measurement signals (34) from the at least two different measurement cycles (10) with the pause time (Δtb) of between 5 milliseconds and 100 milliseconds between each two subsequent measurement cycles from the at least two measurement cycles (10).