Folded waveguide for antenna

This document describes a folded waveguide for antenna. The folded waveguide may be an air waveguide and includes a hollow core that forms a rectangular opening in a longitudinal direction at one end, a closed wall at an opposite end, and a sinusoidal shape that folds back and forth about a longitudinal axis that runs in the longitudinal direction through the hollow core. The hollow core forms a plurality of radiation slots, each including a hole through one of multiple surfaces that defines the hollow core. The radiation slots are arranged on the one surface to produce a particular antenna pattern. The radiation slots and sinusoidal shape enable the folded waveguide to prevent grating lobes from appearing in the particular antenna pattern on either side of a horizontal-polarity, main beam, or to prevent X-band lobes from appearing in the particular antenna pattern on either side of a vertical-polarity, main beam.

BACKGROUND

Some devices (e.g., radar) use electromagnetic signals to detect and track objects. The electromagnetic signals are transmitted and received using one or more antennas. An antenna may be characterized in terms of gain, beam width, or, more specifically, in terms of the antenna pattern, which is a measure of the antenna gain as a function of direction. Certain applications may benefit from precisely controlling the antenna pattern. A waveguide may be used to improve these antenna characteristics. The waveguide can include perforations that improve an antenna pattern by leaking some of the electromagnetic radiation that is directed towards the antenna. However, these waveguides cannot prevent grating lobes on either side of a horizontal-polarity main beam, nor can they prevent X-band lobes on either side of a vertical-polarity main beam.

SUMMARY

This document describes techniques, apparatuses, and systems utilizing a folded waveguide for antenna. The folded waveguide may be an air waveguide and is referred to throughout this document as simply a waveguide for short. The described waveguide includes a hollow core. The hollow core forms a rectangular opening in a longitudinal direction at one end, a closed wall at an opposite end, and a sinusoidal shape that folds back and forth about a longitudinal axis that runs in the longitudinal direction through the hollow core. The hollow core further forms a plurality of radiation slots, each of the radiation slots including a hole through one of multiple surfaces of the folded waveguide that defines the hollow core. The plurality of radiation slots is arranged on the one of the multiple surfaces to produce a particular antenna pattern at an antenna element when the antenna element is electrically coupled to the opposite end of the hollow core.

This Summary introduces simplified concepts related to a folded waveguide antenna, which are further described below in the Detailed Description and Drawings. This Summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter.

DETAILED DESCRIPTION

Overview

Radar systems are an important sensing technology used in many industries, including the automotive industry, to acquire information about the surrounding environment. An antenna is used in radar systems to transmit and receive electromagnetic (EM) energy or signals. Some radar systems use multiple antenna elements in an array to provide increased gain and directivity over what can be achieved using a single antenna element. In reception, signals from the individual elements are combined with appropriate phases and weighted amplitudes to provide the desired antenna reception pattern. Antenna arrays are also used in transmission, splitting signal power amongst the elements, using appropriate phases and weighted amplitudes to provide the desired antenna transmission pattern. A waveguide can be used to transfer EM energy to and from the antenna elements. Further, waveguides can be arranged to provide the desired phasing, combining, or splitting of signals and energy.

In contrast, this document describes techniques, apparatuses, and systems utilizing a folded waveguide for antenna. The folded waveguide may be an air waveguide and includes a hollow core that forms a rectangular opening in a longitudinal direction at one end, a closed wall at an opposite end, and a sinusoidal shape that folds back and forth about a longitudinal axis that runs in the longitudinal direction through the hollow core. The hollow core forms a plurality of radiation slots, each including a hole through one of multiple surfaces that defines the hollow core. The radiation slots are arranged on the one surface to produce a particular antenna pattern. The radiation slots and sinusoidal shape enable the folded waveguide to prevent grating lobes from appearing in the particular antenna pattern on either side of a horizontal-polarity main beam, or to prevent X-band lobes from appearing in the particular antenna pattern on either side of a vertical-polarity main beam.

This is just one example of the described techniques, apparatuses, and systems of a folded waveguide for antenna. This document describes other examples and implementations.

Example System

FIG. 1illustrates an example system100that includes a folded waveguide for antenna, in accordance with techniques, apparatuses, and systems of this disclosure. The system includes a device102, an antenna104, and a waveguide106. The system100may be part of a vehicle, such as a self-driving automobile. Portions of the system100may be integrated onto a printed circuit board or substrate.

The device102is configured to receive and process signals to perform a function. The device102may be a radar device, an ultrasound device, or other device configured to receive electromagnetic signals. An input to the device102is operatively coupled to the antenna104.

The antenna104is configured to capture electromagnetic signals124and channel them to the device102. The antenna104and the device102may be coupled via wired or wireless links. These links carry electromagnetic signals124from the antenna104to the device102.

The waveguide106is a folded waveguide and configured to channel electromagnetic signals124being transmitted through air to the antenna104and the device102. The waveguide106includes a hollow core108. The folded waveguide106may include metal. The folded waveguide106may include plastic. A combination of plastic and metal may be used to form the waveguide106. InFIG. 1, the waveguide106is viewed from above. A top surface122is visible, which is one of multiple surfaces of the waveguide106that forms the hollow core108.

The hollow core108forms a rectangular opening110in a longitudinal direction112at one end and a closed wall114at an opposite end. This opposite end with the closed wall114is operatively coupled to the antenna104. Electromagnetic signals enter the waveguide106through the opening110, and some signals exit the waveguide106at the opposite end and to the antenna104. The hollow core108forms a sinusoidal shape that folds back and forth about a longitudinal axis116that runs in the longitudinal direction112through the hollow core108.

The hollow core108also forms a plurality of radiation slots118. Each of the radiation slots118includes a respective hole120through one surface122of the multiple surfaces of the folded waveguide106that defines the hollow core108. For example, the top surface122of the waveguide106may include radiation slots118similar to those shown inFIG. 1. The plurality of radiation slots118are arranged on the surface122to produce a particular antenna pattern for the device102and the antenna104that is electrically coupled to the opposite end of the hollow core108.

As shown inFIG. 1, the plurality of radiation slots118are configured to dissipate, from the hollow core108, a portion124′ of electromagnetic-radiation124that enters the rectangular opening110before that portion124′ of the electromagnetic radiation124can reach the antenna104that is electrically coupled to the opposite end of the hollow core108. In other words, the electromagnetic radiation is allowed to leak out the radiation slots118on its way through the hollow core108in the longitudinal direction112. Each of the plurality of radiation slots118is sized and positioned on one of the multiple surfaces to produce the particular antenna pattern at the antenna104that is electrically coupled to the opposite end of the hollow core108.

Example Apparatus

FIG. 2-1illustrates an example folded waveguide106-1for antenna, in accordance with techniques, apparatuses, and systems of this disclosure. The waveguide106-1is an example of the waveguide106. Each radiation slot from the plurality of radiation slots118includes a longitudinal slot that is parallel to the longitudinal axis116to produce a horizontal-polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

As shown inFIG. 2-1, the plurality of radiation slots118are evenly distributed between the rectangular opening110and the closed wall114, and along the longitudinal axis116that runs in the longitudinal direction112through the hollow core108. Each adjacent pair of radiation slots from the plurality of radiation slots118includes two radiation slots that are separated along the longitudinal axis116by a common distance200to produce the particular antenna pattern at the antenna104that is electrically coupled to the opposite end of the hollow core108. The separation by the common distance200can prevent grating lobes. The common distance200is less than one wavelength of the electromagnetic radiation124that reaches the opposite end of the hollow core108.

Each of the plurality of radiation slots118is sized and positioned on the surface122to produce a particular antenna pattern. The holes120of the plurality of radiation slots118have a larger size202near the wall114at the opposite end of the hollow core108and a smaller size204near the rectangular opening110. The specific size and position of the radiation slots118can be determined by building and optimizing a model of the waveguide106to produce the particular desired antenna pattern. The radiation slots118are fed in-phase, hence the reason to be the common distance200apart.

FIG. 2-2illustrates an antenna pattern associated with the example folded waveguide for antenna shown inFIG. 2-1. Because each radiation slot is a longitudinal slot that is parallel to the longitudinal axis116, the waveguide106is tuned to produce a horizontal-polarized antenna pattern206at the antenna104. As shown inFIG. 2-2, the grating lobes can be avoided if the pitch of common distance200is less than the electromagnetic-radiation124wavelength. Elevation of the side lobe can be controlled by changing the size or length of the radiation slots118.

FIG. 2-3illustrates an antenna pattern208without the example folded waveguide for antenna shown inFIG. 2-1. A drawback to such other waveguides includes the grating lobes shown in the antenna pattern208that appear on either side of the horizontal-polarity main beam.

FIG. 3-1illustrates another example folded waveguide106-2for antenna, in accordance with techniques, apparatuses, and systems of this disclosure. The waveguide106-2is an example of the waveguide106. Each radiation slot from the plurality of radiation slots118includes a lateral slot that is perpendicular to the longitudinal axis116to produce a vertical-polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core108.

As shown inFIG. 3-1, the plurality of radiation slots118are evenly distributed between the rectangular opening110and the closed wall114, and along the longitudinal axis116that runs in the longitudinal direction112through the hollow core108. Each adjacent pair of radiation slots from the plurality of radiation slots118includes two radiation slots that are separated along the longitudinal axis116by a common distance300to produce the particular antenna pattern at the antenna104that is electrically coupled to the opposite end of the hollow core108. The separation by the common distance300or pitch can prevent X-band lobes. The common distance300is much less than one wavelength of the electromagnetic radiation124that reaches the opposite end of the hollow core108.

Each of the plurality of radiation slots118is sized and positioned on the surface122to produce a particular antenna pattern. The holes120of the plurality of radiation slots118have a larger size302near the wall114at the opposite end of the hollow core108and a smaller size304near the rectangular opening110. The specific size and position of the radiation slots118can be determined by building and optimizing a model of the waveguide106to produce the particular antenna pattern desired.

FIG. 3-2illustrates an antenna pattern associated with the example folded waveguide for the antenna shown inFIG. 3-1. Because each radiation slot is a lateral slot that is perpendicular to the longitudinal axis116, the waveguide106is tuned to produce a vertical-polarized antenna pattern306at the antenna104. As shown inFIG. 3-2, the X-band lobes can be avoided if the pitch of common distance300is less than the electromagnetic-radiation124wavelength. Elevation of the side lobe can be controlled by changing the size or length of the radiation slots118.

FIG. 3-3illustrates an antenna pattern308without the example folded waveguide for antenna shown inFIG. 3-1. A drawback to such other waveguides includes the X-band lobes shown in the antenna pattern308that appear on either side of the vertical-polarity main beam.

FIG. 4-1illustrates another example folded waveguide106-3for antenna, in accordance with techniques, apparatuses, and systems of this disclosure.FIG. 4-1represents a combination of the waveguide106-1and106-2and is therefore an example of the waveguide106. As shown inFIG. 4-1, a first half of the plurality of radiation slots comprises a longitudinal slot that is parallel to the longitudinal axis, and a second half of the plurality of radiation slots comprises a lateral slot that is perpendicular to the longitudinal axis to produce a circular antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

FIG. 4-2illustrates an antenna pattern associated with the example folded waveguide for antenna shown inFIG. 4-1. Because a combination of lateral slots and longitudinal slots are used, the waveguide106is tuned to produce a circularly polarized antenna pattern406at the antenna104. As shown inFIG. 4-2, the grating lobes and the X-band lobes can be avoided if the pitch of common distance between radiation slots is less than the electromagnetic-radiation124wavelength. Elevation of the side lobe can be controlled by changing the size or length of the radiation slots118.

FIG. 5illustrates another example folded waveguide106-4for antenna, in accordance with techniques, apparatuses, and systems of this disclosure.FIG. 5is an example of the waveguide106, having radiation slots in a different surface500than what is illustrated as the surface122inFIGS. 1, 2-1, 3-1, and 4-1. The surface500is perpendicular to the surface122, which folds back and forth about the axis114. As shown inFIG. 5, the plurality of radiation slots120comprises a combination of longitudinal slot that are parallel to the longitudinal axis, and lateral slots that are perpendicular to the longitudinal axis, although only longitudinal, or only lateral slots may be used depending on the particular antenna pattern desired. For instance, the combination shown inFIG. 5produces a circular antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core. If only longitudinal slots are used, a horizontal-polarity antenna pattern is produced. If only lateral slots are used, a vertical-polarity antenna pattern is produced.

Example Method

FIG. 6depicts an example method that can be used for manufacturing a folded waveguide for antenna, in accordance with techniques, apparatuses, and systems of this disclosure. The process600is shown as a set of operations602through606, which are performed in, but not limited to, the order or combinations in which the operations are shown or described. Further, any of the operations602through606may be repeated, combined, or reorganized to provide other methods. In portions of the following discussion, reference may be made to the environment100and entities detailed in above, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities.

At602, a folded waveguide for antenna is formed. For example, the waveguide106can be stamped, etched, cut, machined, cast, molded, or formed in some other way. At604, the folded waveguide is integrated into a system. For example, the waveguide106is electrically coupled to the antenna104. At606, electromagnetic signals are received via the waveguide at an antenna of the system. For example, the device102receives signals captured from air by the waveguide106and routed through the antenna104.

Additional Examples

In the following section, additional examples of a folded waveguide for antenna are provided.

Example 1. An apparatus, the apparatus comprising: a folded waveguide comprising a hollow core, the hollow core forming: a rectangular opening in a longitudinal direction at one end; a closed wall at an opposite end; a sinusoidal shape that folds back and forth about a longitudinal axis that runs in the longitudinal direction through the hollow core; and a plurality of radiation slots, each of the radiation slots comprising a hole through one of multiple surfaces of the folded waveguide that defines the hollow core, the plurality of radiation slots being arranged on the one of the multiple surfaces to produce a particular antenna pattern for a device and an antenna element that is electrically coupled to the opposite end of the hollow core.

Example 2. The apparatus of any preceding example, wherein each of the plurality of radiation slots is configured to dissipate, from the hollow core, a portion of electromagnetic-radiation that enters the rectangular opening before that portion of the electromagnetic-radiation can reach the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 3. The apparatus of any preceding example, wherein each of the plurality of radiation slots is sized and positioned on the one of the multiple surfaces to produce the particular antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 4. The apparatus of any preceding example, wherein the plurality of radiation slots is evenly distributed between the rectangular opening and the closed wall, and along the longitudinal axis that runs in the longitudinal direction through the hollow core.

Example 5. The apparatus of any preceding example, wherein each adjacent pair of radiation slots from the plurality of radiation slots comprises two radiation slots that are separated along the longitudinal axis by a common distance to produce the particular antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 6. The apparatus of any preceding example, wherein the common distance is less than one wavelength of electromagnetic radiation that reaches the hollow core.

Example 7. The apparatus of any preceding example, wherein each adjacent pair of radiation slots from the plurality of radiation slots comprises two radiation slots that are separated along the longitudinal axis by a common distance to prevent grating lobes or X-band lobes within the particular antenna pattern.

Example 8. The apparatus of any preceding example, wherein each radiation slot from the plurality of radiation slots comprises a lateral slot that is perpendicular to the longitudinal axis to produce a vertical-polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 9. The apparatus of any preceding example, wherein each radiation slot from the plurality of radiation slots comprises a longitudinal slot that is parallel to the longitudinal axis to produce a horizontal-polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 10. The apparatus of any preceding example, wherein a first half of the plurality of radiation slots comprises a longitudinal slot that is parallel to the longitudinal axis, and a second half of the plurality of radiation slots comprises a lateral slot that is perpendicular to the longitudinal axis to produce a circularly polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 11. The apparatus of any preceding example, wherein the folded waveguide comprises metal.

Example 12. The apparatus of any preceding example, wherein the folded waveguide comprises plastic.

Example 13. A system, the system comprising: an antenna element; a device configured to transmit or receive electromagnetic signals via the antenna; and a folded waveguide comprising: a hollow core forming: a rectangular opening in a longitudinal direction at one end; a closed wall at an opposite end that is electrically coupled to the antenna element; a sinusoidal shape that folds back and forth about a longitudinal axis that runs in the longitudinal direction through the hollow core; and a plurality of radiation slots, each of the radiation slots comprising a hole through one of multiple surfaces of the folded waveguide that defines the hollow core, the plurality of radiation slots being arranged on the one of the multiple surfaces to produce a particular antenna pattern at the antenna element.

Example 14. The system of any preceding example, wherein the device comprises a radar device.

Example 15. The system of any preceding example, further comprising a vehicle comprising the antenna element, the device, and the folded waveguide.

Example 16. The system of any preceding example, wherein each of the plurality of radiation slots is configured to dissipate, from the hollow core, a portion of electromagnetic-radiation that enters the rectangular opening before that portion of the electromagnetic-radiation can reach the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 17. The system of any preceding example, wherein each of the plurality of radiation slots is sized and positioned on the one of the multiple surfaces to produce the particular antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 18. The system of any preceding example, wherein each radiation slot from the plurality of radiation slots comprises a lateral slot that is perpendicular to the longitudinal axis to produce a horizontal-polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core; wherein each radiation slot from the plurality of radiation slots comprises a longitudinal slot that is parallel to the longitudinal axis to produce a vertical-polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core; or wherein a first portion of the plurality of radiation slots comprises a longitudinal slot that is parallel to the longitudinal axis, and a second portion of the plurality of radiation slots comprises a lateral slot that is perpendicular to the longitudinal axis to produce a circularly polarized antenna pattern at the antenna element that is electrically coupled to the opposite end of the hollow core.

Example 19. The system of any preceding example, wherein each of the plurality of radiation slots comprises a hole through a particular surface of the multiple surfaces, the particular surface being one of two surfaces that folds back and forth about the longitudinal axis that runs in the longitudinal direction through the hollow core.

Example 20. The system of any preceding example, wherein each of the plurality of radiation slots comprises a hole through a particular surface of the multiple surfaces, the particular surface being one of two surfaces that is perpendicular to two other surfaces that fold back and forth about the longitudinal axis that runs in the longitudinal direction through the hollow core.

CONCLUSION

While various embodiments of the disclosure are described in the foregoing description and shown in the drawings, it is to be understood that this disclosure is not limited thereto but may be variously embodied to practice within the scope of the following claims. From the foregoing description, it will be apparent that various changes may be made without departing from the spirit and scope of the disclosure as defined by the following claims.