阅读说明：本技术 雷达装置和用于产生不同方向特性的方法 (Radar apparatus and method for generating different directional characteristics ) 是由 P·舍茨 于 2019-08-01 设计创作，主要内容包括：本发明涉及一种雷达装置(10),其具有至少一个天线(11),该天线具有取决于频率的方向特性(12)。雷达装置(10)包括发射器电路(13),其被设计为产生具有第一中心频率的第一FMCW频率斜坡(14)和具有不同于第一中心频率的第二中心频率的至少一个第二FMCW频率斜坡(15)。发射器电路(13)被设计为,利用第一FMCW频率斜坡(14)和第二FMCW频率斜坡(15)驱控至少一个天线(11),以便利用第一FMCW频率斜坡产生至少一个天线(11)的第一方向特性(12-1)和利用第二FMCW频率斜坡产生至少一个天线的不同的第二方向特性(12-2)。因此可以利用所谓的天线斜视效应来提高角分辨率。(The invention relates to a radar device (10) having at least one antenna (11) with a frequency-dependent directional characteristic (12). The radar device (10) comprises a transmitter circuit (13) designed to generate a first FMCW frequency ramp (14) having a first center frequency and at least one second FMCW frequency ramp (15) having a second center frequency different from the first center frequency. The transmitter circuit (13) is designed to actuate the at least one antenna (11) using a first FMCW frequency ramp (14) and a second FMCW frequency ramp (15) in order to produce a first directional characteristic (12-1) of the at least one antenna (11) using the first FMCW frequency ramp and a different second directional characteristic (12-2) of the at least one antenna using the second FMCW frequency ramp. The so-called antenna squint effect can thus be utilized to improve the angular resolution.)

1. A radar apparatus (10; 60; 70) comprising:

at least one antenna (11) having a frequency-dependent directional characteristic (12);

a transmitter circuit (13) designed to generate a first FMCW frequency ramp (14) having a first center frequency and at least one second FMCW frequency ramp (15) having a second center frequency different from the first center frequency, and for driving the at least one antenna (11) with the first FMCW frequency ramp (14) and the second FMCW frequency ramp (15) to generate a first directional characteristic (12-1) of the at least one antenna (11) with the first FMCW frequency ramp and a different second directional characteristic (12-2) of the at least one antenna with the second FMCW frequency ramp.

2. Radar apparatus (10; 60; 70) according to claim 1, wherein the at least one antenna (11) has a first emission angle when driven with the first frequency ramp (14) and a second emission angle when driven by the second frequency ramp (15).

3. The radar apparatus (10; 60; 70) according to claim 1 or 2, wherein the at least one antenna (11) is designed for a nominal frequency, and wherein the first center frequency is smaller than the nominal frequency and the second center frequency is larger than the nominal frequency.

4. Radar apparatus (10; 60; 70) according to any one of the preceding claims, wherein the transmitter circuit (13) is designed to drive the at least one antenna (11) with the first and second FMCW frequency ramps (14, 15) in different time intervals.

5. Radar apparatus (10; 60; 70) according to any one of the preceding claims, wherein the transmitter circuit (13) is designed to drive the at least one antenna (11) with a plurality of successive first FMCW frequency ramps (14) having the first center frequency in a first time interval and with a plurality of successive second FMCW frequency ramps (15) having the second center frequency in a second time interval which does not overlap the first time interval.

6. Radar apparatus (10; 60; 70) according to any one of the preceding claims, wherein the directional characteristic (12) of the at least one antenna (11) is frequency dependent in the elevation direction.

7. Radar apparatus (10; 60; 70) according to any one of the preceding claims, comprising an antenna array having a plurality of antennas, wherein the antenna array has a frequency dependent directional characteristic.

8. Radar apparatus (10; 60; 70) according to claim 7, wherein the transmitter circuit (13) is designed to drive a first antenna (11-1) of the antenna array with the first FMCW frequency ramp (14) in a first time interval and with the second FMCW frequency ramp (15) in a second time interval, and to drive a second antenna (11-2) of the antenna array with the first FMCW frequency ramp (14) in a third time interval and with the second FMCW frequency ramp (15) in a fourth time interval.

9. Radar apparatus (10; 60; 70) according to any one of the preceding claims, further comprising:

a receive antenna array (61) having a plurality of receive antennas; and

a receiver circuit (63) designed to change a reception direction characteristic (62) of the reception antenna array (61) by adjusting a phase offset between reception signals of the reception antennas.

10. Radar apparatus (10; 60; 70) according to claim 8, wherein the reception direction characteristic (62) of the receive antenna array (61) is variable in azimuth direction.

11. Radar apparatus (10; 60; 70) according to claim 8 or 9, wherein the receiver circuitry (63) comprises digital beamforming circuitry.

12. A radar apparatus (10; 60; 70) for a motor vehicle, comprising:

at least one transmitting antenna (11) having a frequency-dependent transmission direction characteristic in a first direction;

a transmitter circuit (13) which is designed to generate a first FMCW frequency ramp having a first center frequency and at least one second FMCW frequency ramp having a second center frequency, wherein the second center frequency is different from the first center frequency, and which is designed to actuate the at least one transmitting antenna (11) with the first FMCW frequency ramp and the second FMCW frequency ramp to generate a first transmit directional characteristic of the at least one transmitting antenna (11) with the first FMCW frequency ramp and a different second transmit directional characteristic of the at least one transmitting antenna with the second FMCW frequency ramp;

a receive antenna array (61) having a plurality of receive antennas, wherein a receive direction characteristic (62) of the receive antenna array is variable in a second direction; and

a digital beamforming circuit (63) designed to change the reception directional characteristics of the reception antenna array by adjusting the phase offset between the reception signals of the reception antennas.

13. Radar apparatus according to claim 12, wherein the at least one transmitting antenna (11) has a first transmission angle in the elevation direction when driven with the first frequency ramp and a different second transmission angle in the elevation direction when driven with the second frequency ramp, and wherein the reception directional characteristic of the receiving antenna array (61) is adjustable in the azimuth direction.

14. A method (80) for producing different directional characteristics, comprising:

generating (81) a first FMCW frequency ramp having a first center frequency and at least one second FMCW frequency ramp having a second center frequency different from the first center frequency; and

controlling (82) at least one antenna (11) with the first and second FMCW frequency ramps, the at least one antenna having a frequency-dependent directional characteristic, to produce a first directional characteristic of the at least one antenna with the first FMCW frequency ramp and a different second directional characteristic of the at least one antenna with the second FMCW frequency ramp.

15. The method (80) of claim 14, wherein the at least one antenna (11) transmits at a positive transmission angle relative to a reference transmission angle when driven with the first FMCW frequency ramp, and wherein the at least one antenna (11) transmits at a negative transmission angle relative to the reference transmission angle when driven with the second FMCW frequency ramp.

16. The method (80) of claim 14 or 15, further comprising:

receiving a first reflected signal relative to the first FMCW frequency ramp with a receive antenna array (61) comprising a plurality of receive antennas;

receiving a second reflected signal with respect to the second FMCW frequency ramp with the receive antenna array (61); and

determining a first distance and a second distance to an object based on the first reflected signal and the second reflected signal.

17. The method (80) of claim 16, further comprising

Changing the reception direction characteristic of the reception antenna array (61) by adjusting a phase offset between the reception antennas.

18. The method of any of claims 14 to 17, wherein the method further comprises:

generating a first digital value based on receiving the first reflected signal;

generating a second digital value based on receiving the second reflected signal;

performing a first fourier transform based on the first digital value and a second fourier transform based on the second digital value;

generating distance-velocity information based on results of the first Fourier transform and the second Fourier transform.

Technical Field

Embodiments of the present invention relate generally to radar applications and more particularly to frequency modulated continuous wave radar systems for automotive vehicles.

Background

Frequency modulated continuous wave radar systems are also known as Frequency Modulated Continuous Wave (FMCW) radar systems. Here, for example, in linear frequency modulation of a transmitted signal, the amount of frequency difference Δ f between the transmitted and received signals at any point in time is a measure of the transit time (Δ t) and thus the distance. Signal processing in an FMCW radar system basically involves the measurement of the difference frequency af, which results from the mixing of the echo signal and the current transmission frequency.

The angular resolution of such FMCW radar systems depends to a large extent on the size of the antenna aperture. In conventional automotive radar sensors, this can be increased by using a greater number of physical HF channels (HF ═ radio frequency, HF channels comprising transmitters and/or receivers), which are combined in a multiple-input multiple-output (MIMO) method into a virtual antenna array. However, a larger number of physical HF channels requires a higher cost for the required hardware and is disadvantageous in the automotive field due to the large number of components.

There is therefore a need to improve the achievable angular resolution of FMCW radar sensors with a constant number of HF channels.

Disclosure of Invention

This need is met by the apparatus and method of the independent claims. In some cases, advantageous developments are the subject matter of the dependent claims.

According to a first aspect of the present disclosure, a radar apparatus is provided. The radar apparatus comprises at least one antenna having a frequency dependent directional characteristic. The radar apparatus also includes a transmitter circuit designed to generate a first FMCW frequency ramp having a first center frequency and at least one second FMCW frequency ramp having a second center frequency different from the first center frequency. The transmitter circuit drives the at least one antenna with the first and second FMCW frequency ramps to produce a first directional characteristic of the at least one antenna with the first FMCW frequency ramp and a different second directional characteristic of the at least one antenna with the second FMCW frequency ramp.

By driving at least one antenna with different FMCW frequency ramps according to the center frequency (this is also referred to as analog beamforming in the following), the angular resolution of the radar arrangement can be achieved with a constant number of HF channels. The focusing direction of the antenna is controlled by means of the so-called "antenna squint effect". The desired focus direction can be controlled according to the center frequency of the FMCW frequency ramp.

According to some embodiments, at least one antenna of the radar apparatus has a first transmission angle when driven with a first frequency ramp and a second transmission angle when driven by a second frequency ramp. Depending on the design and/or arrangement of the at least one antenna, different transmission angles in the azimuth direction and/or the elevation direction may be involved here, for example.

According to some embodiments, the at least one antenna, or the physical dimensions thereof, is designed for a predetermined nominal frequency. For example, the first center frequency may be less than the nominal frequency and the second center frequency may be greater than the nominal frequency. Thereby, the respective emission angles starting from the reference emission angle at the nominal frequency are pivoted in different directions at different center frequencies. For example, the first emission angle at the first center frequency may be greater than the reference emission angle, and the second emission angle at the second center frequency may be less than the reference emission angle. The reverse is of course possible depending on the antenna design and/or the selected frequency.

According to some embodiments, the transmitter circuit is designed to drive the at least one antenna with the first and second FMCW frequency ramps in different time intervals. Thereby, different directional characteristics or emission angles of the at least one antenna may be obtained in different (e.g. consecutive) time intervals, and the angular resolution of the radar apparatus as a whole may be increased.

According to some embodiments, the transmitter circuit is designed to drive the at least one antenna with a plurality of consecutive first FMCW frequency ramps having a first center frequency and with a plurality of consecutive second FMCW frequency ramps having a second center frequency in a second time interval that does not overlap with the first time interval. Thus, with suitable signal processing (e.g. fourier transformation) a first so-called range-doppler plot based on the first directional characteristic may be obtained in a first time interval and a second range-doppler plot based on the second directional characteristic may be obtained in a second time interval.

According to some embodiments, the directional characteristic of the at least one antenna in the elevation direction is frequency dependent. Thus, due to the strabismus effect, one can "look" in different elevation directions with different FMCW frequency ramps.

According to some embodiments, at least one antenna is designed as a patch antenna having a plurality of patch elements connected in series as seen from a terminal. The physical dimensions of the individual patch elements may be different. Thereby, focusing of the directional characteristic can be achieved.

According to some embodiments, the radar apparatus comprises an antenna array having a plurality of antennas, wherein the antenna array has a frequency dependent directional characteristic. The antenna array may usefully be used for both transmit and receive directions, for example to improve the spatial resolution of the radar apparatus. In some embodiments, the at least one antenna may be part of an antenna array, or may itself form an antenna array.

According to some embodiments, the transmitter circuit is designed to steer a first antenna of the antenna array with a first FMCW frequency ramp in a first time interval and to steer the first antenna of the antenna array with a second FMCW frequency ramp in a second time interval, and to steer a second antenna of the antenna array with the first FMCW frequency ramp in a third time interval and to steer the second antenna of the antenna array with the second FMCW frequency ramp in a fourth time interval. Thus, the first and second antennas of the antenna array may be continuously driven as transmit antennas with varying transmission angles.

According to some embodiments, the radar apparatus further comprises a receiving antenna array having a plurality of receiving antennas, and a receiver circuit designed to change a receiving directional characteristic of the receiving antenna array by adjusting a phase offset between the receiving antennas or the respective received signals, respectively. In some embodiments, at least one antenna may be used as part of a receive antenna array. Therefore, in the reception direction, the reception direction characteristic can be changed by beamforming. In this case, the reception direction characteristic of the reception antenna array may vary in the azimuth direction. Preferably, but not necessarily, the receiver circuit is designed as a digital beamforming circuit.

According to another aspect of the present disclosure, a radar apparatus for a motor vehicle is provided. The radar device comprises at least one transmitting antenna having a transmission directional characteristic which is frequency-dependent in a first direction. The radar apparatus further comprises a transmitter circuit arranged to generate a first FM-frequency ramp having a first center frequency and at least one second FMCW frequency ramp having a second center frequency, wherein the second center frequency is different from the first center frequency, and the transmitter circuit is designed to drive the at least one transmitting antenna with the first FMCW frequency ramp and the second FMCW frequency ramp to generate a first transmit directional characteristic of the at least one transmitting antenna with the first FMCW frequency ramp and a different second transmit directional characteristic of the at least one transmitting antenna with the second FMCW frequency ramp. The radar apparatus further includes a receiving antenna array having a plurality of receiving antennas, wherein a receiving direction characteristic of the receiving antenna array is variable in the second direction. Furthermore, the radar apparatus includes a digital beam forming circuit designed to change the reception direction characteristics of the reception antenna array by adjusting the phase offset between the respective reception antennas or between the respective reception signals.

According to some embodiments, when used, the at least one transmit antenna has a first transmit angle in the elevation direction when controlled with a first frequency ramp and a different second transmit angle in the elevation direction when controlled with a second frequency ramp. Instead, the reception direction characteristic of the reception antenna array is adjustable in the azimuth direction. Thus, increased angular resolution in both the elevation and azimuth directions can be achieved.

According to another aspect of the present disclosure, a method of generating different directional characteristics is provided. The method includes generating a first FMCW frequency ramp having a first center frequency and at least one second FMCW frequency ramp having a second center frequency different from the first center frequency, driving the at least one antenna with the first FMCW frequency ramp and the second FMCW frequency ramp to generate a first directional characteristic of the at least one antenna with the first FMCW frequency ramp, and generating a different second directional characteristic of the at least one antenna with the second FMCW frequency ramp. Thus, an increased angular resolution can be achieved.

According to some embodiments, at least one antenna transmits at a positive transmission angle relative to a reference transmission angle when driven with a first FMCW frequency ramp, and at least one antenna transmits at a negative transmission angle relative to the reference transmission angle when driven with a second FMCW frequency ramp.

According to some embodiments, the method further comprises receiving a first reflected signal relative to the first FMCW frequency ramp with a receive antenna array comprising a plurality of receive antennas, receiving a second reflected signal relative to the second FMCW frequency ramp with the receive antenna array, and determining the first and second distances to the object based on the first and second reflected signals.

According to some embodiments, the reception directional characteristics of the receive antenna array are changed by adjusting the phase offset between the receive antennas or their respective receive signals.

According to some embodiments, the first digital value is generated based on receiving the first reflected signal. A second digital value is generated based on receiving the second reflected signal. A first fourier transform is performed based on the first digital value and a second fourier transform is performed based on the second digital value. Distance-velocity information is generated based on the results of the first and second fourier transforms.

Aspects described herein may achieve the above objectives through a combination of digital and analog beamforming. Thereby, the angular resolution can be increased at constant hardware cost. Due to the integration of analog beamforming, the interference of other road participants (interference) to the radar device can be reduced. A combination with existing methods is easily achieved, for example azimuth measurement by means of digital beamforming and elevation measurement by means of analog beamforming by exploiting the squint effect as proposed herein.

Drawings

Some examples of the apparatus and/or methods are explained in detail below, by way of example only, with reference to the accompanying drawings. The figures show that:

FIG. 1 shows a block diagram of a radar apparatus according to an embodiment;

fig. 2 shows an example of an antenna of the radar arrangement according to fig. 1;

fig. 3 shows different antenna directional characteristics obtained by FMCW frequency ramps with different center frequencies;

fig. 4 shows the actuation of at least one antenna in time division multiplexing;

fig. 5 shows the actuation of several antennas in time division multiplexing;

FIG. 6 shows an example of a radar transceiver;

FIG. 7 shows an embodiment that may be applied in a remote radar (LRR); and

fig. 8 shows a flow diagram of a method according to an embodiment.

Detailed Description

Various examples will now be described in more detail with reference to the accompanying drawings, in which some examples are shown. In the drawings, the strength of lines, layers and/or regions may be exaggerated for clarity.

Accordingly, while other examples of various modifications and alternative forms are suitable, certain specific examples thereof are shown in the drawings and will be described below in detail. However, the detailed description does not limit further examples to the particular forms described. Other examples may cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. The same or similar reference numerals throughout the description of the drawings denote the same or similar elements, which may be modified the same or compared with each other while providing the same or similar functions.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, the element can be connected or coupled directly or through one or more intervening elements. When using "or" in combination with two elements a and B, it is understood that all possible combinations are disclosed, i.e. only a, only B and a and B, unless explicitly or implicitly defined otherwise. Alternative expressions for the same combination are "at least one of a and B" or "a and/or B". The same applies mutatis mutandis to combinations of more than two elements.

The terminology used to describe certain examples is not intended to be limiting of other examples. While the use of the singular forms "a," "an," and "the," and the use of only a single element, are implicitly and imperatively undefined, other instances may use multiple elements to achieve the same functionality, and other instances may use a single element or a single processing entity to achieve the same functionality if the functionality is described below as being achieved using multiple elements. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used, specify the presence of stated features, integers, steps, operations, procedures, elements, components, and/or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, procedures, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) are used herein in their ordinary meaning in the art to which examples pertain.

The development of FMCW radar transceivers towards higher HF bandwidths and the ability to generate complex and flexible frequency ramp cases enables integration of frequency swept beamforming into FMCWMIMO radar. It is proposed herein to use the "antenna squint effect" to control the focusing direction of the antenna. Depending on the center frequency of the frequency ramp, the desired focus direction can be steered. In automotive radar sensors, the current limitation due to the low number of physical HF channels is angular resolution (defined by the antenna aperture) rather than range resolution (defined by the HF bandwidth). In modern radar transceivers with a modulation bandwidth of a few GHz, the available range resolution can be exchanged for the angular resolution, for example in "trading".

Fig. 1 shows a schematic block diagram of a radar apparatus 10 according to an embodiment of the present disclosure.

The radar apparatus 10 includes an antenna 11 having a frequency-dependent directional characteristic 12, and is designed to produce an antenna squint effect. The radar device 10 further comprises a transmitter circuit 13 designed to generate a signal having a first center frequency f₁And has a first center frequency f different from the first FMCW frequency ramp 14₁Second center frequency f₂At least one second FMCW frequency ramp 15, that is to say f₁≠f₂. The transmitter circuit 13 drives the antenna 11 with a first FMCW frequency ramp and a second FMCW frequency ramp to produce a first directional characteristic 12-1 of at least one antenna 11 with the first FMCW frequency ramp 14 and at least one antenna with the second FMCW frequency ramp 15A different second directional characteristic 12-2.

By the center frequency of the FMCW frequency ramp, for a linear frequency ramp, for example, the lowest frequency f of the FMCW frequency ramp can be understood_lowAnd the highest frequency f_highAverage frequency in between, e.g. (f)_low+f_high)/2。

The radar apparatus 10 may be a radar transmitter or a radar transmitter receiver for automotive applications. Thus, the radar apparatus 10 may be used as a Long Range Radar (LRR), a Medium Range Radar (MRR), a corner or circumferential radar, for example, in a motor vehicle. Typical frequencies for these applications are currently in the range of 24GHz (K-band), 76GHz or 96GHz (W-band). Since the antenna 11 is matched with its physical dimensions to a nominal frequency in one of these frequency bands, the different adjusting frequencies of the FMCW frequency ramps 14 and 15 are f₁And f₂Preferably in the selected frequency band, where they are now different from each other. This results in a spectral shift of the first FMCW frequency ramp 14 relative to the second FMCW frequency ramp 15. Thus, the "antenna squint effect" can be utilized to control the antenna pattern or the focusing direction of the antenna 11. The degree of the antenna squint effect depends inter alia on the center frequency f₁And f₂The difference between them.

As an antenna 11 for automotive radar applications, for example, a panel antenna is considered. However, those skilled in the art will appreciate that other antenna designs may be used. A schematic diagram of a possible panel antenna 11 is shown in fig. 2.

The planar board antenna 11 has a signal terminal 21 from which a plurality of patch elements 22 are connected in series as a radiation area. In the illustrated embodiment, the geometric dimensions of the individual patch elements 22 are different, which has an effect on the focused emission characteristics. The series connected patch elements 22 may be considered a hardwired antenna array. The phase shift between the individual patch elements 22 depends on their physical spacing from each other and the frequency used. With a given physical spacing between patch elements 22, the main emission angle of antenna 11 varies with the frequency used. The focusing is also frequency dependent. That is, different emission angles and/or focusing may be achieved with different frequencies. Of course, this also applies to other antenna designs, which, as in the example shown, act as antenna arrays.

If the panel antenna 11 is installed horizontally, its transmission angle changes in the azimuth direction while the FMCW frequency ramps with different center frequencies. If the panel antenna 11 is vertically installed, its transmission angle changes in the elevation direction when the FMCW frequency is ramped with a different center frequency. Both are basically possible and depend on the intended application. In the following we consider a vertically mounted antenna 11, whose transmission angle is changed in the elevation direction by the proposed analog beamforming concept.

If the first center frequency f₁Now for example less than the nominal frequency, the respective emission angle of the antenna 11 continues to pivot downwards starting from the reference emission angle at the nominal frequency. On the contrary, if the second center frequency f₂Above the nominal frequency, the respective emission angle of the antenna 11 continues to pivot upwards, starting from the reference emission angle. This is schematically illustrated in the side view of fig. 3, where φ ref represents the reference emission angle at nominal frequency, φ 1 represents the first center frequency f₁The emission angle of time, phi 2, denotes the second center frequency f₂The angle of emission of time.

One method of steering the antenna 11 with the first and second FMCW frequency ramps 14, 15 is a time division multiplexing method. Thus, the transmitter circuit 13 may be designed to drive the antenna 11 during successive and non-overlapping time intervals of the first and second FMCW frequency ramps 14, 15. An example of which is shown in figure 4.

Here, the transmitter circuit 13 is exemplarily designed so as to be at a first time interval Δ T₁To have a first center frequency f₁And does not drive the antenna 11 by a first time interval deltat from the first FMCW frequency ramp 14₁Overlapping second time interval Δ T₂With a second centre frequency f₂To drive the antenna, 15. At a subsequent third time interval Δ T₃To have a first center frequency f₁Drives the antenna 11 for a subsequent fourth time interval deltat at a first FMCW frequency ramp 14₄With a second centre frequencyRate f₂To drive the antenna, 15. Those skilled in the art will readily appreciate that the time interval and/or FMCW frequency ramp may also be different. For example, more than two FMCW frequency ramps with different center frequencies may be used. The angular resolution or accuracy of the emission angle control can be further increased by using more than two FMCW frequency ramps with different center frequencies. In fig. 4, the respective frequency ramps assigned to a time interval are controlled such that the end frequency of a ramp is seamlessly connected to the start frequency of the next ramp in a subsequent time interval. However, in other embodiments, the end frequency of a ramp and the start frequency of a subsequent ramp may be spaced from one another. In this case, the end frequency of the previous ramp may be less than the start frequency of the immediately adjacent ramp. However, the final frequency of the preceding ramp may also be greater than the starting frequency of the immediately adjacent ramp, so that there is some overlap in frequency. It should also be noted that the embodiment in fig. 4 has a linear frequency ramp with a ramp steepness. Furthermore, the frequency ramp may be formed by a plurality of linear sections, each having a different ramp steepness. Likewise, in other embodiments, the use of a non-linear frequency ramp is contemplated.

For the FMCW frequency ramps 14, 15, each own range-doppler plot can be created in a manner known per se. In particular, to obtain velocity or doppler information, it may be possible to have a first center frequency f in a first time interval₁Repeatedly drives the antenna 11 with a plurality (series) of successive first FMCW frequency ramps 14. In a second time interval not overlapping the first time interval, a second frequency with a second center frequency f may be used₂Repeatedly drives the steering antenna 11 with a plurality (series) of successive second FMCW frequency ramps 15. The number of consecutive FMCW frequency ramps with the same center frequency may be selected, e.g., 64, 128 or more, depending on the application. The back-reflected signal is down-converted using an appropriate LO signal for further processing. That is, the transmitted backreflected signal of the first FMCW frequency ramp 14 is mixed with the LO signal corresponding to the first FMCW frequency ramp 14, that is to say with f₁The center frequency of (c). All in oneLikewise, the transmitted backreflected signal of the second FMCW frequency ramp 15 is mixed with the LO signal corresponding to the second FMCW frequency ramp 15, that is to say with f₂The center frequency of (c).

Having a first centre frequency f upon reception and down-conversion by a corresponding LO signal₁After the transmitted reflection signal of the FMCW frequency ramp 14, the IF (intermediate frequency) signal assigned to the frequency ramp 14 is digitized and subjected to a first digital fourier transform (e.g., a first distance fast fourier transform). Likewise, has a second center frequency f during reception and down-conversion₂After the reflected signal of FMCW frequency ramp 15, the IF signal assigned to the frequency ramp 15 phase is digitized and subjected to a second digital fourier transform (e.g., a second distance fast fourier transform). After the first or second range fast fourier transform, an additional first or second doppler fast fourier transform may be performed. Thus, for example, a so-called range-doppler plot based on the first directional characteristic 12-1 can be obtained with a fast fourier transform assigned to a first time interval, and a second range-doppler plot based on the second directional characteristic 12-2 can be obtained with a fast fourier transform assigned to a second time interval. Thus, as described above, to generate the corresponding range-doppler plots, the signals based on the first FMCW frequency ramp 14 may be processed together, and the signals based on the second FMCW frequency ramp 15 may also be processed together. Thus, in this embodiment, the fourier transform is based only on signal points that are at the same type of frequency ramp, i.e. at frequency ramps with the same center frequency.

For each center frequency or emission angle obtained therefrom, a separate range-doppler plot may be determined. Thus, for each emission angle, information about the distance and velocity of objects present at that angle can be obtained. Furthermore, by selecting and configuring an appropriate number of respectively different center frequencies, the angular resolution can be set without changing the hardware components. The reliability of the automotive radar system can also be greatly improved.

In some embodiments, multiple antennas 11 may be connected to the transmitter circuit 13, rather than just the transmitter circuitOnly one antenna 11. In such an embodiment, the transmitter circuit 13 may be designed to transmit the signal at the first time interval Δ T, as shown in FIG. 4₁At a first FMCW frequency ramp 14 and at a second time interval deltat₂Drives the first antenna 11-1 of the antenna array with the second FMCW frequency ramp 15 and, for a third time interval Δ T₃At a first FMCW frequency ramp 14 and at a fourth time interval deltat₄To drive the second antenna 11-2 of the antenna array with a second FMCW frequency ramp 15. Here, transmit diversity may additionally be received by at least two (transmit) antennas 11-1 and 11-2 and thus an improved signal-to-noise power ratio is obtained.

Another way of using multiple antennas is schematically shown in fig. 5. Four transmitting antennas 11-1, 11-2, 11-3 and 11-4 in the form of patch antennas, which have been discussed above, are shown as examples.

At a first time interval Δ T₁In which all four antennas 11-1, 11-2, 11-3 and 11-4 are parallel-connected to have a first center frequency f₁Is driven by a plurality of successive first FMCW frequency ramps 14. This results in a first transmission angle phi for the four antennas 11-1, 11-2, 11-3 and 11-4₁. At a second subsequent time interval Δ T₂In which four antennas 11-1, 11-2, 11-3 and 11-4 are arranged in parallel to have a second center frequency f₂≠f₁Is driven by a continuous second FMCW frequency ramp 15. This results in a second transmission angle phi for the four antennas 11-1, 11-2, 11-3 and 11-4₂≠φ₁. At a subsequent third time interval Δ T₃In which four antennas 11-1, 11-2, 11-3 and 11-4 are arranged in parallel to have a third center frequency f₃≠f_1，2Is driven by a plurality of consecutive third FMCW frequency ramps. This results in a third transmission angle phi for the four antennas 11-1, 11-2, 11-3 and 11-4₃≠φ_1，2。

Embodiments are contemplated in which all antennas are connected to a common physical radar channel that can produce (e.g., continuous) different FMCW frequency ramps with different center frequencies. On the other hand, different antennas may also be connected to different physical radar channels, each producing its own FMCW frequency ramp with a corresponding center frequency.

In order to calculate the range-doppler plots already mentioned, a receiver circuit is of course also required. In the simplest case, a receiving antenna is provided in order to obtain in each case a different transmission angle φ in the elevation direction₁，φ₂，φ₃Distance doppler information of (2). However, it is quite common to use receive antenna arrays with multiple receive antennas. Thus, reflections from different (e.g., azimuth) directions may be received by the beamforming mechanism. Along with the different launch angles in the elevation direction, a multi-dimensional range-doppler plot is generated.

An example of a radar transceiver 60 according to one embodiment is shown in fig. 6.

Fig. 6 shows a radar device 60 with (at least one) transmitting antenna 11 having a frequency-dependent transmission direction characteristic in a first direction. The transmitter circuit 13 is designed to generate a signal having a first center frequency f₁And a first FMCW frequency ramp 14 having a second center frequency f₂I.e. with a first center frequency f₁At least one second FMCW frequency ramp 15 of a different second center frequency, and means for controlling the transmitter antenna 11 with the first FMCW frequency ramp and the second FMCW frequency ramp to produce a first transmit direction characteristic 12-1 of the transmit antenna 11 with the first FMCW frequency ramp and a different second transmit direction characteristic 12-2 of the transmit antenna with the second FM frequency ramp. The radar apparatus 60 further comprises a receive antenna array 61 with a plurality of receive antennas 61-1, 61-2, 61-3 and 61-4, wherein a receive direction characteristic 62 of the receive antenna array 61 is variable in the second direction 61. The digital beam forming circuit 63 is designed to change the reception direction characteristic 62 of the reception antenna array 61 by adjusting or changing the phase offset between the reception signals of the reception antennas 61-1, 61-2, 61-3 and 61-4.

In fig. 6, as an example, the first direction is an elevation direction and the second direction is an azimuth direction. This configuration can be used, for example, in a side view radar (SLR) for automatic parking. The transmitting antenna 11 thus has a first transmission angle in the first elevation direction when driven with the first frequency ramp 14, and a different second transmission angle in the second elevation direction when driven with the second frequency ramp 15. The reception direction characteristic 62 of the reception antenna array 61 is adjustable in the azimuth direction.

Assuming that a number of different azimuth angles that can be set by digital beamforming will be N and a number of elevation angles that can be set by different center frequencies will be M, by mixing the transmit and receive signals N x M, a measurement with several measurements (analog-to-digital converted samples) can be obtained. By evaluating the successive FMCW frequency ramps of each pair (n, m), a range-doppler plot can be generated for each pair (n, m) and evaluated accordingly. Thereby, the speed and distance of the object with respect to the spatial direction in azimuth and elevation can be detected and separated.

Fig. 7 shows another embodiment that may be used for applications such as remote radar (LRR). It is advantageous for the LRR to have good azimuthal resolution and height measurement capability in addition to a high measurement range. These requirements can be achieved by the method shown in fig. 7.

Here, three transmitting antennas 11-1, 11-2 and 11-3 are exemplarily shown, which respectively have a frequency-dependent transmission direction characteristic in the elevation direction. The transmitting antennas 11-1, 11-2 and 11-3 may be applied with FMCW frequency ramps having different ramp center frequencies alternately or in parallel, thereby producing different directional characteristics in the elevation direction with different FMCW frequency ramps according to frequency, respectively. The transmitting antennas 11-1, 11-2 and 11-3 may be connected to different physical radar channels for this purpose, wherein each radar channel generates its own FMCW frequency ramp with a respective center frequency. A receive antenna array 71 is provided having a plurality of receive antennas 71-1, 71-2, 71-3 and 71-4 whose receive direction characteristics 72 are variable in both the azimuth and elevation directions. In this case, the reception direction characteristics of the reception antenna array 71 in the azimuth direction may be changed, for example, by digital beamforming (phase shift). In the elevation direction, the reception direction characteristic can be realized by using FMCW frequency ramps having different ramp center frequencies.

A radar with an antenna arrangement similar to that of figure 7 combines analog and digital beamforming in the elevation direction. In the azimuth direction, high angular resolution due to MIMO principles can only be achieved by digital beamforming.

In summary, FIG. 8 illustrates a method 80 of generating different directional characteristics according to the concepts described herein.

The method 80 comprises generating 81 a signal having a first ramp center frequency f₁And has a center frequency f different from the first ramp 14₁Second slope center frequency f₂At least one second FMCW frequency ramp 15. The method 80 further includes driving 82 at least one antenna 11 having a frequency-dependent directional characteristic with a first FMCW frequency ramp 14 and a second FMCW frequency ramp 15 to produce a first directional characteristic of the at least one antenna 11 with the first FMCW frequency ramp and a different second directional characteristic of the at least one antenna 11 with the second FMCW frequency ramp by an antenna squint effect.

To this end, a first reflected signal corresponding to a first FMCW frequency ramp may be received with a receive antenna array comprising a plurality of receive antenna elements. A second reflected signal corresponding to a second FMCW frequency ramp may also be received using the receive antenna array. First and second distances to an object that has reflected the FMCW frequency ramp may then be determined based on the first and second reflected signals.

Aspects and features described in connection with one or more of the previous detailed examples and figures may also be combined with one or more other examples to replace the same features of another example or to supplement it additionally.

The specification and drawings merely illustrate the principles of the disclosure. In addition, all examples provided herein are explicitly for illustration only to aid the reader in understanding the principles of the disclosure and concepts for furthering the art as contributed by the inventor. All statements herein reciting principles, aspects, and examples of the disclosure, as well as specific examples thereof, encompass equivalents thereof.

A functional block referred to as "means for performing a specified function" may refer to a circuit configured to perform the specified function. Thus, a "means for something" may be implemented as a "means designed for or suitable for something", e.g. a means or a circuit designed for or suitable for a specific task.

In the drawings, the functional blocks designated as including the functions of the various elements shown in the respective "means" for providing a signal "," means for generating a signal ", etc., may take the form of dedicated hardware, such as hardware capable of executing software" in an appropriate software "of a signal provider associated" with, for example, a signal processing unit, a processor, a control system, etc. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may or may not be shared. However, the term "Processor" or "controller" is by no means limited to hardware capable of executing only software, and may be Digital Signal Processor hardware (DSP-hardware), a network Processor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Read Only Memory (ROM) for storing software, a Random Access Memory (RAM), and a non-volatile Memory (storage). Other hardware, conventional and/or custom, may also be included.

For example, the block diagrams may represent coarse circuit diagrams implementing the principles of the present disclosure. Similarly, flowcharts, state transition diagrams, pseudocode, and the like may represent various processes, operations, or steps which, for example, are substantially represented in computer readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. The methods disclosed in the specification or claims may be implemented by an apparatus having means for performing each respective step of the methods.

It should be understood that the disclosure of steps, processes, operations or functions disclosed in the specification or claims should not be construed as to be in any particular order, e.g., for technical reasons, unless explicitly or implicitly. Thus, the disclosure of multiple steps or functions does not limit them to any particular order unless, for technical reasons, the steps or functions are not interchangeable. Moreover, in some examples, a single step, function, process, or operation may include and/or be divided into multiple sub-steps, functions, processes, or operations. These sub-steps may be included and are part of the disclosure of the single step unless explicitly excluded.

Furthermore, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate example. Although each claim may stand on its own as a separate example, it should be understood that while a dependent claim may refer to a particular combination of one or more other claims in a claim, other examples also include combinations of a dependent claim with the subject matter of each other dependent or independent claim. Such combinations are expressly set forth herein unless it is stated that a particular combination is not intended. Furthermore, the features of the claims are to be included for each other independent claim, even if that claim does not directly refer to the independent claim.