JP4323440B2 - Antenna device - Google Patents

Description

  The present invention relates to a small antenna device suitable for in-vehicle use, and more particularly to an antenna device in which a patch antenna structure antenna body and a circuit board on which a low-noise amplifier circuit and the like are unitized and housed and held in a radome. .

  In recent years, the demand for this type of antenna device is rapidly increasing as an antenna for an ETC (automatic toll collection system) or a GPS (global positioning system) antenna mounted on a moving body such as a vehicle.

  Conventionally, this type of antenna device generally has a configuration in which an antenna unit is housed in a casing made up of a pair of upper and lower radomes, and the antenna unit is connected to an external circuit via a coaxial cable. The antenna unit includes a circuit board having a wiring pattern and semiconductor parts disposed on the lower surface, an antenna body such as a dielectric patch antenna having a radiation conductor mounted on the circuit board, and a lower surface side of the circuit board. A shield case made of a metal plate is attached so as to cover it, and a feeding point of the radiation conductor and a wiring pattern of the circuit board are connected via a feeding pin or the like. The shield case is connected to the ground via the outer conductor of the coaxial cable. This shield case prevents undesired radiation of the low noise amplifier circuit consisting of wiring patterns and semiconductor parts from adversely affecting the antenna characteristics, and does not adversely affect the low noise amplifier circuit due to disturbance waves coming from the outside. It is for doing so.

  However, the antenna device having the above-described configuration, in which the antenna unit casing is composed of a pair of synthetic resin radomes (upper radome and lower radome), requires a dedicated die for both radomes. However, it has been difficult to reduce the manufacturing cost of the entire device.

Therefore, an antenna device that can be manufactured at low cost by adopting a configuration in which the bottom opening of one radome for storing and holding the antenna unit is closed with a metal plate cover to reduce the housing cost has been proposed. (For example, refer to Patent Document 1). In such a conventional proposal, an antenna device can be easily mounted at an arbitrary position of a metal exposed portion or a metal buried portion of a vehicle by incorporating a magnet into a recess formed in a cover made of a metal plate.
JP-A-7-326914 (page 2-3, FIG. 2)

  As described above, the manufacturing cost of the antenna device can be reduced by combining the cover made of a metal plate with the radome, but on the other hand, when static electricity charged on the human body or the like is applied to the cover, the circuit board Another problem arises that the semiconductor components mounted on the semiconductor device are susceptible to electrostatic breakdown. That is, the cover made of a metal plate and the radiation conductor of the antenna body are arranged substantially in parallel, and these function like a parallel plate capacitor, so that an excessive induced current caused by static electricity applied to the cover May flow into the wiring pattern of the circuit board from the radiation conductor and destroy the semiconductor component. Although it is conceivable to attach an electrostatic breakdown prevention circuit to the circuit board, this complicates the circuit configuration and inevitably increases costs, so the cost merit of using a metal plate cover is lost. End up.

  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 an antenna device that can be manufactured at low cost and can prevent electrostatic breakdown.

  In order to achieve the above object, in an antenna device according to the present invention, a circuit board having a wiring pattern on one side and a semiconductor component mounted on the inside of a casing, and a coaxial cable covering one side of this circuit board A shield case connected to the ground via an external conductor, a radiation conductor arranged substantially in parallel with a predetermined interval on the other surface side of the circuit board, and a gap between the radiation conductor and the wiring pattern An antenna unit including a power supply member provided is housed, the antenna unit is connected to an external circuit via the coaxial cable, and the housing houses and holds the antenna unit. The shield is composed of a synthetic resin radome and a metal cover that closes the bottom opening of the radome where the shield case protrudes, and is opposed to each other It was decided to conduct and said metal cover and over scan.

  Since the antenna device configured in this manner can quickly release the static electricity to the shield case even when static electricity is applied to the metal cover that contributes to the reduction of the housing cost, the semiconductor component mounted on the circuit board Can be prevented.

  In the above configuration, it is preferable that the tongue piece provided on the shield case is elastically contacted with the metal cover, because conduction between the shield case and the metal cover can be realized very easily. In this case, if a tongue piece is provided in the shield case in the region near the outer conductor of the coaxial cable, it is possible to reliably prevent electrostatic damage that is a concern until static electricity reaches the outer conductor of the coaxial cable. More preferable. In this case, it is preferable that the convex portion formed on the free end side of the tongue piece is elastically contacted with the metal cover. When such a configuration is adopted, the convex portion having a small contact area between the tongue piece and the metal cover is formed. Therefore, it is possible to prevent occurrence of noise by eliminating resistance fluctuation at the contact portion against vibration.

  Further, in the above configuration, the radiation conductor is made of a metal plate facing the circuit board through an air layer, and a metal piece extending from the metal plate is folded back to the circuit board side to form the power feeding member. In this case, a sheet metal patch antenna capable of forming the antenna body from a single metal plate can be realized, so that the manufacturing cost of the antenna device can be greatly reduced as compared with the case where a dielectric patch antenna is used.

  In the antenna device of the present invention, the housing cost of the antenna unit is reduced by configuring the housing of the antenna unit with a synthetic resin radome and a metal cover, and the shield case is electrically connected to the metal cover by a tongue piece or the like. Therefore, even if static electricity is applied to the metal cover, the semiconductor component can be prevented from electrostatic breakdown. Therefore, an antenna device that can be manufactured at low cost and has high reliability can be obtained.

  1 is a cross-sectional view of an antenna device according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the antenna device, and FIG. 3 is used for the antenna device. FIG.

  The antenna apparatus shown in these drawings includes a housing 1 configured by fitting a radome 2 and a metal cover 3, a seal member 4 attached to a fitting portion 1 a of the radome 2 and the metal cover 3, and a metal It is mainly configured by a magnet 5 attached to the bottom surface side of the cover 3 and an antenna unit 6 housed in the internal space of the housing 1, and the antenna unit 6 is connected to the external circuit (not shown) via the coaxial cable 7. (Receiving circuit, etc.). The antenna unit 6 includes a circuit board 8 having an electronic circuit unit such as a low-noise amplifier circuit, an antenna body 9 that is a sheet metal patch antenna, and a shield case 10 made of a metal plate. A ground pattern (not shown) provided on almost the entire surface and the radiation conductor plate 11 of the antenna body 9 face each other with a predetermined distance. In addition, a wiring pattern (not shown) is provided on the lower surface of the circuit board 8 and a semiconductor component 12 or the like connected to the wiring pattern is mounted. The electronic circuit is formed by the semiconductor component 12 and the wiring pattern. The part is composed.

  The radome 2 is a molded product made of a synthetic resin, and has a bottom opening 2a that is open at the bottom. An antenna unit 6 is housed and held inside the radome 2, and the entire antenna unit 6 is covered with the radome 2 as shown in FIG. The metal cover 3 is formed by pressing a metal plate, and the bottom opening 2a of the radome 2 is closed. The metal cover 3 has a recess 3a formed at the center on the bottom surface side, and the magnet 5 is fixed in the recess 3a. Can be easily installed. The metal cover 3 is larger than the radiation conductor plate 11 of the antenna body 9 and functions as a reflector. As shown in FIG. 1, the housing 1 is assembled by fitting a radome 2 and a metal cover 3. Between the radome 2 and the metal cover 3, there is a frame-like fitting portion 1 a close to a square. A cable outlet 1b adjacent to the fitting portion 1a is formed. Then, by attaching the ring-shaped ring portion 4a of the seal member 4 to the fitting portion 1a and attaching the cable insertion portion 4b of the seal member 4 to the cable outlet 1b, the fitting portion 1a or A gap existing in the cable outlet 1b is sealed.

  The seal member 4 is a molded product made of an elastic material such as rubber, and an annular portion 4a and a cable insertion portion 4b are integrally formed. The ring portion 4a is formed in a frame shape close to a square shape substantially the same as the fitting portion 1a, and the cable insertion portion 4b is inserted into a convex body having an outer shape to be fitted into the cable outlet 1b. The axial direction of the insertion hole 4c coincides with the axial direction of the annular portion 4a in an unloaded state. That is, since one side of the ring portion 4a is made continuous with one corner of the cable insertion portion 4b, the cable insertion portion 4b is rotatable along the circumferential direction of the one side of the ring portion 4a. . The insertion hole 4c of the cable insertion portion 4b is for inserting the coaxial cable 7. When the seal member 4 is assembled to the housing 1, after the coaxial cable 7 is inserted into the insertion hole 4c, the cable insertion portion 4b is elastically rotated about 90 degrees and attached to the cable outlet 1b. Then, the ring portion 4a is attached to the fitting portion 1a.

  The antenna unit 6 is obtained by unitizing a circuit board 8, an antenna body 9, and a shield case 10. An inner conductor (core wire) 7 a of the coaxial cable 7 is soldered to the wiring pattern provided on the lower surface of the circuit board 8. Connected by attaching. The circuit board 8 is formed with through holes 8a (see FIG. 1) at positions corresponding to mounting legs 13 and power supply pieces 14 to be described later, and concave notches 8b at a plurality of locations on the outer periphery. ing.

  The antenna body 9 includes a radiating conductor plate 11 facing the ground pattern through an air layer having a predetermined thickness, mounting legs 13 formed by folding four corners of the radiating conductor plate 11 toward the circuit board 8, and a radiating conductor plate. 11 is provided with a power feeding piece 14 formed by folding back two portions closer to the center of the circuit board 8 toward the circuit board 8 side. The four mounting legs 13 and the two power supply pieces 14 are respectively inserted into the corresponding through holes 8 a and soldered on the lower surface side of the circuit board 8. As a result, each power feeding piece 14 is connected to the wiring pattern, the radiation conductor plate 11 and the electronic circuit portion are electrically connected, and each mounting leg 13 is electrically connected to the wiring pattern. Since the antenna body 9 is mechanically connected to the independent solder land, the antenna body 9 is securely held on the circuit board 8.

  The shield case 10 covers the low noise amplifier circuit including the semiconductor component 12 on the lower surface side of the circuit board 8. As a result, the antenna characteristics are degraded by unwanted radio waves radiated from the low-noise amplifier circuit, and the possibility that external interference will adversely affect the low-noise amplifier circuit is greatly reduced. It becomes easy to secure. In the shield case 10, through holes 10 a are formed at a plurality of locations facing the soldering site on the lower surface side of the circuit board 8. Further, elastic locking pieces 10b are projected upward at a plurality of locations on the outer periphery of the shield case 10, and these elastic locking pieces 10b are snap-fitted into corresponding notches 8b of the circuit board 8. Then, it is soldered to the ground pattern on the upper surface side of the circuit board 8. Further, the shield case 10 is provided with a cable holding part 10c for press-fitting and positioning and holding a tip part where the outer conductor 7b of the coaxial cable 7 is exposed, in a substantially U shape, A tongue piece 10d is formed so as to protrude obliquely downward between the center portion and the cable holding portion 10c. A convex portion 10e is formed at the tip (free end) of the tongue piece 10d. As shown in FIG. 1, the convex portion 10e receives the elastic force of the tongue piece 10d and contacts the metal cover 3. is doing. As a result, the shield case 10 is connected to the ground via the outer conductor 7b of the coaxial cable 7, and the metal cover 3 is electrically connected to the shield case 10 via the tongue piece 10d.

  The antenna device configured as described above is operated as a circularly polarized antenna by performing two-point power feeding to the radiation conductor plate 11 via the two power feeding pieces 14 connected to the wiring pattern of the circuit board 8. be able to. That is, when a predetermined high-frequency signal is supplied to the radiating conductor plate 11 via the low noise amplification circuit, circularly polarized radio waves are radiated from the radiating conductor plate 11 and the signal radio waves are received by the radiating conductor plate 11. The electrical signal is output to an external receiving circuit via the low noise amplifier circuit and the coaxial cable 7.

  In the antenna device according to the present embodiment, the antenna unit 6 including the circuit board 8, the radiation conductor plate 11, and the like is housed in the housing 1, and the fitting portion 1a and the cable of the housing 1 are provided. Since the sealing member 4 is attached to the take-out port 1b, it is possible to ensure dustproofness and waterproofness. In addition, this antenna device is less expensive than an antenna device in which the casing 1 is composed of a synthetic resin radome 2 and a metal cover 3, and thus a pair of upper and lower radomes are fitted together to form the casing. The metal cover 3 that also functions as a reflector can suppress radiation in an undesired direction and increase the gain.

  In addition, the antenna device according to the present embodiment has the tongue piece 10d provided in the shield case 10 elastically contacted with the metal cover 3 so that the shield case 10 and the metal cover 3 are electrically connected. Even if the charged static electricity is applied to the metal cover 3, the static electricity can be quickly released to the shield case 10. Therefore, it is unlikely that an unexpected situation in which an excessive induced current due to static electricity applied to the metal cover 3 flows from the radiating conductor plate 11 to the wiring pattern of the circuit board 8 will occur. The reliability can be improved because it can be prevented. Moreover, a convex portion 10e is formed at the tip of the tongue piece 10d, and this convex portion 10e is elastically contacted with the metal cover 3, and the tongue piece 10d and the metal cover 3 are interposed via the convex portion 10e having a small contact area. Since the elastic contact is stable, the resistance variation at the contact portion with respect to vibration is eliminated, and the generation of noise can be prevented. If the tongue piece 10d is provided in the shield case 10 in a region near the outer conductor 7b of the coaxial cable 7 as in the present embodiment, the static electricity reaches the outer conductor 7b of the coaxial cable 7. Therefore, the reliability can be further improved.

  In the antenna device according to this embodiment, the radiating conductor plate 11 is made of a metal plate facing the circuit board 8 through an air layer, and a metal piece extending from the metal plate is folded back to the circuit board 8 side. Since the sheet metal patch antenna that can form the antenna body 9 from a single metal plate is employed, the manufacturing cost of the antenna device is greatly increased compared to the case where a dielectric patch antenna is used. Can be reduced.

  The shape of the antenna body 9, the feeding method, and the like can be selected as appropriate. For example, the present invention can be applied to a linearly polarized antenna device or the like of a one-point feeding method.

It is sectional drawing of the antenna device which concerns on the example of embodiment of this invention. It is a disassembled perspective view of this antenna apparatus. It is a perspective view of the shield case used for this antenna device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Radome 2a Bottom opening 3 Metal cover 4 Seal member 5 Magnet 6 Antenna unit 7 Coaxial cable 7a Inner conductor 7b Outer conductor 8 Circuit board 9 Antenna body 10 Shield case 10d Tongue piece 10e Convex part 11 Radiation conductor plate 12 Semiconductor component 14 Power supply piece

Claims (5)

  A circuit board having a wiring pattern on one side and a semiconductor component mounted on the inside of the housing, a shield case that covers one side of the circuit board and is connected to the ground via an outer conductor of a coaxial cable, An antenna unit including a radiation conductor disposed substantially in parallel with a predetermined interval on the other surface side of the circuit board, and a power feeding member interposed between the radiation conductor and the wiring pattern is accommodated. The antenna unit is connected to an external circuit via the coaxial cable, and the casing is made of a synthetic resin radome that houses and holds the antenna unit, and the shield case projects. An antenna comprising: a metal cover that closes the bottom opening of the radome; and the shield case and the metal cover that face each other are electrically connected. Apparatus.   2. The antenna device according to claim 1, wherein a tongue piece provided on the shield case is elastically contacted with the metal cover.   3. The antenna device according to claim 2, wherein the tongue piece is provided in a region of the shield case near the outer conductor of the coaxial cable.   4. The antenna device according to claim 2, wherein a convex portion is formed on a free end side of the tongue piece, and the convex portion is elastically contacted with the metal cover. 5. The circuit board according to claim 1, wherein the radiation conductor is made of a metal plate facing the circuit board with an air layer interposed therebetween, and a metal piece extending from the metal plate is directed to the circuit board side. An antenna device, wherein the antenna device is folded to form the power feeding member.

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