Patent Publication Number: US-2023146641-A1

Title: Slot antenna and slot antenna array

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2018/009596, filed on Aug. 21, 2018, which claims the benefit of U.S. Provisional Application No. 62/550,135, filed on Aug. 25, 2017, the contents of which are all incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a slot antenna which may be utilized in a lidar that detects an object located in vicinity of a vehicle. 
     BACKGROUND ART 
     A vehicle is an apparatus that transports a user riding therein in a desired direction. A representative example of a vehicle may be an automobile. 
     A variety of sensors and electronic devices are mounted in vehicles for convenience of a user who uses the vehicle. In particular, for driving convenience, an Advanced Driver Assistance System (ADAS) has been actively studied. In addition, enormous efforts have been being made to develop autonomous vehicles. 
     In order to implement the ADAS or an autonomous vehicle, a radar for a vehicle is used. A radar for a vehicle according to an existing technology utilizes a frequency domain with a 1 GHz bandwidth of 76 to 77 GHz in in millimeter-wave frequency bands. 
     In recent years, a radar for a vehicle using a frequency domain with a 4 GHz bandwidth of 77 to 81 GHz with has been developed. If the 4 GHz bandwidth of 77 to 81 GHz is used, the radar may exhibit better range resolution due to broadband frequency characteristics. In addition, in this case, the radar may play a role of an ultrasonic sensor and hence it may be used in parking assistance, autonomous parking, and other applications which require high resolution in a short range. 
     A microstrip antenna conventionally used at frequencies of a 1 GHz has a short-range available bandwidth and thus it is not suitable to be used within a 4 GHz bandwidth. Thus, there are demands for an antenna capable of being used in a 4 GHz bandwidth. 
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in view of the above problems, and it is one object of the present invention to provide an antenna used in a radar for a vehicle with a wide-range available bandwidth. 
     Objects of the present invention should not be limited to the aforementioned objects and other unmentioned objects will be clearly understood by those skilled in the art from the following description. 
     Technical Solution 
     In order to accomplish the above object, a slot antenna according to an embodiment of the present invention may include a substrate integrated waveguide (SIW) having a plurality of bent slots formed therein. 
     The details of other embodiments are included in the following description and the accompanying drawings. 
     Advantageous Effects 
     According to the present invention, there are one or more effects as follows. 
     First, there is an advantageous effect in providing an antenna having a small size but able to be used within a 4 GHz bandwidth of 77 to 81 GHz. 
     Second, there is an advantageous effect in manufacturing an antenna with low manufacturing costs. 
     Third, there is an advantageous effect in making it easy to couple. 
     Effects of the present invention may not be limited to the above and other objects which are not described may be clearly comprehended by those of skill in the art to which the embodiment pertains through the following description. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG.  1    is a diagram showing an external appearance of a vehicle according to an embodiment of the present invention; 
         FIG.  2    is a diagram showing a slot antenna according to an existing technology; 
         FIG.  3    is a perspective view of a slot antenna according to an embodiment of the present invention; 
         FIG.  4    is a cross-section view A-A′ of  FIG.  3   ; 
         FIG.  5    is a cross-section view B-B′ of  FIG.  3   ; 
         FIG.  6    is a diagram showing a surface current at a point in time on a substrate integrated waveguide (SIW) according to an embodiment of the present invention; 
         FIG.  7    is a top view of a slot antenna according to an embodiment of the present invention; 
         FIG.  8    is an enlarged view of a portion of  FIG.  7   ; 
         FIGS.  9  and  10    are diagrams for explanation of a slot antenna array according to an embodiment of the present invention; 
         FIG.  11    is a diagram for explanation of a terminator according to an embodiment of the present invention; and 
         FIG.  12    is a cross-section view C-C′ of  FIG.  11   . 
     
    
    
     BEST MODE 
     Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, and the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings and redundant descriptions thereof will be omitted. In the following description, with respect to constituent elements used in the following description, the suffixes “module” and “unit” are used or combined with each other only in consideration of ease in the preparation of the specification, and do not have or serve as different meanings. Accordingly, the suffixes “module” and “unit” may be interchanged with each other. In addition, in the following description of the embodiments disclosed in the present specification, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the embodiments disclosed in the present specification rather unclear. In addition, the accompanying drawings are provided only for a better understanding of the embodiments disclosed in the present specification and are not intended to limit the technical ideas disclosed in the present specification. Therefore, it should be understood that the accompanying drawings include all modifications, equivalents and substitutions included in the scope and sprit of the present invention. 
     It will be understood that although the terms “first,” “second,” etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another component. 
     It will be understood that when a component is referred to as being “connected to” or “coupled to” another component, it may be directly connected to or coupled to another component or intervening components may be present. In contrast, when a component is referred to as being “directly connected to” or “directly coupled to” another component, there are no intervening components present. 
     As used herein, the singular form is intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     In the present application, it will be further understood that the terms “comprises”, “includes,” etc. specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof. 
     A vehicle as described in this specification may include an automobile and a motorcycle. Hereinafter, a description will be given based on an automobile, however it will be understood that the disclosure is not limited thereto. Further, although discussed herein with respect to use in vehicles, it will be understood by those of ordinary skill in the art that the features of the disclosure, such as the configurations of antennas, antenna arrays, and the like, including the use thereof, may be applicable to other applications, environments, devices, machines, products, and the like related or unrelated to vehicle detection systems, and that such implementations and applications of the various embodiments discussed herein are considered by and included in this disclosure. 
     A vehicle as described in this specification may include all types of vehicles, including those having an engine as a power source, a hybrid vehicle including both an engine and an electric motor as a power source, and an electric vehicle including an electric motor as a power source, and the like. 
     In the following description, “the left side of the vehicle” refers to the left side in the forward driving direction of the vehicle, and “the right side of the vehicle” refers to the right side in the forward driving direction of the vehicle. 
       FIG.  1    is a diagram showing an external appearance of a vehicle according to an embodiment of the present invention. 
     Referring to  FIG.  1   , a vehicle  1  may be an autonomous vehicle or a manual driving vehicle. The vehicle  1  may switch to an autonomous driving mode or a manual driving mode based on a user input. For example, the vehicle  1  may switch from the manual driving mode to the autonomous driving mode or vice versa based on a user input received through a user interface device  200 . In some cases, the vehicle  1  may switch to the autonomous driving mode or the manual driving mode based on driving situation information. 
     The driving situation information may include at least one of information on an object outside the vehicle, navigation information, or vehicle state information. For example, based on driving situation information generated by an object detection apparatus  300 , the vehicle  1  may switch from the manual driving mode to the autonomous driving mode or vice versa. In another example, based on driving situation information received through a communication apparatus  400 , the vehicle  1  may switch from manual driving mode to the autonomous driving mode or vice versa. 
     Based on information, data, or a signal provided from an external device, the vehicle  1  may switch from the manual driving mode to the autonomous driving mode or vice versa. 
     Here, “overall length” means the length from the front end to the rear end of the vehicle  1 , “width” means the width of the vehicle  1 , and “height” means the distance from the lower end of a wheel to the top of the roof of the vehicle  1 . In the following description, the overall length direction L may be the direction based on which the overall length of the vehicle  1  is measured, the width direction W may be the direction based on which the width is measured, and the height direction H may be the direction based on which the height is measured. 
     The vehicle  1  may include a radar  50  for the vehicle. The radar  50  may be disposed at an appropriate position external to the vehicle to sense an object located at the front, rear, or either side of the vehicle. 
     The radar  50  may include an antenna. In some implementations, the antenna included in the radar  50  may function as a transmit antenna and a receive antenna. In some implementations, the radar  50  may include a transmit antenna and a receive antenna. 
     The radar  50  may detect an object located in the vicinity of the vehicle  1 . The radar  50  may acquire a position of the detected object, a distance to the detected object, and a speed relative to the detected object. 
     The object located in vicinity of the vehicle  1  may include for example, a lane or lane marker, another vehicle, a pedestrian, a two-wheeled vehicle, a traffic signal, light, a road, a structure, a speed bump, a geographical feature, an animal, and the like. 
     The lane or corresponding markers may be the lane in which the vehicle  1  is currently traveling, a lane next to the lane in which the vehicle  1  is traveling, or a lane in which an opposing vehicle is traveling. The lane may include left and right lines that define the lane. The lane may include an intersection. 
     Another vehicle may be a vehicle that is travelling in the vicinity of the vehicle  1 . The other vehicle may be a vehicle within a predetermined distance from the vehicle  1 . For example, the other vehicle may be a vehicle travelling ahead of the vehicle  1  or following the vehicle  1 . 
     The pedestrian may be a person located in the vicinity of the vehicle  1 . The pedestrian may be a person located within a predetermined distance from the vehicle  1 . For example, the pedestrian may be a person located on a sidewalk or a roadway. 
     The two-wheeled vehicle may be a vehicle that is located in the vicinity of the vehicle  1  and moves with two wheels. The two-wheeled vehicle may be a vehicle that has two wheels within a predetermined distance from the vehicle  1 . For example, the two-wheeled vehicle may be a motorcycle or a bicycle on a sidewalk or a roadway. 
     The traffic signal may include a traffic signal lamp, a traffic sign, or a pattern or text painted on a road surface. 
     The light may be light generated by a lamp provided in another vehicle. The light may be light generated by a streetlight. The light may be solar light. 
     The road may include a road surface, a curve, or slopes, such as an upward slope and a downward slope. 
     The structure may be an object located in the vicinity of the road and fixed to the ground. For example, the structure may include a streetlight, a roadside tree, a building, a signal lamp, a bridge, a curb, or a wall surface, and the like. 
     The geographical feature may include a mountain, a hill, etc. 
     The object may be classified as a movable object or a stationary object. For example, a movable object may include another vehicle and a pedestrian. A stationary object may include a traffic signal, a road, or a structure, another vehicle in a stopped state, a pedestrian in a stopped state, and the like. 
       FIG.  2    is a diagram showing a slot antenna according to an existing technology. 
     Referring to  FIG.  2   , a slot antenna  10  according to an existing technology has a slot formed on one surface of a waveguide  11  to thereby radiate electromagnetic waves into a free space. 
     As shown in  FIG.  2   , the slot antenna  10  according to the existing technology utilizes a wide-range available bandwidth but has a volume that is too large to be used in a vehicle. In order to solve this problem, a slot antenna according to an embodiment of the present invention is proposed. 
       FIG.  3    is a perspective view of a slot antenna according to an embodiment of the present invention.  FIG.  4    is a cross-section view A-A′ of  FIG.  3   .  FIG.  5    is a cross-section view B-B′ of  FIG.  3   .  FIG.  6    is a diagram showing a surface current at a point in time on a substrate integrated waveguide (SIW) according to an embodiment of the present invention.  FIG.  7    is a top view of a slot antenna according to an embodiment of the present invention.  FIG.  8    is an enlarged view of a portion of  FIG.  7   . 
     Referring to  FIGS.  3  to  8   , an antenna  100  may include a substrate integrated waveguide (SIW)  200 . 
     The SIW  200  may be implemented using a printed circuit board (PCB). Via holes may be formed to surround one region of the PCB, and the SIW  200  may be formed by inserting metal into the via holes. The via holes formed to surround one area of the PCB may be referred to as a via fence. 
     As such, the SIW  200  is implemented using the PCB, and hence, it may be relatively easy to electrically connect to an electronic component (e.g., Monolithic Microwave Integrated Circuit (MMIC)) of a radar  50  and it is possible to minimize a volume occupied by the radar  30  in the vehicle. In addition, it is possible to use a bandwidth wider than in existing technologies. 
     The SIW  200  may include a first metal plate  210 , a second metal plate  220 , a dielectric material  230 , and a via fence. 
     The first metal plate  210  may be formed of copper (Cu). The first metal plate  210  may be referred to as a thin copper foil or a copper plate. 
     The second metal plate  220  may be formed of copper (Cu). The second metal plate  220  may be referred to as a thin copper foil or a copper plate. The second metal plate  220  may be electrically connected to the first metal plate  210  through a plurality of via holes  240 . The plurality of via holes  240  may be formed to surround one region. The plurality of via holes  240  may be referred to as a via fence. 
     The dielectric material  230  may be interposed between the first metal plate  210  and the second metal plate  220 . The dielectric material  230  may be a low loss dielectric material. 
     The SIW  200  may be defined as a stereoscopic shape surrounded by the via fence and having a length, a width, and a height. A length direction of the SIW  200  may be construed as Y direction and −Y direction in  FIG.  3   . A width direction of the SIW  200  may be construed as X direction and −X direction in  FIG.  3   . A height direction of the SIW  200  may be construed as Z direction and −Z direction in  FIG.  3   . 
     When power is supplied, a surface current may be formed on the SIW  200 . The surface current may be formed on at least one of the first metal plate  210  or the second metal plate  220 . The surface current may be in the form of standing waves because a short-circuit surface may be formed by the via fence. The short-circuit surface may be formed on a surface opposite to a power supply direction in the SIW  200 . 
     The SIW  200  may have a guided wavelength λg. 
     A plurality of bent slots  300 , also referred to herein as slots  300 , may be formed in the SIW  200 . 
     The plurality of bent slots  300  may be formed on the first metal plate  210 . 
     The plurality of bent slots  300  may cause discontinuity in the surface current of the SIW  200 . As such, discontinuity is caused in the surface current of the SIW  200 , whereby electromagnetic waves may be radiated into a free space. 
     As shown in  FIG.  8   , each of the plurality of slots  300  may include a first slot  300   a , a second slot  300   b , and a third slot  300   c . The first slot  300   a  may be elongated in the length direction of the SIW  200 . The second slot  300   b  may be formed from the end of the first slot in a direction different from the length direction of the SIW  200 . The third slot  300   c  may be elongated from the end of the second slot in the length direction of the SIW  200 . 
     In the SIW  200 , there may be formed the first slot elongated in the length direction of the SIW  200  (e.g., Y direction), the second slot  300   b  formed from the end of the first slot  300   a  in a direction (e.g., a diagonal direction) different from the length direction of the SIW  200 , and the third slot  300   c  elongated from the end of the second slot  300   b  in the length direction of the SIW  200  (e.g., Y direction). 
     The first slot  300   a  may be formed to be offset in a first direction (e.g., −X direction) from a virtual center line  800  extending in the length direction of the SIW  200 . A virtual center line  810  in a horizontal direction of the first slot  300   a  may be spaced apart from the virtual center line  800 , which extends in the length direction of the SIW  200 , by a first distance D in the first direction (e.g., −X direction). 
     The third slot  300   c  may be formed to be offset in a direction (e.g., X direction), which is opposite to the first direction, from the virtual center line  800  extending in the length direction of the SIW  200 . A center line  830  in a horizontal direction of the third slot  300   c  may be spaced apart from the virtual center line  800 , which extends in the length direction of the SIW  200 , by the first distance D in a direction (e.g., X direction) opposite to the first direction. Here, the spacing distance is equal to the distance of the center line  810  of the first slot  300   a  from the virtual center line  800 . 
     One end of the second slot  300   b  may be connected to the first slot  300   a , and the other end of the second slot  300   b  may be connected to the third slot  300   c . At least a portion of the second slot  300   b  may intersect the virtual center line  800  extending in the length direction of the SIW  200 . 
     As such, the first slot  300   a  has an offset in the first direction and the third slot  300   c  has an offset in a direction opposite to the first direction, and hence, it is possible to radiate electromagnetic waves in accordance with change in phase of currents over time and within a wide-range bandwidth. 
     As shown in  FIG.  7   , a first bent slot  310  and a second bent slot  320  may be formed in the SIW  200 . 
     The first bent slot  310  may be formed such that the center thereof is spaced apart from the short-circuit surface  610  by one half the guided wavelength λg in the length direction of the SIW  200 . The center of the first bent slot  310  may be construed as the central point of the total length of the first bent slot  310 . The center of the first bent slot  310  may be positioned on the virtual center line  800  extending in the length direction of the SIW  200 . 
     The second bent slot  320  may be formed such that the center thereof is spaced apart from the first bent slot  310  by the guided wavelength λg in the length direction of the SIW  200 . The center of the second bent slot  320  may be construed as the central point of the total length of the second bent slot  310 . The center of the second bent slot  320  may be positioned on the virtual center line  800  in the length direction of the SIW  200 . 
     In some implementations, the SIW  200  may have further bent slots  330  and  430  formed therein. The plurality of bent slots  300  may be spaced apart by a distance of the guided wavelength λg. 
     Each of the plurality of bent slots  300  may have a length that corresponds to one half a wavelength of a resonant frequency used to transmit and receive electromagnetic waves. 
       FIGS.  9  and  10    are diagrams for explanation of a slot antenna array according to an embodiment of the present invention. 
       FIG.  9    shows an example of a slot antenna array including a plurality of slot antennas. 
     Referring to  FIG.  9   , a slot antenna array  1000  may include a plurality of slot antennas  100 . The description about the slot antenna  100  in  FIGS.  1  to  8    may apply to the plurality of slot antennas  100  in  FIGS.  9  and  10   . 
     The slot antenna array  1000  may be provided in a radar  50  that detects an object located in vicinity of a vehicle  1 . 
     The slot antenna array  1000  may include a first slot antenna  100   a , and a second slot antenna  100   b  electrically connected with the first slot antenna  100   a.    
     The first slot antenna  100   a  may include a first SIW having a plurality of bent slots formed therein. The description about the plurality of bent slots  300  in  FIGS.  1  to  8    may apply to the plurality of bent slots in  FIG.  9   . The description about the SIW  200  in  FIGS.  1  to  8    may apply to the first SIW in  FIG.  9   . 
     The second slot antenna  100   b  may include a second SIW having a plurality of bent slots. The description about the plurality of bent slots  300  in  FIGS.  1  to  8    may apply to the plurality of bent slots in  FIG.  9   . The description about the SIW  200  in  FIGS.  1  to  8    may apply to the second SIW in  FIG.  9   . 
       FIG.  10    shows an example of a slot antenna array including a plurality of slot antennas and a plurality of dummy antennas. 
     Referring to  FIG.  10   , edge effects may occur in the slot antenna array  1000  in  FIG.  9   . Since an outer slot antenna and an inner slot antenna have different characteristics (e.g., impedance characteristics), this difference may affect overall performance of the slot antenna array  1000 . In addition, the plurality of slot antennas may interfere with one another, possibly distorting a radiation pattern of the slot antenna array  1000 . 
     In order to improve the radiation pattern distortion, the slot antenna array  1000  may further include at least one dummy antenna  900  that is disposed in the vicinity of at least one of the first slot antenna  100   a  or the second slot antenna  100   b.    
     As the at least one dummy antenna  900 , the slot antenna  100  described above with reference to  FIGS.  1  to  8    may be used. The at least one dummy antenna  900  is not connected with an electronic device and another antenna of the radar  50 . 
     The at least one dummy antenna  900  may be interposed between the plurality of slot antennas  100 . The at least one dummy antenna  900  may be interposed between the first slot antenna  100   a  and the second slot antenna  100   b . The at least one dummy antenna  900  may be disposed external to the outermost antenna among the plurality of slot antennas  100 . 
     For impedance matching of the at least one dummy antenna  900 , the slot antenna array  1000  may further include at least one terminator  950  respectively connected to the at least one dummy antenna. The terminator  950  may be provided in a number corresponding to the number of dummy antennas  900 . 
     While the slot antenna  100  is impedance matched and connected to an electronic component of the radar  50 , the at least one dummy antenna  900  is not connected to any electronic component of the radar  50  and therefore the terminator  950  is needed for additional impedance matching. 
     The terminator  950  may be implemented by forming a predetermined pattern on a PCB through etching or the like. The pattern may be in a serpentine shape in which a single line continues so as not to intersect in the width direction and the length direction of the SIW  200 . 
     The terminator  950  may be formed in a layer different from a layer on which the first slot antenna  100   a  and the second slot antenna  100   b  are formed. As the first terminator  950  is positioned on the layer different from the layer in which the first slot antenna  100   a  and the second slot antenna  100   b  are formed, transmission and reception functions of the first slot antenna  100   a  and the second slot antenna  100   b  are not affected. 
     Meanwhile, the at least one dummy antenna  900  may be formed in the layer on which the first slot antenna  100   a  and the second slot antenna  100   b  are formed. A slot penetrating the at least one dummy antenna  900  may be formed in at least a portion of the at least one dummy antenna  900 . The at least one dummy antenna  900  and the terminator  950  formed in the layer different from the layer on which the at least one dummy antenna  900  is formed may be electrically connected with each other through the slot. The slot formed in the at least one dummy antenna  900  may be in the shape of H. 
       FIG.  11    is a diagram for explanation of a terminator according to an embodiment of the present invention. 
       FIG.  12    is a cross-section view C-C′ of  FIG.  11   . 
     Referring to  FIGS.  11  and  12   , the at least one dummy antenna  900  may include a first metal plate  210 , a second metal plate  220 , a dielectric material  230 , a via fence  240 , a third metal plate  1230 , a fourth metal plate  1240 , a first high loss dielectric material  1210 , and a second high loss dielectric material  1220 . 
     Description provided with reference to  FIGS.  1  to  10    may apply to the first metal plate  210 , the second metal plate  220 , the dielectric material  230 , and the via fence  240 . 
     The terminator  950  may include the third metal plate  1230 , the fourth metal plate  1240 , the first high loss dielectric material  1210 , and the second high loss dielectric material  1220 . 
     The first metal plate  1230  may be formed of copper (Cu). The third metal plate  1230  may be referred to as a thin copper foil or a copper plate. The third metal plate  1230  may be interposed between the first high loss dielectric material  1210  and the second high loss dielectric material  1220 . 
     A first strip line  951  and a second strip line  952  may be formed in the third metal plate  1230 . The first strip line  951  may be formed in a serpentine shape in which a single line continues so as not to intersect in the width direction and the length direction of the SIW  200 . The second strip line  952  may be formed in a shape to surround the first strip line  951 . 
     The fourth metal plate  1240  may be formed of copper (Cu). The fourth metal plate  1240  may be referred to as a thin copper foil or a copper plate. 
     The first high loss dielectric material  1210  may be interposed between the second metal plate  220  and the third metal plate  1230 . 
     The second high loss dielectric material  1220  may be interposed between the third metal plate  1230  and the fourth metal plate  1240 . 
     An H-shaped slot  1110  may be formed in the second metal plate  220 . In the SIW  200 , a signal may be transmitted to the terminator  950  through the H-shaped slot  1110  formed in the second metal plate  220 . 
     Since the first strip line  951  is surrounded by the first high loss dielectric material  1210  and the second high loss dielectric material  1220 , a considerable amount of signal loss occurs in the first strip line  951 . The signal transmitted through the H-shaped slot  1110  may disappear due to the first micro strip  951  and the first and second high loss dielectric materials  1210  and  1220 . In this case, the second strip line  952  may prevent a leakage of the signal so as not to affect other antennas. 
     Therefore, in all aspect, the detailed description of present invention is intended to be understood and interpreted as an exemplary embodiment of the present invention without limitation. The scope of the present invention shall be decided based upon a reasonable interpretation of the appended claims of the present invention and shall come within the scope of the appended claims and their equivalents.