WO2020183016A1

WO2020183016A1 - Antenna for 2d electronical beam-steering using multiple pre-shaped beams

Info

Publication number: WO2020183016A1
Application number: PCT/EP2020/056978
Authority: WO
Inventors: Andreas Schwager; Ramona Hotopan; Gerd Spalink; Ralf Boehnke
Original assignee: Sony Corporation; Sony Europe B.V.
Priority date: 2019-03-14
Filing date: 2020-03-13
Publication date: 2020-09-17
Also published as: DE112020001217T5; CN113615001A

Abstract

A planar antenna array comprises a first linear array comprising a first group and a second group of first radiation elements, a second linear array comprising a first group and a second group of second radiation elements, and a common feed port for transmission and/or reception of a feed signal to or from the first linear array and the second linear array, wherein the first linear array and the second linear array are intersecting and wherein the common feed port is arranged at an intersection point of the first linear array and the second linear array.

Description

ANTENNA FOR 2D ELECTRONICAL BEAM-STEERING USING MULTI

PLE PRE-SHAPED BEAMS

BACKGROUND

FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to a planar antenna array, an antenna de vice and an automotive radar system.

DESCRIPTION OF RELATED ART

[0002] The automotive radar is becoming a key technology for the future. Intel ligent sensor transportation systems and millimeter-wave systems are getting more im portant because they allow higher bandwidth and smaller antenna dimensions. Industrial as well as automotive applications require very challenging antenna setups. These require-

ments include the antenna size, low fabrication cost, loss, beam characteristics, field of view, thermal stability, bandwidth and the possibility of high integration.

[0003] In the automotive sector, apart from detecting objects located directly in front of a vehicle, it is becoming increasingly important to detect objects with higher angular deviations, such as pedestrians going to cross a street. Similarly, the detection of a curve area is an important objective. This way, the end of a traffic jam behind a curve, for example, may be detected earlier. In order to realize this aim, beam-forming and beam steering in azimuth direction is necessary. Preferably, beam-forming and beam-steering in azimuth direction is complemented with beam-forming and beam-steering in elevation to detect objects on a hilltop or in a valley. Furthermore, automotive radars should be able to detect such objects in distances of 100m or more. However, today’s automotive long range radar antenna cannot steer a beam in 2D.

[0004] The“background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.

SUMMARY

[0005] It is an object to provide a planar antenna array, an antenna device and an automotive radar system, which allow 2D electronical beam-steering in azimuth as well as elevation.

[0006] According to an aspect there is provided a planar antenna array compris ing: a first linear array comprising a first group and a second group of first radiation elements,

a second linear array comprising a first group and a second group of second radiation elements, and

a common feed port for transmission and/or reception of a feed signal to or from the first linear array and the second linear array,

wherein the first linear array and the second linear array are intersecting and wherein the common feed port is arranged at an intersection point of the first linear array and the second linear array.

[0007] According to a further aspect there is provided an antenna device com prising a plurality of planar antenna arrays as disclosed herein.

[0008] According to a further aspect there is provided an automotive radar sys tem comprising at least one radar sensor,

wherein the radar sensor comprises a plurality of planar antenna arrays as disclosed herein and/or an antenna device as disclosed herein.

[0009] Embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed antenna device and automotive radar system have similar and/or identical preferred embodiments as the claimed planar antenna array, in particular as defined in the dependent claims and as disclosed herein.

[0010] One of the aspects of the disclosure is to provide an antenna array which is configured to radiate electromagnetic radiation with a fixed radiation pattern in elevation (vertical) and azimuth (horizontal) planes. Preferably, the antenna array is cross-shaped (also called plus-shaped) and provides a pencil beam shape.

[0011] Arranging a plurality of planar antenna arrays in a plane, wherein the individual antenna arrays have shaped and/or focussed beams in azimuth as well as elevation, a variety of beams can be combined to different beam shapes in azimuth and/or elevation. This allows to create a long range radar including two-dimensional beam steering, beam-forming and angle-of arrival (AoA) processing. The disclosed 2D antenna device can be used as transceiver, transmitter or receiver antenna. If the arrangement is applied to transmit antenna arrays, the transmitted beam can be tilted into a desired direction. In fact, a radar device configured to steer and/or focus its transmission beam into any angular direction may detect targets with increased signal to noise ratio at a particular angle. If the arrangement is used for receiving antenna arrays, an incoming signal's AoA can be determined in post processing.

[0012] The foregoing paragraphs have been provided by way of general intro duction, and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A more complete appreciation of the disclosure and many of the at tendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Figs. 1 A and IB show a top view of a first embodiment of a planar antenna array and a corresponding antenna beam pattern according to the present disclosure,

Figs. 2A and 2B show a top view of a second embodiment of a planar antenna array and a corresponding antenna beam pattern according to the present disclo sure,

Figs. 3 A and 3B show a top view of a third embodiment of a planar antenna array and a corresponding antenna beam pattern according to the present disclosure, Fig. 4 shows a top view of a fourth embodiment of a planar antenna array according to the present disclosure,

Fig. 5 shows a top view of a fifth embodiment of a planar antenna array according to the present disclosure,

Fig. 6 shows a top view of a sixth embodiment of a planar antenna array according to the present disclosure,

Figs. 7 A and 7B show an arrangement of antenna elements in x-z-plane and a corresponding antenna beam pattern achievable with the arrangement of antenna ele ments,

Figs. 8A, 8B and 8C show a first embodiment of an antenna device, a corresponding antenna beam pattern achievable with the first embodiment of an antenna device and a corresponding sectional view of said antenna beam pattern according to the present disclosure,

Figs. 9A, 9B and 9C show a second embodiment of an antenna device, a corresponding antenna beam pattern achievable with the second embodiment of an antenna device and a corresponding sectional view of said antenna beam pattern according to the present disclosure,

Fig. 10 shows a top view of a third embodiment of an antenna device ac cording to the present disclosure, and

Fig. 11 shows an application example of an exemplary automotive radar system according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] Referring now to the drawings, wherein like reference numerals desig nate identical or corresponding parts throughout the several views, Fig. 1 A and IB show a top view of a first embodiment of a planar antenna array 10 and a corresponding antenna beam pattern according to the present disclosure. The first embodiment of a planar antenna array 10 as shown in Fig. 1A comprises a (vertical) first linear array 12 comprising a first group of first radiation elements 16 and a second group of first radiation elements 18 and a (horizontal) second linear array 22 comprising a first group of second radiation elements 26 and a second group of second radiation elements 28. The first radiation elements 14 are patch antenna elements in this embodiment, whereas the second radiation elements 24 are comb-line antenna elements, i.e. the horizontal as well the vertical antenna strip lines are each composed of the same antenna radiation elements. In particular, each group of first radiation elements 14 comprises four patch antenna elements and each group of second radiation elements 24 comprises five comb-line antenna elements. However, each group of first and second radiation elements may comprise a different number of radiation elements.

[0015] The first linear array 12 and the second linear array 22 are arranged in a substantially perpendicular manner, i.e. the angle between the first linear array 12 and the second linear 22 is 90°±10°, particularly 90°±5°, more particularly 90°. Accordingly, the first embodiment of the planar antenna array 10 is plus-shaped center fed antenna array. Since the antenna array consists of patch array elements in the first linear array 12 and comb-line elements in the second linear array 22, all radiation elements radiate or receive identical polarization.

[0016] At the intersection point of the first linear array 12 and the second linear array 22 there is arranged a common feed port 20 for transmission and/or reception of a feed signal to or from the first linear array 12 and the second linear array 22. The common feed port 20 is connected to the first and second radiation elements via a strip line. In fact, there are four strip lines leaving the common feed port 20, wherein each strip line corre sponds to a group of first or second radiation elements. Generally, the strip lines are configured to match the impedance of a feed line to or from the common feed port. In case the antenna array is a printed circuit board (PCB) antenna, said feed line is on the other side of PCB than the strip lines. Preferably, the sum of the impedances of the four strip lines is configured to equal the feeding line's impedance.

[0017] Within each group of antenna elements (i.e. radiation elements), the patch antenna elements and the comb-line antenna elements, respectively, are equally spaced apart. Preferably, the element spacing is l/2 (or close to l/2), wherein l represents the wavelength of transmitted and received electromagnetic radiation to generate an in phase excitation among all elements at a given design frequency. However, the two patch antenna elements neighboring the common feed port 20, have different distances from the common feed port 20. The same applies to the comb-line antenna elements. In fact, there is arranged a first phase shifting element 30 between the common feed port 20 and the first group of first radiation elements 16 and a second phase shifting element 32 between the common feed port 20 and the first group of second radiation elements 26, wherein the first phase shifting element 30 and the second phase shifting element 32 comprise a strip line element of a predefined length. Both the first and the second phase shifting element are configured to shift the phase of the feed signal by 180°. However, generally, the shifting elements may be configured to shift the phases of the feed signal to any phase value between 0° and 360°.

[0018] Fig. IB shows an antenna beam pattern as emitted from the first embod iment of a planar antenna array 10 as shown in Fig. 1A. The axes shown in Fig. IB repre sent the positions of the first and second linear array, respectively. The antenna beam pattern particularly shows the far-field realized gain values, wherein the darker grey levels at the positions of the first and second linear array indicate a higher gain than other re gions. The concatenated antenna array as shown in Fig. 1A is configured to radiate with a fixed focused radiation pattern in elevation (vertical) and azimuth (horizontal) planes.

[0019] Fig. 2A shows a top view of a second embodiment of a planar antenna ar ray 10 according to the present disclosure. The second embodiment of a planar antenna array 10 comprises a first linear array 12 and a second linear array 22, wherein both arrays are arranged in a cross-shaped manner. The first linear array 12 comprises a first group of first radiation elements 16 and a second group of first radiation elements 18, wherein both groups comprise two patch antenna elements in this embodiment. The second linear array 22 comprises a first group of second radiation elements 26 and a second group of second radiation elements 28, wherein both groups comprise two comb-line antenna elements. At the point of intersection of the first linear array 12 and the second linear array 22, there is arranged a common feed port 20 configured to transmit and/or receive a feed signals to or from the first linear array 12 and the second linear array 22.

[0020] Between the common feed port 20 and the nearest patch antenna element of the first group of first radiation elements 16 the strip line is prolonged in comparison with the strip line between the common feed port 20 and the nearest patch antenna element of the second group of first radiation elements 18. In fact, the prolonged distance between the common feed port 20 and the nearest patch antenna element of the first group of first radiation elements 16 causes a phase shift in the feed signal, preferably by 180°. Further more, between the common feed port 20 and the nearest comb-line antenna element of the first group of second radiation elements 26 the strip line is prolonged in comparison with the strip line between the common feed port 20 and the nearest comb-line antenna element of the second group of second radiation elements 28. The prolonged distance between the common feed port 20 and the nearest comb-line antenna element of the first group of second radiation elements 26 causes a phase shift in the feed signal, preferably by 180°.

[0021] Fig. 2B shows an antenna beam pattern corresponding to the second em bodiment of a planar antenna array 10 according to the present disclosure. The antenna beam pattern particularly shows the far-field realized gain values, wherein the darker grey levels at the positions of the first and second linear array indicate a higher gain than other regions. Compared to the antenna beam pattern shown in Fig. IB of the first embodiment of an antenna array the center-fed plus shape antenna array radiation pattern shown in Fig. 2B presents a wider pencil beam shape radiation pattern. Due to the reduced number of radiation elements in the strip lines, the second embodiment of a planar antenna array shows a wider viewing angle in the corresponding radiation planes as the first embodiment of a planar antenna array.

[0022] Fig. 3A shows a top view of a third embodiment of a planar antenna ar ray 10 according to the present disclosure. In this third embodiment the planar antenna array 10 comprises a first linear array 12 and a second linear array 22, wherein the number of radiation elements of the first linear array 12 is different from the number of radiation elements of the second linear array 22. In particular, the first linear array 12 comprises three radiation elements in each group of radiation elements and the second linear array 22 comprises radiation elements in each group. Accordingly, the planar antenna array 10 is an asymmetric element center fed antenna array. The arrangement of more or less radiation elements in the array configuration 10 allows for a fixed frequency-independent custom ized radiation pattern. In other words, by toggling the number of radiation elements in the array configuration, a fixed frequency-independent customized radiation pattern may be obtained.

[0023] Fig. 3B shows an antenna radiation pattern corresponding to the third embodiment of a planar antenna array 10 according to the present disclosure. The antenna radiation pattern particularly shows the far-field realized gain values, wherein the darker grey levels at the positions of the first and second linear array indicate a higher gain than other regions. As can be seen by comparing the radiation pattern of Fig. 3B with the radiation pattern of Fig. 2B, the viewing angle in the radiation plane of the first linear array 12 is narrower for the third embodiment. This is due to the fact, that the number of radia tion elements in the first linear array is higher for the third embodiment than for the second embodiment of a planar antenna array. Furthermore, the first linear array is longer than the second linear array. In general, an increase in the number of antenna elements causes an increase in the antenna aperture and consequently the angle of the main beam to tilt towards the broadside of the antenna. As can be seen from Fig. 3B the antenna array 10 provides a wide illumination and viewing angle in horizontal (i.e. azimuth direction) and a narrow illumination and viewing angle in vertical (i.e. elevation direction), wherein the first linear array 12 extends in elevation direction and the second linear array 22 extends in azimuth direction. This property for a radiation/sensitivity pattern is particularly desired in automotive short range or medium range applications. [0024] Fig. 4 shows a top view of a fourth embodiment of a planar antenna array 10 according to the present disclosure. In this embodiment the strip lines of the first linear array 12 and the second linear array 22 are twisted with respect to the radiation elements 14 and 24 thereon (as compared to the antenna array shown in Fig. 3A, for example). However, the angle between the first linear array 12 and the second linear array 22 is still 90°.. The angle between the comb-line antenna elements and the strip lines of the second linear array 22 is configured to be 45°. This way, the patch array elements in the first linear array 12 and the comb-line elements in the second linear array 22 radiate or receive identical polarization.

[0025] In general, the angle between the linear arrays needs not necessarily to be 90°, but may also be smaller or larger, e.g. in a range between 45° and 135°. Preferably, the radiation elements of a twisted second linear array are twisted by the same angle as the second linear array is twisted with respect to the first linear array.

[0026] Generally, a planar antenna array may comprise more than two linear ar rays. For example, an antenna array may comprise two linear arrays which are arranged in parallel and a further linear array crossing said linear arrays, preferably in a perpendicular manner. Furthermore, antenna strip lines may be rotated by any angle and/or truncated or extended in length. Accordingly, the planar antenna array may be arranged in a star-like formation. Furthermore, the planar antenna array topology of the present invention is not restricted to certain numbers of radiation elements per array. Figs. 1A, 2A, 3A and 4 only show center fed antenna arrays using combination of patch array elements with comb-line elements. However, any combination with SIW (substrate-integrated waveguide) slot elements or other antenna element types is possible. Still, the polarizations of the electrical and magnetic field as radiated from or received by the linear arrays of the antenna should match. Otherwise there is the risk of signal elimination. For example, in case of two linear arrays arranged like a cross, the first linear array 12 and the second linear array 22 are preferably configured to transmit and/or receive electromagnetic radiation of the same polarization in a far field. In other words, the first linear array and the second linear array are configured to transmit and/or receive signals of different polarizations with respect to their orientation.

[0027] Apart from that a group of radiation elements may comprise two or more branches of radiation elements. In other words, the antenna array may comprise a strip line comprising multiple strip line branches. Accordingly, many different antenna topologies can be employed for 2D beam steering and beam forming.

[0028] Fig. 5 shows a top view of a fifth embodiment of a planar antenna array 10 according to the present disclosure. In the fifth embodiment of the planar antenna array 10 the first group of first radiation elements 16 comprises two branches of first radiation elements 13a and 13b and the second group of first radiation elements 18 comprises two branches of first radiation elements 15a and 15b. The two branches of first radiation elements 13a and 13b are arranged in parallel and are aligned with the strip line of the first group of first radiation elements 16 extending from the common feed port 20. Also the two branches of first radiation elements 15a and 15b of the second group of first radiation elements 18 are arranged in parallel to each other and to the strip line they are originating from. However, in general, a branch may be rotated by any angle with respect to the strip line it originates from. Furthermore, the length of different branches may vary. According ly, a branch may be truncated or extended in length. This also implies that the number of radiation elements of different branches may be different.

[0029] Fig. 6 shows a top view of a sixth embodiment of a planar antenna array 10 according to the present disclosure. In the fifth embodiment of the planar antenna array 10 the first group of first radiation elements 16 comprises two branches of first radiation elements 14 and the second group of first radiation elements 18 comprises two branches of first radiation elements 14. Likewise, the first group of second radiation elements 26 comprises two branches of second radiation elements 24, 23a and 23b, and the second group of second radiation elements 28 comprises two branches of second radiation ele ments 24, 25a and 25b. The antenna array configuration 10 depicted in Fig. 6 allows to bring a maximum number of radiating elements onto a minimum substrate area. This minimizes the antenna aperture and maximizes the antenna efficiency of the array. By its arrangement, the antenna array 10 allows to generate roundly shaped beams. In general, a splitting of branches into two or more sub-branches may be cascaded multiple times.

[0030] Fig. 7A shows an arrangement of single radiation elements in x-z-plane. “Rx” radiation elements are receiving antenna elements, whereas antenna elements denot ed with“Tx” are transmitting antenna elements. There are arranged sixteen“Rx” antenna elements and one“Tx” antenna element in a Costas array. The“Rx” and“Tx” radiation elements are configured to receive and transmit, respectively, electromagnetic radiation of (substantially) the same frequency. The“Rx” antenna elements are configured to receive signals that have been transmitted before by the“Tx” antenna element. In general, small frequency differences between the“Tx” and“Rx” signals may be caused by chirping or by Doppler effects in an FMCW (frequency modulated continuous wave) Radar application. The axes shown in Fig. 7A help recognize the distance between the radiation elements. The axes are normalized to a grid spacing of l/2, wherein l represents the wavelength of transmitted and received electromagnetic radiation, respectively.

[0031] Fig. 7B shows a corresponding antenna beam pattern in case that each individual antenna of the Costas array is represented by an isotropic radiator. In particular, Fig. 7B shows the far-field realized gain values of the antenna arrangement in azimuth and elevation. The corresponding gain scale is depicted on the right hand side of Fig. 7B, wherein the gain is given in decibels (dB). The radiation pattern shown in Fig. 7B provides a side-lobe suppression of about 8.5dB.

[0032] Fig. 8 A shows a first embodiment of an antenna device 100 according to the present disclosure. The antenna device 100 may be used as signal transmitter as well as a receiver. In this embodiment multiple planar antenna arrays are arranged as a Costas array in a plane. The planar antenna arrays comprise first linear arrays of patch antenna elements and perpendicular thereto second linear arrays of comb-line antenna elements. The planar antenna arrays each provide a pencil beam shape, which cannot be tilted electronically. However, by arranging a plurality of planar antenna arrays 10 in a plane there is generated an antenna device 100 which allows beam- forming and beam-steering in both azimuth and elevation. Arranging the antenna arrays 10 in a Costas array allows to use a minimum number of antenna arrays 10 while achieving a maximum aperture and resolution for the antenna device 100.

[0033] In this embodiment, the antenna array 10c is configured as a transmitting antenna array, whereas all other antenna arrays are configured as receiving antennas. While some antenna arrays are symmetric center fed antenna arrays, i.e. some antenna arrays comprise the same number of antenna elements in each strip line, other antenna arrays in the Costas array are asymmetric center fed antenna arrays. For example, antenna arrays 10a and 10b are asymmetric, whereas array 10c is symmetric. In particular, the first group of second radiation elements 26a of the antenna array 10a comprises a singe comb-line antenna element, while the second group of second radiation elements 28a comprises two comb-line antenna elements. On the other hand, the first group of second radiation ele ments 26b of the antenna array 10b comprises two comb-line antenna elements, while the second group of second radiation elements 28b comprises a single comb-line antenna element.

[0034] The reduced number of radiation elements in particular strip lines allows to place certain antenna arrays within a limited space and particularly allows a placing of antenna arrays in accordance with a Costas array. In fact, compared with the arrangement of single antenna elements as shown in Fig. 7A, each beam may be focused into a sharper pencil when replacing each antenna element by antenna arrays. In fact, the antenna beam pattern achievable with the first embodiment of an antenna device 100 as shown in Fig. 8B indicates that the resulting antenna beam is much more focused than the beam shown in Fig. 7B. Accordingly, the Costas array antenna device 100 as shown in Fig. 8A allows for beam-forming and beam-steering even for remote distances. Generally, in order to steer the antenna beam of the antenna device 100 to different directions, the common feed ports of the planar antenna arrays may be turned on and off individually, or it may be controlled to which of the feed ports (e.g. to only one, or two, or three, or all) the feed signal is provid ed. Further, it may optionally be possible to switch the input phases of the common feed ports, preferably at least between 0° and 180°.

[0035] Fig. 8C shows a sectional view of the Costas array beam pattern accord ing to the present disclosure. Particularly, the side lobes' level and width corresponding to the antenna beam pattern as shown in Fig. 8B can be derived from Fig. 8C.

[0036] Generally, if the space between the planar antenna arrays 10 is getting too narrow, individual strip (or comb lines) may be mirrored on a horizontal or vertical axis through the common feed port. In fact, such a flipping may not have any impact on the resulting antenna beam. If the space between the antenna arrays is still too narrow, the strip lines of an antenna array may be cut, i.e. truncated. In fact, this is shown multiple times in Fig. 8A. For example, the antenna array located at x-position 4*l and at y-position 4*l, i.e. the planar antenna array 10a, comprises a truncated strip line in the first group of second radiation elements 26a. If the identical number of elements is cut on the opposite side of the common feed port, i.e. in the second group of second radiation elements 28b, the resulting beam direction may not be influenced. However, the beam width may become slightly increased due to the reduction of radiation elements. Taking the antenna device 100 as shown in Fig. 8A, the side lobes are of around -19dB° and are +/ -16.5° wide (33° in total).

[0037] The antenna arrays' centers (i.e. the common feed ports) in the example of Fig. 8A are aligned to a grid raster of l/2. This enables a beam-steering from -90° to +90° in elevation and azimuth. A wider spacing than l/2 may result in an increased directivity. An individual antenna array with four elements in each direction, i.e. in each strip line, may have a beam-width of about 33°. This implies that beam-steering over the total orbit (-90°... +90°) is not advisable. Increasing the antenna’s center grid raster may limit the steering capability to smaller angles with the tradeoff that grating-lobes may occur. Grating-lobes may generate ambiguities in the angular domain. The beam width of the individual antennas and the angle where grating-lobes occur may have to be aligned. An increased antenna center grid-spacing may also relax the narrow spaces between two individual antennas.

[0038] Generally, the relationship

holds, wherein d is the antenna spacing and 0_max the maximum angle of the steering. In the case of eight-patch or comb-line (four in each linear array) elements e_max equals 33° or +/- 16.5°. Accordingly, d = l*0.78.

[0039] Fig. 9A shows a second embodiment of an antenna device 100 according to the present invention. The antenna device 100 comprises a plurality of planar antenna arrays arranged as Costas array. The antenna spacing grid in this embodiment is l*0.86. None of antenna arrays of this embodiment comprises a strip line which is cut. In fact, each antenna array shown in Fig. 9A is a symmetric eight-antenna-element array. Fig. 9B shows an antenna beam pattern achievable with the second embodiment of an antenna device 100 and Fig. 9C shows a measurement of the side lobes' level and width corresponding to the antenna beam pattern as shown in Fig. 8B. In particular, Figs. 8B and 8C show that the second embodiment allows to generate a very sharp pencil beam.

[0040] Instead of using only a single“Tx” antenna array, multiple transmitting antenna arrays may be used in the device 100. Accordingly, the device's beam may be pre shaped in azimuth as well as elevation. If there are multiple“Tx” antenna arrays used in the device 100, the beam may be steered into a region of interest, e.g. into a curve in the case of an automotive application. [0041] Fig. 10 shows a top view of a third embodiment of an antenna device 100 according to the present disclosure. While in the first and second embodiment of an antenna device as shown in Figs. 8A and 9A all first linear arrays and all second linear are arranged in parallel, respectively, some planar antenna arrays of the third embodiment are rotated with respect to the remaining arrays. For example, the first linear array 12a of the antenna array 10a is rotated by 45° with respect to the first linear array 12c of antenna array 10c. Likewise, the first linear array 12b of antenna array 10b is rotated by 45°. However, the array 10b is rotated the opposite direction with respect to the rotation direc tion of array 10a. By rotating the antenna arrays both their first linear and second linear arrays are rotated, however the patch antenna elements and the comb-line antenna elements of all linear antenna arrays are arranged in parallel, respectively. This guarantees that the polarizations of all elements in the antenna device 100 are identical.

[0042] Fig. 11 shows an application example of an exemplary automotive radar system 200 according to the present disclosure. In particular, Fig. 10 shows an automotive radar system comprising two radar sensors 100a and 100b, wherein each radar sensor comprises a plurality of planar antenna arrays. The automotive radar system allows beam forming and beam-steering in azimuth and elevation direction over long ranges, i.e. for distances of 100m or more. Hence, objects on a hilltop, in a valley or in a curve may be detected early.

[0043] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0044] In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine-readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure. Further, such a software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommuni cation systems.

[0045] The elements of the disclosed devices, apparatus and systems may be implemented by corresponding hardware and/or software elements, for instance appropri ated circuits. A circuit is a structural assemblage of electronic components including conventional circuit elements, integrated circuits including application specific integrated circuits, standard integrated circuits, application specific standard products, and field programmable gate arrays. Further a circuit includes central processing units, graphics processing units, and microprocessors which are programmed or configured according to software code. A circuit does not include pure software, although a circuit includes the above-described hardware executing software.

[0046] It follows a list of further embodiments of the disclosed subject matter:

1. A planar antenna array (10) comprising:

a first linear array (12) comprising a first group and a second group of first radiation elements (14),

a second linear array (22) comprising a first group and a second group of second radiation elements (24), and

a common feed port (20) for transmission and/or reception of a feed signal to or from the first linear array (12) and the second linear array (22),

wherein the first linear array (12) and the second linear array (22) are intersecting and wherein the common feed port (20) is arranged at an intersection point of the first linear array (12) and the second linear array (22).

2 The planar antenna array (10) as defined in embodiment 1, wherein the first linear array (12) is arranged substantially perpendicular to the second linear array (14).

3. The planar antenna array (10) as defined in embodiment 1 or 2,

wherein the common feed port (20) is arranged between the first group of first radiation elements (16) and the second group of first radiation elements (18) and between the first group of second radiation elements (26) and the second group of second radiation elements (28).

4. The planar antenna array (10) as defined in any of the preceding embodi ments,

wherein the first radiation elements (14) of the first linear array (12) and the second radiation elements (24) of the second linear array (22) are configured to transmit and/or receive electromagnetic radiation of the same polarization in a far field.

5. The planar antenna array (10) as defined in any of the preceding embodi ments, wherein the first linear array (12) is configured to transmit and/or receive signals of a polarization different to its orientation and wherein the second linear array (22) is configured to transmit and/or receive signals of a polarization same as its orientation.

6. The planar antenna array (10) as defined in embodiments 1 to 5,

wherein the first linear array (12) is oriented to transmit and/or receive signals of horizon tal polarization and wherein the second linear array (22) is oriented to transmit and/or receive signals of vertical polarization and/or

wherein the first linear array (12) is oriented to transmit and/or receive signals of clockwise circular polarization and wherein the second linear array (22) is oriented to transmit and/or receive signals of counterclockwise circular polarization.

7. The planar antenna array (10) as defined in any of the preceding embodi ments, wherein the first linear array (12) is longer than the second linear array (22). 8. The planar antenna array (10) as defined in any of the preceding embodi ments, wherein the number of first radiation elements (14) is higher than the number of second ration elements (24).

9. The planar antenna array (10) as defined in any of the preceding embodi ments,

wherein the first radiation elements (14) comprise a first type of antenna elements and wherein the second radiation elements (24) comprise a second type of antenna elements, wherein the first type of antenna elements is different from the second type of antenna elements.

10. The planar antenna array (10) as defined in embodiment 9,

wherein the first type and the second type of antenna elements comprises any type of 2D planar antenna elements, in particular any of patch antenna elements, slotted waveguide elements, substrate-integrated-waveguide elements, comb-line antenna elements, dipole antenna elements and loop elements.

11. The planar antenna array (10) as defined in any of the preceding embodi ments,

further comprising a first phase shifting element (30) between the common feed port (20) and the first group of first radiation elements (16) and/or a second phase shifting element (32) between the common feed port (20) and the first group of second radiation elements (26).

12. The planar antenna array (10) as defined embodiment 11,

wherein the first phase shifting element (30) and/or the second phase shifting element (32) is configured to shift the phase of the feed signal by 180°.

13. The planar antenna array (10) as defined in embodiments 11 or 12, wherein the first phase shifting element (30) and/or the second phase shifting element (32) comprises a strip line element of a predefined length.

14. The planar antenna array (10) as defined in any preceding embodiment, wherein at least the first group of first radiation elements (16) comprises two or more branches of first radiation elements (13a, 13b) and/or wherein at least the first group of second radiation elements (23a, 23b) comprises two or more branches of second radiation elements.

15. The planar antenna array (10) as defined in embodiment 14,

wherein the two or more branches of first radiation elements (13a, 13b) and/or the two or more branches of second radiation elements (23a, 23b) are arranged in parallel.

16. The planar antenna array (10) as defined in any preceding embodiment, wherein the common feed port (20) is arranged asymmetrically between the neighboring first radiation elements of the first and second groups of the first linear array and/or asymmetrically between the neighboring second radiation elements of the first and second groups of the second linear array.

17. An antenna device (100) comprising a plurality of planar antenna arrays (10) as defined in any preceding embodiment, wherein the plurality of planar antenna arrays (10) is arranged in a plane.

18. The antenna device (100) as defined in embodiment 17,

further comprising a signal source for generating a plurality of feed signals and for provid ing said feed signals to the common feed ports (20) of the planar antenna arrays (10).

19. The antenna device (100) as defined in embodiment 17 or 18, wherein the common feed ports (20) of the planar antenna arrays (10) are arranged on a grid with a grid spacing corresponding to a half of a wavelength of transmitted and/or received electromagnetic radiation.

20. The antenna device (100) as defined in any of the embodiments 17 to 19, wherein the planar antenna arrays are arranged in a Costas array.

21. The antenna device (100) as defined in any of the embodiments 17 to 20, wherein the first linear arrays (12) of at least two of the planar antenna arrays (10) are parallel to each other and/or wherein the second linear arrays (22) of at least two of the planar antenna arrays (10) are parallel to each other.

22. The antenna device (100) as defined in any of the embodiments 17 to 21, wherein for at least two of the planar antenna arrays (10) the number of first radiation elements (14) of the first and the second group of first radiation elements is different and/or the number of second radiation elements (24) of the first and the second group of second radiation elements is different.

23. The antenna device (100) as defined in embodiment 22,

wherein the overall number of first radiation elements (14) of the first groups of first radiation elements (16) of the plurality of planar antenna arrays (10) is equal to the number of first radiation elements (14) of the second groups of first radiation elements (18) and wherein the overall number of second radiation elements (24) of the first groups of second radiation elements (26) of the plurality of planar antenna arrays (10) is equal to the number of second radiation elements(24) of the second groups of second radiation elements (28).

23. An automotive radar system (200) comprising at least one radar sensor

(150a, 150b), wherein the radar sensor comprises a plurality of planar antenna arrays (10) as defined in any of the embodiments 1 to 14 and/or an antenna device as defined in any of the embodiments 15 to 21.

Claims

1. A planar antenna array (10) comprising:

2. The planar antenna array (10) as claimed in claim 1,

wherein the first linear array (12) is arranged substantially perpendicular to the second linear array (14).

3. The planar antenna array (10) as claimed in claim 1,

4. The planar antenna array (10) as claimed in claim 1,

5. The planar antenna array (10) as claimed in claim 2, wherein the first linear array (12) is configured to transmit and/or receive signals of a polarization different to its orientation and wherein the second linear array (22) is config ured to transmit and/or receive signals of a polarization same as its orientation.

6. The planar antenna array (10) as claimed in claim 1,

7. The planar antenna array (10) as claimed in claim 6,

8. The planar antenna array (10) as claimed in claim 1,

9. The planar antenna array (10) as claimed in claim 8,

10. The planar antenna array (10) as claimed in claim 8,

wherein the first phase shifting element (30) and/or the second phase shifting element (32) comprises a strip line element of a predefined length.

11. The planar antenna array (10) as claimed in claim 1,

wherein at least the first group of first radiation elements (16) comprises two or more branches of first radiation elements (13a, 13b) and/or wherein at least the first group of second radiation elements (23a, 23b) comprises two or more branches of second radiation elements.

12. The planar antenna array (10) as claimed in claim 1,

wherein the common feed port (20) is arranged asymmetrically between the neighboring first radiation elements of the first and second groups of the first linear array and/or asymmetrically between the neighboring second radiation elements of the first and second groups of the second linear array.

13. An antenna device (100) comprising a plurality of planar antenna arrays (10) as claimed in claim 1, wherein the plurality of planar antenna arrays (10) is arranged in a plane.

14. The antenna device (100) as claimed in claim 13,

15. The antenna device (100) as claimed in claim 13,

wherein the common feed ports (20) of the planar antenna arrays (10) are arranged on a grid with a grid spacing corresponding to a half of a wavelength of transmitted and/or received electromagnetic radiation.

16. The antenna device (100) as claimed in claim 13,

wherein the planar antenna arrays (10) are arranged in a Costas array.

17. The antenna device (100) as claimed in claim 13, wherein the first linear arrays (12) of at least two of the planar antenna arrays (10) are parallel to each other and/or wherein the second linear arrays (22) of at least two of the planar antenna arrays (10) are parallel to each other.

18. The antenna device (100) as claimed in claim 13,

wherein for at least two of the planar antenna arrays (10) the number of first radiation elements (14) of the first and the second group of first radiation elements is different and/or the number of second radiation elements (24) of the first and the second group of second radiation elements is different.

19. The antenna device (100) as claimed in claim 18,

20. An automotive radar system (200) comprising at least one radar sensor (150a, 150b), wherein the radar sensor comprises a plurality of planar antenna arrays (10) as claimed in claim 1 and/or an antenna device as claimed in claim 13.