JP2007166388A - On-vehicle antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an on-vehicle antenna device that facilitates correction of an impedance and an axis ratio of a circularly-polarized wave patch antenna in a two-point feeding system. <P>SOLUTION: The antenna device 1 is provided with an antenna element being a sheet-metal patch antenna mounted onto a circuit board and a sheet-metal frame body rectangularly surrounding the antenna element. The antenna element is provided with a radiation conductor plate 35, first and second feeding leg pieces as a cut-raised piece, and a plurality of mounting leg pieces 38 or the like. First-fourth notches 31-34 are formed at equidistant four places in an outer edge part of the radiation conductor plate 35. Each deepest part of the first and second notches 31, 32 is located at a base end part of each feeding leg piece so as to be feeding-parts P1, P2. The impedance is corrected by differentiating lengths D1, D2 from the center of the radiation conductor plate 35 to the respective feeding parts P1, P2. The axis ratio is corrected by differentiating lengths D3, D4 from the center of the radiation conductor plate 35 to the respective third and fourth notches 33, 34. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a small antenna device installed in a vehicle interior, and more particularly to a vehicle-mounted antenna device including a two-point feeding antenna element that operates as a circularly polarized patch antenna.

  In recent years, it has become common to install a receiving antenna for GPS (Global Positioning System), a transmitting / receiving antenna for ETC (Automatic Toll Collection System), and the like in a passenger compartment of an automobile. Such an in-vehicle antenna device has an antenna element connected to an external circuit through a coaxial cable or the like, and when receiving or transmitting circularly polarized waves such as GPS signals and ETC signals. An antenna element having a patch antenna structure is often used. In addition, weak radio waves that travel from a distance, such as satellite waves, need to be amplified and transmitted to an external circuit. Therefore, a preamplifier is mounted on a circuit board on which an antenna element is mounted, and is attached to this circuit board. 2. Description of the Related Art A vehicle-mounted antenna device having a configuration in which an electronic component such as a preamplifier is electromagnetically shielded by a sheet metal shield member is widely known.

  By the way, a general circularly polarized patch antenna as an antenna element of this type of in-vehicle antenna device has a one-point feeding method and a two-point feeding method, and the feeding circuit can be simplified by adopting the one-point feeding method. However, when the two-point power feeding method is adopted, there is an advantage that the bandwidth is widened and the axial ratio characteristic can be improved. Therefore, a two-point feeding type patch antenna is suitable as an antenna element that receives weak circularly polarized waves such as GPS signals.

In the conventional circularly polarized patch antenna of the two-point feeding system, the radiation conductor is square (or circular), and the two feeding parts of the radiation conductor are in a positional relationship 90 degrees apart from each other. Is set so that the phase difference of the power supply signal supplied to is 90 degrees. Further, the radiation conductor is formed on one side of a substrate made of a dielectric or the like, and a ground conductor layer is formed on the entire other surface of the substrate (see, for example, Patent Document 1).
JP 2003-298342 A (page 3-4, FIG. 1)

  As described above, when a two-point feed type circularly polarized patch antenna is used as an antenna element, the axial ratio characteristics are improved and the antenna sensitivity can be improved. However, due to factors other than the antenna element, impedance mismatch or shaft The ratio may be deteriorated, and in such a case, the impedance and the axial ratio must be corrected by appropriate means. For example, in addition to a small GPS antenna and an ETC antenna, a relatively large diversity antenna for receiving a terrestrial wave transmitted from a base station is expected to be highly demanded as an in-vehicle antenna device. It is preferable to provide a diversity antenna preamplifier on a circuit board of a small antenna device for use, for example, because the antenna mechanism can be integrated and wiring can be simplified. However, in this case, if the shape of the shield member covering the preamplifier is not a rectangular shape or the like that is different from the circularly polarized patch antenna, it will hinder downsizing. However, there is a high possibility that the impedance characteristics and axial ratio characteristics of the circularly polarized patch antenna will be adversely affected, and correction thereof is necessary. However, the two-point feed type circularly polarized patch antenna according to the conventional example cannot easily correct the impedance and the axial ratio, and is forced to perform complicated work such as changing the design of the 90-degree phase difference circuit. For this reason, there is a problem in that cost increases and correction failures tend to occur.

  The present invention has been made in view of the actual situation of the prior art, and an object thereof is to provide an in-vehicle antenna device capable of easily correcting the impedance and axial ratio of a circularly polarized patch antenna of a two-point feeding method. There is to do.

  In order to achieve the above object, in the vehicle-mounted antenna device of the present invention, a circuit board provided with a ground conductor layer and a power feeding circuit, an antenna element made of a metal plate mounted on the circuit board, and the circuit board are provided. A frame made of a metal plate that holds and surrounds the antenna element in a rectangular shape, and the antenna element is made of a metal flat plate facing the ground conductor layer at a predetermined interval and having an outer edge 90. A radiating conductor plate having a first notch and a second notch cut in two radial positions, and the first and second notches serving as a feeding portion of the radiating conductor plate. A first feeding leg piece and a second feeding leg piece formed as a pair of cut and raised pieces extending from each innermost part to the circuit board side and connected to the feeding circuit; and an outer edge of the radiation conductor plate From a plurality of locations A plurality of mounting leg pieces formed as cut-and-raised pieces extending toward the board side and fixed to the circuit board, and from the center of the radiation conductor plate to the innermost part of the second notch Is set shorter than the length from the center to the innermost part of the first cutout by the amount of impedance correction, and the frame body extends in the longitudinal direction of the rectangle through the cutout of the first cutout. The short side direction is arranged along the cut direction of the second notch along the direction.

  The in-vehicle antenna device having such a configuration is a sheet metal patch antenna having a two-point power feeding antenna element, and a pair of notches corresponding to the pair of power feeding leg pieces are formed on the outer edge portion of the radiation conductor plate. However, considering that the frame made of a metal plate surrounds the antenna element in a rectangular shape and the influence of the ground on the radiation conductor plate is biased, radiation from the innermost part (feeding part) of each notch Impedance is corrected by making the length to the center of the conductor plate different. That is, among the two resonance modes orthogonal to each other electrically and spatially of the radiation conductor plate, the resonance mode along the longitudinal direction of the rectangle is strongly affected by the ground as compared with the resonance mode along the short direction. If the length from the center of the radiating conductor plate to each feeding portion is equal, impedance mismatch occurs and the return loss increases, but the center of the radiating conductor plate from the innermost part of the second notch increases. If the correction is performed such that the length of the first notch is set shorter by a predetermined amount than the length from the innermost part of the first notch to the center, the return loss can be reduced by matching the impedance. Therefore, it is not necessary to perform complicated correction work such as changing the design of the 90-degree phase difference circuit. Further, since this antenna element can be stably fixed to the circuit board by the mounting leg pieces, it is easy to ensure the mechanical strength.

  In the above configuration, a third notch is formed at a position substantially symmetric with the first notch and a fourth notch is formed at a position substantially symmetric with the second notch at the outer edge portion of the radiation conductor plate, If the length from the center of the conductor plate to the innermost part of the third notch is set shorter than the length from the center to the innermost part of the fourth notch by the axial ratio correction, It is also possible to correct the axial ratio by causing a required difference between the resonance lengths of two resonance modes that are electrically and spatially orthogonal. That is, since the resonance mode along the longitudinal direction of the rectangle is strongly influenced by the ground as compared with the resonance mode along the short direction, if the lengths of the third notch and the fourth notch are equal, The resonance ratio of both modes is different due to the influence of the ground, and the axial ratio is deteriorated. However, if the length from the center of the radiation conductor plate to the innermost part of the third notch is set shorter than the length from the center to the innermost part of the fourth notch by the axial ratio correction, 90. The axial ratio can be corrected without performing complicated correction work such as changing the design of the phase difference circuit. In this case, if the frame is provided with a partition plate arranged between the rectangular side plate on the short side and the antenna element, the frame and the antenna element are deformed. Since deterioration of an axial ratio can be reduced, it is preferable.

  In addition, in the above configuration, when a preamplifier connected to an external antenna is disposed in an area of the circuit board that is outside the antenna element and inside the frame, the antenna mechanism can be integrated. It is preferable because it can be functionalized. For example, in an in-vehicle antenna device that is attached to a glass surface of a vehicle and has a radiating conductor plate facing the glass surface, if the external antenna is a diversity antenna disposed on the glass surface, the front of the diversity antenna The preamplifier can be arranged without difficulty, so that the attenuation of the received signal can be suppressed, and the sensitivity can be increased by making the radiation conductor plate substantially face in the direction in which the desired radio wave comes in.

  Further, in the above configuration, a plurality of lands facing the ground conductor layer are provided on the circuit board, and when a plurality of mounting leg pieces are soldered to the lands, the lands facing each mounting leg piece Since the electrostatic capacity is loaded during this period, the antenna element can be reduced in size, which is preferable.

  The in-vehicle antenna device of the present invention is a sheet metal patch antenna having a two-point power feeding antenna element, and a pair of notches corresponding to a pair of power feeding leg pieces are formed on the outer edge portion of the radiation conductor plate. Considering that the frame made of a metal plate surrounds the antenna element in a rectangular shape and the influence of the ground on the radiating conductor plate is biased, the radiating conductor plate starts from the innermost part (feeding part) of each notch. The impedance is corrected by making the length to the center of the difference. That is, among the two resonance modes orthogonal to each other electrically and spatially of the radiation conductor plate, the resonance mode along the longitudinal direction of the rectangle is strongly affected by the ground as compared with the resonance mode along the short direction. If the length from the center of the radiating conductor plate to each feeding part is equal, impedance mismatch occurs and the return loss increases, but from the innermost part of the second notch to the center of the radiating conductor plate If the correction is performed such that the length is set shorter by a predetermined amount than the length from the innermost part of the first notch to the center, the return loss can be reduced by matching the impedance. Therefore, it is not necessary to perform complicated correction work such as a design change of the 90-degree phase difference circuit for correcting the impedance, and a circularly polarized patch antenna having good impedance characteristics can be manufactured at low cost.

  In such an in-vehicle antenna device, the third notch is formed in the outer edge portion of the radiating conductor plate at a position substantially symmetric with the first notch and the fourth notch at the position substantially symmetric with the second notch. And the length from the center of the radiation conductor plate to the innermost part of the third notch is set shorter than the length from the center to the innermost part of the fourth notch by the axial ratio correction. Thus, the axial ratio can be corrected by causing a required difference between the resonance lengths of the two resonance modes of the radiation conductor plate. Therefore, it is not necessary to perform complicated correction work such as a design change of the 90-degree phase difference circuit to correct the axial ratio, and a circularly polarized patch antenna having a good axial ratio characteristic can be manufactured at low cost.

  An embodiment of the invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a vehicle-mounted antenna device according to an embodiment of the present invention, FIG. 2 is a front view of the antenna device, and FIG. FIG. 4 is a front perspective view corresponding to FIG. 3, and FIG. 5 is a rear view showing a state in which a signal cable of a diversity antenna is connected to the antenna device. 6 is an explanatory diagram in which the signal cable and the bracket are omitted from FIG. 5 and the cable insertion portion is clearly shown, and FIG. 7 is a rear view showing the overall arrangement of the antenna device and the diversity antenna. FIG. 8 is a front view corresponding to FIG.

  The antenna device 1 shown in these drawings is an in-vehicle antenna device that is used by being mounted on a surface on the passenger compartment side of a glass surface 50 (see FIGS. 7 and 8) such as a windshield of an automobile. It can be attached to the center of the upper end. The antenna device 1 includes a circuit board 2 provided with a ground conductor layer and a feeding circuit (not shown), a GPS antenna element 3 and an ETC antenna element 4 mounted on one surface (front surface) of the circuit board 2. A shield cover 5 mounted on the other surface (back surface) of the circuit board 2, a connector portion 6 fixed to one end of the circuit board 2 and connected to an external circuit such as a transmission / reception circuit, and the circuit board 2. A sheet metal frame 7 that holds and surrounds the antenna elements 3, 4, an unillustrated preamplifier for an external antenna that receives terrestrial digital waves, a connector terminal 10 of the preamplifier, and the like. Yes. In other words, the antenna device 1 is an integrated antenna device having both a GPS antenna and an ETC antenna, and a multi-function incorporating a preamplifier of a pair of diversity antennas 20 (see FIGS. 7 and 8) as external antennas. Antenna device.

  The circuit board 2 is provided with a ground conductor layer in a region facing the antenna elements 3 and 4, and an electronic circuit portion (including a feeding circuit) for the antenna elements 3 and 4 in a region covered with the shield cover 5. ) Is provided. A preamplifier for each diversity antenna 20 and a connector terminal 10 of the preamplifier are disposed on the left and right edges of the circuit board 2, and two corners of the circuit board 2 are cut out. Each connector terminal 10 is mounted in the vicinity of the relief portion 2a formed.

  The antenna element 3 is a sheet metal patch antenna formed by pressing a metal plate or the like, and is manufactured as a two-point feed type circularly polarized patch antenna suitable for receiving GPS signals. The antenna element 3 includes a radiating conductor plate 35 made of a metal flat plate in which a square opening 30 is formed in the center and first to fourth cutouts 31 to 34 are formed at four equally spaced outer edges, The first power supply leg piece 36 and the second power supply formed as a pair of cut and raised pieces extending from the innermost portions of the first and second cutouts 31 and 32 of the radiation conductor plate 35 to the circuit board 2 side. The circuit board includes four leg pieces 37, four attachment leg pieces 38 formed as cut-and-raised pieces extending from the four corners of the radiation conductor plate 35 to the circuit board 2 side, and four equidistant positions on the periphery of the opening 30. And four short-circuit leg pieces 39 formed as cut-and-raised pieces extending to the two sides. Here, the radiation conductor plate 35 faces the ground conductor layer on the circuit board 2 with a predetermined interval, and each short-circuit leg piece 39 is soldered to the ground conductor layer. The pair of power supply leg pieces 36 and 37 penetrates the circuit board 2 without contact with the ground conductor layer, and is connected to the power supply circuit in a region covered with the shield cover 5. Further, each mounting leg piece 38 penetrates the circuit board 2 without contact with the ground conductor layer and is soldered to a land (not shown) in an area covered by the shield cover 5. Capacitance is loaded between the conductor layers and contributes to the miniaturization of the antenna element 3. As described above, the four positions of the outer edge portion and the four inner edge portions of the radiation conductor plate 35 are held in a balanced manner by the mounting leg piece 38 and the short-circuit leg piece 39, respectively. Is supported.

  The outer shape of the radiation conductor plate 35 is a substantially regular octagon, and the central portion of each side excluding the four corner sides where the mounting leg pieces 38 exist is cut inwardly (in the radial direction) to form first to fourth cutouts 31 to 31. 34. And since the innermost part of the 1st notch 31 is a base end part of the 1st electric power feeding leg piece 36, it becomes the 1st electric power feeding part P1, and the innermost part of the 2nd notch 32 is similarly 2nd. Since it is the base end portion of the power feeding leg piece 37, it becomes the second power feeding portion P <b> 2. The pair of power feeding portions P1 and P2 are supplied with power feeding signals whose phases are shifted by 90 degrees, so that the radiating conductors are in two resonance modes that are electrically and spatially orthogonal and have the same amplitude. The plate 35 can resonate to emit circularly polarized waves.

However, the antenna device 1 is provided with a sheet metal frame 7 for electromagnetically shielding the preamplifier of the diversity antenna 20, and this frame 7 operating as a ground is different from the antenna element 3. Since the antenna element 3 is surrounded by this, the impedance characteristic and the axial ratio characteristic of the antenna element 3 may be slightly deteriorated due to the influence of the frame 7. Therefore, in the present embodiment, the impedance is corrected by changing the length from the first and second cutouts 31 and 32 which are the power feeding parts P1 and P2 to the center of the radiation conductor plate 35 by a predetermined amount, In addition, the axial ratio is corrected by varying the length from the third and fourth cutouts 33 and 34 to the center of the radiation conductor plate 35 by a predetermined amount. That is, the side plates 71 and 72 of the frame body 7 surrounding the antenna element 3 in a rectangular shape have a pair of side plates 71 on the long side extending along the cutting direction of the first and third cutouts 31 and 33. Further, since the pair of side plates 72 on the short side extends along the cutting direction of the second and fourth cutouts 32, 34, when the radiation conductor plate 35 is excited, a resonance mode along the side plate 71 on the long side is generated. Compared with the resonance mode along the side plate 72 on the short side, it is strongly influenced by the ground. Therefore, if the length from the center of the radiation conductor plate 35 to each of the power feeding portions P1 and P2 is equal, impedance mismatch occurs and the return loss increases. However, as shown in FIG. The length D2 from the center O of the conductor plate 35 to the innermost part (second feeding part P2) of the second notch 32 is set to the innermost part (first feeding part P1) of the first notch 31 from the center O. If the correction is performed such that the predetermined amount is set shorter than the length D1), the return loss can be reduced by matching the impedance. If the length D3 from the center O of the radiating conductor plate 35 to the innermost part of the third notch 33 is equal to the length D4 to the innermost part of the fourth notch 34, both modes Although the resonance frequency is different and the axial ratio is deteriorated, if the length D3 is set to be appropriately shorter than the length D4 in advance, the deterioration of the axial ratio can be corrected. The frame body 7 is provided with a pair of partition plates 73 in parallel with the side plates 72 on the short side, and by arranging these partition plates 73 between the side plates 72 and the antenna element 3, a shielding effect can be obtained. Therefore, the antenna element 3 can be arranged in a substantially square space defined by the side plate 71 and the partition plate 73, and this also suppresses deterioration of the axial ratio caused by the frame body 7. Yes.

  The antenna element 4 is a sheet metal patch antenna formed by pressing a metal plate or the like, and is manufactured as a two-point feeding type circularly polarized patch antenna suitable for receiving an ETC signal. Compared to 3, it has a small diameter and a low profile. The antenna element 4 includes a radiating conductor plate 41 made of a flat metal plate and having cutouts 42 at four equally spaced outer edge portions, and two notch portions that are 90 ° apart from the outer edge portion of the radiating conductor plate 41. The first power supply leg piece 43 and the second power supply leg piece 44 formed as a pair of cut-and-raised pieces extending from the innermost portions of the circuit board 2 to the circuit board 2 side, and the circuit board from the four corners of the radiation conductor plate 41 The radiating conductor plate 41 protrudes into the opening 30 of the antenna element 3 for GPS. Further, the pair of power supply leg pieces 43 and 44 penetrates the circuit board 2 in a non-contact manner with the ground conductor layer and is connected to the power supply circuit in a region covered with the shield cover 5. Further, each mounting leg piece 45 penetrates the circuit board 2 without contact with the ground conductor layer and is soldered to a land (not shown) in a region covered with the shield cover 5. Capacitance is loaded between the conductor layer and the antenna element 4 is reduced in size. As described above, since the four portions of the outer edge portion of the radiation conductor plate 41 are held in a balanced manner by the mounting leg pieces 45, the antenna element 4 is stably supported on the circuit board 2.

  The radiating conductor plate 41 of the antenna element 4 is opposed to the ground conductor layer on the circuit board 2 with a predetermined interval, but compared with the interval between the circuit board 2 and the radiating conductor plate 35 of the antenna element 3, The distance between the circuit board 2 and the radiation conductor plate 41 is narrow. That is, the radiating conductor plate 41 is smaller in height than the radiating conductor plate 35 having the opening 30. By doing so, two types of antenna elements 3 and 4 having different tuning frequencies can be arranged on the circuit board 2 in a space-efficient manner, and also due to interference of radio waves radiated from the radiation conductor plates 35 and 41. Noise generation can be suppressed. Since the antenna element 3 is provided with four short-circuit leg pieces 39 so as to surround the antenna element 4, both the antenna elements 3 and 4 are electromagnetically coupled by the shielding effect of the short-circuit leg pieces 39. Isolation is enhanced.

  Each side plate 72 on the short side of the frame body 7 is formed with a notch 74 whose upper end is an open end and a substantially L-shaped notch groove 75 whose lower end is an open end. The frame body 7 is formed with a support piece 76, a bent tongue piece 77, and a locking piece 78 as bent and raised pieces extending inward from the side plates 72. The support piece 76 is a cut-and-raised piece bent at a substantially right angle with respect to the side plate 72 and protrudes into the escape portion 2a of the circuit board 2. A part of the support piece 76 is near the escape portion 2a. The circuit board 2 is supported from above. The bent tongue piece 77 is a cut-and-raised piece extending obliquely inward from the side plate 72 and supports the circuit board 2 from below, and the distal end portion of the bent tongue piece 77 is located near the connector terminal 10. positioned. The locking piece 78 is a cut-and-raised piece extending inwardly from the side plate 72 in a substantially C shape, and supports the circuit board 2 from above. Thus, since the left and right edges of the circuit board 2 are sandwiched in the plate thickness direction by the support piece 76, the locking piece 78, and the bent tongue piece 77, the frame 7 can easily and reliably hold the circuit board 2. Can be held in. The frame body 7 is connected to a ground circuit of the circuit board 2 by soldering.

  The cutout groove 75 of the frame body 7 is a substantially L-shaped cutout including a space generated in the side plate 72 when the bent tongue piece 77 is cut and raised, and the signal channel of the diversity antenna 20 inserted into the cutout groove 75. The bull 21 is guided by the bent tongue 77 and guided to the connector terminal 10. That is, as shown in FIGS. 7 and 8, since a pair of diversity antennas 20 are arranged as, for example, film antennas on the left and right sides of the upper center portion of the glass surface 50 on which the antenna device 1 is mounted, It is necessary to connect the output end portion of the signal cable 21 derived from the diversity antenna 20 to the pair of connector terminals 10 mounted on the circuit board 2. The cutout groove 75 and the bent tongue piece 77 provided in the frame body 7 are for smoothly connecting the signal cable 21. Further, since the signal cable 21 guided along the bent tongue 77 can avoid contact with the sharp edge of the metal plate, there is no possibility that the signal cable 21 is damaged due to vibration during traveling.

  As described above, the antenna device 1 according to this embodiment is configured such that the antenna elements 3 and 4 are disposed on the circuit board 2 so that the GPS signal can be received and the ETC signal can be transmitted and received. Since the preamplifier for the diversity antenna 20 to be received and the connector terminals 10 of the preamplifier are arranged on the left and right edges of the circuit board 2 to integrate the antenna mechanism, it is multifunctional and simplifies wiring. This is an excellent in-vehicle antenna device that has a good space factor. Further, the antenna device 1 is mounted on a glass surface 50 such as a windshield, and the radiation conductor plates 35 and 41 of the antenna elements 3 and 4 are opposed to the glass surface 50. A good sensitivity can be expected because the GPS signal and the ETC signal can be almost directly opposed to each other. Moreover, as shown in FIGS. 7 and 8, the diversity antennas 20 are disposed on the left and right sides in the vicinity of the antenna device 1 on the glass surface 50, so that the preamplifiers are provided in the vicinity of the diversity antennas 20. Therefore, attenuation of the received terrestrial digital wave signal can be suppressed.

  Further, since the antenna device 1 is arranged such that the radiation conductor plate 41 of the antenna element 4 having a small diameter and a low profile protrudes into the opening 30 of the radiation conductor plate 35 of the antenna element 3, each antenna element 3. , 4 can be arranged on the circuit board 2 in a space-efficient manner and can be easily reduced in size, and complicated processing for ensuring radiation efficiency with respect to the circuit board 2 (partly changing the plate thickness) Etc.) is not necessary. Then, the heights of the antenna elements 3 and 4 on the circuit board 2 are made different to hold the radiating conductor plates 35 and 41 in different planes, and a plurality of pieces are provided along the periphery of the opening 30 of the antenna element 3. Since the antenna element 4 is surrounded by the short-circuit leg piece 39, the electromagnetic isolation between the antenna elements 3 and 4 is increased. Therefore, generation of noise due to interference of radio waves radiated from the radiation conductor plates 35 and 41 is effectively suppressed. Since these antenna elements 3 and 4 are all sheet metal patch antennas, they are easy to manufacture and it is easy to ensure mechanical strength. In addition, since the antenna elements 3 and 4 are two-point feeding type circularly polarized patch antennas, it is easy to increase the bandwidth and improve the axial ratio characteristics.

  However, in this antenna device 1, the frame 7 that is a shield member of the preamplifier for the diversity antenna 20 is different from the antenna element 3 and surrounds the antenna element 3. 3 may have an adverse effect on the impedance characteristics and the axial ratio characteristics. Therefore, the radial dimension of the radiation conductor plate 35 and the positions of the power feeding portions P1 and P2 are set in consideration of the correction. That is, the antenna element 3 has a length D2 from the center O of the radiating conductor plate 35 to the second feeding part P2 (the innermost part of the second notch 32) from the center O to the first feeding part P1 (first The impedance is corrected by setting a predetermined amount shorter than the length D1 (the innermost part of the first notch 31) and the innermost part of the third notch 33 from the center O of the radiation conductor plate 35. Since the axial ratio is corrected by setting the length D3 to the portion shorter than the length D4 from the center O to the innermost portion of the fourth notch 34 by a predetermined amount, the 90 ° phase difference circuit is Good impedance characteristics and axial ratio characteristics can be obtained without complicated correction work such as design changes. Further, by arranging the partition plate 73 attached to the frame body 7 between the side plate 72 and the antenna element 3, not only the shielding effect is enhanced, but also the deterioration of the axial ratio caused by the frame body 7 is suppressed. ing.

  In this antenna device 1, the left and right edges of the circuit board 2 are formed by engaging the supporting piece 76 and the locking piece 78 on one side of the circuit board 2 and engaging the bent tongue 77 on the other side. Since the simple support structure of sandwiching the portion in the plate thickness direction is employed, the frame body 7 can hold the circuit board 2 easily and reliably. In addition, since the support piece 76 supports the circuit board 2 in the vicinity of the connector terminal 10 from the back side, the circuit board 2 is pushed in when the signal cable 21 of the diversity antenna 20 is connected to the connector terminal 10 by a connector. However, the circuit board 2 supported by the support piece 76 from the back side does not bend, so that damage to the circuit board 2 and the mounted components can be avoided, and reliability is increased.

  Further, in this antenna device 1, the frame 7 that is a shield member of the preamplifier for the diversity antenna 20 also has a function of guiding the signal cable 21 for the diversity antenna 20 to the connector terminal 10. That is, since the signal cable 21 is guided to the connector terminal 10 via the cutout groove 75 and the bent tongue piece 77 of the frame body 7, the signal cable 21 can be smoothly passed without being damaged. The connector terminal 10 can be connected to the connector.

  Although the antenna device 1 mounted on the glass surface 50 has been described in the above embodiment, the present invention can be applied to a stationary antenna device that is not a glass mounting type.

1 is an exploded perspective view of an antenna device according to an embodiment of the present invention. It is a front view of the antenna device. It is a perspective view of the back side which shows the state which removed this antenna device from the bracket. FIG. 4 is a front perspective view corresponding to FIG. 3. It is a perspective view of the back side which shows the state which connected the signal cable of the diversity antenna to this antenna apparatus with a connector. FIG. 6 is an explanatory diagram in which the signal cable and the bracket are omitted from FIG. 5 and the cable insertion portion is clearly shown. It is a rear view which shows arrangement | positioning of this antenna device and this diversity antenna whole. FIG. 8 is a front view corresponding to FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 2 Circuit board 3, 4 Antenna element 5 Shield cover 7 Frame 10 Connector terminal 20 Diversity antenna 21 Signal cable 30 Opening 31-34 1st-4th notch 35 Radiation conductor plate 36 1st electric power feeding Leg piece 37 Second feeding leg piece 38 Mounting leg piece 39 Short-circuit leg piece 41 Radiation conductor plate 43 First feeding leg piece 44 Second feeding leg piece 45 Mounting leg piece 50 Glass surface 71, 72 Side plate 73 Partition plate P1 , P2 Power supply unit

Claims (6)

A circuit board provided with a ground conductor layer and a feeding circuit, an antenna element made of a metal plate mounted on the circuit board, and a frame made of a metal plate that holds the circuit board and surrounds the antenna element in a rectangular shape With body,
The antenna element includes a first notch and a second notch that are formed by a metal flat plate facing the ground conductor layer at a predetermined interval and that are radially cut at two locations that are 90 ° apart from each other at the outer edge. A radiating conductor plate in which a notch is formed, and a pair of cut and raised pieces extending from the innermost portions of the first and second notches serving as a feeding portion of the radiating conductor plate to the circuit board side. The circuit is formed as a first feeding leg piece and a second feeding leg piece connected to the feeding circuit, and a cut-and-raised piece extending from a plurality of locations on the outer edge of the radiation conductor plate to the circuit board side. A plurality of mounting leg pieces fixed to the substrate, and the length from the center of the radiation conductor plate to the innermost part of the second notch is from the center to the innermost part of the first notch. Is set to be shorter than the length to the part by the impedance correction. And the frame body is arranged so that the longitudinal direction of the rectangle is along the cut direction of the first cutout and the short side is along the cut direction of the second cutout. An in-vehicle antenna device characterized by the above.   The third notch according to claim 1, wherein a third notch is formed at an outer edge portion of the radiation conductor plate at a position substantially symmetric with the first notch and a fourth notch at a position substantially symmetric with the second notch. And the length from the center of the radiating conductor plate to the innermost part of the third notch is set shorter than the length from the center to the innermost part of the fourth notch by an axial ratio correction. An in-vehicle antenna device characterized by comprising:   3. The in-vehicle antenna device according to claim 2, wherein a partition plate disposed between the side plate on the short side of the rectangle and the antenna element is provided on the frame body.   The preamplifier connected to an external antenna is disposed in the circuit board according to any one of claims 1 to 3 in a region outside the antenna element and inside the frame. An in-vehicle antenna device characterized by comprising:   5. The in-vehicle device according to claim 4, wherein the radiating conductor plate is mounted on a glass surface of a vehicle so that the radiation conductor plate faces the glass surface, and the external antenna is a diversity antenna disposed on the glass surface. Antenna device.   6. The circuit board according to claim 1, wherein a plurality of lands facing the ground conductor layer are provided on the circuit board, and the plurality of mounting leg pieces are soldered to the lands. An in-vehicle antenna device characterized by the above.

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