JP2007013857A - Planar antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar antenna system which can be manufactured at low cost and can also be easily small-sized. <P>SOLUTION: A planar antenna unit comprises: a capacitor electrode part 8 approximately orthogonally extending from an outer edge of a radiation conductor layer 7; a ground conductor layer 10 provided on an upper surface of a circuit board 5 and facing the radiation conductor layer 7 at a predetermined interval therebetween; a metal case 2 including an upper opening 2a exposing the radiation conductor layer 7 and electrically connected with the ground conductor layer 10; and a resin case 3 assembled in the metal case 2 for closing the upper opening 2a. The radiation conductor layer 7, the circuit board 5 and the like are housed and held inside a housing 1 formed from the metal case 2 and the resin case 3, and a side wall part 2b of the metal case 2 electrically operating as a ground is disposed outside the capacitor electrode part 8 so as to face the capacitor electrode part so that the side wall part 2b and the capacitor electrode part 8 are capacitively coupled. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a small planar antenna device having a patch antenna structure, and more particularly to a planar antenna device suitable for in-vehicle use.

  In recent years, the demand for on-vehicle small antenna devices such as antennas for ETC (automatic toll collection system) and antennas for GPS (global positioning system) is rapidly increasing. As this type of antenna device, a flat antenna device having a patch antenna structure that can easily cope with circular polarization used in ETC and GPS is widely used.

Conventional planar antenna devices known for in-vehicle use generally have a dielectric substrate having a radiating conductor layer on the upper surface, and a ground conductor layer on the upper surface side on which the dielectric substrate is mounted, and electrons on the lower surface side. A circuit board provided with a circuit part; and a shield case made of a metal plate attached to the circuit board and covering the electronic circuit part. The electronic circuit unit is electrically connected (see, for example, Patent Document 1). In such a conventional planar antenna device, since the electronic circuit portion is electrically connected to an external circuit via a coaxial cable or the like, a circular deviation of a predetermined frequency band is obtained by exciting the radiating conductor layer by feeding with a feeding pin. Waves or linearly polarized waves can be received and transmitted. In addition, since the electronic circuit section is covered with a shield case and electromagnetically shielded, it is less susceptible to noise from undesired external radio waves. If this electronic circuit section is provided with a low-noise amplification circuit, It is suitable for reception of weak radio waves in GPS or the like. Further, since the dielectric substrate is interposed between the radiating conductor layer and the ground conductor layer, downsizing is easily promoted by the wavelength shortening effect of the dielectric substrate.
Japanese Patent Laying-Open No. 2004-88444 (page 2-3, FIG. 5)

  By the way, in the conventional planar antenna device described above, a relatively expensive dielectric substrate is interposed between the radiating conductor layer and the ground conductor layer in order to reduce the size. There was a problem that it was difficult to do. In addition, this type of planar antenna device is often used by being installed in a passenger compartment, and if the size is insufficient, the installation location may be limited and may interfere with the view of the passenger. Therefore, further miniaturization is demanded.

  The present invention has been made in view of such a state of the art, and an object of the present invention is to provide a planar antenna device that can be manufactured at low cost and can be easily downsized.

  In order to achieve the above object, in the planar antenna device according to the present invention, a flat radiating conductor layer and a metal piece continuous to the outer edge of the radiating conductor layer are arranged substantially at right angles to the radiating conductor layer. A metal electrically connected to the ground conductor layer having a capacitor electrode portion, a ground conductor layer facing the radiation conductor layer with a predetermined gap, and an upper opening projecting the radiation conductor layer A case and a resin case that is assembled to the metal case and closes at least the upper opening, and the radiation conductor layer and the ground conductor layer are disposed inside a housing formed by the metal case and the resin case. While storing and holding, the side wall portion of the metal case is disposed outside the capacitor electrode portion so as to face each other, thereby capacitively coupling the side wall portion and the capacitor electrode portion.

  The planar antenna device configured in this manner capacitively couples the capacitor electrode portion extending substantially at right angles from the outer edge portion of the radiation conductor layer and the side wall portion of the metal case that operates as an electrical ground, Since the resonance frequency of the radiation conductor layer can be lowered, it is possible to easily promote downsizing of the radiation conductor layer that resonates at a desired frequency. Further, since the resin case functioning as a radome covers the radiation conductor layer, the wavelength shortening effect by this resin case can also be used. Therefore, this planar antenna device is extremely advantageous for miniaturization, and an expensive dielectric substrate is not required.

  In addition to the above configuration, when a circuit board having a ground conductor layer on one side and an electronic circuit part on the other side is provided, the feeding point of the radiating conductor layer and the electronic circuit part of the circuit board are connected by a feeding conductor. It is preferable because a highly reliable power supply structure of coupling can be adopted and the electronic circuit portion can be electromagnetically shielded by a metal case.

  Further, in addition to any of the above configurations, the radiation conductor layer is made of a metal flat plate, and a metal plate extending outward from the outer edge of the metal flat plate is bent at a substantially right angle to form a capacitor electrode portion. Is used, the number of parts can be reduced and the manufacturing process is simplified, so that a small planar antenna device can be manufactured at a very low cost. In this case, a bent piece formed by cutting and raising a part of the metal flat plate for the radiating conductor layer is used as a feeding conductor (feeding pin), and the radiating conductor layer is fed through the feeding conductor. Since the number of parts can be further reduced and the manufacturing process is further simplified, cost reduction can be promoted.

  Further, when the sheet metal structure in which the radiating conductor layer is formed of a metal flat plate as described above, the radiating conductor layer and the circuit board are attached by attaching the metal flat plate to the circuit board or the resin case via an insulating spacer. In addition to this, the distance between the radiation conductor layer and the resin case can be defined with high precision. In addition to this, if adhesive layers are provided on the upper and lower surfaces of the spacer, the assemblability is improved. In addition, when such a sheet metal structure is employed, an opening is provided in the approximate center of the metal flat plate (radiation conductor layer), and a plurality of metal plates formed by cutting and raising a part of the metal flat plate at the periphery of the opening. The leg pieces may be provided, and these leg pieces may be fixed to the circuit board. In this way, the spacer can be omitted. Further, when such a sheet metal structure is not adopted, the radiation conductor layer may be printed on the ceiling surface of the resin case, and in this way, the entire apparatus can be thinned.

  The planar antenna device of the present invention stores and holds a radiating conductor layer and a grounding conductor layer inside a housing formed of a metal case and a resin case, and extends from the outer edge of the radiating conductor layer at a substantially right angle. Therefore, it is possible to easily reduce the size of the radiation conductor layer by lowering the resonance frequency of the radiating conductor layer, and it is possible to omit a dedicated dielectric substrate and to reduce the component cost.

  FIG. 1 is a cross-sectional view of a planar antenna device according to a first embodiment of the present invention, and FIG. 2 is a plan view showing the antenna device with a part cut away. FIG. 3 is an exploded perspective view of the antenna device.

  The planar antenna device shown in these drawings is a circularly polarized antenna for vehicle use that is suitable as a GPS antenna, for example, and is used by being installed on a dashboard in a vehicle cabin, a window glass, or the like. This planar antenna device is schematically configured by housing and holding a sheet metal antenna element 4, a circuit board 5, a spacer 6, and the like inside a housing 1 that is a combination of a metal case 2 and a resin case 3. The antenna element 4 includes a radiation conductor layer (radiation conductor plate) 7 made of a highly conductive metal flat plate, a capacitor electrode portion 8 extending at four locations on the outer edge of the radiation conductor layer 7, and the radiation conductor layer 7. And a power supply conductor (power supply pin) 9 extending to the power supply point. A ground conductor layer 10 is provided on the upper surface of the circuit board 5, and an electronic circuit unit 11 is provided on the lower surface of the circuit board 5. The spacer 6 is made of an insulating material, and adhesive layers 6a and 6b are provided on both upper and lower surfaces thereof. Then, by adhering these adhesive layers 6a and 6b to the central portion of the radiation conductor layer 7 and the circuit board 5, respectively, the radiation conductor layer 7 and the circuit board 5 are bonded and fixed via the spacers 6, respectively. The capacitor electrode portion 8 faces the side wall portion 2b of the metal case 2 at a close distance.

  As shown in FIG. 2, the radiating conductor layer 7 is formed in a substantially square shape with two cutouts at the four corners. The pair of cutout portions constitute the degenerate separation element 7a, and electric fields in diagonal directions orthogonal to each other. By causing a phase difference of 90 degrees in the mode, circularly polarized light can be radiated by one-point feeding. The capacitor electrode portion 8 is formed by bending a metal piece continuous with the radiating conductor layer 7 toward the circuit board 5 at a substantially right angle, and the capacitor electrode portions 8 are disposed at the central portions of the four sides of the radiating conductor layer 7, respectively. Yes. In other words, these capacitor electrode portions 8 are arranged at the outer edge portions of the metal flat plate forming the radiation conductor layer 7 at both ends of two bisectors forming an angle of 45 degrees with respect to the diagonal line. A metal piece extending in the direction is bent at a substantially right angle. The power supply conductor 9 is a bent piece formed by cutting and raising a part of a metal flat plate forming the radiation conductor layer 7, and the leading end of the power supply conductor 9 penetrates the circuit board 5 to form an electronic circuit. Soldered to the part 11.

  The ground conductor layer 10 is formed of copper foil or the like on almost the entire upper surface of the circuit board 5, and the center portion of the ground conductor layer 10 and the center portion of the radiation conductor layer 7 are bonded and fixed to the spacer 6. The outer peripheral portion of the ground conductor layer 10 and the outer peripheral portion of the radiation conductor layer 7 are opposed to each other with an air layer having a predetermined thickness. The ground conductor layer 10 has a slightly larger diameter than the radiation conductor layer 7, but the ground conductor layer 10 and the feed conductor 9 are kept in non-contact because the portion corresponding to the feed conductor 9 is an escape portion 10 a. ing. In addition, the electronic circuit unit 11 provided on the lower surface of the circuit board 5 includes a low noise amplifier circuit on which various electronic components are mounted, and thus is suitable for receiving weak radio waves such as GPS. The electronic circuit unit 11 is connected to an external circuit such as a receiving circuit via an inner conductor of a coaxial cable (not shown).

  The metal case 2 is formed in a bottomed box shape having a square upper opening 2a from which the radiation conductor layer 7 protrudes, and side wall portions 2b are erected at positions corresponding to the four sides of the upper opening 2a. . A locking groove 2c for holding the circuit board 5 is formed on the inner wall surface of the side wall portion 2b, and an engaging convex portion 2d for engaging the resin case 3 is formed on the outer wall surface of the side wall portion 2b. Has been. The metal case 2 includes the antenna element 4, the spacer 6, and the circuit board 5, as shown in FIG. 1, by fitting the peripheral edge of the circuit board 5 on which the antenna element 4 is mounted into the locking groove 2c. A laminated body can be hold | maintained by the side wall part 2b. When the laminate is thus held by the metal case 2, the capacitor electrode portion 8 is disposed at a position facing the side wall portion 2 b at a close distance, and the electronic circuit portion 11 is covered with the metal case 2. The metal case 2 is electrically connected to the ground conductor layer 10, and both 2 and 10 are connected to the ground via an outer conductor of a coaxial cable (not shown). Therefore, an additional capacitance is generated between the capacitor electrode portion 8 extending on the outer edge portion of the radiation conductor layer 7 and the side wall portion 2b of the metal case 2 during power feeding. In addition, since the electronic circuit unit 11 including the low-noise amplifier circuit is covered with the metal case 2 and electromagnetically shielded, the electronic circuit unit 11 is less susceptible to noise caused by undesired external radio waves.

  The resin case 3 is formed in a bottomed box shape having a lower opening 3a. The resin case 3 functions as a radome because it is covered with a metal case 2 and the upper opening 2a is closed. An engagement recess 3b is formed on the inner wall surface of the resin case 3 at a position corresponding to the engagement protrusion 2d of the metal case 2. When the resin case 3 is assembled to the metal case 2, the engagement recess 3b Both cases 2 and 3 are integrated into the housing 1 by fitting the engaging projection 2d therein. That is, after a laminated body composed of the antenna element 4, the spacer 6, and the circuit board 5 is assembled in the metal case 2, the resin case 3 is assembled to the metal case 2, so that the laminated body is accommodated inside the housing 1. The planar antenna device as shown is obtained by being held.

  In the planar antenna device configured as described above, the capacitor electrode portion 8 extending substantially at right angles from the outer edge portion of the radiation conductor layer 7 and the side wall portion 2b of the metal case 2 that operates as an electrical ground are capacitively coupled. As a result, the resonance frequency of the radiating conductor layer 7 can be lowered, so that the size reduction of the radiating conductor layer 7 that resonates at a desired frequency can be facilitated. Further, since the resin case 3 functioning as a radome covers the radiation conductor layer 7, the wavelength shortening effect by the resin case 3 can also be used. Therefore, this planar antenna device is extremely advantageous for miniaturization, and even if it is installed on a dashboard or a window glass in the passenger compartment, there is little possibility of getting in the way or obstructing the view of the passenger. Further, this planar antenna device has an advantage that the cost of parts can be reduced because an expensive dielectric substrate is omitted. Moreover, in this planar antenna device, the distance between the radiating conductor layer 7 and the ground conductor layer 10 can be defined with high accuracy by the plate thickness of the spacer 6, so that the assemblability and reliability are also good.

  Further, in the first embodiment, the antenna element 4 includes the radiation conductor layer 7 made of a metal flat plate, and a metal piece extending from the outer edge of the metal flat plate is bent to form the capacitor electrode portion 8. Since a part of the metal flat plate is cut and raised to form the power supply conductor 9, the radiating conductor layer 7, each capacitor electrode portion 8, and the power supply conductor 9 can be collectively formed by pressing or the like, realizing a significant cost reduction. it can. That is, when the antenna element 4 having a sheet metal structure is employed in this way, the number of components can be reduced and the manufacturing process is simplified, so that the planar antenna device can be manufactured at a very low cost.

  FIG. 4 is a cross-sectional view of the planar antenna device according to the second embodiment of the present invention, and the same reference numerals are given to portions corresponding to those in FIG.

  In this second embodiment, the radiating conductor layer 7 is fixed to the ceiling surface 3c of the resin case 3 by the spacer 6, and the radiating conductor layer is assembled by assembling the resin case 3 to the metal case 2 incorporating the circuit board 5. 7 faces the ground conductor layer 10 with a predetermined distance. That is, the second embodiment is different from the first embodiment in the mounting position of the spacer 6.

  FIG. 5 is a cross-sectional view of a planar antenna device according to a third embodiment of the present invention. The same reference numerals are given to the portions corresponding to those in FIG.

  In the third embodiment, an opening 7b is provided in the approximate center of the metal flat plate forming the radiation conductor layer 7, and a part of the metal flat plate is cut and formed at the peripheral edge of the opening 7b. A plurality of leg pieces 7c are provided, and these leg pieces 7c are fixed to the circuit board 5 by soldering or the like. That is, in the third embodiment, the radiation conductor layer 7 is supported on the circuit board 5 via the plurality of leg pieces 7c, so that the spacer is omitted as compared with the first and second embodiments described above. The number of parts is reduced as much as possible.

  FIG. 6 is a cross-sectional view of a planar antenna device according to a fourth embodiment of the present invention, and the same reference numerals are given to portions corresponding to those in FIG.

  The fourth embodiment is an example in which the antenna element 4 is not a sheet metal structure, and the radiation conductor layer 12 is printed on the ceiling surface 3c of the resin case 3, so that the metal incorporating the circuit board 5 is used. By assembling the resin case 3 to the case 2, the radiation conductor layer 12 faces the ground conductor layer 10 with a predetermined interval. In the fourth embodiment, since it is not necessary to secure a clearance between the radiation conductor layer 12 and the ceiling surface 3c of the resin case 3, the entire apparatus is thinner than the first to third embodiments described above. It has become.

  FIG. 7 is a cross-sectional view of a planar antenna device according to a fifth embodiment of the present invention, and portions corresponding to those in FIG.

  In the fifth embodiment, the lower surface of the metal case 2 is covered with a resin cover 13, and the resin case 13 and the resin case 3 surround the entire metal case 2. That is, in the fifth embodiment, the metal case 2 is made invisible from the outside by the resin cover 13, and the second to fourth embodiments may be adopted as the internal structure of the antenna element 4. The resin case 3 and the resin cover 13 can be integrated.

  In each of the above embodiments, the case where the radiation conductor layer 7 and the radiation conductor layer 12 are fed by the pin feeding method has been described. However, other feeding methods, for example, a microstrip line provided on the circuit board 5 are used. It is also possible to feed power by electromagnetically coupling with the radiation conductor layer.

  In each of the above embodiments, the case where the present invention is applied to a GPS antenna has been described. However, the present invention can also be applied to other ETC antennas, in which case the low-noise amplifier circuit is omitted. Since the height of the metal case 2 and the resin case 3 can be reduced, further reduction in thickness can be promoted. Furthermore, it goes without saying that the present invention is applicable not only to circularly polarized antennas but also to linearly polarized antennas.

It is sectional drawing of the planar antenna apparatus which concerns on the example of 1st Embodiment of this invention. It is a top view which shows this antenna apparatus partially fractured | ruptured. It is a disassembled perspective view of this antenna apparatus. It is sectional drawing of the planar antenna apparatus which concerns on the 2nd Example of this invention. It is sectional drawing of the planar antenna apparatus which concerns on the 3rd Example of this invention. It is sectional drawing of the planar antenna apparatus which concerns on the example of 4th Embodiment of this invention. It is sectional drawing of the planar antenna apparatus which concerns on the example of 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Metal case 2a Upper opening 2b Side wall part 3 Resin case 3c Ceiling surface 4 Antenna element 5 Circuit board 6 Spacer 6a, 6b Adhesion layer 7,12 Radiation conductor layer 8 Capacitor electrode part 9 Feeding conductor (feeding pin)
10 Grounding conductor layer 11 Electronic circuit part 13 Resin cover

Claims (8)

  A flat radiating conductor layer, a capacitor electrode portion arranged substantially perpendicular to the radiating conductor layer with a metal piece continuous to the outer edge of the radiating conductor layer, and a predetermined distance from the radiating conductor layer. A grounding conductor layer facing each other, a metal case having an upper opening for projecting the radiation conductor layer and electrically connected to the grounding conductor layer, and being assembled to the metal case to cover at least the upper opening A resin case that is closed, and housing and holding the radiation conductor layer and the ground conductor layer inside a casing formed by the metal case and the resin case, and a side wall portion of the metal case as the capacitor electrode portion A planar antenna device, wherein the side wall portion and the capacitor electrode portion are capacitively coupled to each other by being disposed outside and facing each other.   2. The planar antenna device according to claim 1, further comprising a circuit board having the ground conductor layer on one side and the electronic circuit part on the other side.   3. The capacitor electrode portion according to claim 1, wherein the radiation conductor layer is made of a metal flat plate, and a metal piece extending outward from an outer edge portion of the metal flat plate is bent substantially at a right angle. A planar antenna device characterized.   4. The method according to claim 3, wherein a bent piece formed by cutting and raising a part of the metal flat plate is used as a power supply conductor, and the radiation conductor layer is supplied with power through the power supply conductor. Planar antenna device.   5. The planar antenna device according to claim 3, wherein the metal flat plate is attached to the circuit board or the resin case via an insulating spacer.   6. The planar antenna device according to claim 5, wherein adhesive layers are provided on both upper and lower surfaces of the spacer.   In Claim 3 or 4, while providing an opening part in the approximate center of the said metal flat plate, the several leg piece formed by cutting and raising a part of said metal flat plate is provided in the peripheral part of this opening part, These A planar antenna device, wherein a leg piece is fixed to the circuit board.   3. The planar antenna device according to claim 1, wherein the radiation conductor layer is printed on the ceiling surface of the resin case.

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