Waveguide device and radar device

Abstract

In order to use a waveguide resonant grating (WRG) to realize a waveguide device of a new structure for setting an interval between a pair of adjacent radiation holes to a dimension of 1 λo or less, a waveguide device of the present invention comprises: an antenna unit having a first member with at least an electroconductive lower surface, and two slots obtained by forming, in the first member, two radiation holes each having an approximately oval shape from a top view and having an electroconductive inner surface, with the two slots being adjacently arranged in a first direction, which is the minor axis direction of the radiation holes; and a WRG structure part having two ridges arranged on the lower surface side of the first member and a plurality of rods arranged in an area adjacent to at least the two ridges. The two ridges each have abutting ends at terminal ends extending in a direction along the first direction and approaching each other, and at least a portion of each upper surface connected to the ridges is arranged at a position overlapping at least a portion of an opening of each slot in a top view.

Description

Waveguide device and radar device

[0001] The present invention relates to a waveguide device and a radar device.

[0002] In recent years, radar applications have been increasing the number of detection points by increasing the number of transmission and reception channels, and higher resolution has been achieved by using MIMO (Multi-Input Multi-Output) and MRA (Minimum Redundancy Array) technologies. In doing so, the field of view (FOV), or the detection angle, must also be widened. In addition, many applications require even higher resolution for detecting more distant or close-range objects. Therefore, antennas that support high gain and multi-channelization using low-loss, wideband transmission paths are in demand. Conventional low-loss, wideband waveguides include waveguides (see, for example, Patent Documents 1 and 2). Waveguides require high-precision three-dimensional metal processing, which increases costs and space requirements, resulting in limited flexibility in waveguide wiring. Waffle iron ridge waveguides (WRGs) have attracted attention as a waveguide that fundamentally overcomes these drawbacks. In MRA, shortening the spacing between the smallest adjacent aperture pairs to closer to half a wavelength moves the grating lobes away from the main beam (or they disappear below half a wavelength), thereby widening the beam scanning angle (FOV).

[0003] JP 2002-333035 A JP 2008-232257 A

[0004] When a pair of adjacent radiation holes is fabricated using the conventional waveguide, the minimum spacing between adjacent radiation holes must be equal to or greater than the wavelength λo, where λo is the free-space wavelength of the electromagnetic wave at the center frequency of the operating frequency. A specific example will be described below. FIGS. 16(a), 16(b), and 16(c) are diagrams showing an example of the schematic configuration of a conventional waveguide device 1000. As shown in FIGS. 16(a) to 16(c), the waveguide device 1000 includes an antenna section 1010 and a waveguide section 1020. The antenna section 1010 includes a horn antenna pair (waveguide pair) 1013 having horns 1015a and 1015b formed adjacent to a conductor plate 1011 that is rectangular in top view. The waveguide section 1020 includes waveguide grooves 1023a and 1023b that extend from near the center of the upper surface of the conductor plate 1021 that is rectangular in top view toward one end and the other end in the longitudinal direction, respectively. Furthermore, the conductor plate 1021 includes a choke groove 1025 formed along the short side between the longitudinally opposing ends of the waveguide grooves 1023a and 1023b, and back-short portions 1027a and 1027b formed from blocks separated by the choke groove 1025. The back-short portions 1027a and 1027b are structural components for broadband impedance matching between the waveguide grooves 1023a and 1023b and the horn antenna pair 1013. The lower surface of the conductor plate 1011 and the upper surface of the conductor plate 1021 are joined together without any gaps and in an electrically conductive structure, forming a metal joint with sufficient mechanical contact area and strength. Furthermore, the choke groove 1025 prevents electromagnetic wave leakage.

[0005] Here, the wavelength of the electromagnetic wave propagating within waveguide section 1020 is λg. In the example shown in Figures 16(a) to 16(c), λg is 6 mm and λo is 4 mm. In this case, as shown in Figures 16(a) and 16(c), the conventional waveguide device 1000 has a width w of 2.54 mm and a height h of 1.27 mm for waveguide grooves 1023a and 1023b, a distance between the center of each of horns 1015a and 1015b and backshort sections 1027a and 1027b of λg / 4 = 1.5 mm, and a distance between the center of choke groove 1025 and the end wall surfaces on the opposing sides of waveguide grooves 1023a and 1023b of λo / 4, or 1 mm. Therefore, the distance d between horns 1015a and 1015b (antenna distance) is d = 1.5 mm x 2 + 1 mm x 2 = 5 mm. The antenna spacing is 5 mm, but since the free-space wavelength λo is 4 mm, this is greater than one wavelength. In other words, the conventional method using a waveguide cannot achieve the requirement that two adjacent horns be spaced 1 λ or less apart. The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to realize a waveguide device with a new structure using a WRG that enables the spacing between adjacent radiation hole pairs to be 1 λo or less (for example, a dimension close to or equal to half the wavelength).

[0006] a waveguide device including at least a first member having at least a conductive lower surface, two slots penetrating the member in a vertical direction and forming two radiation holes, the two slots having a substantially oval or rectangular shape in a top view and conductive inner surfaces, the two slots being adjacent to each other in a first direction that is a minor axis direction of the slots, and a second member disposed on the bottom surface of the first member and having at least two ridges on its top surface that face the bottom surface of the first member and a plurality of rods having conductive surfaces disposed at least in regions adjacent to the two ridges, the two ridges each having a butting end at an end portion extending in a direction along the first direction toward each other, and at least a portion of the top surface of each ridge connected to the butting end of the two ridges being positioned so as to overlap at least a portion of the opening of the respective slot in a top view. Here, "along" the first direction includes not only a direction identical to the first direction but also a direction tilted within a range of ±45° with respect to the first direction. In the above configuration, the slot may have a U-shaped shape in a top view, and the minor axis direction of the slot may be the maximum electric field direction of the U-shaped slot. In the above configuration, when the free space wavelength of electromagnetic waves at the center frequency of the operating frequency band is λo, the opposing distance between the two butting ends may be λo / 4 or less. In the above configuration, the second member may have at least one butting rod having a conductive surface arranged between the two butting ends. In the above configuration, the butting end of at least one of the two ridges may be located outside the through-hole of the slot in a top view. In the above configuration, the butting end of at least one of the two ridges may be located inside the through-hole of the slot in a top view. In the above configuration, when the free space wavelength of electromagnetic waves at the center frequency of the operating frequency band is λo, the opposing distance between the two butting ends may be λo / 2 or less.In the above configuration, the two ridges may have two parallel straight portions extending linearly at a predetermined interval, and the two butting ends may be formed on one ends of the two straight portions. In the above configuration, the two ridges may have bent portions formed between the two butting ends and the two straight portions, respectively.

[0007] In the above configuration, for at least one of the two ridges, a part of the through portion of the slot may be disposed at a position overlapping, in a top view, with the ridge upper surface of the bent portion of one of the ridges or the ridge upper surface extending from the bent portion to the butting end. In the above configuration, a horn may be provided above the slot.

[0008] The present invention provides a radar device comprising: a waveguide device having the above-described configuration; two first waveguides that are other waveguides electromagnetically connected to the ends of the two ridges that form the waveguide, opposite to the butting ends of the two ridges; and a mounting substrate provided with high-frequency circuits that feed electromagnetic waves to the two ridges via the two first waveguides, wherein the electromagnetic waves propagated via second waveguides formed by the conductive upper surfaces of the two ridges and the conductive lower surface of the first member are radiated from the two slots. In the above configuration, the radar device may further comprise a radar calculation unit that calculates position and relative velocity information of a detection target based on the electromagnetic waves transmitted and received through the two slots.

[0009] According to the present invention, it is possible to realize a waveguide device in which the spacing between adjacent radiation hole pairs is 1λo or less.

[0010] 1 is a plan view showing a schematic configuration example of a waveguide device 1 according to a first embodiment. FIG. 1 is a plan view showing a schematic configuration example of an antenna unit 2 according to the first embodiment. FIG. 1 is a plan view showing a schematic configuration example of a WRG structure unit 3 according to the first embodiment. A cross-sectional view taken along line AA' in FIG. 1. A cross-sectional view taken along line BB' in FIG. 1. A partially enlarged view of a portion where each end of the waveguide device 1 overlaps with each slot. A diagram showing the electromagnetic field distribution of the waveguide device 1. A diagram showing simulation results of the transmission characteristics and reflection characteristics of electromagnetic waves of the waveguide device 1. FIG. 1 is a plan view showing a schematic configuration example of a waveguide device 1A according to a second embodiment. A plan view showing a schematic configuration example of an antenna unit 2A according to the second embodiment. A plan view showing a schematic configuration example of a WRG structure unit 3A according to the second embodiment. A partially enlarged view of a portion where each end of the waveguide device 1A overlaps with each slot. A plan view showing a schematic configuration example of a waveguide device 1B according to a third embodiment. A partially enlarged view of a portion where each end of the waveguide device 1B overlaps with each slot. 1 is a plan view showing a schematic configuration example of a waveguide device 1C according to a fourth embodiment; FIG. 2 is a partially enlarged view of a portion where each butting end of the waveguide device 1C overlaps with each slot; FIG. 3 is a partially enlarged view showing a schematic configuration example of a waveguide device 1D according to a fifth embodiment; FIG. 4 is a partially enlarged view showing a schematic configuration example of a waveguide device 1E according to a sixth embodiment; and FIG. 5 is a block diagram showing a schematic configuration example of a radar device 500. (a) to (c) are diagrams showing an example of a waveguide device having a conventional configuration.

[0011] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention. Note that the embodiment described below is an example of a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is not limited to the following embodiment. Furthermore, in the description of the drawings below, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and conceptual, and the vertical and horizontal dimensions and scales of components or parts differ from those of the actual parts. Therefore, the specific dimensions and scales should be determined with reference to the following description. Furthermore, it goes without saying that the drawings also include parts with different dimensional relationships and ratios. [Terminology]

[0012] "Millimeter waves" refer to electromagnetic waves with frequencies ranging from 30 GHz to 300 GHz. The wavelength of "millimeter waves" in a vacuum ranges from 1 mm to 10 mm. Electromagnetic waves with wavelengths ranging from 10 mm to 30 mm are sometimes called "quasi-millimeter waves." The frequency band handled by the waveguide device of the present disclosure may be a band with a lower frequency than millimeter waves, or may be a band with a higher frequency than millimeter waves. The waveguide device may be used, for example, to propagate electromagnetic waves in the terahertz wave band (approximately 300 GHz or higher and 3 THz or lower).

[0013] A "high frequency circuit" is a chip or package of a semiconductor integrated circuit that generates or processes high frequency waves in the millimeter wave band. A "package" is a package that includes one or more semiconductor integrated circuit chips that generate or process high frequency waves in the millimeter wave band. A millimeter wave IC in which one or more millimeter wave ICs are integrated on a single semiconductor substrate is particularly called an MMIC (Monolithic Microwave Integrated Circuit). In this disclosure, examples using an "MMIC" as the "millimeter wave IC" will be mainly described. [First embodiment] [Configuration]

[0014] First, a first embodiment of the present invention will be described. FIGS. 1 to 5B are diagrams illustrating the first embodiment. As shown in FIGS. 1, 2A, and 2B, a waveguide device 1 includes an antenna unit 2 and a WRG structure 3 disposed on the underside of the antenna unit 2. The antenna unit 2 includes a first member 200 and two slots 202a and 202b that penetrate the first member 200 in the vertical direction and form two antenna radiation holes. The first member 200 is composed of a conductor or a member having a conductive surface on at least the lower surface of its upper and lower surfaces. The slots 202a and 202b are approximately oval in top view and are arranged adjacent to each other with a predetermined gap in the first direction, which is the minor axis direction of the slots. These adjacent slots 202a and 202b form adjacent radiation holes. Furthermore, the inner portions of the slots 202a and 202b are conductive. That is, when the first member 200 is configured such that the surface (at least the lower surface) of a member such as a dielectric substrate is coated with a conductor, the inner portions of the slots 202 a and 202 b are also coated with a conductor. In the example shown in Fig. 3A, the first member 200 is configured such that the lower surface of the dielectric substrate and the inner portions of the slots 202 a and 202 b are coated with a conductor 201.

[0015] Here, the term "top surface" refers to the collection of surfaces (including a single surface) that includes all surfaces included in the field of view when viewing an object such as the first member 200 from a far point above the Z axis, with the +Z direction of the Z axis in Figures 1, 2A, and 2B defined as up and the -Z direction as down. Similarly, the term "bottom surface" refers to the collection of surfaces that includes all surfaces included in the field of view when viewing the object from below the Z axis. In other words, even for an object with a complex shape with multiple surfaces, such as a stepped shape, the collection of these multiple surfaces is the top surface or bottom surface. Furthermore, whether or not the bottoms of recesses or holes present on the surface of each surface are included in the top and bottom surfaces is defined on a case-by-case basis. Furthermore, even if the object is flipped 180 degrees and the top surface defined in Figures 1, 2A, and 2B faces downward (in the -Z direction), it is still considered the top surface. Similarly, even if the bottom surface faces upward (in the +Z direction), it is still considered the bottom surface. The same applies when the object faces in other directions. Therefore, expressions such as "upper," "lower," and "upper and lower directions" in this specification and claims are used merely for convenience to facilitate understanding and should be interpreted appropriately. Furthermore, "upper side" means upward, including the upper surface. Similarly, "lower side" means downward, including the lower surface. Furthermore, in the following Figures 1, 2A, and 2B, the +X direction is the forward direction, the -X direction is the rearward direction, the +Y direction is the leftward direction, and the -Y direction is the rightward direction. This also applies to subsequent figures from similar viewpoints.

[0016] As shown in FIGS. 2B, 3A, and 3B, the WRG structure 3 includes a second member 300, multiple ridges including ridges 301a and 301b provided on the upper surface of the second member 300, multiple rods 302 arranged in the peripheral regions of the sides of each ridge, and abutting rods 305. The WRG structure 3 further includes multiple waveguides including waveguides 303a and 303b arranged adjacent to the front ends of each ridge, which are the ends on the forward (+X direction) side of the extension direction of each ridge, and which penetrate the second member 300 in the vertical direction. Below, a more detailed configuration will be described, focusing on one pair of ridges 301a and 301b. The ridges 301a and 301b each have linear portions 31a and 31b extending parallel to each other in the front-to-rear direction facing the conductive lower surface 201S of the first member 200, and rear ends 32a and 32b, which are the ends on the rear (-X direction) side of the linear portions 31a and 31b. The straight portions 31a and 31b and the rear ends 32a and 32b have waveguide surfaces 35a and 35b formed of conductive upper surfaces.

[0017] The rear ends 32a and 32b of the ridges 301a and 301b have bent portions 33a and 33b that gradually change the direction of extension from the rear to the left (+Y) and right (-Y) directions, respectively. Furthermore, the bent portions 33a and 33b extend straight from their tips to the left and right, respectively, and are provided with abutment ends 34a and 34b at their terminal ends.

[0018] With this configuration, the portions of the ridges 301a and 301b extending from the bent portions 33a and 33b to the end portions 34a and 34b extend straight from the tips of the bent portions 33a and 34b in the left and right directions, respectively. Additionally, the end portions 34a and 34b face each other closely, with a predetermined distance between them. Specifically, the distance between the end portions 34a and 34b is set to λo / 2 or less. The rod 305 is located between the end portions 34a and 34b and prevents electromagnetic waves leaking from each end portion from propagating to the other end portion.

[0019] The rods 302 form an electromagnetic wave shielding wall 310. The electromagnetic wave shielding wall 310 formed by the conductive rods 302 and the butting rod 305 constitutes an artificial magnetic wall. The rods 302 forming the artificial magnetic wall are called an artificial magnetic conductor. The confinement effect of the electromagnetic wave shielding wall 310 formed by the artificial magnetic conductor prevents leakage of high-frequency electromagnetic fields. As a result, the opposing conductive lower surface 201S of the first member 200 and the conductive waveguiding surfaces 35a and 35b of the ridges 301a and 301b form waveguides, respectively, and the high-frequency electromagnetic field propagates through these waveguides. The rods 302 and the butting rod 305 (hereinafter sometimes simply referred to as "rods 305") extend upward from the second member 300. In the example shown in FIGS. 3A and 3B, the lengths (heights) of the rods 302 are generally the same. The waffle iron structure of the WRG structure 3 will be described in detail later, so only an outline will be given here.

[0020] The conductive lower surface 201S of the first member 200 extends two-dimensionally along a plane (a plane parallel to the XY plane) perpendicular to the axial direction (Z direction) of the rods 302 and 305. This range includes at least the region facing the ridges 301a and 301b and the rods 302 and 305. In the first embodiment, the conductive lower surface 201S is a smooth plane, but the conductive lower surface 201S does not necessarily have to be a smooth plane. In the first embodiment, the space between the conductive lower surface 201S of the first member 200 and the conductive upper surface 300S of the WRG structure 3 is filled with air. It is to be noted that the space may be filled with gas, vacuum, or the like, instead of air, or at least a portion of the space may be filled with a dielectric. Waveguides 303a and 303b are holes provided vertically penetrating ridges 301a and 301b and second member 300, and serve as waveguides that propagate electromagnetic waves from a high-frequency circuit (not shown) such as an MMIC (Monolithic Microwave Integrated Circuit). Note that the arrangements of ridges, rods, waveguides, etc. in the drawings in this specification, such as Figures 2B, 3A, and 3B, are illustrative drawings intended only to explain the various components in the waveguide device according to the present invention, and are not based on an arrangement intended to achieve a specific function unless explicitly stated.

[0021] 1 and 3A, in the waveguide device 1, at least the slot 202a is disposed above the upper surface of the ridge 301a extending from the bent portion 33a to the end 34a, and the slot 202b is disposed above the upper surface of the ridge 301b extending from the bent portion 33b to the end 34b. Furthermore, in the first embodiment, as shown in Fig. 4, the opening (through portion) of the slot 202a is disposed in a structure in which, in a top view, a portion of the opening (through portion) of the slot 202a overlaps with either or both of the upper surface of the ridge 301a at the bent portion 33a and the upper surface of the ridge 301a extending from the bent portion 33a to the end 34a. Additionally, the opening of the slot 202b is disposed in a structure in which, in a top view, a portion of the opening of the slot 202b overlaps with either or both of the upper surface of the ridge 301b at the bent portion 33b and the upper surface of the ridge 301b extending from the bent portion 33b to the end 34b. That is, a portion of the opening of slot 202a overlaps with the upper surface of ridge 301a extending from bend 33a to end 34a, and a portion of the opening of slot 202b overlaps with the upper surface of ridge 301b extending from bend 33b to end 34b. Due to this overlapping relationship, end 34a and end 34b are configured to be aligned along the minor axis direction of slots 202a and 202b (the direction in which the electric field of the slot is maximized). Here, "along" includes the following meanings. In other words, in the first embodiment, this includes the same direction (with this being the reference angle of 0°) as the first direction in which ridge 301a extending from bend 33a to end 34a and ridge 301b extending from bend 33b to end 34b extend, but it does not necessarily have to be the same direction. The slots 202a and 202b may extend in a direction other than one direction, for example, in a direction tilted within a range of ±45° from the first direction, as long as the radiation characteristics of the electromagnetic waves from the slots 202a and 202b are not affected. The term "along" is used in this specification and claims to include this meaning. Furthermore, the spacing (center-to-center distance) between the slots 202a and 202b is configured to be the minimum spacing when, for example, MRA technology is applied.

[0022] With the configuration described above, electromagnetic waves propagated through waveguides 303a and 303b propagate from the front to the rear through the two waveguides formed by conductive lower surface 201S of first member 200 and ridges 301a and 301b. As a result, electromagnetic waves propagating along ridge 301a propagate leftward through bend 33a toward end 34a. Similarly, electromagnetic waves propagating along ridge 301b propagate rightward through bend 33b toward end 34b. As a result, the currents flowing through conductive lower surface 201S on the ridge 301a and ridge 301b sides are blocked by slots 202a and 202b. As a result, an electric field is generated in slots 202a and 202b in the direction indicated by the dotted arrows in FIG. 4 , and the electric field is radiated from slots 202a and 202b to the outside.

[0023] Next, based on FIGS. 4, 5A, and 5B, we will explain the results of a simulation performed using an electromagnetic field simulator to propagate electromagnetic waves through a waveguide formed by the ridge 301a of the waveguide device 1. In the simulation, as shown in FIG. 4, the free-space wavelength (λo) was set to 4 mm, and the inter-slot distance (antenna spacing) between the slots 202a and 202b was set to 3.25 mm. Furthermore, the distances between the end ends 34a and 34b and the centers of the slots 202a and 202b were set to 0.86 mm (approximately λo / 4), respectively. FIG. 5A shows the state of the electromagnetic field when electromagnetic waves are supplied only to the ridge waveguide at the left end of the figure. As shown in this figure, the electromagnetic waves propagating through the ridge 301a propagate without leaking to the ridge 301b side and are radiated to the outside from the slot 202a, confirming the electromagnetic wave propagation shielding effect of the end rod 305. Although not shown in the drawings, a similar shielding effect was confirmed when electromagnetic waves were propagated through the ridge 301b.

[0024] Further, S parameters were measured under the same conditions. Here, as shown in FIG. 2B , the end of ridge 301a on the waveguide 303a side was designated port 1 (P1), and the end of ridge 301b on the waveguide 303b side was designated port 2 (P2). In this case, the S parameter S11 is the ratio (reflected power / input power) of the power of the electromagnetic wave input to port 1 to the power of the electromagnetic wave reflected by the load and returned to port 1. The smaller this value (reflection coefficient) is, the less reflection there is. However, in FIG. 5B , the return loss is converted into a negative dB value, and the larger the absolute value of the numerical value, the less reflection there is. Furthermore, the S parameter S21 is the ratio (output power / input power) of the power of the electromagnetic wave input to port 1 to the power of the electromagnetic wave output from port 2. The smaller this value (transmission coefficient) is, the better the shielding effect is.

[0025] As shown by the solid line in FIG. 5B, the simulation results for the S-parameter S11 were smallest at approximately 79.5 GHz, at approximately 40 dB. The S-parameter S11 was also smallest at 75 GHz, at both ends of the target frequency range of 75 to 82 GHz, at approximately 37 dB, at 82 GHz, at approximately 32.5 dB, and at 78 GHz, at approximately 28 dB. These simulation results indicated that good results were obtained with small return loss in the target frequency range. Furthermore, as shown by the dashed line in FIG. 5B, the simulation results for the S-parameter S21 were approximately 30 dB across almost the entire target frequency range of 75 to 82 GHz. These simulation results indicated that good results were obtained in terms of shielding effect in the target frequency range of 75 to 82 GHz. [Effects of the First Embodiment]

[0026] As described above, the waveguide device 1 of the first embodiment includes the first member 200 having at least the conductive lower surface 201S, the antenna section 2 having the slots 202a and 202b that penetrate the first member 200 from top to bottom and form two radiation holes that are approximately oval in top view and have conductive inner surfaces, and that are arranged adjacent to each other in a first direction that is the minor axis direction (maximum electric field direction), the ridges 301a and 301b that are arranged on the lower surface side of the first member 200 and have waveguide surfaces 35a and 35b on their upper surface sides that face the lower surface of the first member 200, and the ridges 301a and 301b that are arranged in regions at least adjacent to the ridges 301a and 301b. The WRG structure 3 includes a plurality of rods 302 having conductive surfaces, and the ridges 301a and 301b have abutting ends 34a and 34b, respectively, at their ends as they extend toward each other along the first direction. At least a portion of the upper surfaces of the ridges 301a and 301b connected to the abutting ends 34a and 34b (i.e., the upper surfaces of either or both of the bent portions 33a and 33b and the portions between the bent portions 33a and 33b and the abutting ends 34a and 34b) are positioned so as to overlap at least a portion of the openings of the slots 202a and 202b in a top view. The WRG structure 3 further includes an abutting rod 305 having a conductive surface disposed between the abutting ends 34a and 34b of the second member 300. Furthermore, the distance between the abutting ends 34a and 34b is equal to or less than half of the free-space wavelength λo.

[0027] With this configuration, a waveguide device in which the spacing between slots 202a and 202b (pairs of adjacent radiation holes) is 1λ or less can be realized by using a waveguide member including ridges 301a and 301b having butt ends 34a and 34b made of WRG. This makes it possible to prevent the device from becoming large when configuring a waveguide device that applies MRA technology, which is a type of sparse array.

[0028] [Correspondence in the First Embodiment] In the first embodiment, the antenna unit 2 corresponds to the first member, the first member 200 corresponds to the member, and the WRG structural unit 3 corresponds to the second member. [Second Embodiment] [Configuration]

[0029] Next, a second embodiment of the present invention will be described. FIGS. 6 to 8 are diagrams illustrating the second embodiment. Below, differences from the first embodiment will be described in detail, and similar parts will be denoted by the same reference numerals and will not be described again as appropriate. As shown in FIGS. 6, 7A, and 7B, a waveguide device 1A according to the second embodiment includes an antenna unit 2A and a WRG structure 3A. The WRG structure 3A is similar to the WRG structure 3 of the first embodiment except that the abutting rod 305 is removed and ridges 301Aa and 301Ab are provided instead of the ridges 301a and 301b. The ridges 301Aa and 301Ab include rear ends 32Aa and 32Ab instead of the rear ends 32a and 32b of the ridges 301a and 301b of the first embodiment. The rear ends 32Aa and 32Ab include bent portions 33a and 33b and abutting ends 34Aa and 34Ab. The abutting ends 34Aa and 34Ab are configured to be longer in the first direction than the abutting ends 34a and 34b of the first embodiment, respectively, and the distance between both ends is configured to be shorter. Specifically, the distance between both ends is configured to be λo / 4 or less.

[0030] On the other hand, the antenna unit 2A includes slots 202Aa and 202Ab instead of the slots 202a and 202b in the antenna unit 2 of the first embodiment. The slots 202Aa and 202Ab have a longer distance from the bent portions 33a and 33b to the end portions 34Aa and 34Ab, and the shorter distance between the two ends results in a shorter distance between the two slots. For example, if the free-space wavelength λo is 4 mm, the inter-slot distance can be 2.0 mm (approximately λo / 2) and the distance between the end portions can be 0.5 mm (approximately λo / 8), as shown in FIG. 8 . In the second embodiment, the opening of the slot 202Aa is arranged so that, in a top view, a portion of the opening overlaps with either or both of the upper surface of the ridge 301a at the bent portion 33a and the upper surface of the ridge 301a from the bent portion 33a to the end portion 34Aa. In addition, a portion of the opening of the slot 202Ab is arranged in a structure in which, in a top view, it overlaps with either or both of the upper surface of the ridge 301b at the bent portion 33b and the upper surface of the ridge 301b from the bent portion 33b to the end portion 34Ab. Although not shown, a simulation was performed using an electromagnetic wave simulator for the above numerical example. As a result, similar to the simulation results for the first embodiment, a good shielding effect was confirmed between the ridges 301Aa and 301Ab. Also, good results were obtained for return loss. [Effects of the Second Embodiment]

[0031] As described above, the waveguide device 1A of the second embodiment includes the first member 200 having at least the conductive lower surface 201S, the antenna unit 2A having the slots 202Aa and 202Ab that penetrate the first member 200 vertically and form two radiation holes that are approximately oval in top view and have conductive inner surfaces, and that are arranged adjacent to each other in a first direction that is the minor axis direction (maximum electric field direction) of the slots, the ridges 301Aa and 301Ab that are arranged on the lower surface side of the first member 200 and have waveguide surfaces 35a and 35b on their upper surface sides that face the lower surface of the first member 200, and a plurality of ridges 301Aa and 301Ab that have conductive surfaces that are arranged at least in areas adjacent to the ridges 301Aa and 301Ab. The ridges 301Aa and 301Ab have abutment ends 34Aa and 34Ab, respectively, at their terminal ends extending toward each other in a direction along the first direction of the slots 202Aa and 202Ab, and at least a portion of the upper surfaces of the ridges 301Aa and 301Ab connected to the abutment ends 34Aa and 34Ab (i.e., the upper surfaces of either or both of the bent portions 33a and 33b and the portions between the bent portions 33a and 33b and the abutment ends 34Aa and 34Ab) are positioned so as to overlap at least a portion of the openings of the slots 202Aa and 202Ab in a top view. Furthermore, the distance between the abutment ends 34Aa and 34Ab is equal to or less than ¼ of the free space wavelength λo.

[0032] With this configuration, a waveguide device can be realized in which the spacing between the slots 202Aa and 202Ab (nearby radiation hole pairs) is 1λo or less using the ridges 301Aa and 301Ab having the butting ends 34Aa and 34Ab formed by WRGs. In particular, compared to the first embodiment, the spacing between the butting ends 34Aa and 34Ab can be narrower and the spacing between the slots 202Aa and 202Ab can be narrower without providing the butting rod 305. This allows the spacing between the slots 202Aa and 202Ab to be approximately λo / 2. As a result, for example, a waveguide device can be realized that widens the beam scanning angle (FOV) of an array antenna using MRA technology and further reduces false detections due to pseudo signals folded back by grating lobes. [Correspondence in the Second Embodiment] In the second embodiment, the antenna unit 2A corresponds to the first member, the first member 200 corresponds to the member, and the WRG structural unit 3A corresponds to the second member. [Third Embodiment]

[0033] Next, a third embodiment of the present invention will be described. FIGS. 9 and 10 are diagrams illustrating the third embodiment. Below, differences from the first embodiment will be described in detail, and similar parts will be denoted by the same reference numerals and will not be described again as appropriate. As shown in FIGS. 9 and 10, the waveguide device 1B includes an antenna section 2B and a WRG structure section 3. The antenna section 2B includes a horn antenna 203 instead of the slot antenna formed by slots 202a and 202b in the antenna section 2 of the first embodiment. The horn antenna 203 includes horns 203a and 203b above each slot that forms a substantially oval radiation hole. Specifically, the inner peripheries of the horns 203a and 203b have a substantially truncated cone shape. The structure of the antenna section 2B illustrated in FIGS. 9 to 10 can also be applied to the waveguide device 1A of the second embodiment. [Effects of the Third Embodiment]

[0034] As explained above, the waveguide device 1B of the third embodiment has horns 203a and 203b above the slots that form the substantially oval radiation holes in the waveguide device 1 or 1A of the first or second embodiment. With this configuration, compared to the slot antenna configurations of the first and second embodiments, it is possible to optimize the directivity of the radiated electromagnetic waves by changing the shape of the inner peripheral surface of the horn. [Correspondence in the Third Embodiment] In the third embodiment, the antenna unit 2B corresponds to the first member, the first member 200 corresponds to the member, and the WRG structure unit 3 corresponds to the second member. [Fourth Embodiment]

[0035] Next, a fourth embodiment of the present invention will be described. FIGS. 11 and 12 are diagrams illustrating the fourth embodiment. Below, differences from the first embodiment will be described in detail, and similar parts will be denoted by the same reference numerals and omitted as appropriate. A waveguide device 1C according to the fourth embodiment includes an antenna unit 2C and a WRG structure 3, as shown in FIGS. 11 and 12 . The antenna unit 2C includes slots 205a and 205b, which are configured by tilting slots 202a and 202b at a predetermined angle relative to the first direction, instead of slots 202a and 202b. Specifically, each slot is rotated around the Z axis so that the rear side of the longitudinal direction of each slot is closed inward and the front side is open outward. However, with the orientation adjacent to the first direction as the reference (0°), each slot is tilted within a range of +45° or -45°. As a result, the electromagnetic waves radiated from the slots 205a and 205b can be obliquely polarized or circularly polarized.

[0036] As explained above, the waveguide device 1C of the fourth embodiment is the waveguide device 1 or 1A of the first or second embodiment, in which the slots 205a and 205b are arranged at an inclination within a range of up to +45° or -45° with respect to the first direction. With this configuration, the electromagnetic waves radiated from the slots can be obliquely polarized or circularly polarized depending on the inclination angle. [Correspondence in the Fourth Embodiment] In the fourth embodiment, the antenna unit 2C corresponds to the first member, the first member 200 corresponds to the member, and the WRG structure unit 3 corresponds to the second member. [Fifth Embodiment]

[0037] Next, a fifth embodiment of the present invention will be described. FIG. 13 is a diagram illustrating the fifth embodiment. Below, differences from the first embodiment will be described in detail, and similar parts will be denoted by the same reference numerals and will not be described again as appropriate. As shown in FIG. 13 , a waveguide device 1D according to the fifth embodiment includes an antenna unit 2 and a WRG structure 3D. The WRG structure 3D includes rear ends 32Da and 32Db instead of the rear ends 32a and 32b of the WRG structure 3 of the first embodiment. The rear ends 32Da and 32Db include bent portions 33Da and 33Db and end ends 34Da and 34Db. While the first embodiment described above had the end ends extending in the same direction as the first direction of the slots 202a and 202b, the fifth embodiment is configured to extend in a direction tilted within a range of ±45° with respect to the first direction. That is, in the example shown in FIG. 13, the ridges extending from the bent portions 33Da and 33Db toward the end portions 34Da and 34Db extend obliquely in a V-shape.

[0038] Furthermore, instead of the abutting rod 305 of the first embodiment, a rod 307 having a pentagonal shape in top view and having opposing surfaces facing both abutting ends 32Da and 32Db, and a plurality of rods 302 are arranged along the diagonally extending ridge in a V-shape, respectively. The electromagnetic wave blocking wall formed by these rods 307 and 302 prevents the electromagnetic waves propagating on the ridge from leaking toward the tip. Furthermore, in the configuration of the fifth embodiment, as in the fourth embodiment, the electromagnetic waves radiated from the slots 202a and 202b can be obliquely polarized or circularly polarized. [Effects of the fifth embodiment]

[0039] As described above, the waveguide device 1D of the fifth embodiment is the same as the waveguide device 1 or 1A of the first or second embodiment, except that the ridges 301a and 301b extending from the bends 33Da and 33Db to the butt ends 34Da and 34Db extend in a direction inclined obliquely within a range of ±45° relative to the first direction of the slots 202a and 202b. With this configuration, the electromagnetic waves radiated from the slots 202a and 202b can be obliquely polarized or circularly polarized, depending on the angle of inclination. [Correspondence in the Fifth Embodiment] In the fifth embodiment, the antenna unit 2 corresponds to the first member, the first member 200 corresponds to the member, and the WRG structure 3D corresponds to the second member. [Sixth Embodiment] Next, a sixth embodiment of the present invention will be described. FIG. 14 is a diagram illustrating the sixth embodiment. Below, differences from the first embodiment will be described in detail, and similar parts will be designated by the same reference numerals and will not be described again as appropriate. As shown in FIG. 14 , the waveguide device 1E includes an antenna unit 2D and a WRG structure unit 3. The antenna unit 2D includes slots 207a and 207b instead of the slots 201a and 201b, which are oval in top view, in the antenna unit 2 of the first embodiment. In the example shown in FIG. 14 , the slot 207a is U-shaped in top view (a shape obtained by rotating a U-shape 90 degrees counterclockwise) and the slot 207b is in an inverted U-shape in top view (a shape obtained by rotating a U-shape 90 degrees clockwise). That is, the slots 207a and 207b have radiation holes that are U-shaped or inverted U-shaped in top view. Note that the U-shapes of the slots 207a and 207b may be oriented left-right opposite to the orientation illustrated in FIG. 14 , or both may be oriented in the same direction. 14, the directions of the left and right arrows correspond to the maximum electric field directions of slots 207a and 207b and correspond to the first direction. That is, in the example shown in Fig. 14, the configuration is such that a part of the portion of the opening of slots 207a and 207b in the maximum electric field direction overlaps, in top view, either or both of the upper surfaces of ridges 301a and 301b of bent portions 33a and 33b and the upper surfaces of ridges 301a and 301b extending from bent portions 33a and 33b to butt ends 34Aa and 34Ab.The structure of the antenna unit 2D shown in FIG. 14 can also be applied to the waveguide device 1A of the second embodiment. [Effects of the Sixth Embodiment] As described above, the waveguide device 1E of the sixth embodiment includes slots 207a and 207b having U-shaped radiation holes in a top view in the waveguide device 1 or 1A of the first or second embodiment. With this configuration, compared to the slot antenna configurations of the first and second embodiments, adjusting the length of each leg of the U-shape allows for dual resonance characteristics, thereby enabling a wider bandwidth. [Correspondence in the Sixth Embodiment] In the sixth embodiment, the antenna unit 2D corresponds to the first member, the first member 200 corresponds to the member, and the WRG structure 3 corresponds to the second member. [Details of the Waffle Iron Structure]

[0040] Next, the waffle iron structure of the WRG structure will be described in more detail with reference to FIG. 3B. As shown in FIG. 3B, the multiple rods 302 arranged on the second member 300 each have a tip 302a facing the conductive lower surface 201S. In the illustrated example, the tip 302a of the multiple rods 302 are substantially coplanar. This plane forms the surface 302c of the artificial magnetic conductor. Each rod 302 does not need to be conductive throughout; it is sufficient that a conductive layer extends along at least the top and side surfaces of the rod-shaped structure. This conductive layer may be located on the surface of the rod-shaped structure, but the surface layer may be made of an insulating coating or resin layer, and no conductive layer may be present on the surface of the rod-shaped structure. Furthermore, the second member 300 does not need to be conductive throughout as long as it can support the multiple rods 302 and realize the artificial magnetic conductor.

[0041] It is sufficient that the conductive upper surface 300S of the second member 300, which is the surface on which the multiple rods 302 are arranged, is conductive, and the surfaces of the multiple adjacent rods 302 are electrically connected by a conductor. The conductive layer of the second member 300 may be covered with an insulating coating or a resin layer. In other words, it is sufficient that the entire combination of the second member 300 and the multiple rods 302 has an uneven conductive layer facing the conductive lower surface 201S of the first member 200.

[0042] The space between the surface 302c of each artificial magnetic conductor and the conductive lower surface 201S of the first member 200 does not allow electromagnetic waves having frequencies within a specific frequency band to propagate. Such a frequency band is called a "forbidden band." The artificial magnetic conductor is designed so that the frequency of the electromagnetic waves propagating within the waveguide device (hereinafter sometimes referred to as the "operating frequency") is included in the forbidden band. The forbidden band can be adjusted by the height of the rods 302, i.e., the depth of the grooves formed between adjacent rods 302, the width and spacing of the rods 302, and the size of the gap between the tip ends 302a of the rods 302 and the conductive lower surface 201S.

[0043] The waveguide device is used for at least one of transmitting and receiving electromagnetic waves in a predetermined band (hereinafter referred to as the "operating frequency band"). The free-space wavelength of electromagnetic waves at the center frequency in the operating frequency band of the waveguide device is denoted as λo. The end of each rod 302 that contacts the second member 300 is referred to as the "base." Each rod 302 has a tip 302a and a base 302b. Examples of the dimensions, shape, and arrangement of each member are as follows. For example, as shown in FIG. 3B , the width (size in the X and Y directions) of the rod 302 can be set to less than λo / 2. Within this range, the occurrence of lowest-order resonance in the X and Y directions can be prevented. Note that resonance may occur not only in the X and Y directions but also in the diagonal directions of the XY cross section. Therefore, it is preferable that the length of the diagonal line of the XY cross section of the rod 302 is also less than λo / 2. Furthermore, the distance from the base 302b of the rod 302 to the conductive lower surface 201S of the first member 200 can be set to be longer than the height of the rod 302 and less than λo / 2. If this distance is λo / 2 or more, resonance occurs between the base 302b of the rod 302 and the conductive lower surface 201S, and the electromagnetic wave confinement effect is lost.

[0044] Furthermore, the distance L from the tip 302a of the rod 302 to the conductive lower surface 201S is set to be less than λo / 2. This is because if this distance is λo / 2 or greater, a propagation mode occurs in which electromagnetic waves travel back and forth between the tip 302a of the rod 302 and the conductive lower surface 201S, making it impossible to confine the electromagnetic waves. The tip 302a of each of the multiple rods 302 is not in electrical contact with the conductive lower surface 201S. Here, the state in which the tip 302a of the rod 302 is not in electrical contact with the conductive lower surface 201S refers to either a state in which there is a gap between the tip 302a and the conductive lower surface 201S, or a state in which an insulating layer exists on either the tip 302a or the conductive lower surface 201S, and the tip 302a of the rod 302 is in contact with the conductive lower surface 201S via the insulating layer. In order to ensure ease of manufacture, when electromagnetic waves in the millimeter wave band are propagated, the distance L can be set to, for example, λo / 16 or more.

[0045] Furthermore, the gap between two adjacent rods 302 among the multiple rods 302 has a width of, for example, less than λo / 2. The width of the gap between two adjacent rods 302 is defined by the shortest distance from one surface (side surface) of the two rods 302 to the other surface (side surface) of the two rods 302. The width of this gap between the rods is determined so that the lowest-order resonance does not occur in the region between the rods. The conditions for resonance are determined by a combination of the height of the rods 302, the distance between the two adjacent rods, and the capacitance of the gap between the tip end 302a of the rod 302 and the conductive lower surface 201S. Therefore, the width of the gap between the rods is determined appropriately depending on other design parameters. Although there is no clear lower limit to the width of the gap between the rods, in the case of propagating millimeter-wave electromagnetic waves to ensure ease of manufacturing, it may be, for example, λo / 16 or greater. Note that the width of the gap does not need to be constant. As long as it is less than λo / 2, the gap between the rods 302 may have various widths.

[0046] Furthermore, the arrangement of the multiple rods 302 is not limited to the illustrated example, as long as it functions as an artificial magnetic conductor. The multiple rods 302 do not need to be arranged in orthogonal rows and columns; the rows and columns may intersect at angles other than 90 degrees. The multiple rods 302 do not need to be arranged in a straight line along the rows or columns; they may be distributed without any simple regularity. The shape and size of each rod 302 may also vary depending on its position on the second member 300. Furthermore, the surface 124c of the artificial magnetic conductor formed by the tips 302a of the multiple rods 302 does not need to be strictly flat; it may be a flat or curved surface with minute irregularities. In other words, the height of each rod 302 does not need to be uniform; individual rods 302 may have diversity within the range in which the arrangement of the rods 302 functions as an artificial magnetic conductor.

[0047] Each rod 302 is not limited to the illustrated rectangular column shape and may have, for example, a cylindrical shape. Furthermore, each rod 302 does not need to have a simple columnar shape. An artificial magnetic conductor can be realized by structures other than an array of rods 302, and various artificial magnetic conductors can be used in the waveguide device of the present disclosure. When the tip 302a of each rod 302 is rectangular column-shaped, the length of its diagonal is preferably less than λo / 2. When the tip 302a is elliptical, the length of its major axis is preferably less than λo / 2. Even if the tip 302a has another shape, the diameter of the tip 302a is preferably less than λo / 2 at its longest point. The height of the rod 302, i.e., the length from the base 302b to the tip 302a, can be set to a value shorter than the distance (less than λo / 2) between the conductive lower surface 201S and the conductive upper surface 300S, for example, λo / 4.

[0048] 3B, the conductive upper surface 300S is planar, but the embodiment of the present disclosure is not limited to this. For example, the conductive upper surface 300S may be the bottom of a surface whose cross section parallel to the XZ plane is shaped like a U or V. The conductive upper surface 300S has such a structure when the rod 302 has a shape (tapered shape) in which the width increases from the tip 302a to the base 302b. Even with such a structure, the illustrated device can function as a waveguide device in the embodiment of the present disclosure as long as the distance between the conductive lower surface 201S and the conductive upper surface 300S is shorter than half the wavelength λo. [Application Example to Radar Device]

[0049] Next, a radar device 500 including a waveguide device according to an embodiment of the present disclosure will be described with reference to FIG. 15 . Each of the waveguide devices 1 to 1E according to the first to sixth embodiments includes waveguides 303a and 303b (corresponding to first waveguides), second waveguides formed between the upper surfaces (waveguide surfaces) of the two ridges and the conductive lower surface 201S of the first member 200, and an antenna unit. The radar device 500 can function as a radar device by adding a signal processing device including an MMIC or a radar calculation IC. That is, as shown in FIG. 15 , the radar device 500 includes an array antenna 510 and a radar signal processing device 520. The array antenna 510 includes any of the waveguide devices 1 to 1E according to the first to sixth embodiments, and includes a transmitting antenna 511, which is a transmitting array antenna, and a receiving antenna 512, which is a receiving array antenna. Although not shown, the radar signal processing device 520 includes an MMIC connected to the array antenna 510 and a signal processing circuit for radar calculations (e.g., a radar calculation IC) connected to the MMIC. The signal processing circuit performs processing such as estimating the direction of an incoming wave based on a signal received by the MMIC. The signal processing circuit may be configured to execute an algorithm such as the MUSIC method, the ESPRIT method, or the SAGE method to estimate the direction of the incoming wave and output a signal indicating the estimation result. The signal processing circuit may further be configured to estimate the distance to a detection object that is the source of the incoming wave, the relative speed of the detection object, and the direction of the detection object using a known algorithm, and output a signal indicating the estimation result. Such a radar device 500 may be suitably used in a radar system mounted on a moving object such as a vehicle, a ship, an aircraft, or a robot. [Modification]

[0050] In the above embodiment, the upper ends of the rods forming the electromagnetic wave shielding wall are not in contact with the conductive lower surface 201S of the first member 200. However, this configuration is not limited thereto, and the upper ends of the rods may be bonded to the conductive lower surface 201S. Here, "bonded" refers to a state in which each rod is part of the conductive lower surface 201S of the first member 200 or is integrally fixed thereto by diffusion bonding, caulking, screwing, or the like. Furthermore, a structure in which a conductive material, such as a conductive adhesive, conductive oil, conductive rubber, or elastic conductive resin, is interposed between the upper surface of each rod and the conductive lower surface 201S may be used. The upper surface of each rod and the conductive lower surface 201S may have a minute gap therebetween or may be electrically separated by a thin non-conductive film. Even in this case, the rods can still suppress electromagnetic wave leakage, but the effect is weaker than when the side surfaces of each rod are electrically connected to the conductive lower surface 201S.

[0051] Furthermore, in the above embodiment and its modified examples, a configuration in which both of the two butting ends are located outside the slot's through-hole has been described as an example. However, this configuration is not limited to this, and at least one of the two butting ends may be located inside the slot's through-hole. Furthermore, in the above embodiment and its modified examples, multiple rods are provided to form an electromagnetic wave shielding wall. However, this configuration is not limited to this. For example, a wall portion may be provided on the front or rear side of the ridge. The upper end of the wall portion may also be configured to be in contact with or bonded to the conductive lower surface 201S. Furthermore, in the above embodiment and its modified examples, a configuration in which only one butting rod 305 is provided has been described as an example. However, this configuration is not limited to this. A configuration in which multiple butting rods 305 are provided may also be used. Furthermore, in the above embodiment and its modified examples, a configuration in which the slot's radiation hole (opening) has an oval or U-shaped shape in top view has been described as an example. However, this configuration is not limited to this, and other shapes, such as an elongated rectangular shape in top view, an H-shape in top view, or a crank-shaped shape in top view, may also be used.

[0052] 1, 1A to 1E... Waveguide device, 2, 2A to 2D... Antenna part, 3, 3A, 3D... WRG structure part, 31a, 31b... Straight part, 32a, 32Aa, 32Da, 32b, 32Ab, 32Db... Rear end part, 33a, 33Da, 33b, 33D b...Bending portion, 34a, 34Aa, 34Da, 34b, 34Ab, 34Db...Abutting end, 35a, 35b...Waveguide surface, 200...First member, 201...Conductor, 201S...Conductive lower surface, 202a, 202Aa, 205a, 202b, 20 2Ab, 205b, 207a, 207b...slots, 203...horn antenna, 203a, 203b...horn slots, 300...second member, 300S...conductive upper surface, 301a, 301Aa, 301Da, 301b, 301Ab, 301Db...ridges, 302, 307...rods, 303a, 303b...waveguides, 305...end rods, 500...radar device, 510...array antenna, 511...transmitting antenna, 512...receiving antenna, 520...radar signal processing device

Claims

1. A waveguide device comprising at least a first member having at least a member with a conductive lower surface, and two slots that penetrate the member in the vertical direction and form two radiation holes, each of which has a roughly oval or roughly rectangular shape in a top view and has conductive inner surfaces, the two slots being arranged adjacent to each other in a first direction which is the short axis direction of the slots, and a second member that is arranged on the bottom surface of the first member and has on its top surface at least two ridges that have strip-shaped conductive upper surfaces that face the bottom surface of the first member, and a plurality of rods with conductive surfaces that are arranged in areas at least adjacent to the two ridges, wherein the two ridges each have abutting ends at terminal ends that extend in a direction along the first direction and in directions approaching each other, and at least a portion of the top surface of each ridge that is connected to the abutting ends of the two ridges is arranged in a position that overlaps at least a portion of the opening of each slot in a top view.

2. A waveguide device according to claim 1, wherein the slot has a U-shaped shape when viewed from above, and the minor axis direction of the slot is the direction of maximum electric field in the U-shaped slot.

3. A waveguide device according to claim 1, wherein the distance between the two opposing butting ends is λo / 4 or less, where λo is the free space wavelength of an electromagnetic wave at the center frequency of the operating frequency band.

4. A waveguide device as claimed in claim 1, wherein said second member comprises at least one butted rod having a conductive surface disposed between said two butted ends.

5. A waveguide device according to any one of claims 1 to 4, wherein the abutting end of at least one of the two ridges is positioned outside the through portion of the slot in top view.

6. A waveguide device according to any one of claims 1 to 4, wherein the butting end of at least one of the two ridges is positioned within the through-portion of the slot in top view.

7. A waveguide device according to claim 3, wherein the distance between the two opposing butting ends is λo / 2 or less, where λo is the free space wavelength of an electromagnetic wave at the center frequency of the operating frequency band.

8. A waveguide device according to any one of claims 1 to 4, wherein the two ridges have two parallel straight sections extending linearly at a predetermined distance from each other, and the two butting ends are formed at one end of the two straight sections.

9. The waveguide device according to claim 8, wherein the two ridges each have a bent portion formed between the two abutting ends and the two straight portions.

10. A waveguide device as described in claim 9, wherein for at least one of the two ridges, a portion of the slot's through-portion is positioned so as to overlap, in a top view, with at least a portion of the ridge top surface at the bent portion of one of the ridges or the ridge top surface from the bent portion to the butting end.

11. A waveguide device according to any one of claims 1 to 4, further comprising a horn above said slot.

12. A radar device comprising: a waveguide device according to any one of claims 1 to 4; first waveguides which are two other waveguides electromagnetically connected to the ends of the two ridges forming the waveguide opposite to the butting ends; and a mounting substrate on which high-frequency circuits are provided which feed electromagnetic waves to the two ridges via the two first waveguides, wherein electromagnetic waves propagated via second waveguides formed by the conductive upper surfaces of the two ridges and the conductive lower surface of the first member are radiated from the two slots.

13. The radar device according to claim 12, further comprising a radar calculation unit that calculates information on the position and relative velocity of a detection target based on electromagnetic waves transmitted and received through said two slots.

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