Substrate integrated antenna with frequency beam direction adjusting function

Abstract

A frequency beam steering leaky-wave antenna adapted to be integrated in a substrate, such as a printed circuit board, includes a waveguide formed by a first conductive surface and a second conductive surface, the first and second conductive surfaces forming an upper surface and a lower surface of the waveguide, and a conductive via forming a first sidewall and a second sidewall disposed between the upper surface and the lower surface along a length of the waveguide. The waveguide has a slotted opening distributed along the upper surface, and a width of the waveguide is defined by a distance between the two sidewalls that varies along the length of the waveguide. A portion of radio frequency energy traveling along the length of the waveguide radiates away from the waveguide through the slotted opening. Performance characteristics of the antenna, such as directivity and operational bandwidth of the antenna, may be adjusted by adjusting the geometry of the slot-shaped opening and the positioning of the through-hole.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to waveguide-based radio frequency and microwave (RFMW) antennas formed within a substrate such as a printed circuit board. Background Art

[0002] Passenger vehicles equipped with advanced driver assistance systems (ADAS) and other safety and navigation systems increasingly use radar-based sensing to determine the position of nearby objects, such as other vehicles, pedestrians, and road obstacles. To achieve angle-resolved information, antenna arrays are typically used, including electrically steerable antennas such as phased arrays and other steerable antennas. Summary of the Invention

[0003] In an exemplary embodiment, a device includes a circuit substrate and a leaky-wave antenna formed within the circuit substrate. The antenna comprises a hollow or dielectric-filled conductive waveguide having a length along a first direction that defines a propagation direction of a radio frequency (RF) signal within the waveguide. The waveguide is formed by: a first conductive surface defining an upper surface of the waveguide, the upper surface having slot-shaped openings distributed along the length of the waveguide on the upper surface, the slot-shaped openings configured to cause a portion of the RF signal traveling within the waveguide along the propagation direction to radiate out of the waveguide; a second conductive surface parallel to the upper surface, the second conductive surface defining a lower surface of the waveguide; and a conductive via extending through the circuit substrate between the upper and lower surfaces of the waveguide, the conductive via defining a first sidewall of the waveguide and a second sidewall of the waveguide, the second sidewall being opposite the first sidewall of the waveguide. The width of the waveguide varies along the length of the waveguide and is defined by a variable distance between the first and second sidewalls along a second direction perpendicular to the first direction.

[0004] In another example embodiment, a method includes forming a conductive via through a circuit substrate between a first conductive surface of the substrate and a second conductive surface of the substrate. The first conductive surface defines an upper surface of a conductive hollow or dielectric-filled waveguide. The second conductive surface is parallel to the first conductive surface and defines a lower surface of the waveguide. The conductive via defines a first sidewall of the waveguide and a second sidewall of the waveguide, the second sidewall being opposite the first sidewall of the waveguide. The conductive via is configured and dimensioned to reflect an incident RF signal having a frequency within a predetermined operating frequency range of the antenna such that the incident RF signal coupled to a first end of the waveguide is directed toward the second end of the waveguide along a propagation direction of the waveguide. The width of the waveguide varies along the length of the waveguide and is defined by a variable distance between the first sidewall and the second sidewall along a second direction perpendicular to the propagation direction of the waveguide. The method also includes forming slot-shaped openings distributed on the upper surface along the length of the waveguide, the slot-shaped openings being configured to radiate a portion of the RF signal traveling within the waveguide along the propagation direction away from the waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The present disclosure is illustrated by way of examples, embodiments, and the like, and is not limited by the accompanying drawings, in which like reference numerals indicate like elements. The elements in the drawings are illustrated for simplicity and clarity and are not necessarily drawn to scale. The accompanying drawings, together with the detailed description, are incorporated into and form part of this specification and serve to further illustrate examples, embodiments, and the like, and to explain various principles and advantages according to the present disclosure. In the drawings:

[0006] Figure 1A is a schematic perspective view of a leaky wave antenna formed using a substrate-integrated waveguide according to one or more embodiments;

[0007] Figure 1B yes Figure 1A An expanded plan view of a portion of a substrate integrated waveguide;

[0008] Figure 1C It shows Figure 1A and Figure 1B Circuit diagram of the lumped circuit model of the unit cell of the substrate integrated waveguide;

[0009] Figure 2A is shown in more detail Figure 1A and Figure 1B An expanded plan view of the elements of the leaky-wave antenna;

[0010] Figure 2B is shown in more detail Figure 1A 、 Figure 1B and Figure 2AAn expanded plan view of the elements of the leaky-wave antenna;

[0011] Figure 3 is shown with Figure 1A 、 1B , Smith chart of the performance characteristics of leaky wave antennas obtained by changing the geometry of the waveguide sidewalls, related to the antennas of 2A and 2B;

[0012] Figure 4A is shown with Figure 1A 、 1B , Smith charts of performance characteristics of leaky wave antennas obtained by varying the geometry of the slot openings in the waveguide, related to the antennas of 2A and 2B;

[0013] Figure 4B It further shows Figure 4A Plot of the performance characteristics of the leaky-wave antenna shown in ;

[0014] Figure 5A is a plot of directional radiation patterns of a leaky-wave antenna at different operating frequencies according to one or more embodiments;

[0015] Figure 5B is Figure 5A Another plot showing the directional radiation pattern of a leaky-wave antenna; and

[0016] Figure 6 is a flow chart illustrating an example process for designing a leaky-wave antenna in accordance with one or more embodiments. DETAILED DESCRIPTION

[0017] The following detailed description provides examples for the purpose of understanding and is not intended to limit the invention or the application and use of the invention. In addition, it is not intended to be bound by any explicit or implicit theory presented in the foregoing technical field, background technology or the following detailed description.

[0018] For simplicity and clarity of illustration, the drawings show a general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessary obfuscation of the present invention. In addition, the elements in the drawings are not necessarily drawn to scale. For example, the dimensions of some elements or areas in the drawings may be exaggerated relative to other elements or areas to help improve understanding of the embodiments of the present invention. Unless otherwise indicated, directional references, such as "top", "bottom", "left", "right", "above", "below", etc., are not intended to require any preferred orientation, but are described for illustrative purposes with reference to the orientation of the corresponding one or more figures.

[0019] As radar sensing systems become commonplace for commercial applications such as passenger cars, including advanced driver assistance systems (ADAS) and other safety and navigation systems, there is a growing demand for miniaturization, cost reduction, and energy efficiency of radar components. Existing solutions that use phased arrays and other methods to provide spatially resolved beams may not be suitably space-efficient and / or cost-effective for some applications. Therefore, compact, electronically steerable antennas for millimeter-wave radars are desirable.

[0020] One approach to frequency-based beam steering in directional antennas utilizes so-called "leaky wave" antennas. One type of leaky wave antenna is formed by adding openings in a conventional hollow or dielectric-filled conductive waveguide. The openings allow a portion of the radio frequency signal traveling through the waveguide to "leak" through the openings (i.e., radiate out of the waveguide). When there are many openings in the waveguide, the radiated signal may interfere constructively and destructively at various locations around the waveguide. When the openings are properly arranged, directional radiation patterns can be achieved, and the angular orientation of these patterns will depend on the frequency or frequencies of the radio frequency (RF) signal associated with the lateral propagation mode of the waveguide. Although existing waveguide-based leaky wave antennas can allow beam steering by adjusting the frequency of the RF signal coupled to the waveguide, it can be difficult to obtain a suitable impedance match with typical transmitter devices and other structures, and the impedance can vary significantly with frequency, thereby limiting the operating bandwidth of such antennas.

[0021] According to this idea, Figure 1A A schematic perspective view shows a portion of an electronic device provided with an example leaky-wave antenna according to one or more embodiments, which enables frequency-based beam steering that can exhibit improved performance characteristics (e.g., wider operating bandwidth, lower return loss, etc.) compared to previous approaches. Because antennas according to embodiments herein are formed from a modified waveguide structure, the antennas may be referred to as waveguides or waveguide antennas. Figure 1AThe waveguide antenna (referred to as waveguide 120) is a leaky wave antenna formed on or within substrate 110, which is related to known hollow and dielectric-filled waveguides having conductive walls. Waveguide 120 is defined by a lower surface 131, an upper surface 132, and vertical sidewalls extending between lower surface 131 and upper surface 132. Each of these surfaces and sidewalls is sufficiently conductive to guide an incident radio frequency (RF) signal coupled to a first end 122 of waveguide 120 toward second end 124 along a propagation direction 195 (or toward first end 122 for an RF signal coupled to second end 124 of the waveguide) for signals having frequencies within the operating bandwidth of the waveguide 120 as determined by the cross-section of the waveguide 120. In the following description, the "length" of waveguide 120 is defined by its extent along propagation direction 195, while the width of waveguide 120 is defined by its extent along direction 197, which is parallel to upper surface 132 and lower surface 131. Meanwhile, the "height" of the waveguide is defined by its extent in vertical direction 199.

[0022] As shown, the upper surface 132 of the waveguide 120 includes a plurality of slot-shaped openings 140 (which may be Figure 1B ). The slot-shaped openings 140 are areas where the conductive material of the upper surface 132 is absent or sufficiently thinned to allow RF energy propagating within the waveguide 120 to "leak out" (i.e., radiate out of the waveguide into the surrounding environment). Therefore, the waveguide 120 and associated structures may be referred to as leaky-wave antennas. It will be appreciated that the signals radiating out of the waveguide 120 via the slot-shaped openings 140 may constructively or destructively interfere with each other at different points in the space surrounding the waveguide 120. It will also be appreciated that parameters such as the number of slot-shaped openings 140, their dimensions, and their relative positions along the propagation direction 195 at least partially determine where constructive and destructive interference will occur.

[0023] Unlike existing waveguide-based leaky wave antennas, leaky wave antennas (e.g., waveguide 120) according to one or more embodiments have an effective width that varies along propagation direction 197 (measured along an in-plane direction 197 that is parallel to upper surface 132 and perpendicular to the length of waveguide 120 along propagation direction 195). This arrangement can be based on Figure 1B To understand, Figure 1B 1 shows an expanded top plan view of a portion of the waveguide 120. In one or more embodiments, the openings in the waveguide, such as the slot-shaped openings 140 in the waveguide 120, are arranged in groups, such as the group 141 of slot-shaped openings 140. Figure 1A and 1BIn the example of FIG. 1 , variable width of the waveguide 120 is achieved by varying the placement of the conductive vias 135 in the substrate 110 (e.g., a printed circuit board substrate). In one or more embodiments, as shown, vias such as the conductive vias 135 form waveguide sidewalls having corrugations or "notches" (regions in which some of the vias are displaced "inwardly" toward the interior of the waveguide relative to vias in nearby locations along the length of the waveguide 120 corresponding to the propagation direction 195). It will be appreciated that for RF signals having a wavelength greater than the spacing between the vias, discrete conductive structures such as the conductive vias 135 may collectively appear as continuous reflective structures, such as the sidewalls of the waveguide 120.

[0024] In one or more embodiments, Figure 1B As shown, vias such as conductive via 135 are displaced to form notches that occur periodically along the length of the waveguide (indicated by the period p). In one or more such embodiments, as Figure 1B As shown, the through holes corresponding to the notches are located at positions corresponding to the edges of the slot-shaped opening groups (e.g., group 141 of slot-shaped openings 140). Figure 1B As shown, the widths of the slot openings, such as slot opening 140 (ie, along the in-plane direction 197), vary in an orderly manner within each group. Figure 1B As shown, the width of the slots in a group is greatest at the center of the group and decreases toward the edge of the group. Such a configuration will be referred to herein as "tapering" of the slot-shaped opening groups in the waveguide.

[0025] It should be understood that nothing herein is intended to require that the sidewalls of a waveguide, such as waveguide 120, or the corrugations in those sidewalls, be formed by vias, such as conductive via 135. However, it should be understood that in certain applications, it may be advantageous to use vias, such as conductive via 135, to form a waveguide having corrugated sidewalls. For example, it may be difficult to form a continuous corrugated sidewall with sufficient dimensional uniformity using conventional printed circuit board manufacturing techniques. Additionally, it should be understood that the use of individual vias, such as conductive via 135, may require less metal than would be required for a continuous sidewall. If the vias are appropriately sized and spaced relative to the desired operating frequency of the waveguide, such a "via fence" may function comparable to a solid metal sidewall.

[0026] It will be appreciated that lower surface 131 and upper surface 132 may be formed of any suitable conductive material and dimensioned in any manner suitable for confining and directing RF signals along direction of propagation 195. Along these lines, it will be appreciated that while lower surface 131 and upper surface 132 may be depicted as extending beyond the sidewalls formed by conductive vias 135, this is not required. However, such an arrangement may be convenient; for example, lower surface 131, upper surface 132, or both surfaces may be formed of a metal layer that may serve as a ground plane or other conductive surface in a printed circuit board.

[0027] The arrangement of slot openings, such as slot opening 140, and discrete vias, such as conductive via 135, can be viewed as a composite of left-handed and right-handed metamaterials that behaves as a single antenna. Such structures are sometimes referred to as composite left-handed ("CRLH") metamaterials. Thus, waveguide 120 can be modeled as a circuit having lumped elements corresponding to left-handed transmission line structures and other lumped elements corresponding to right-handed transmission line structures.

[0028] According to this idea, Figure 1C is a two-port lumped circuit model of the waveguide 120. Like other rectangular conductive waveguides, the waveguide 120 can be modeled as a combination of a series inductor and capacitor (LR and CL) coupled to a parallel inductor and capacitor (LL and CR). V is used to account for the variable effective width of the waveguide 120. As will be described in more detail below, this additional degree of freedom can enable improved RF impedance matching when compared to existing approaches.

[0029] Figure 2A FIG2 is a plan view of the upper surface 132 of the waveguide 120, illustrating the corrugated sidewall of the waveguide 120 in greater detail. As shown, some conductive vias 135 are positioned at a first distance from the center of the waveguide 120, while some conductive vias 135 are displaced up to a distance 295 from other conductive vias 135 to form corrugations in the sidewall of the waveguide 120. In this example, the width of the sidewall follows the width variation in the slot openings 140, with the maximum displacement 295 in the conductive vias 135 just exceeding the outermost slot opening 140 in each group 141 of slot openings 140. The shape of the sidewall, including the amount of corrugation (i.e., the magnitude and direction of the displacement 295), can be varied to achieve desired performance characteristics. Specifically, the corrugated sidewall pattern can be used to adjust the desired operating bandwidth, center frequency of the operating bandwidth, and impedance of a waveguide antenna, such as the waveguide 120.

[0030] Figure 2Bis another plan view of the upper surface 132 showing design choices for the groups of slot openings 140 in each group 141. The length (L) of each slot opening 140 can vary along the width (w) of the waveguide 120. In this example, each group 141 of slot openings 140 includes six slot openings. The two center slot openings have a maximum length (L1), while the slot openings on the other side of the first two slot openings have a length L2. The next two openings have a width L3, and the last two openings have a width L4. Meanwhile, the "baseline" width of the waveguide 120 outside of any corrugated portion is W. The maximum displacement 295 (denoted by the "via dt ”). The center-to-center spacing of the conductive vias 135 is indicated by “via s ", and the radius of each through hole is represented by "via r "Indicates. Figure 2B In the example shown, the conductive via 135 with the largest displacement coincides with the position of the shortest slot opening 140 in each group 141. The length distribution and width of slot openings, such as slot openings 140, can be varied to achieve a desired radiation pattern, including adjusting overall directivity and sidelobe power. The number of slot openings in a group (e.g., in a unit cell) can also be varied.

[0031] Figure 3 is a Smith chart showing the relationship between the slot geometry (e.g. Figure 2A and Figure 2B The effect of varying the amount of corrugation in a waveguide antenna, such as 120, over an operating bandwidth of 18.7% relative to a center frequency in the millimeter-wave range, is shown in the arrangement 140 shown in FIG. “Corrugation depth” refers to the magnitude and direction of displacement of a sidewall of the antenna (e.g., conductive vias 135 of waveguide 120), where negative values ​​represent displacement along the propagation direction of the waveguide away from a central axis of the waveguide (e.g., a centerline of the waveguide 120 parallel to the propagation direction 195), and positive values ​​represent displacement toward the central axis.

[0032] exist Figure 3 In the example shown, curve 302 is a circle corresponding to a constant reflection coefficient value of 0.25 or approximately 10 dB return loss. Curves 310, 312, 314, 316, and 320 correspond to the reflection coefficients for corrugation depths of -0.2 mm, 0.1 mm, no corrugation, +0.1 mm, and +0.2 mm, respectively, over the same operating bandwidth. As shown, by selecting an appropriate corrugation depth (e.g., Figure 2A The magnitude and direction of the displacement 295 shown), the reflection coefficient can be maintained below 0.25 over the desired operating bandwidth (see curve 318 corresponding to a corrugation depth of +0.1 mm).

[0033] Figure 4A Show changes Figure 3The effect of the geometry of the same designed slot opening groups (e.g., group 141 of slot openings 140) simulated in FIG. The "tapering degree" is defined by the slot length difference between the innermost slots in each slot opening group (e.g., reference Figure 2B , the taper will be calculated as L1-L4). As shown, changing the taper can significantly affect the observed reflection loss from an antenna according to embodiments herein (e.g., waveguide 120). Along similar lines, Figure 4B Is for Figure 4A The same taper as shown in Figure 4A The return loss (S) of the antenna design simulated in FIG. 1 is over an operating bandwidth equal to approximately 18% of the center frequency. 11 ) plotted.

[0034] Figure 5A is a plot showing the E-plane of an antenna designed similarly to the waveguide 120 described above (e.g., including Figure 1A Directivity of the radiation pattern in the plane of propagation direction 195 in the vertical direction 199). Figure 5B Shown corresponding to Figure 5A The accompanying H-plane of the E-plane pattern shown (e.g., including Figure 1A The radiation pattern of the plane of propagation direction 195 and direction 197 is shown. Figure 5A and Figure 5B As can be seen from the plot, by varying the center frequency over a 5 GHz bandwidth, a highly directional radiation pattern can be achieved, which can be steered over 25 degrees. Figure 5A As shown, antennas according to embodiments herein may have a beam direction in the E-plane (also referred to as the "maximum power direction" of the radiation pattern) having a component that points backward or opposite to the direction of propagation of RF energy in the waveguide (e.g., opposite to the propagation direction 195 in the waveguide 120) at one or more frequencies within the antenna's operating bandwidth. However, it should be understood that according to embodiments herein, not all antennas need exhibit one or more "backward" beam directions.

[0035] Figure 5A and Figure 5B The plot of represents the simulated performance of an antenna having 30 unit cells (ie, incorporating 30 groups of slot openings, such as group 141 of slot openings 140). Figure 5A and Figure 5B The performance characteristics of the antenna are shown with slot lengths equal to {1.22 mm, 0.98 mm, 0.66 mm, 0.42 mm} (see Figure 2B {L1, L2, L3, L4}). The baseline width of the waveguide (e.g., Figure 2B The W in the figure is 1.62 mm. The corrugation depth (e.g., maximum displacement 295 or viadt ) is +0.1 mm, and the width of each slot opening (e.g. Figure 2B w) is 0.1mm. Through hole (see Figure 2B The center-to-center distance between the through holes in the Figure 2B The thickness of the substrate core (e.g., the thickness of the dielectric material of the substrate 110 enclosed by the waveguide 120 between the lower surface 131 and the upper surface 132) is 0.254 mm. The total length of each unit cell is 2.16 mm.

[0036] It should be understood that the design of leaky-wave antennas according to embodiments herein can be varied to achieve desired performance characteristics over a desired frequency range. The total radiation pattern of such an antenna can be described as the sum of the radiation patterns of the individual unit cells (e.g., the individual groups 141 of slot-shaped openings 140 and the accompanying sidewalls of each unit cell formed by structures such as conductive vias 135). When the unit cells are identical to one another, the total radiation pattern can be expressed as a function of the following variables: the spacing between the unit cells (d), the free-space wave number (k), the amount of incident power radiated from each unit cell (α), and the phase shift across each cell (β).

[0037] Therefore, the total radiation pattern AP total It can be expressed as

[0038]

[0039] Equation 1 can be rearranged as follows:

[0040]

[0041] Subtracting Equation 2 from Equation 1 yields

[0042] AP total ×[1-αe j(kdsinθ+β) ]=AP cell ×(1-α N e j(kdsinθ+β)N )[Equation 3].

[0043] Equation 3 can also be simplified to:

[0044] Referring to Equation 4, it should be understood that for a sufficiently large value of N (the number of unit cells, eg, the number of groups 141 of slot-shaped openings 140 ),

[0045]

[0046] For a given attenuation factor (α), increasing the number of unit cells will produce higher beam directivity (beam width) and less obvious side lobes. For a fixed number of unit cells (N), increasing the attenuation factor (α) will produce less obvious side lobes at the expense of lower directivity (wider beam width), resulting in lower side levels but lower directivity (beam width). It should be understood that the performance characteristics of the antenna according to the embodiments of the present invention can be adjusted by changing the number of unit cells and the attenuation factor of each unit cell (i.e., the amount of power radiated out of each unit cell compared to the power coupled to the unit cell). The attenuation factor is largely determined by the size of the slot opening. Directivity, including beam width, is affected by the total width of the waveguide and the length of the slot opening.

[0047] Figure 6 6 is a flow chart illustrating a simplified example process for designing a leaky-wave antenna based on a substrate-integrated waveguide, such as waveguide 120. Process 600 includes steps 610, 620, 640, 645, 650, 655, and 660. In step 610, the desired operating frequency range for the antenna is selected. In step 620, a baseline width (W) is selected to support the lowest-frequency TE10 mode within the desired range. This width is given by: Where c is the speed of light in vacuum, f c is the selected cutoff frequency, and ε r is the relative permittivity of the dielectric material within the waveguide (e.g., the material forming the bulk of the substrate 120). As a non-limiting example, a rectangular waveguide having a width W is selected as a baseline waveguide structure, which is iteratively modified as needed to meet desired performance specifications, such as maximum acceptable return loss, minimum acceptable directivity, and maximum acceptable sidelobe power level.

[0048] At step 630, the design is modified to include one or more unit cells having corresponding groups of slot-shaped openings (e.g., group 141 of slot-shaped openings 140). Next, at step 630, an initial pattern of corrugations in the waveguide sidewalls is selected, resulting in a structure having corrugated sidewalls and slot-shaped openings that is related to the design of waveguide 120.

[0049] At step 640, the process includes determining whether the antenna design has a return loss that is less than a maximum acceptable return loss across the antenna's intended operating bandwidth. If the return loss is acceptable, the process proceeds to step 650. At step 650, the process includes determining whether the antenna design has an acceptable radiation pattern. As non-limiting examples, this may include determining whether the center beamwidth has a sufficiently narrow angular width, whether the antenna can generate a "backward" beam (a beam with a directional component that opposes the direction of energy propagation within the waveguide) at a desired subset of frequencies within the desired operating bandwidth, and whether the antenna's radiation pattern exhibits an acceptable amount of power in the sidelobes of the center beam.

[0050] At step 640, if the return loss exceeds a desired maximum return loss at one or more frequencies within the desired operating bandwidth, the process proceeds to step 645 and the corrugation depth is iteratively adjusted until an acceptable return loss is achieved.

[0051] At step 650, if the radiation pattern meets the desired performance characteristics, then a suitable design is generated at step 660. Otherwise, if the radiation pattern does not yet meet the desired performance characteristics, then the process proceeds to step 655.

[0052] At step 655, the slot dimensions, the baseline width of the waveguide, or both are adjusted appropriately, and the process returns to step 645. Different modifications to the design may be performed depending on the particular way in which the radiation pattern deviates from the desired performance characteristics. As an example, if the frequency beam steering range (the angular range of beam directions in the E-plane over the desired operating bandwidth) is too wide, the length of the slot opening of each unit cell (e.g., any one or more of the lengths L1, L2, L3, L4) may be reduced and the baseline width (W) of the waveguide may be increased, and the slot configuration may then be altered to adjust the attenuation factor of each unit cell (e.g., by changing the number of slots, the length of each slot, and its width (in Figure 2B Similarly, if the frequency beam steering range is too narrow, the slot length or lengths in each unit cell can be increased, and the baseline width of the waveguide can be reduced, and the slot configuration can then be changed as needed to adjust the attenuation factor.

[0053] As another example, if the frequency beam steering range is acceptable, but the overall direction of the beam at each frequency needs adjustment, increasing the slot length and increasing the baseline width of the waveguide will rotate the beam direction "forward" (i.e., reduce the angle between the beam direction and the propagation direction of the RF energy in the E-plane within the waveguide). At the same time, decreasing the slot length and decreasing the baseline width of the waveguide will rotate the beam direction "backward" (i.e., increase the angle between the beam direction and the propagation direction of the RF energy in the E-plane within the waveguide).

[0054] It should be appreciated that process 600 is described above to provide a simplified example of how a leaky wave antenna according to embodiments herein can be designed to have a desired operating bandwidth and achieve desired performance characteristics (e.g., broadband impedance matching with the feed network and other components, a desired beam steering range, desired directivity of the radiation pattern, etc.). However, it should be appreciated that any suitable method can be used to design a leaky wave antenna having corrugated sidewalls and slot-shaped openings according to embodiments herein. Along these lines, it should be appreciated that although the example antenna is described as having multiple unit cells, nothing herein is intended to require that the same unit cells be used to form a leaky wave antenna, such as waveguide 120 or similar antennas according to embodiments herein.

[0055] example

[0056] Features of the embodiments may be understood with the aid of one or more of the following examples.

[0057] Example 1: A method or apparatus comprising a circuit substrate and a leaky-wave antenna formed within the circuit substrate. The antenna comprises a hollow or dielectric-filled conductive waveguide having a length along a first direction, the first direction defining a propagation direction of a radio frequency (RF) signal within the waveguide. The waveguide comprises a first conductive surface, a second conductive surface, and a conductive via. The first conductive surface defines an upper surface of the waveguide. The second conductive surface is parallel to the upper surface and defines a lower surface of the waveguide. The conductive via passes through the circuit substrate between the upper and lower surfaces of the waveguide, the conductive via defining a first sidewall of the waveguide and a second sidewall of the waveguide, the second sidewall being opposite the first sidewall of the waveguide. The waveguide has slot-shaped openings distributed along the length of the waveguide on the first conductive surface. The slot-shaped openings are configured to cause a portion of an RF signal traveling within the waveguide along the propagation direction to radiate out of the waveguide. The width of the waveguide varies along the length of the waveguide and is defined by a variable distance between the first and second sidewalls along a second direction perpendicular to the first direction.

[0058] Example 2: An apparatus or method according to Example 1, wherein the conductive via is configured and dimensioned to reflect an incident RF signal having a frequency within a predetermined operating frequency range of the antenna so that the incident RF signal is guided along the propagation direction of the waveguide.

[0059] Example 3: The device or method of example 1 or example 2, wherein the slot-shaped openings in the first conductive surface are arranged in groups of slot-shaped openings.

[0060] Example 4: The apparatus or method of Example 3, wherein the width of the waveguide narrows at locations corresponding to edges of each group of slot-shaped openings.

[0061] Example 5: An apparatus or method according to Example 3 or Example 4, wherein the slots within each group of slot-shaped openings extend toward the first and second side walls of the waveguide and have a varying length along a second direction perpendicular to the length of the waveguide.

[0062] Example 6: A device or method according to any of Examples 1-5, wherein the groups of slot-shaped openings are periodically arranged along the length of the waveguide according to a first period, and the width of the waveguide is periodically narrowed along the first direction according to the first period.

[0063] Example 7: The apparatus or method of any of Examples 3-6, wherein the width of the waveguide narrows at locations along the length of the waveguide corresponding to the shortest slot or slots in each slot group.

[0064] Example 8: An apparatus or method according to any of Examples 1-7, wherein the antenna exhibits a directional radiation pattern defined by a maximum power direction, wherein the maximum power direction corresponds to an angle with respect to the upper surface of the waveguide at which the amount of radiated power has a maximum value.

[0065] Example 9: The apparatus or method of Example 8, wherein the direction of maximum power of the waveguide antenna depends on the center frequency of the incident RF signal.

[0066] Example 10: The apparatus or method of any of Examples 1-9, wherein for a first center frequency of the incident RF signal, the antenna has a first maximum power direction corresponding to a first angle with respect to an upper surface of the waveguide; and for a second center frequency of the incident RF signal, the waveguide antenna has a second maximum power direction corresponding to the first angle with respect to the upper surface of the waveguide. The second center frequency is 100 MHz greater than the first center frequency. The first maximum power direction is angularly offset from the second maximum power direction by at least 0.5 degrees.

[0067] The foregoing detailed description and examples are merely illustrative in nature and are not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Any embodiment described herein as exemplary is not necessarily to be construed as preferred or advantageous over other embodiments. Furthermore, the present invention is not intended to be bound by any expressed or implied theory presented in the preceding technical field, background, or detailed description.

[0068] It will be understood that the application of the present invention is not limited to the details of construction and arrangement of the parts set forth in the foregoing description or shown in the accompanying drawings. The present invention is capable of other embodiments and can be practiced or carried out in various ways. In addition, it will be understood that the words and terms used herein are for descriptive purposes and are not to be construed as limiting. The use of "including," "comprising," or "having," and variations thereof, herein is intended to encompass the items listed thereafter and their equivalents as well as additional items. Unless otherwise specified or limited, the terms "mounted," "connected," "supported," and "coupled," and variations thereof, are used broadly and encompass direct and indirect mounting, connection, support, and coupling. In addition, "connected" and "coupled" are not limited to physical or mechanical connections or couplings.

[0069] The terms "first," "second," "third," "fourth," and the like in the description and claims, if any, may be used to distinguish similar elements and are not necessarily used to describe a particular sequential order or time order. It will be understood that the terms so used are interchangeable where appropriate, such that the embodiments of the invention described herein are, for example, capable of operating in other sequences that are different from the sequence shown or described herein. It will be understood that the steps of the various processes described herein are non-limiting examples of suitable processes according to the embodiments and are for illustrative purposes. The embodiments herein may use any suitable process, including processes that omit the steps of the example processes described herein, perform those steps in a different order, and similar steps, and the like. It will also be understood that well-known techniques and features may be omitted for clarity.

[0070] As used herein, the terms "substantially" and "substantially" mean sufficient to achieve the stated purpose in a practical manner and that minor defects, if any, are not material for the stated purpose. Unless expressly stated otherwise, when used herein to refer to measurable quantities (including but not limited to dimensions), the terms "approximately" and "substantially" shall mean that one quantity is equal to the stated value, or that two quantities are equal to one another within an amount determined by the acceptable tolerances of the process selected for manufacturing the relevant structure and / or the acceptable measurement accuracy of the method and / or measuring device selected for measuring the described dimension or other characteristic.

[0071] Furthermore, the terms "including," "having," and any variations thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term "coupled," as used herein, is defined as connected directly or indirectly, electrically or non-electrically.

[0072] The foregoing description refers to elements or nodes or features being "connected" or "coupled" together. As used herein, unless expressly stated otherwise, "connected" means that one element is directly connected to (or is in direct communication with) another element, and not necessarily mechanically. Similarly, unless expressly stated otherwise, "coupled" means that one element is directly or indirectly connected to (or is in direct communication with, electrically or otherwise, another element), and not necessarily mechanically. Thus, although the schematic diagrams shown in the figures depict one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in one or more embodiments of the depicted subject matter.

[0073] The foregoing discussion is presented to enable those skilled in the art to make and use embodiments of the present invention. Without departing from embodiments of the present invention, those skilled in the art will readily appreciate various modifications to the illustrated embodiments, and the principles herein may be applied to other embodiments and applications. Therefore, embodiments of the present invention are not intended to be limited to the embodiments illustrated, but rather should be given the widest scope consistent with the principles and features disclosed herein. The foregoing detailed description should be read with reference to the accompanying drawings, in which identical elements in different figures have identical reference numerals. The accompanying drawings, which are not necessarily drawn to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the present invention. Those skilled in the art will recognize that the examples provided herein have many useful alternatives and are within the scope of embodiments of the present invention.

[0074] The connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and / or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in one or more embodiments of the subject matter. Additionally, certain terms may also be used herein for reference purposes only, and therefore these terms are not intended to be restrictive, and unless the context clearly indicates otherwise, the terms "first," "second," and other such numerical terms referring to structures do not imply an order or sequence.

Claims

1. A device, characterized in that include: a circuit substrate and a leaky-wave antenna formed in the circuit substrate; wherein the antenna comprises a hollow or dielectric-filled conductive waveguide having a length along a first direction defining a direction of propagation of a radio frequency (RF) signal within the waveguide; and wherein the waveguide is formed by: a first conductive surface defining an upper surface of the waveguide, the upper surface having slot-shaped openings distributed on the upper surface along the length of the waveguide, the slot-shaped openings being configured to cause a portion of the RF signal traveling in the waveguide along the propagation direction to radiate out of the waveguide; a second conductive surface parallel to the upper surface, the second conductive surface defining a lower surface of the waveguide; as well as a conductive via extending through the circuit substrate between the upper surface and the lower surface of the waveguide, the conductive via defining a first sidewall of the waveguide and a second sidewall of the waveguide, the second sidewall being opposite the first sidewall of the waveguide; and The width of the waveguide varies along the length of the waveguide and is defined by a variable distance between the first sidewall and the second sidewall along a second direction perpendicular to the first direction.

2. The device according to claim 1, characterized in that The slot-shaped openings in the first conductive surface are arranged into slot-shaped opening groups; and The width of the waveguide narrows at a position corresponding to an edge of each group of slot-shaped openings.

3. The device according to claim 2, characterized in that The slot-shaped opening groups are periodically arranged along the length of the waveguide according to a first period, and the width of the waveguide is periodically narrowed along the first direction according to the first period.

4. The device according to claim 2, characterized in that The slots within each group of slot-shaped openings extend toward the first sidewall and the second sidewall of the waveguide and have varying lengths along the second direction perpendicular to the length of the waveguide.

5. The device according to claim 1, characterized in that the antenna exhibits a directional radiation pattern defined by a maximum power direction corresponding to an angle with respect to the upper surface of the waveguide at which the amount of radiated power has a maximum value; and The maximum power direction of the waveguide antenna depends on the center frequency of the incident RF signal.

6. A method for forming an antenna, characterized in that: The method comprises: forming a conductive via through the circuit substrate between a first conductive surface of the circuit substrate and a second conductive surface of the circuit substrate; wherein said first conductive surface defines an upper surface of a conductive hollow or dielectric-filled waveguide; wherein the second conductive surface is parallel to the first conductive surface and defines a lower surface of the waveguide; wherein the conductive via defines a first sidewall of the waveguide and a second sidewall of the waveguide, the second sidewall being opposite to the first sidewall of the waveguide; wherein the conductive via is configured and dimensioned to reflect an incident RF signal having a frequency within a predetermined operating frequency range of the antenna such that the incident RF signal coupled to the first end of the waveguide is directed toward the second end of the waveguide along a propagation direction of the waveguide; wherein the width of the waveguide varies along the length of the waveguide and is defined by a variable distance between the first sidewall and the second sidewall along a second direction perpendicular to the propagation direction of the waveguide; and wherein the method further comprises: Slot-shaped openings are formed on the upper surface distributed along the length of the waveguide, the slot-shaped openings being configured to cause a portion of the RF signal traveling along the propagation direction within the waveguide to radiate out of the waveguide.

7. The method according to claim 6, characterized in that The slot-shaped openings in the first conductive surface are arranged into slot-shaped opening groups; and The width of the waveguide narrows at locations along the length of the waveguide corresponding to edges of each group of slot-shaped openings.

8. The method according to claim 7, characterized in that The slot-shaped opening groups are periodically arranged along the length of the waveguide according to a first period, and the width of the waveguide is periodically narrowed along the first direction according to the first period.

9. The method according to claim 7, characterized in that The slots within each group of slot-shaped openings extend toward the first sidewall and the second sidewall of the waveguide and have varying lengths along the second direction perpendicular to the length of the waveguide.

10. The method according to claim 6, characterized in that the antenna exhibits a directional radiation pattern defined by a maximum power direction corresponding to an angle with respect to the upper surface of the waveguide at which the amount of radiated power has a maximum value; and The maximum power direction of the waveguide antenna depends on the center frequency of the incident RF signal.

Images