JP2018182556A - Low profile antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-profile antenna device capable of reducing the height without deteriorating antenna performance. A low-profile antenna device for a vehicle includes a base plate 10, a circuit board 20, a top load element 30, a coil 40, and a retracting portion 50. The circuit board 20 has a solid earth area 22 and a blank area 23, has an amplifier circuit 21 mounted on the solid earth area 22, and has a feeding terminal 24 arranged in the blank area 23. The top load element 30 functions as a capacitive antenna for the first frequency band. The coil 40 is arranged in a blank area 23 of the circuit board and is adjusted to function as a resonance antenna for the second frequency band by a series circuit with the top load element 30. The retracting portion 50 is provided on the top load element 30 and has a shape such that the distance from the coil 40 is increased. [Selection diagram] Fig. 1

Description

  The present invention relates to a low profile antenna device, and more particularly to a low profile antenna device for a vehicle.

  At present, various antenna devices are mounted on vehicles. As such antenna devices, there are, for example, an antenna for AM / FM radio that can receive AM broadcast and FM broadcast. A rod antenna is generally used as an antenna for AM / FM radio. The rod antenna is composed of an element portion in which an element (helical element) made of a spiral-shaped conductor is covered with a cover, and a base plate for mounting the element portion.

  This rod antenna, when attached to the vehicle body, causes the element part to project greatly from the vehicle body, which impairs the aesthetics and design of the vehicle and may be damaged during garage parking or car wash. There is also a possibility that the element unit may be stolen.

  From such a problem, the height of the entire antenna device is made lower than that of the rod antenna, and the element is housed in the antenna case to protect it from exposure to the outside of the vehicle. There has been proposed a low profile antenna device configured in a shark fin shape (shark fin shape). Such a low-profile antenna device often has a height of 70 mm or less and a length in the longitudinal direction of about 200 mm, in consideration of legal restrictions and the like.

  However, such an antenna device has a problem that the radiation efficiency is easily reduced due to the influence of the conductor loss (shortening of the element length) of the antenna due to the low attitude of 70 mm or less, which causes the sensitivity deterioration. . For example, Patent Document 1 discloses a low profile antenna device in which a coil is inserted between a top load element and an amplifier circuit for the purpose of solving sensitivity deterioration. In patent document 1, the top load element is arrange | positioned on the element holder standingly arranged on a circuit board, and the coil is arrange | positioned at this element holder. Since the performance degradation of the coil causes a reduction in the antenna gain, the element is placed in the middle between the top load element and the circuit board so that there is no conductor around the coil that lowers the Q value of the coil. The holder was provided with a grip.

JP, 2012-204996, A

  However, in Patent Document 1, an extra holding portion is required in the element holder so that the coil is disposed in the middle between the top load element and the circuit board. Furthermore, since the top load element is a metal body, in the case of a structure in which the top load element is brought close to the coil, performance degradation of the coil becomes a problem, and it is difficult to further reduce the height. Furthermore, while preventing the performance deterioration of the coil, it is also desired to increase the number of top load elements for improving the antenna characteristics.

  An object of the present invention is to provide a low profile antenna device which can be reduced in height without reducing antenna performance.

  In order to achieve the object of the present invention described above, a low profile antenna device according to the present invention is a base plate fixed to a vehicle, and a circuit board disposed on the base plate, wherein a solid earth area and solid earth where solid earth exists A circuit board having an amplifier circuit placed in a solid ground area and having a feed terminal disposed in the blank area, and an interval in the height direction with respect to the base plate A top load element disposed and connected to the feed terminal and functioning as a capacitive antenna for the first frequency band, and a coil disposed in a blank area of the circuit board, the top load element and the amplifier circuit of the circuit board Connected between them and functions as a resonant antenna for the second frequency band by the series circuit of top load element and coil It is adjusted to so that a coil, a retreat portion provided in the top load element, in which includes a retracting portion having a shape such that the distance between the coil leaves a.

  Here, the retracting portion may have any shape as long as the coil is exposed when viewed from the top side of the low profile antenna device.

  In addition, the top load element may have a planar body having a flat surface in the short side direction and a planar inclined portion between the feed terminal and the retracting portion provided in the planar inclined portion.

  In addition, the top load element may have a streamline shape having a longitudinally extending top portion and side portions extending to both sides from the top portion, and the retraction portion may be provided on the side portion.

  Also, the blank area may be disposed on the circuit board so as to be disposed in the vicinity of the end of the base plate.

  Further, the feed terminal and the coil may be disposed at positions far from the solid earth area of the blank area.

  Further, the feeding terminal is disposed on the circuit board so as to be offset with respect to the longitudinal center line of the base plate, and the coil is disposed offset to the side opposite to the feeding terminal with respect to the longitudinal center line of the base plate That's fine.

  In addition, the top load element may be disposed so as to straddle over the solid earth area from above the blank area.

  The solid ground area of the circuit board is a solid ground on both sides of the circuit board, the noise generating component of the amplifier circuit is disposed on the base plate side of the solid ground area, and the solid ground on the opposite side of the base plate side of the solid ground area is a noise generation It only needs to function as a shield for parts.

  Further, in the solid earth area of the circuit board, solid earth exists on both sides of the circuit board, and the cable to the amplifier circuit may be connected to the base plate side of the solid earth area.

  Further, the retracting portion may have a shape such that the distance to the amplifier circuit is further increased.

  Furthermore, the low-profile antenna device of the present invention includes an antenna element for the third frequency band, and an adjustment for the third frequency band disposed in a blank area of the circuit board and connected to the antenna element for the third frequency band. A pattern may be included.

  Here, the adjustment pattern may be arranged as long as it is separated from the pattern between the coil and the amplifier circuit which are arranged in the blank area of the circuit board.

  The low profile antenna device of the present invention has the advantage that it can be reduced in height without degrading the antenna performance.

FIG. 1 is a schematic partial sectional view for explaining a low profile antenna device of the present invention. FIG. 2 is a schematic view for explaining a circuit board used for the low profile antenna device of the present invention. FIG. 3 is a gain characteristic in the FM frequency band of the low profile antenna device of the present invention. FIG. 4 is a gain characteristic in the FM frequency band according to the presence or absence of the noise countermeasure by the solid earth area of the low profile antenna device of the present invention. FIG. 5 is a schematic partial sectional view for explaining another example of the retracting portion of the low profile antenna device of the present invention. FIG. 6 is a schematic partial cross-sectional view for explaining another example of the low profile antenna device of the present invention. FIG. 7 is a schematic partial cross-sectional view for explaining still another example of the low profile antenna device of the present invention.

  Hereinafter, a mode for carrying out the present invention will be described with an example shown in the drawings. 1 (a) is a side view and FIG. 1 (b) is a front view, and FIG. 1 (a) is a side view, and FIG. c) is a plan view. As illustrated, the low profile antenna device according to the present invention mainly includes a base plate 10, a circuit board 20, a top load element 30, a coil 40, and a retracting portion 50. The low-profile antenna device of the present invention may be any device as long as it corresponds to at least two frequency bands, a first frequency band and a second frequency band. Specifically, for example, it may be configured as a composite antenna capable of receiving signals in both the FM frequency band and the AM frequency band.

  The base plate 10 is fixed to a vehicle. Specifically, the base plate 10 may be a so-called resin base formed of an insulator such as a resin, or may be a so-called metal base formed of a conductor such as a metal. Also, the base plate 10 may be a composite base of resin and metal. For example, screw bosses 11 are provided on the base plate 10. The screw boss 11 is inserted into a hole provided in a roof or the like of the vehicle, and the base plate 10 is fixed by sandwiching the roof or the like from the vehicle interior with a nut. A cable 26 such as a power supply cable or a signal cable for connecting the inside of the vehicle and the antenna device is inserted into the screw boss 11. Further, the base plate 10 is configured to be covered by the antenna cover 1. The antenna cover 1 has an internal space for accommodating elements, circuits, etc., and defines the outer shape of the low profile antenna device.

  The circuit board 20 is disposed on the base plate 10. FIG. 2 shows a circuit board used for the low profile antenna device of the present invention. FIG. 2 is a schematic view for explaining a circuit board used in the low profile antenna device of the present invention, FIG. 2 (a) is a top view thereof, and FIG. 2 (b) is a bottom view thereof; FIG.2 (c) is the side enlarged view. In the figure, the part which attached | subjected the code | symbol same as FIG. 1 has shown the same thing. As illustrated, the circuit board 20 is one on which the amplifier circuit 21 is mounted. The amplifier circuit 21 is used to amplify the received signal. For example, when the low profile antenna device of the present invention is configured as a composite antenna capable of receiving signals in both the FM frequency band and the AM frequency band, the amplifier circuit 21 also has a plurality of frequency bands, that is, the FM frequency band. And a plurality of frequency band separate amplifier circuits provided in accordance with the AM frequency band. The amplifier circuit 21 may include a power supply circuit and the like.

  The circuit board 20 of the example of illustration showed the example in which the solid earth exists on the both surfaces. However, the present invention is not limited to this, and solid earth may be provided only on one side. Here, the solid earth area 22 is an area where a so-called solid earth exists, and a metal thin film such as a copper foil is present in a planar manner on the substrate to be a ground of the circuit board. The blank area 23 is an area where no solid earth exists. That is, it is an area where the metal thin film is etched away. In the example shown in FIG. 2C, the circuit board 20 is locked by the locking portion 12 provided in the vicinity of the tip of the base plate 10.

  The amplifier circuit 21 is mounted on the solid earth area 22. More specifically, electronic components such as transistors and resistors used in the amplifier circuit 21 are appropriately placed on the solid ground area 22 on the front and back sides of the circuit board 20. A circuit pattern is appropriately formed by etching in the solid earth area 22, and an amplifier circuit 21 is formed using a predetermined electronic component. In the present specification, the base plate 10 side is referred to as the back surface side, and the surface opposite thereto is referred to as the front surface side.

  Further, the feed terminal 24 is disposed in the blank area 23. The feed terminal 24 serves as a terminal for connecting the antenna element to the amplifier circuit 21 of the circuit board 20. The feed terminal 24 in the illustrated example is a female terminal having a sandwiching terminal structure. The blank area 23 is disposed on the circuit board 20 so as to be disposed in the vicinity of the end of the base plate 10.

  The top load element 30 functions as a capacitive antenna for the first frequency band. That is, it is a so-called capacitive loading antenna element. Specifically, in the AM frequency band, the top load element 30 functions as a capacitive antenna. The top load elements 30 are arranged at intervals in the height direction with respect to the base plate 10. In the example shown in FIG. 1, the top load element 30 has an example in which the planar body 31 having a flat surface in the short side direction and the planar inclined portion 32 between the feed terminal 24 are provided. Also, the sheet 31 is shown to extend parallel to the base plate 10. However, the present invention is not particularly limited to the shape of the illustrated example, and any shape may be used as long as it functions as a capacitively-loaded antenna element. The top load element 30 is connected to the feed terminal 24. In the example of illustration, the top load element 30 showed the example connected to the electric power feeding terminal 24 using the strip | belt-shaped connecting wire 37. As shown in FIG. That is, by connecting the strip-like connection line 37 as a male terminal, the connection is made by sandwiching the feed terminal 24 of the female terminal. However, the present invention is not limited to this, and the top load element 30 may be connected to the feeding terminal 24 by a wire or the like. The top load element 30 may be appropriately fixed using a base, an antenna cover or the like.

  Here, the top load element 30 is arranged to straddle over the solid earth area 22 from above the blank area 23 of the circuit board 20. That is, the circuit board 20 is disposed on the base plate 10 such that the blank area 23 side is located near the tip of the base plate 10. In the present specification, the side on which the circuit board 20 of the base plate 10 is disposed is referred to as the front side. Since the feed terminal 24 is disposed at a position far from the solid earth area 22 of the blank area 23, the feed terminal 24 is disposed in the vicinity of the front end. Thus, the top load element 30 can be extended to the lower end portion of the antenna cover 1. Therefore, it becomes possible to effectively utilize the lower end portion of the antenna cover 1.

  The coil 40 is connected between the top load element 30 and the amplifier circuit 21 of the circuit board 20. In the illustrated example, specifically, it is connected between the amplifier circuit 21 and the feeding terminal 24. The coil 40 is adjusted by the series circuit of the top load element 30 and the coil 40 to function as a resonant antenna for the second frequency band. For example, the inductor is selected to function as a resonant antenna in the FM frequency band. The series circuit of the top load element 30 and the coil 40 may be adjusted to a desired target frequency in a state (passive antenna) not connected to the amplifier circuit 21. In addition, the coil 40 is disposed in the blank area 23 of the circuit board 20. In the illustrated example, it is disposed on the surface side of the blank area 23. That is, although the coil 40 is disposed on the circuit board 20, at this time, the coil 40 is disposed in the blank area 23 where the metal thin film of the circuit board 20 does not exist. As a result, a conductor that lowers the Q value of the coil 40 is configured not to exist around the coil 40, and the performance deterioration of the coil 40 is prevented. Furthermore, in the low profile antenna device of the present invention, the feed terminal 24 and the coil 40 may be arranged at a position far from the solid ground area 22 of the blank area 23. Thereby, the influence of the solid ground area 22 on the coil 40 can be further reduced.

  Further, the coil 40 may be disposed on the circuit board by soldering with a spirally wound conductive wire, but may be surface mountable on the circuit board 20 by a chip mounter, for example. Furthermore, although the coil 40 is shown as a single coil in the illustrated example, the present invention is not limited to this, and may be a coil group in which a plurality of coils are connected in series or in parallel. Furthermore, the coil 40 may be patterned on the circuit board 20. That is, for example, a meandering wiring pattern may be formed by etching on the circuit board 20, or a spiral wiring pattern may be formed by etching using the front and back surfaces of the circuit board 20. In the illustrated example, although the winding axis of the coil 40 is parallel to the base plate 10, the present invention is not limited to this, and the winding axis of the coil may be perpendicular to the base plate 10 It may be arranged in

  The low-profile antenna device of the present invention has a retracting portion 50. The evacuation unit 50 is provided on the top load element 30. The retracting portion 50 has a shape in which the distance to the coil 40 is separated. That is, in order to separate the top load element 30 and the coil 40, a retracting portion 50 is provided. Since the top load element 30 is also a conductor, it may be a cause of lowering the Q value of the coil 40. Therefore, by providing the retraction portion 50, the influence of the top load element 30 is reduced. In the example shown in FIG. 1, the retracting portion 50 is configured to have a shape such that the coil 40 is exposed as viewed from the top side of the low profile antenna device. Specifically, the retracting portion 50 in the illustrated example is provided in the planar inclined portion 32. In the illustrated example, the feed terminals 24 are disposed on the circuit board 20 so as to be offset from the longitudinal center line of the base plate 10. That is, the feed terminal 24 is disposed offset to the left as viewed from the front side. Further, the coil 40 is disposed to be shifted to the opposite side of the feed terminal 24 with respect to the center line in the longitudinal direction of the base plate 10. That is, the coil 40 is disposed offset to the right when viewed from the front side. Thus, the planar inclined portion 32 is configured to be offset with respect to the longitudinal center line of the base plate 10. Therefore, the planar inclined portion 32 of the top load element 30 closer to the coil 40 can be shifted to the feed terminal 24 side, and as a result, the retracting portion 50 is provided on the top load element 30 closer to the coil 40. Become. That is, in the example shown in FIG. 1, the retracting portion 50 is provided by making the shape of the top load element 30 asymmetrical to be shifted leftward from the longitudinal center line.

  In the low-profile antenna device of the present invention, such a configuration makes it possible to reduce the height without degrading the antenna performance. FIG. 3 shows gain characteristics in the FM frequency band of the low profile antenna device of the present invention, and FIG. 3 (a) shows comparative characteristics when the height of the low profile antenna device is changed. Is the comparison characteristic depending on the presence or absence of the evacuation part. In FIG. 3A, the solid line is the gain characteristic when the height of the low profile antenna device is 45 mm, and the dotted line is the gain characteristic when the height of the low profile antenna device is 70 mm. In the example of 70 mm in height, the top load element is a streamlined shape having a longitudinally extending top portion and side portions extending to both sides from the top portion, and does not have a retraction portion. The one of As shown in the drawing, it can be seen that, even if the height is lowered to 45 mm, the low profile antenna device of the present invention can obtain gain characteristics substantially equivalent to those of the prior art.

  Further, in FIG. 3B, the solid line is the gain characteristic when the retracting portion is provided, and the dotted line is the gain characteristic when the retracting portion is not provided. As illustrated, in the low profile antenna device of the present invention, it can be seen that the gain characteristic is improved by providing the retracting portion. Specifically, the frequency is improved by 0.26 dB in the FM frequency band.

  Here, referring to FIG. 2 again, the solid earth area 22 of the circuit board 20 of the low profile antenna device of the present invention has solid earth on both the front and back sides of the circuit board 20. The noise generating component 25 of the amplifier circuit 21 is disposed on the base plate 10 side of the solid earth area. Specifically, a noise generating component 25 such as a transistor or a tuner IC is disposed on the base plate 10 side of the solid ground area 22 of the circuit board 20. In this configuration, the solid earth on the opposite side to the base plate side of the solid earth area 22 also functions as a shield for noise generating parts. As a result, noise suppression can be performed, and therefore, it is possible to further reduce the deterioration of the antenna characteristics. In the low profile antenna device of the present invention, all the noise generating components 25 do not necessarily have to be arranged on the base plate 10 side, and noise measures may be taken by arranging them on the base plate 10 side as needed.

  Further, as shown in FIG. 2, the cable 26 such as a power supply cable or a signal cable to the amplifier circuit 21 may be connected to the base plate 10 side of the solid ground area 22. In this configuration, the solid earth on the opposite side of the solid earth area 22 to the base plate also functions as a shield of the cable 26. As a result, it is possible to take measures against noise on the input power supply, and it is possible to further reduce the deterioration of the antenna characteristics.

  FIG. 4 shows the gain characteristics in the FM frequency band according to the presence or absence of the noise countermeasure by the solid earth area of the low profile antenna device of the present invention. In the figure, the solid line is the gain characteristic when the noise countermeasure is taken in the solid earth area, and the dotted line is the gain characteristic when it is not applied. As illustrated, in the low profile antenna device of the present invention, it can be understood that the gain characteristic is enhanced by taking the above-mentioned measures against noise. Specifically, it is improved by 1.1 dB in the FM frequency band.

  Furthermore, as shown in FIG. 2, the low profile antenna device of the present invention may be configured to be able to receive the third frequency band. Specifically, for example, the adjustment pattern 60 for the third frequency band is a blank of the circuit board 20 in order to receive a signal of the DTV frequency band higher than the first frequency band or the second frequency band. It is arranged in the area 23. The adjustment pattern 60 in the illustrated example has a meander shape, but the present invention is not limited to this, and may be a chip coil or the like. The adjustment pattern 60 adjusts the top load element to function as a resonant antenna for the third frequency band. At this time, in the adjustment pattern 60, the coil 40 disposed in the blank area 23 of the circuit board 20 and the wiring pattern 27 between the amplifier circuit 21 may be spaced apart. As a result, isolation between the wiring pattern 27 for the second frequency band and the adjustment pattern 60 can be obtained, and signals can be sufficiently separated even when the frequency bands are close.

  In the low profile antenna device of the present invention, as shown in FIG. 2C, an antenna element 70 for the fourth frequency band may be further provided. For example, the fourth frequency band is a higher frequency band for V2X or TEL. Also in this case, isolation can be achieved by arranging the antenna element 70 for the fourth frequency band apart from the wiring pattern 27 and the adjustment pattern 60.

  Here, in the example of FIG. 1, the feed terminal 24 is disposed on the circuit board 20 while being shifted with respect to the center line in the longitudinal direction of the base plate 10, but the present invention is not limited thereto. FIG. 5 is a schematic partial cross-sectional view for explaining another example of the retracting portion of the low profile antenna device of the present invention, FIG. 5 (a) is a side view, and FIG. 5 (b) is a plan view. FIG. In the figure, the part which attached | subjected the code | symbol same as FIG. 1 has shown the same thing. In the example shown in FIG. 5, the feed terminal 24 is disposed on the longitudinal center line of the base plate 10. And the evacuation unit 50 is provided by cutting out the top load element 30. More specifically, the retracting portion 50 is provided by cutting out the top load element 30 so that the coil 40 is exposed as viewed from the top side of the low profile antenna device. Further, the top load element 30 shown in FIG. 1 is a plane in which the planar body 31 extends in parallel to the base plate 10. However, the present invention is not limited to this. In the example shown in FIG. 5, the top load element 30 has a shape in which the planar body 31 whose plane in the short side direction is flat is along the upper surface of the antenna cover 1. And the junction of the planar inclined part 32 and the planar body 31 is not clear, but is continuous. Even in such an example, the antenna characteristic can be improved by providing the retracting portion 50 in the planar inclined portion 32 in a portion close to the coil 40.

  In the example shown in FIG. 5, the feed terminal 24 is disposed on the center line in the longitudinal direction of the base plate 10, and the coil 40 is disposed to be shifted to the right when viewed from the front side. It is not limited to this. For example, a coil may be further added on the left side as viewed from the front side, and the retraction portion 50 may be provided on the added coil side. That is, the retracting portion 50 may be arranged symmetrically with respect to the center line of the base plate 10 in the longitudinal direction.

  Also, the coil 40 shown in FIG. 1 is shown to be disposed in a direction in which the winding axis is parallel to the base plate 10 and perpendicular to the longitudinal direction of the base plate 10, but FIG. The illustrated coil 40 is disposed in a direction parallel to the longitudinal direction of the base plate 10. For this reason, the retracting portion 50 is cut out long in the longitudinal direction of the base plate 10 in accordance with the arrangement direction of the coil 40. Further, in the illustrated example, the retracting portion 50 is provided so as to have a shape such that the distance to the amplifier circuit 21 is large. That is, deterioration of the antenna performance due to the top load element 30 being coupled to the amplifier circuit 21 is prevented. Thereby, the antenna characteristics can be further improved.

  Next, another example of the low profile antenna device of the present invention will be described with reference to FIG. FIG. 6 is a schematic partial cross-sectional view for explaining another example of the low profile antenna device according to the present invention, FIG. 6 (a) is a side view, and FIG. 6 (b) is a front view. 6 (c) is a plan view. In the figure, the part which attached | subjected the code | symbol same as FIG. 1 has shown the same thing. In the illustrated example, the top load element 30 has been shown to be of streamlined shape having a longitudinally extending apex 35 and side portions 36 extending laterally from the apex 35. In the example of FIG. 1, the feed terminal 24 is disposed on the circuit board 20 while being offset from the center line in the longitudinal direction of the base plate 10. However, in FIG. An example of being placed on the center line of the direction is shown. Then, an example in which the retracting portion 50 is provided on the side surface portion 36 of the top load element 30 has been shown. More specifically, the retracting portion 50 is provided by cutting out the side surface portion 36 of the top load element 30 so that the coil 40 is exposed as viewed from the top portion 35 side of the low profile antenna device. In the illustrated example, not only the side surface portion 36 but also the strip-like connecting line 37 is cut out, thereby providing an example in which the retracting portion 50 is provided. Moreover, in the example of illustration, what was arrange | positioned so that the winding axis of the coil 40 may become a perpendicular | vertical direction with respect to the baseplate 10 was shown. By providing the retracting portion 50, even if the winding axis of the coil 40 is arranged to be perpendicular to the base plate 10, the influence of the top load element 30 can be reduced.

  As described above, the low-profile antenna device of the present invention reduces the antenna performance by providing a retracting portion having a shape such that the distance from the coil is long regardless of the shape of the top load element 30. Can be suppressed.

  Even in the streamlined top load element 30 as shown in FIG. 6, the feed terminal 24 is disposed offset with respect to the longitudinal center line of the base plate 10, as shown in FIG. The retracting portion 50 may be provided by making the shape of the top load element 30 asymmetric with respect to the longitudinal center line.

  In the above description, the low profile antenna apparatus of the present invention has been described focusing on the shape of a shark fin or the like installed on the roof of a vehicle, but the low profile antenna apparatus of the present invention is not limited thereto. FIG. 7 shows still another example of the low profile antenna device of the present invention. FIG. 7 is a schematic partial cross-sectional view for explaining still another example of the low-profile antenna device of the present invention, and FIG. 7 (a) is a side view, and FIG. is there. In the figure, the part which attached | subjected the code | symbol same as FIG. 1 has shown the same thing. In the illustrated example, the base plate 10 as a main component, the circuit board 20, the top load element 30, the coil 40, and the retracting portion 50 are accommodated in the box cover 2. The box cover 2 is, for example, made of resin as long as it can transmit a desired reception frequency signal. Further, the base plate 10 has a role of a lid that closes the opening of the bottom surface of the box cover 2. The base plate 10 may be substituted by the circuit board 20, and the opening of the bottom surface of the box cover 2 may be closed by the circuit board 20. In addition, the top load element 30 is formed of the sheet-like body 31, and an example in which the top load element 30 is connected by the strip-like connecting line 37 has been shown. The circuit board 20 in the illustrated example has a size that substantially covers the entire bottom surface of the box cover 2. The blank area 23 of the circuit board 20 on which the coil 40 is provided is the same as the illustrated example described above, but the solid earth area 22 of the circuit board 20 is the open end of the top load element 30 (the side far from the feeding terminal 24) It is provided to extend to the bottom of the As a result, for example, the low-profile antenna device of the illustrated example can be incorporated in a spoiler, a pillar, a dashboard or the like which can not secure the ground by the metal body. The other structures are the same as those described above, and thus the detailed description is omitted. Even in the low-profile antenna device as illustrated, the antenna characteristic can be improved by providing the retracting portion 50 in the top load element 30.

  The low-profile antenna device of the present invention is not limited to the illustrated example described above, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 antenna cover 2 box cover 10 base plate 11 boss 12 latching | locking part 20 circuit board 21 amplifier circuit 22 solid earth area 23 blank area 24 electric power feeding terminal 25 noise generating components 26 cable 27 wiring pattern 30 top load element 31 planar body 32 planar inclination Part 35 Top part 36 Side part 37 Band connecting wire 40 Coil 50 Retracting part 60 Adjustment pattern 70 Antenna element for 4th frequency band

Claims (13)

A low profile antenna device for a vehicle, said low profile antenna device comprising
A base plate fixed to the vehicle,
A circuit board disposed on the base plate, having a solid ground area in which solid ground exists and a blank area in which solid ground is absent, having an amplifier circuit mounted on the solid ground area, and disposed in the blank area A circuit board having a feed terminal;
A top load element disposed at an interval in the height direction with respect to the base plate, connected to a feeding terminal, and functioning as a capacitive antenna for a first frequency band;
A coil disposed in a blank area of the circuit board, connected between the top load element and the amplifier circuit of the circuit board, and functioning as a resonant antenna for the second frequency band by a series circuit of the top load element and the coil The coil, adjusted to
A retracting portion provided on the top load element, the retracting portion having a shape such that the distance to the coil is separated;
A low profile antenna device comprising:   The low profile antenna device according to claim 1, wherein the retracting portion has a shape such that the coil is exposed when viewed from the top side of the low profile antenna device. The low profile antenna device according to claim 1 or 2, wherein the top load element has a planar inclined portion between a planar body having a planar short side direction and a feeding terminal,
The low-profile antenna device is characterized in that the retreating portion is provided on a planar inclined portion. The low profile antenna device according to claim 1 or 2, wherein the top load element has a streamline shape having a longitudinally extending top portion and side portions extending to both sides from the top portion.
The low profile antenna device according to claim 1, wherein the retracting portion is provided on a side surface portion.   The low profile antenna device according to any one of claims 1 to 4, wherein the blank area is disposed on a circuit board so as to be disposed in the vicinity of an end of the base plate. Antenna device.   The low profile antenna device according to any one of claims 1 to 5, wherein the feed terminal and the coil are disposed at a position distant from a solid ground area of a blank area. The low-profile antenna device according to any one of claims 1 to 6, wherein the feed terminal is disposed on the circuit board so as to be offset with respect to a longitudinal center line of the base plate.
The coil is disposed offset to the side opposite to the feed terminal with respect to the longitudinal center line of the base plate.
Low profile antenna device characterized by   The low profile antenna apparatus according to any one of claims 1 to 7, wherein the top load element is arranged to straddle over a solid area from above the blank area. Antenna device. The low profile antenna device according to any one of claims 1 to 8, wherein a solid ground area of the circuit board is a solid ground on both sides of the circuit board,
Noise generation components of the amplifier circuit are placed on the base plate side of the solid earth area,
The solid ground on the side opposite to the base plate side of the solid earth area also functions as a shield for noise generating parts,
Low profile antenna device characterized by The low profile antenna device according to any one of claims 1 to 9, wherein a solid ground area of the circuit board is a solid ground on both sides of the circuit board,
A low profile antenna device characterized in that a cable to an amplifier circuit is connected to a base plate side of a solid ground area.   The low profile antenna device according to any one of claims 1 to 10, wherein the retracting portion further has a shape such that the distance from the amplifier circuit is further apart. The low profile antenna device according to any one of claims 1 to 11, further comprising: an antenna element for a third frequency band;
An adjustment pattern for a third frequency band disposed in the blank area of the circuit board and connected to the antenna element for the third frequency band;
A low profile antenna device comprising:   The low profile antenna device according to claim 12, wherein the adjustment pattern is disposed apart from a pattern between a coil disposed in a blank area of a circuit board and an amplifier circuit. Antenna device.