Patent Application
20250038417
The present disclosure relates to an antenna device for use in automotive radar applications.
U.S. Pat. No. 5,170,174 A, published on 8 Dec. 1992 by Thomson CSF relates to a patch-excited non-inclined radiating slot waveguide wherein the waveguide has slots perpendicular to the axis of the waveguide which are cut in a narrow wall of the waveguide and a printed circuit plate. The plate has patches for coupling with the energy which is propagated in the waveguide and microstrip lines connected to the patches to excite the slots with the energy thus tapped. These slot waveguides can be used particularly in array antennas
U.S. Pat. No. 4,435,715 A published on 6 Mar. 1984 by Hughes Aircraft Co. relates to a rod-excited waveguide slot antenna, which power-radiating slotted waveguide comprises one or more rods mounted inside the waveguide adjacent a non-inclined slot. The rod causes power to be radiated and because the slot is non-inclined, undesirable cross-polarized radiation is minimized. The energy radiated from the slot can be varied by varying the area between the rod and the waveguide walls.
U.S. Pat. No. 5,422,652 A: published on 6 Jun. 1995 by Thomson CSF relates to a waveguide with non-inclined radiating slots excited by flat metal plates, which waveguide has slots perpendicular to the axis of the waveguide, cut out in a narrow wall of the waveguide, there are positioned, on each side of each slot, pairs of metal flat plates symmetrical with respect to the central axis of the slot. These flat plates modify the electrical field at the associated slot and make it possible to excite it, the value of the coupling being set by the adjusting of the size of the flat plates and of their position with respect to the corresponding radiating slot.
The herein described antenna devices are designed as Multi-Input-Multi-Output (MIMO) antennas, e.g. for radar applications in automotive applications. Such antenna devices typically require individual antenna elements and/or waveguide channel segments which are configured for sending and/or receiving signals simultaneously and/or according to a specific pattern. Depending on the field of application, preferred variations of the antenna device may comprise at least two individual waveguide channel segments. The at least two individual waveguide channel segments can be operated independently from each other.
Especially for automotive applications typically a vertical polarization of the radiated signal is desired. In known antenna devices with a waveguide structure, a vertical polarization is usually implemented by arranging the waveguide apertures angularly displaced with respect to the main extension direction of the waveguide channel segments. In order to be able to excite a signal through the waveguide apertures, at least some part of the waveguide propagating currents must be oriented essentially perpendicular to the orientation of the waveguide apertures. Therefore, the waveguide apertures of the known antenna devices are typically angularly displaced such that they can radiate a signal. However, this creates an undesired partial horizontal polarization of the radiated signal.
Alternatively, for certain applications also a horizontal polarization of the excited signal can be required. A horizontal signal is typically excited from known antenna devices, by placing the waveguide apertures parallel to the main extension direction of the waveguide channel segment. Unlike the previous case, the neighboring waveguide apertures must be spaced with one guided wavelength distance with respect to each other to keep a uniform phase between neighboring waveguide apertures. As a result, to be able to place a sufficient number of waveguide apertures to be able to also realize more complex radiation patterns, the waveguide channel segments need to be comparatively long, which results in an undesired size of the overall antenna device.
One objective which is addressed by the present disclosure can be seen in influencing the field and current characteristics of the signal within the waveguide channel segment to obtain a space saving design with a high accuracy of the antenna directivity.
An antenna device according to the present disclosure typically comprises an antenna plate having a front face and a back face. The disclosed antenna device can be part of an antenna assembly which typically comprises the antenna device, a printed circuit board and a thereon arranged electronic component which is interconnected to the antenna plate. To keep the manufacturing costs low in view of the vast quantities, it is desirable to design antenna devices that comprise no more than two stacked layers (parts). Good results can be achieved when the antenna plate comprises a back part and front part, wherein the back part and the front part are interconnected to each other along a front face of the back part and a back face of the front part. The front face of the back part and a back face of the front part do not have to be essentially flat. If appropriate, the front part and/or the back part can be skeletonized to reduce a contact surface. This is advantageously as the minimized contact area increases the surface pressure of the contact area and therefore results in a more accurate alignment of the front and the back part in the area of the waveguide channel and/or a waveguide channel segment. Usually, the two parts are assembled together, wherein a part of the waveguide channel segment is arranged in the front face of the back part and a part of the waveguide channel segment is arranged in the back face of the front part, which are aligned congruently. The back part and/or the front part can be made by injection molding of at least one plastic material. An advantageous construction can be achieved, when at least one waveguide channel and/or a waveguide channel segment extends at least partially in the front face of the back part and/or the back face of the front part.
To even further reduce the manufacturing effort, the antenna plate can also be designed as a single layered antenna plate with an electromagnetic band gap structure (EBG). Instead of combining two metallized plastic layers, the antenna plate can comprise only one metallized plastic layer, interconnected to a printed circuit board (PCB). To assemble the antenna plate and the PCB together and avoid leakage of power, there are different alternative ways. E.g. conductive glue, soldering, etc.
In a preferred variation, the antenna plate can consist of only one layer, wherein a number of pillars are arranged at the back face of the antenna plate, which are configured to define at least part of the contour of the waveguide channel segment. An EBG structure as mentioned before implies that the antenna plate is not flat respectively planar, but is structured, e.g. corrugated respectively recessed, with the EBG elements projecting away from the generally flat respectively planar back face of the antenna plate. Such a design allows connecting the antenna plate to a flat respectively planar PCB. The font part and/or the back part may preferably at least partially comprise pillars at least partially forming the outer contour of the waveguide channel segment. As said above the font part and the back part can be made integrally as a single layered antenna plate. The pillars are typically configured to guide the signal through the waveguide channel segment. The EBG structures are arranged essentially around the hollow waveguide channel segments. An electromagnetic band gap structure allows to block electromagnetic waves at a given range of frequencies, behaving as a conductive wall without the need to have direct and/or ohmic contact between the antenna plate and the PCB, thereby still implementing a waveguide structure. Alternatively, or in addition, the antenna plate can consist of only one flat respectively planar layer, wherein a printed circuit board is interconnected to the antenna plate comprising mushroom-shaped electromagnetic band gap elements. The mushroom-shaped electromagnetic band gap elements may for example extend from the back face of the PCB and/or through the body of the PCB. The mushroom-shaped electromagnetic band gap elements can be arranged in between, respectively around the PCB waveguide passages, thereby improving the electromagnetic isolation respectively decoupling.
A preferred antenna device according to the present disclosure usually comprises at least one waveguide channel segment which has a front section and a back section which are preferably arranged in the antenna plate. The cross-section of the waveguide channel segment is typically essentially rectangular. In case that the antenna plate is made by injection molding, the edges of the waveguide channel segment can be designed slightly inclined such that the antenna plate can be demolded from the mold more easily. To improve the radiation efficiency, the front section can have a bigger cross-section than the back section. Therefore, front and back section can be symmetrically with respect to a parting plane. In a variation with an antenna plate comprising a front and a back layer, the parting plane between the front and the back layer can divide the waveguide channel segment in two halves. As the thickness of the front and the back layer may differ, the half of the front section and the half of the back section may be symmetrically with respect to the parting plane. The waveguide channel segment within the antenna plate typically extends in a first direction parallel to the front face of the antenna plate. The first direction typically corresponds to the main extension direction of the waveguide channel segment. In a preferred variation the waveguide channel segment comprises a cross section out of the group of the following geometries or a combination thereof: Rectangle, rhomb, ellipse, circle, wherein a main extension direction of the cross section is essentially perpendicular to the first direction.
For radiating an outgoing or receiving an incoming signal, the antenna device comprises waveguide apertures which are usually arranged in the antenna plate. The waveguide apertures typically extend between and interconnect the front section of the waveguide channel segment and the front face of the antenna plate. Typically, several waveguide apertures extend between and interconnect the front section of one waveguide channel segment and the front face forming an array of waveguide apertures. The waveguide apertures of an array are preferably arranged in a line. The waveguide apertures of an array are usually energized by a common waveguide channel which is interconnected to a respective radiating element usually at the back side of the antenna device. In certain constellations it would be possible to arranged the radiating element and the thereto related opening at a side of the antenna device. Depending on the design, the waveguide apertures of the array are configured to radiate and/or receive a signal. Typically, the waveguide apertures can be designed as slots. Depending on the field of application, the radiating openings may have different geometries as will become apparent from the variations shown hereinafter in more detail. Usually, the waveguide apertures have a cross-section with a longer extension and a shorter extension in the region of their rear end. The rear end is the end adjacent to the waveguide channel segment, whereas the front end is the end facing the front face of the antenna plate. In a preferred variation the waveguide apertures have an essentially rectangular cross-section, wherein the waveguide apertures can have a funnel shaped design with a narrowing cross-section in an inward direction before they merge into the waveguide channel segment or a section thereof.
In addition, the antenna device can comprise scattering elements which are arranged adjacent to the waveguide apertures. Rays which impact in the area of the scattering elements can at least be partially reflected by the scattering elements and thereby separated into first secondary rays and second secondary rays. The first secondary rays and the second secondary rays are different such that they cancel out each other at least partially by interference. Favorably the scattering elements are designed as protrusions and/or indentations or a combination thereof, which are arranged at the front face. Depending on the design, the depth of the at least one indentation may be linked to the specific phase distribution that is targeted to obtain a reflection that cancels out the rays reflected in an unwanted manner by interference. The phase change is typically induced by the reflection on the bottom surface of the at least one indentation. Good results can be achieved, when the bottom surface of the at least one indentation is an essentially planar surface which is arranged essentially parallel with respect to the front face of the antenna plate. Preferably the scattering elements are having in the front face a layout (footprint) which is at least one element out of the group of the following elements or a combination thereof: rectangle, square, circle, ellipse, C-shaped, ring-shaped, S-shaped. The scattering elements can be designed with a single polarization (rectangular, elliptical, s-shaped, c-shaped) or with multiple polarizations (squared/circular/ring). The at least one indentation has a layout which is related to the working operating frequency and the polarization of the electromagnetic waves.
In a preferred variation the waveguide apertures comprise longitudinally shaped openings with half a guided wavelength spacing with respect to each other. Such an arrangement is necessary, given the particular distribution of the electric currents that would excite the openings out of phase if they were, for instance, placed with a shorter distance with respect to each other. Having the openings aligned collinear or in line with respect to each other with the longer extension being arranged perpendicular with respect to a first axis, however, represents an advantage. It allows to realize a uniform phase orientation of the excited signal and avoids unwanted lobes outside of the main radiation planes.
The front section and/or the back section of the waveguide channel segment can comprise indentations in the form of protrusions extending from a channel wall into the front section and/or the back section of the waveguide channel segment. Good results can be achieved when the indentations are designed as inwardly directed protrusions or alternatively in form of a septum which is arranged in the channel wall. The indentations can be configured to help dividing the signal between the left and the right section of the waveguide channel segment and/or to perturb the field. Good results can be achieved when between neighboring waveguide apertures alternately first protrusions are arranged in the front section of the waveguide channel segment. The first protrusions can have a trapezoid cross-section. Said first protrusions can be configured to perturb the field such that the signal is radiated vertically polarized. By arranging the longer extension of the cross-section perpendicular to the first direction, the waveguide apertures would usually not excite a signal. In order to excite a signal from the waveguide aperture, the front section comprises the alternately arranged first protrusions. Preferably the first protrusions can be wedge shaped. The multiple alternately arranged first protrusions create a shape of the front section of the waveguide channel segment which is essentially shaped like a saw blade. The first protrusions perturb the currents such that the waveguide apertures can radiate a signal. The first protrusions can be arranged alternately configured to compensate the 180° phase change between neighboring waveguide apertures, which are arranged at the waveguide channel segment separated with half a guided wavelength distance.
In a preferred variation of the antenna device, the longer extension of the cross-section may be arranged perpendicular to the first direction and the shorter extension may be arranged parallel to the first direction. Preferably the cross section of the waveguide aperture is essentially rectangular. As the waveguide aperture radiation coupling is proportional to the size of the first protrusions, their shape can be varied to tune the amplitude of the waveguide apertures and influence their radiation pattern. The depth of the indentations can control the waveguide aperture radiation. Alternatively, or in addition, the length of the longer extension can be adjusted to alter the excitation phase of the waveguide aperture, which can be useful for tuning the radiation pattern.
The radiation pattern of the waveguide apertures can be adjusted in the elevation plane tuning the number of waveguide apertures or by influencing the size, and shape of the first protrusions. The first protrusions are configured to compensate a 180° phase change between adjacent waveguide apertures, which are arranged with a distance of essentially half a guided wavelength with respect to each other. Nevertheless, the azimuth plane becomes invariant to these changes, showing a wide beamwidth due to the low directivity of the individual waveguide apertures. In a preferred variation the azimuth pattern can be tuned by arranging a cavity on top of the waveguide aperture which focuses the fields and reduces the azimuth beamwidth. Depending on the height and width of the cavity, different patterns can be obtained. In the case of the elevation plane, the cavity has small effect, though it can help to reduce the beamwidth too. In a preferred variation a funnel shaped horn cavity is arranged at the front end of the waveguide apertures configured to tune the radiation pattern to focus the field and to reduce the beamwidth in one of the main radiation planes. Alternatively, or in addition to the horn cavity can be laterally displaced to influence the directivity.
Besides the first protrusions which are typically arranged in the front section of the waveguide channel segment, alternatively or additionally, at least one second protrusion having a rectangular cross-section can be arranged in the front section of the waveguide channel segment. The at least one second protrusion is configured to divide the signal in the waveguide channel segment to excite in a left section and a right section extending along the first direction. Depending on the distribution to be achieved, the second protrusion can have a cross section which is rectangular, which is typically arranged centered between the left and the right section of the waveguide channel segment, such that the signal is split equally between the left and the right section of the waveguide channel segment. If appropriate, the second protrusion can be a necking which is arranged with respect to a center point between the left and the right section of the waveguide channel segment. When the necking is arranged with an offset to one side between the left and the right section, the signal, respectively its power, is split non-equally between the left and the right section. Due to the performance advantages of the herein described arrangement, the splitting of the power is almost lossless. Only a negligible amount of power is lost during the splitting.
Alternatively, or in addition, a polarization element can be arranged at a front end of each waveguide aperture which is configured to split the field into two orthogonal polarizations with a relative 90° phase shift. The polarization element can be designed to create a circular polarization. The polarization element is typically configured to twist the vertical polarized field which is excited by the waveguide aperture by transforming the vertical polarization of each waveguide aperture into circular polarization. The first protrusions arranged at the front section of the waveguide channel segment is still required such that the waveguide apertures can excite and couple the energy to the polarization element with the desired relative amplitude. The shape of the polarizer is optimized to minimize the axial ratio. In a preferred variation the polarization element may be essentially shaped like two diagonally partially overlapping squares or a bow tie.
In an alternative variation the longer extension of the cross-section is arranged parallel to the first direction and the shorter extension is arranged perpendicular to the first direction. In known antenna devices the waveguide apertures are usually spaced with one guided wavelength distance with respect to each other to keep a uniform phase between the waveguide apertures. The distance between two neighboring waveguide apertures is typically equivalent to more than one free space wavelength leading to excessive grating lobe levels. Third protrusions can be arranged between the waveguide apertures alternately in the back section of the waveguide channel segment with respect to the first direction, wherein the third protrusions are configured to compress the guided wavelength in the first direction within the waveguide channel segment. The third protrusions can reduce the effective wavelength of the waveguide propagating mode. Therefore, the distance between neighboring waveguide apertures can be reduced and mitigate the appearance of undesired grating lobes.
The third protrusions are preferably designed as pillars extending perpendicular to the front face of the antenna plate into the waveguide channel segment, and spaced apart from each other in the first direction in an, in one-dimension glide-symmetric arrangement and the waveguide apertures are arranged with a distance of essentially one guided wavelength to one another along the first direction. The number of pillars arranged at the back section of the waveguide channel segment creates a dented profile. The third protrusions can introduce a periodic structure such that the propagation constant inside the waveguide is increased. This allows to divide the guided wavelength with a factor of roughly two compared to the incoming wavelength. In a third preferred variation every second of a third protrusion is folded upward by mirroring at a parting plane as a fourth protrusion in the front section, such that in two dimensions a glide-symmetric arrangement of the third and the fourth protrusions results. Typically, the protrusions are in form of pillars having a width between essentially 0.2 times the wavelength up to 0.3 times the wavelength. In a preferred variation the third pillars are arranged at the back section and have a height between essentially 0.3 times the wavelength up to 0.5 times the wavelength. In a fourth preferred variation the rectangular cross-section is arranged angularly displaced by an angle α with respect to the first direction of the waveguide channel segment. The polarization can be changed from pure horizontal) (0° or vertical) (90° polarization to a to slant) (±45° polarization. The polarization is preferably twisted by modified first protrusions, such that a smooth transition is achieved. The advantage of the shown variation is that the polarization can be changed without an additional antenna layer. The use of slant polarization is of high interest in automotive applications because it reduces interference between vehicles that are facing each other. Therefore, between neighboring waveguide apertures alternately first and second protrusions can be arranged in the front section of the waveguide channel segment. Alternatively, or in addition, third protrusions may be arranged between waveguide apertures or alternately in the back section of the waveguide channel segment with respect to the first direction.
In a preferred variation a feeding port interconnects the waveguide channel segment to an aperture at the back face of the antenna plate. Side feeding can lead to a very compact design but the asymmetry reduces the bandwidth and generates beams squint. Therefore, the feeding port can be designed as a splitter which is arranged between the left and the right section of the waveguide channel segment, configured to separate or combine the signal. Center feeding via a splitter offers similar performance as side feeding, but allows the routing to be in the same layer, but it is less compact. Bottom feeding: leads to very compact and broadband design but requires an additional layer of routing below. Hybrid feeding: in some cases it may not be possible to feed the radiator from the center due to small separation with the neighboring elements. Depending on the antenna arrangement, a hybrid solution may be feasible in which the antenna is fed from the center but with a given offset as shown in
In case that more directive or complex radiation patterns are required, multiple arrays of waveguide apertures can be arranged in the front face of the antenna plate.
In a preferred variation a feeding port designed as a splitter is arranged between a first column and a second column, configured to separate or combine the signal. Depending on the number of columns, the feeding port can comprise an array of splitters, which are interconnected to each other and are arranged parallel with respect to each other. This design is known as corporate network. The corporate network is designed in a manner such that both columns are fed with a phase and amplitude for the specific radiation pattern. In an alternative variation, the feeding port is designed as a central feeding channel, wherein a number of left and right sections of multiple waveguide channel segments are arranged essentially perpendicular with respect to the central feeding channel and parallel with respect to each other.
Alternatively, or in addition, the waveguide apertures of the two rows can have varying cross sections to further tilt the radiation pattern. The difference between the cross-section of the waveguide apertures can create a phase difference between the radiation of each aperture. The phase difference can cause a tilt in the radiation of the pattern. The impact of the lateral displacement can create local maxima in the antenna directivity. These local maxima can help to focus the antenna energy in certain areas. The tilted pattern can be useful to have a further range in given areas of the radar. Particularly in automotive applications the tilted pattern makes it possible to have a locally wider range. Alternatively, the proximal left and right sections and distal left and right sections may be arranged at the central feeding channel, wherein the distal left and right sections are fed with a phase shift such that a beam tilt is created.
Alternatively, or in addition, the first and second columns of arrays can be arranged adjacent to a central feeding channel. In a preferred variation the first and second columns of arrays are arranged essentially perpendicular with respect to the central feeding waveguide channel. Preferably the distal second columns are fed with a phase shift. The phase shift can create high directive and non-tilted radiation patterns. The feeding port can be designed as a central feeding channel, wherein a number of left and right sections of multiple waveguide channel segments are arranged essentially perpendicular with respect to the central feeding channel and parallel with respect to each other. In a preferred variation two arrays of waveguide apertures are arranged parallel with respect to each other. Preferably the cross sections of the waveguide apertures of the first array are smaller and/or larger than the cross sections of the openings of the second array. This configuration causes a tilt of the radiation pattern. Alternatively, the cross sections of neighboring waveguide apertures within one array can be different, such that a waveguide aperture with a smaller cross section is arranged adjacent to a waveguide aperture with a larger cross section. Alternatively, waveguide apertures with smaller and larger cross sections may be arranged in a line next to each other in alternating manner. This can cause the radiation pattern to be compensated and radiate in a straight manner.
It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.
The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the disclosure described in the appended claims.
Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.
In addition, the shown antenna device 1 comprises scattering elements 53 which are arranged adjacent to the waveguide apertures 17. Rays which impact in the area of the scattering elements 53 can at least be partially reflected by the scattering elements 53 and thereby separated into first secondary rays and second secondary rays. The first secondary rays and the second secondary rays are different such that they cancel out each other at least partially by interference. In the shown variation the scattering elements 53 are with respect to the front face designed as indentations. Depending on the design, the depth of the indentations may be linked to the specific phase distribution that is targeted to obtain a reflection that cancels out the rays reflected in an unwanted manner by interference.
As can best seen in
Alternatively mushroom EBGs can be arranged on the PCB itself, as shown in the variation of
| Number | Date | Country | Kind |
|---|---|---|---|
| CH070791/2021 | Dec 2021 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/084791 | 12/7/2022 | WO |
