Imaging radar system having a random receiving array for determining the angle of objects in two dimensions by means of a spread arrangement of the receiving antennas in one dimension

Abstract

The present invention relates to an apparatus for determining the position of objects in two-dimensional space having a first dimension and a second dimension, the direction vector of which is orthogonal to the direction vector of the first dimension, containing at least one transmitter (I) having at least one transmitting antenna (3) and an imaging receiver circuit (2) having at least one receiving antenna array (Rx Array) with rows (6) of receiving antennas for scanning the first dimension by means of digital beam shaping, wherein the receiving antenna array has a linear array, a sparse array or an array with an enlarged aperture, and wherein the rows (6) of receiving antennas in the receiving antenna array of the receiver circuit (2) are linearly arranged in the first dimension according to a curve function or according to the contour of a two-dimensional geometric object and are spread out in the second dimension, and to a method using the apparatus.

Claims

1. A device for determining the position of objects in two-dimensional space having a first dimension and a second dimension, a direction vector of the first dimension is orthogonal to a direction vector of the second dimension, the device comprising: at least one transmitter having at least one transmitting antenna, and an imaging receiver circuit having at least one receiving antenna array having rows of receiving antennas for scanning the first dimension through digital beamforming, wherein the receiving antenna array has a linear array, a sparse array or an array with an enlarged aperture, and wherein the rows of receiving antennas of the receiving antenna array of the receiver circuit are arranged linearly in the first dimension in accordance with a curve function or in accordance with the contour of a two-dimensional geometric object and are arranged in the second dimension by a random function, wherein a number of discrete positions N.sub.Pos,2D in the second dimension is defined by a number of rows of receiving antennas N.sub.RxANT in accordance with N.sub.Pos,2D≥√{square root over (N.sub.RxANT)}, and further wherein the number of discrete positions in the second dimension is at least 3.

2. The device as claimed in claim 1, wherein the rows of receiving antennas of the receiver circuit are arranged as a straight line, triangle, sawtooth, or sinusoidally in the first dimension, or wherein the rows of receiving antennas of the receiver circuit are arranged as a rectangle, circle, or ellipse in the first dimension.

3. The device as claimed in claim 1, wherein phase centers of the rows of receiving antennas of the receiver circuit are arranged in a non-regular pattern in the second dimension.

4. The device as claimed in claim 1, wherein the receiving antenna array of the receiver circuit is able to be enlarged by at least two switchable transmitting antennas through multiple input multiple output on transmissions (MIMO-on-Tx) to form a virtual receiving antenna array having a number of virtual elements N.sub.RxVirt>N.sub.RxANT.

5. The device as claimed in claim 4, wherein in the second dimension phase centers of the transmitting antennas are identical, or wherein in the second dimension the phase centers of the transmitting antennas are different and an additional offset is formed in the virtual receiving antenna array.

6. A radar comprising the device as claimed in claim 1, wherein the radar is selected from the group consisting of a frequency-modulated CW radar, a digitally modulated radar, and a pulse radar.

7. The device as claimed in claim 1, wherein the number of rows of receiving antennas is at least 4.

8. The device as claimed in claim 1, wherein the at least one transmitting antenna and the imaging receiver circuit are operable in a frequency range of 1 GHz to 300 GHz.

9. A method for determining the position of objects in two-dimensional space having a first dimension and a second dimension, using a device as claimed in claim 1, the method comprising: transmitting a radar signal using the at least one transmitting antenna, receiving a signal using the imaging receiver circuit having the at least one receiving antenna array for scanning the first dimension, digitizing the signal data, carrying out a range fast Fourier transform (FFT) and/or a velocity FFT and digital beamforming; detecting an object and determining a position of the object.

10. The method as claimed in claim 9, wherein the object is detected with respect to the first dimension and the position of the object is determined with respect to the second dimension.

11. The method as claimed in claim 9, wherein upon successful detection of the object in the first dimension, the position of the object is subsequently determined using beamforming for a plurality of beams in the second dimension.

12. The method as claimed in claim 9, wherein upon successful detection of the object in the first dimension, the position of the object is subsequently determined using beamforming and an amplitude monopulse for a plurality of beams in the second dimension.

13. The method as claimed in claim 9, wherein when the rows of receiving antennas of the receiving antenna array are arranged in accordance with a curve function, the position of the object is subsequently determined using two-dimensional (2D) beamforming on the basis of phase centers of the rows of receiving antennas of the receiver circuit.

Description

(1) In the figures:

(2) FIG. 1 shows a front end having 16 Rx antennas and one Tx antenna. Arrangement of the Rx antennas in the 2nd dimension by rand( )*Max. deviation;

(3) FIG. 2 shows an antenna pattern in the 2.sup.nd dimension with three shaped beams by virtue of different positionings of the phase center in the 2.sup.nd dimension;

(4) FIG. 3 shows an antenna pattern in the first dimension for the antenna positions listed in table 1 (1.sup.st dim. linear, 2.sup.nd dimension randomly generated) and for a linear array of the antenna positions without a deviation in the second dimension;

(5) FIG. 4 shows a signal flow diagram of the 2D location determination with the use of FMCW; and

(6) FIG. 5 shows an elliptic array arrangement having 2 Tx and 8 Rx.

(7) FIG. 1 shows such an exemplary implementation of a radar front end consisting of a transmitter (1) having a transmitting antenna (3) and a receiver circuit (2) having 16 rows of receiving antennas (6), wherein the rows of receiving antennas (6) are oriented linearly on a straight line along the first dimension. The array is spread out in the second dimension, which is orthogonal to the first dimension, with the aid of a random function. The associated positions of the linear array having the row spacing 2200 μm in the first dimension and randomly determined positions in the second dimension are presented in table 1:

(8) TABLE-US-00001 Dim 1 (μm) Dim 2 (μm) −1260    0 Rx1 −1620   2200 Rx2 1490   4400 Rx3 −1650   6600 Rx4 −530   8800 Rx5 1610 11 000 Rx6 890 13 200 Rx7 −190 15 400 Rx8 −1830 17 600 Rx9 −1860 19 800 Rx10 1370 22 000 Rx11 −1880 24 200 Rx12 −1830 26 400 Rx13 60 28 600 Rx14 −1200 30 800 Rx15 1430 33 000 Rx16

(9) Table 1: Positioning of the rows of receiving antennas of the array illustrated in FIG. 1 with a linear arrangement in dimension 1 with a row spacing of 2200 μm and a randomly produced arrangement of the antennas in dimension 2.

(10) FIG. 2 shows three resulting beams in the second dimension for the front end having one transmitter and 16 receiving channels as illustrated in FIG. 1. In this case, the spreading of the position of the phase center results in an angle offset of the viewing direction of the beams and thus also allows an evaluation in the second dimension. In this case, the maximum deviation of the spreading from the mean value must be defined in such a way that for a finite number of receiving rows, the beamforming in the first dimension is not critically influenced.

(11) FIG. 3 shows by way of example the antenna pattern produced by digital beamforming for a main beam direction of 0° in a comparison between a linear array without and with a spread-out second dimension. It is evident here that the effects of the spreading in the second dimension are manifested only marginally in the antenna pattern, principally at the sidelobes.

(12) FIG. 4 shows the signal processing for calculating the two-dimensional target position in the form of a signal flow diagram on the basis of the example of an FMCW radar. After the measurement, that is to say the transmission, reception and digitization of a ramp, the basis for the subsequent digital beamforming is firstly established by means of a range FFT and a velocity FFT. The target detection is carried out firstly in the first dimension, e.g. by means of an OSCFAR or a Peak search function, followed by beamforming in the second dimension on the basis of the FFT data at the positions of the targets previously found in the first dimension. The further position determination in the second dimension is carried out as described above. Finally, the two-dimensional data of the so-called range-velo cells are calculated from the combination of both beamformers.

(13) FIG. 5 illustrates an exemplary arrangement of a MIMO-on-TX radar system based on an elliptic arrangement of the antennas. In the arrangement shown, the phase centers of the eight rows of receiving antennas (6) lie on the contour of the ellipse described by the angle-dependent radius r thereof:

(14) ${r\left(\vartheta \right)}^2=\frac{a^2{b}^2}{a^2\sin \left(\vartheta \right)+b^2\cos \left(\vartheta \right)},$

(15) wherein the maximum radius is defined by a and the minimum radius of the ellipse is defined by b. In the arrangement shown, here the radius forms the first dimension, the random distribution being applied to the angle, which accordingly represents the second dimension. The MIMO-on-TX is made possible by means of two switchable transmitting antennas (3), which are positioned in different positions relative to the ellipse.

REFERENCE SIGNS

(16) 1 Transmitter 2 Receiver circuit 3 Transmitting antenna 4 Phase center 5 Row spacing 6 Row of receiving antennas 7 Viewing direction (deviation 1) 8 Directivity characteristic dim. 2 (deviation 1) 9 Viewing direction (deviation 2) 10 Directivity characteristic dim. 2 (deviation 2) 11 Viewing direction (deviation 3) 12 Directivity characteristic dim. 2 (deviation 3) 13 Sidelobes