JP2020096207A - Antenna device - Google Patents

Abstract

To provide an antenna device, having a plurality of antennas in a common case, capable of achieving miniaturization while suppressing degradation in an antenna gain.SOLUTION: An antenna device 1 includes an AM/FM capacity loading element 3 and an AM/FM helical element 5 as a first antenna and a BandIII capacity loading element 8 and a BandIII helical element 10 as a second antenna. The BandIII capacity loading element 8 is positioned more ahead than the AM/FM capacity loading element 3. The presence ranges in the cross direction of the BandIII capacity loading element 8 and the AM/FM capacity loading element 3 are not overlapped.SELECTED DRAWING: Figure 1

Description

The present invention relates to an antenna device including a plurality of antennas in a common case.

In recent years, a vehicle-mounted antenna device called a shark fin antenna has been developed. There is a movement to mount a DAB (Digital Audio Broadcast) antenna in addition to an AM/FM broadcast receiving antenna in an in-vehicle antenna device (for example, Patent Document 1 below).

JP2012-199865A

If a plurality of antennas are provided in a limited space within the case, there is a problem in that the distance between the antennas cannot be secured sufficiently and the gain of the antennas decreases. On the other hand, if the distance between the antennas in the case is increased, the case becomes large and there is a problem that the size cannot be reduced.

The present invention has been made in view of such a situation, and an object thereof is to provide an antenna device that includes a plurality of antennas in a common case and that can be downsized while suppressing a decrease in antenna gain. To do.

One aspect of the present invention is an antenna device. This antenna device
A first and a second antenna provided in a common case,
The first antenna has a first capacitive loading element, resonates in a first resonance frequency band,
The second antenna has a second capacitive loading element, and resonates in a second resonance frequency band higher than the first resonance frequency band,
The second capacitive loading element is located in front of the first capacitive loading element.

The existing ranges of the first and second capacitive loading elements may not overlap in the front-back direction.

A third antenna provided in the common case,
The third antenna may resonate in a third resonance frequency band higher than the second resonance frequency band, and may be located in front of the second capacitive loading element.

The presence ranges of the first and second capacitive loading elements and the third antenna may not overlap in the front-rear direction.

The first antenna has a first helical element between the first capacitive loading element and a first feeding point,
The second antenna may include a second helical element between the second capacitive loading element and the second feeding point.

Both the first and second capacitive loading elements may be sheet metal parts.

It should be noted that any combination of the above constituent elements and one obtained by converting the expression of the present invention between methods and systems are also effective as an aspect of the present invention.

According to the present invention, it is possible to provide an antenna device that includes a plurality of antennas in a common case and that can be downsized while suppressing a decrease in antenna gain.

The perspective view which abbreviate|omitted the outer case 2 of the antenna device 1 which concerns on embodiment of this invention. The left side view. FIG. 3 is an exploded perspective view of the antenna device 1. The perspective view which looked at the L-Band element 16 of FIG. 3 from the right front. The perspective view seen from the same left front. The perspective view which looked at BandIII capacity loading element 8 of Drawing 3 from the left front. The perspective view seen from the same right back. A simulation showing the relationship between the frequency and the average gain in the Band III band in each of the antenna device 1 in which the Band III capacitance loading element 8 has the top portion 8b and the antenna device in which the Band III capacitance loading element 8 does not have the top portion 8b Characteristic diagram. An antenna device in which the Band III capacitive loading element 8 is erected on the metal base 19 and has an additional erected portion connected to the opposite side of the erected portion 8a of the top portion 8b, and an antenna device 1 not having the additional erected portion FIG. 6 is a characteristic diagram by simulation showing the relationship between the frequency of the Band III band and the average gain in each of FIG. The perspective view which shows the 1st modification of BandIII capacity loading element 8. A characteristic diagram by simulation showing the relationship between the frequency in the Band III band and the average gain of the antenna device 1 when the Band III capacitive loading element 8 has the top portion 8b (FIG. 6) and when it has the top portion 8d (FIG. 10). .. The characteristic view by simulation which shows the relationship between the frequency of an FM band, and an average gain of the antenna device 1 in each case same as FIG. The perspective view seen from the left front which shows the 2nd modification of BandIII capacity loading element 8. The perspective view seen from the same right back. The resonance frequency of the BandIII capacitive loading element 8 and the BandIII helical element 10 is set to FM frequency band, and the resonance frequency band of the AM/FM capacitive loading element 3 and AM/FM helical element 5 is set to BandIII frequency band. The characteristic view by simulation which shows the relationship between the frequency of an FM band, and an average gain in each of the antenna device and the antenna device 1 which does not exchange a frequency. FIG. 3 is a simplified left side view of the antenna device 1 in which the BandIII capacitance loading element 8 and the AM/FM capacitance loading element 3 have substantially the same shapes as those in FIG. 2. FIG. 17 is a simplified left side view of the antenna device in which the lower rear portion of the Band III capacity loading element 8 is extended rearward and inserted into the AM/FM capacity loading element 3 existing range in the front-rear direction as compared with FIG. 16. The frequency and average of the FM band in each of the antenna device 1 (FIG. 16) and the overlapping antenna device (FIG. 17) in which the band III capacitive loading element 8 and the AM/FM capacitive loading element 3 do not overlap in the front-back direction existence range. The characteristic diagram by a simulation which shows the relationship with a gain. FIG. 17 is a simplified left side view of the antenna device 1 in which the front lower part of the AM/FM capacitance loading element 3 is obliquely cut as compared with FIG. 16. FIG. 17 is a simplified left side view of the antenna device 1 in which the lower rear portion of the Band III capacitive loading element 8 is obliquely cut as compared with FIG. 16. 20 is a simplified left side view of the antenna device 1 in which the AM/FM capacitance loading element 3 has the same shape as FIG. 19 and the Band III capacitance loading element 8 has the same shape as FIG. 20. The characteristic view by simulation which shows the relationship between the frequency of an FM band, and an average gain in each antenna apparatus 1 of FIGS. FIG. 17 is a simplified left side view of the antenna device in which the front upper part of the AM/FM capacitance loading element 3 is obliquely cut as compared with FIG. 16. FIG. 24 is a characteristic diagram by simulation showing the relationship between the frequency in the FM band and the average gain in each of the antenna device 1 of FIG. 16 and the antenna device of FIG. 23. The circuit diagram of the LC parallel circuit which connects BandIII capacity loading element 8 and BandIII helical element 10. FIG. 3 is a circuit diagram of a capacitor C that connects the BandIII capacitive loading element 8 and the BandIII helical element 10. The perspective view which abbreviate|omitted the outer case 2 of the antenna device 1A which concerns on other embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or equivalent constituent elements, members, and the like shown in each drawing are denoted by the same reference numerals, and duplicated description will be omitted as appropriate. In addition, the embodiments do not limit the invention, but are exemplifications, and all features and combinations described in the embodiments are not necessarily essential to the invention.

FIG. 1 is a perspective view of an antenna device 1 according to an embodiment of the present invention with an outer case 2 omitted. FIG. 2 is a left side view of the same. FIG. 3 is an exploded perspective view of the antenna device 1. 1 and 3, the front-back, up-down, and left-right directions of the antenna device 1 which are orthogonal to each other are defined. The up-down direction is a direction perpendicular to the metal base 19 and the resin base 20. The direction in which the attachment destination (for example, a vehicle) is present with respect to the metal base 19 and the resin base 20 is downward. The front-back direction is the longitudinal direction of the antenna device 1. The left-right direction is the width direction of the antenna device 1. The forward direction is the traveling direction when the antenna device 1 is attached to the vehicle. The left-right direction is determined based on the state of looking forward, which is the traveling direction.

The antenna device 1 is a vehicle-mounted shark fin antenna and is attached to the roof of a vehicle or the like. The antenna device 1 includes an AM/FM capacitive loading element 3 and an AM/FM helical element 5 as a first antenna, a BandIII capacitive loading element 8 and a BandIII helical element 10 as a second antenna, and a third antenna in an outer case 2. The L-Band element 16 as an antenna is provided. In addition, a GPS (Global Positioning System), an XM (satellite radio broadcast) antenna, or the like may be provided.

The AM band frequency is 522 kHz to 1710 kHz, the FM band frequency is 76 MHz to 108 MHz, and the first antenna is for receiving the AM band and the FM band as the first resonance frequency band. The DAB has an L-Band frequency band having a frequency of 1452 MHz to 1492 MHz and a BandIII frequency band having a frequency of 174 MHz to 240 MHz, and the second antenna is for receiving the BandIII frequency band as the second resonance frequency band. And the third antenna is for receiving the L-Band frequency band as the third resonance frequency band.

The outer case 2 is made of a radio wave permeable synthetic resin (molded product made of a resin such as PC, PET, ABS resin or the like) and has a shark fin shape in which both side surfaces are curved inward. A base that forms an internal space that houses each element together with the outer case 2 is a combination of a metal base 19 and a resin base 20. The metal base 19 has a smaller area than the resin base 20, and is attached (fixed) on the resin base 20 by screwing or the like. The resin base 20 is attached (fixed) to the outer case 2 by screwing or the like. The pad 13 is an annular elastic member such as elastomer or rubber, and is clamped (pressed) over the entire circumference by the outer case 2 and the resin base 20, and the outer case 2 and the resin base 20 are sealed with water. Stop. The seal member 21 is an annular elastic member made of elastomer, urethane, rubber, or the like, and is sandwiched between the lower surface of the resin base 20 and the vehicle body (for example, the vehicle roof) to which the antenna device 1 is attached, and the space between them is water. Tightly seal. Bolts (body mounting screws) 23, which are conductors, are screwed onto the metal base 19 via capture fasteners 22, which are conductors, to fix the antenna device 1 to the roof or the like of the vehicle. The roof of the vehicle and the metal base 19 are electrically connected to each other via the capture fastener 22 and the bolt 23.

The holder 4 is made of radio wave permeable synthetic resin (molded product made of resin such as PC, PET, ABS resin), and is attached (fixed) to the inside of the outer case 2 by screwing or the like. In the holder 4, the AM/FM capacitive loading element 3 as the first capacitive loading element is attached (fixed) by screwing or the like, and the BandIII capacitive loading element 8 as the second capacitive loading element is attached to the BandIII element holding portion 4a. And the Band III substrate 9 is held in the Band III substrate holding portion 4b.

The AM/FM capacity loading element 3 is a plate-shaped component formed by processing a tin-plated steel plate (conductor plate), for example. The AM/FM helical element 5 is a conductor wire wound around the AM/FM helical element holder 6. The AM/FM helical element holder 6 is attached (fixed) to the holder 4 by snap fitting or the like. The terminal 5a above the AM/FM helical element 5 is electrically connected to the AM/FM capacitance loading element 3 by soldering or the like. An AM/FM connection fitting 7 is attached to a lower front portion of the AM/FM helical element holder 6. The terminal below the AM/FM helical element 5 is electrically connected by being wound around the AM/FM connection fitting 7 and soldered or crimped. The AM/FM connection fitting 7 is engaged and held (sandwiched) by the AM/FM conductor leaf spring 15. The AM/FM conductor leaf spring 15 is provided on the AM/FM amplifier board 14. The AM/FM amplifier board 14 is mounted (fixed) on the metal base 19 by screwing or the like, and is substantially parallel to the metal base 19. The AM/FM capacitance loading element 3 and the AM/FM helical element 5 are configured to resonate in the FM frequency band as a whole, and the contact point between the AM/FM connection fitting 7 and the AM/FM conductor leaf spring 15 is the feeding point. Has become. At the feeding point, the impedance of the AM/FM helical element 5 is increased (the number of turns is increased) to increase the impedance in the Band III frequency band, and the coupling between the AM/FM capacitive loading element 3 and the Band III capacitive loading element 8 is performed. Has eased. Therefore, even if the AM/FM capacitance loading element 3 and the Band III capacitance loading element 8 are brought close to each other, the average gain in the Band III frequency band can be secured.

The BandIII capacitor loading element 8 is soldered to the BandIII substrate 9. The Band III capacitive loading element 8 is made of metal such as tin-plated steel plate. By using a sheet metal, the productivity is high and the cost is low as compared with the case where the conductor pattern of the substrate is used as in Patent Document 1. The Band III substrate 9 is provided with an LC circuit in which a capacitor C and a coil L shown in FIG. 25 are connected in parallel, or a capacitor C shown in FIG. The LC circuit shown in FIG. 25 acts as a filter that does not pass signals in the FM frequency band, the capacitor C shown in FIG. 26 acts as a filter that does not pass signals in the AM/FM frequency band, and the AM/FM capacitance loading element 3 And the band III capacitive load element 8 are relaxed. The BandIII helical element 10 is a conductive wire wound around the BandIII helical element holder 11. The BandIII helical element holder 11 is screwed to the lower surface of the BandIII substrate 9. The BandIII helical element 10 is arranged on the lower surface of the BandIII capacitive loading element 8 and substantially at the center in the left-right direction. With such a structure, since the Band III helical element 10 is arranged at a position substantially at the center of the design of the outer case 2, the case design can be made thin. The terminal above the BandIII helical element 10 is wound around the BandIII substrate 9 and soldered, and is electrically connected to the LC circuit (FIG. 25) or the capacitor C (FIG. 26) provided on the BandIII substrate 9. A Band III connecting fitting 12 is attached to a lower front portion of the Band III helical element holder 11. By attaching the BandIII connecting fitting 12 to the lower front portion of the BandIII helical element holder 11, the AM/FM helical element 5 and the BandIII helical element 10 can be separated from each other by a large distance, so that the coupling can be further reduced and the mutual performance deterioration can be prevented. can do. The lower end of the Band III helical element 10 is electrically connected to the Band III connection fitting 12 by being wound around and soldered or crimped. The BandIII connection fitting 12 is engaged with and held (sandwiched) by the BandIII conductor leaf spring 18. The Band III conductor leaf spring 18 is provided on the DAB amplifier board 17. The DAB amplifier board 17 is attached (fixed) to the metal base 19 by screwing or the like, and is substantially parallel to the metal base 19. The BandIII capacitive loading element 8 and the BandIII helical element 10 and the LC circuit shown in FIG. 25 or the capacitor C shown in FIG. 26 are configured to resonate in the BandIII frequency band as a whole, and the BandIII connection fitting 12 and the BandIII conductor leaf spring 18 The contact point with is the feeding point. By providing the LC circuit shown in FIG. 25 or the capacitor C shown in FIG. 26, even if the AM/FM capacitance loading element 3 and the Band III capacitance loading element 8 are brought close to each other, for example, within 10 mm, the average gain in the AM/FM frequency band is reduced. Can be secured.

The L-Band element 16 is erected on the DAB amplifier board 17. Although not shown in FIGS. 1 to 3, the L-Band element 16 is a conductor pattern printed (formed) on both surfaces of the substrate 16a as shown in FIGS. 4 and 5. The L-Band element 16 and the conductor pattern on one surface and the other surface of the substrate 16a are electrically connected to each other through a through hole. The conductor pattern 16b, which is a part of the L-Band element 16, is a feeding point of the L-Band antenna, is provided at the lower end of the L-Band element 16, and is electrically connected to the DAB amplifier board 17 by soldering or the like. Connected. The conductor pattern 16c which is a part of the L-Band element 16 is provided for impedance adjustment. The connecting portion 16e, which is a part of the conductor pattern 16c, is electrically connected to the ground of the DAB amplifier board 17 by soldering or the like. The conductor pattern 16c may be omitted. The conductor patterns 16f printed on both sides of the board 16a separately from the L-Band element 16 are for fixing the board 16a to the DAB amplifier board 17, and are not connected to the L-Band element 16 and are attached to the DAB amplifier board 17. It is fixed by soldering. The board 16a is fixed to the upper surface of the DAB amplifier board 17 and substantially at the center in the left-right direction by soldering the conductor patterns 16b, 16e, and 16f to the DAB amplifier board 17, and is perpendicular to the DAB amplifier board 17, that is, a metal base. It stands upright with respect to 19. With such a structure, since the L-Band element 16 is arranged at a position symmetrical with respect to the metal base 19, the directivity is substantially isotropic and suitable for reception performance. .. Further, since the L-Band element 16 is arranged at a position that is substantially the center of the design of the outer case 2 while ensuring the height, the case design can be made thin without degrading the gain.

In order to improve the average gain in the L-Band frequency band, the harmonic frequency of the AM/FM capacitive loading element 3 and the AM/FM helical element 5 and the harmonic frequency of the BandIII capacitive loading element 8 and the BandIII helical element 10 are used. At least one of and is preferably not present in the L-Band frequency band.

(Shape of Band III capacitive loading element 8)
FIG. 6 is a perspective view of the Band III capacitive loading element 8 of FIG. 3 as viewed from the left front side. FIG. 7 is a perspective view seen from the right rear side. The Band III capacitive loading element 8 is preferably made of one sheet metal part and is erected on the metal base 19. The BandIII capacitive loading element 8 has a standing portion 8a as a first portion and a top portion 8b as a second portion. The upright portion 8a is preferably a plane perpendicular to the metal base 19 and not parallel to the left and right side surfaces of the AM/FM capacitance loading element 3. By making the standing portion 8a non-parallel to the left and right side surfaces of the AM/FM capacitance loading element 3, the standing portion 8a and the left and right side surfaces of the AM/FM capacitance loading element 3 should have the same longitudinal separation distance. For example, the coupling between the Band III capacitance loading element 8 and the AM/FM capacitance loading element 3 is relaxed as compared with the case where the right and left side surfaces of the upright portion 8a and the AM/FM capacitance loading element 3 are parallel. The upright portion 8a preferably has a shape in which the height with respect to the metal base 19 increases from the front to the rear, and is, for example, a triangle. The top portion 8b is a plane facing the AM/FM amplifier board 14 (facing the metal base 19 and the resin base 20), and is bent (bent) from the upper end of the standing portion 8a (the side opposite to the metal base 19). It is a part. The upper edge of the standing portion 8a (the edge on the opposite side of the metal base 19) and the left edge of the top portion 8b are in contact with each other. The top portion 8b has a smaller angle with respect to the metal base 19 than the standing portion 8a. The right edge of the top portion 8b is the outer edge of the Band III capacitive loading element 8. The height of the Band III capacitive loading element 8 is, for example, 70 mm or less, and the lateral width dimension of the top portion 8b is, for example, 2 to 15 mm. The size and shape of the Band III capacitive loading element 8 are set so that the capacitance value is, for example, 2 to 4 pF.

FIG. 8 shows the relationship between the frequency in the Band III band and the average gain in each of the antenna device 1 in which the BandIII capacitance loading element 8 has the top portion 8b and the antenna device in which the BandIII capacitance loading element 8 does not have the top portion 8b. It is a characteristic diagram by simulation shown. As shown in FIG. 8, in the antenna device 1, since the BandIII capacitive loading element 8 has the top portion 8b, the area of the BandIII capacitive loading element 8 becomes larger than that in the case where the BandIII capacitive loading element 8 does not have the top portion 8b. The average gain of the band is improved.

FIG. 9 shows an antenna device in which the BandIII capacitive loading element 8 is erected on the metal base 19 and has an additional erected portion connected to the opposite side of the erected portion 8a of the top portion 8b, and the additional erected portion. It is a characteristic view by simulation showing the relationship between the frequency and the average gain in the Band III band in each of the antenna device 1 and the antenna device 1. As shown in FIG. 9, when the BandIII capacitive loading element 8 has the additional standing portion, the average gain in the BandIII frequency band is improved as compared with the case where the additional standing portion is not provided. This is because the area of the Band III capacitance loading element 8 is increased due to the configuration in which the additional standing portion is provided. The shape of the Band III capacitive loading element 8 may be any shape as long as it satisfies a design condition such as a capacitance value. However, the average of the FM frequency band is better than the average gain of the Band III frequency band. When priority is given to securing the gain, it is desirable that the Band III capacitance loading element 8 does not have an additional standing portion.

FIG. 10 is a perspective view showing a first modified example of the Band III capacitance loading element 8. In the Band III capacitive loading element 8 of this modification, the top portion 8b of FIG. 6 is replaced with the top portion 8d. The apex portion 8d is different from the apex portion 8b in that it is connected to the standing portion 8a at an intermediate portion in the left-right direction (the central portion in the illustrated example), and is the same in other points.

FIG. 11 shows the relationship between the frequency in the Band III band and the average gain of the antenna device 1 when the Band III capacitive loading element 8 has the top portion 8b (FIG. 6) and when it has the top portion 8d (FIG. 10), It is a characteristic view by simulation. As shown in FIG. 11, the average gain in the Band III frequency band is almost the same when the Band III capacitive loading element 8 has the top portion 8b and when it has the top portion 8d.

FIG. 12 is a characteristic diagram by simulation showing the relationship between the frequency in the FM band and the average gain of the antenna device 1 in the same cases as in FIG. Here, the result in overseas FM frequency band 88MHz-108MHz is shown. As shown in FIG. 12, the average gain in the FM frequency band is almost the same when the Band III capacitive loading element 8 has the top portion 8b and when it has the top portion 8d.

Comparing the band III capacitive loading element 8 of FIG. 6 and FIG. 10, the one of FIG. 6 can be formed by bending a single metal plate. Therefore, from the viewpoint of productivity, the Band III capacitance loading element 8 of FIG. 6 is superior to the Band III capacitance loading element 8 of FIG.

FIG. 13 is a perspective view showing a second modified example of the Band III capacitive loading element 8 as seen from the left front side. FIG. 14 is a perspective view seen from the right rear side. As shown in these figures, the Band III capacitive loading element 8 may be partially or wholly curved so that the angle with respect to the metal base 19 becomes smaller as it goes upward.

(L-Band, BandIII, and AM/FM front-rear positional relationship)
As shown in FIGS. 1 to 3, the L-Band element 16, the Band III capacitance loading element 8, and the AM/FM capacitance loading element 3 are located in this order from the front to the rear of the antenna device 1. Here, from the frequency band with the highest frequency to the L-Band frequency band, the BandIII frequency band, and the AM/FM frequency band, the L-Band element 16 and the BandIII capacitance are arranged in the order of the shortest length (lowest height). It becomes the loading element 8 and the AM/FM capacity loading element 3. That is, the BandIII capacitance loading element 8 needs to be longer than the L-Band element 16, and the AM/FM capacitance loading element 3 needs to be longer than the BandIII capacitance loading element 8. Therefore, by arranging the L-Band element 16, the BandIII capacitance loading element 8, and the AM/FM capacitance loading element 3 from the front in this order as shown in FIGS. As a result, it is possible to prevent the height of the outer case 2 having a shape increasing from the front to the rear in the vertical direction from increasing. In addition, the L-Band element 16, the BandIII capacitance loading element 8, and the AM/FM capacitance loading element 3 are arranged in the ascending order of the inductance required to resonate (the order in which the area required to configure the inductance is small). Therefore, by arranging the L-Band element 16, the BandIII capacitance loading element 8, and the AM/FM capacitance loading element 3 in this order from the front, it is possible to prevent the height of the outer case 2 in the vertical direction from increasing. ..

In FIG. 15, the resonance frequency of the BandIII capacitive loading element 8 and the BandIII helical element 10 is the FM frequency band, and the resonance frequency band of the AM/FM capacitive loading element 3 and the AM/FM helical element 5 is the BandIII frequency band. It is a characteristic view by simulation which shows the relationship between the frequency of an FM band, and the average gain in each of the antenna device which exchanged and the antenna device 1 which does not exchange frequency. The frequencies were exchanged by adjusting the inductance values of the Band III helical element 10 and the AM/FM helical element 5 without changing the shapes of the Band III capacitive loading element 8 and the AM/FM capacitive loading element 3. As shown in FIG. 15, when the frequencies are exchanged, the average gain in the FM frequency band is significantly reduced. This is because the height of the capacitance loading element becomes low and the area becomes small. Therefore, it is desirable that the Band III capacitance loading element 8 and the AM/FM capacitance loading element 3 are located in this order from the front. Even if the resonance frequency band of the L-Band element 16 is set to the FM frequency band or the Band III frequency band, the same is true. Therefore, the L-Band element 16, the Band III capacity loading element 8, and the AM/FM capacity loading element 3 are located in this order from the front. Is desirable.

FIG. 16 is a simplified left side view of the antenna device 1 in which the Band III capacitance loading element 8 and the AM/FM capacitance loading element 3 have substantially the same shapes as those in FIG. FIG. 17 is a simplified left side view of the antenna device in which the lower rear portion of the BandIII capacitive loading element 8 is extended rearward and inserted into the AM/FM capacitive loading element 3 existing range in the front-rear direction as compared with FIG. .. The trailing edge of the BandIII capacitive loading element 8 is inclined so that it goes backward as it goes downward. The configurations of FIG. 16 and FIG. 17 are the same as each other except that the shape of the rear portion of the Band III capacitance loading element 8 is different.

FIG. 18 shows an antenna device 1 (BandIII capacitive loading device 8 without rearward extension (FIG. 16)) in which the band III capacitive loading device 8 and the AM/FM capacitive loading device 3 do not overlap in the front-back direction existence range (BandIII capacitive loading device 8). FIG. 18 is a characteristic diagram by simulation showing the relationship between the frequency in the FM band and the average gain in each of the cases where the capacitive loading element 8 is extended backward (FIG. 17)). Although extending the rear lower part of the Band III capacitive loading element 8 rearward to enter the AM/FM capacitive loading element 3 within the existence range of the AM/FM capacitive loading element 3 has the effect of increasing the area of the Band III capacitive loading element 8. As shown in (4), it causes a decrease in the average gain in the FM frequency band. Therefore, it is desirable that the AM/FM capacitance loading element 3 and the Band III capacitance loading element 8 do not overlap in the existing range in the front-rear direction. Since the same applies to the L-Band element 16 and the Band III capacitance loading element 8, it is desirable that the L-Band element 16 and the Band III capacitance loading element 8 do not overlap in the existing range in the front-rear direction.

(Shapes of Band III capacitive loading element 8 and AM/FM capacitive loading element 3)
FIG. 19 is a simplified left side view of the antenna device 1 in which the lower front portion of the AM/FM capacity loading element 3 is obliquely cut as compared with FIG. 16 (AM/FM capacity loading element 3 lower cut). The diagonal cut direction in FIG. 19 is a direction in which the front edge of the AM/FM capacitance loading element 3 goes backward as it goes downward. 20 is a simplified left side view of the antenna device 1 in which the lower rear portion of the Band III capacitive loading element 8 is obliquely cut as compared with FIG. 16 (Band III capacitive loading element 8 lower cut). The diagonal cut direction in FIG. 20 is a direction in which the trailing edge of the Band III capacitance loading element 8 goes forward as it goes downward. FIG. 21 is a simplified left side view of the antenna device 1 in which the AM/FM capacity loading element 3 has the same shape as FIG. 19 and the Band III capacity loading element 8 has the same shape as FIG. 20 (both lower cut).

FIG. 22 is a characteristic diagram by simulation showing the relationship between the frequency in the FM band and the average gain in each of the antenna devices 1 of FIGS. 16 and 19 to 21. As shown in FIG. 22, at least one of the lower front portion of the AM/FM capacitance loading element 3 and the lower rear portion of the Band III capacitance loading element 8 is obliquely cut to lower the AM/FM capacitance loading element 3 and the Band III capacitance loading element 3. The average gain in the FM frequency band can be improved by lengthening the distance between the lower portion of the element 8 and the front-back direction. As shown in FIG. 22, when both the lower front portion of the AM/FM capacitive loading element 3 and the lower portion in the direction of the Band III capacitive loading element 8 are obliquely cut, the lower portion of the AM/FM capacitive loading element 3 and the lower portion of the Band III capacitive loading element 8 are cut. Since the distance between and in the front-back direction is the longest, the average gain in the FM frequency band can be improved most.

FIG. 23 is a simplified left side view of the antenna device in which the upper front portion of the AM/FM capacitance loading element 3 is obliquely cut as compared with FIG. The diagonal cut direction in FIG. 23 is a direction in which the front edge of the AM/FM capacitance loading element 3 goes backward as it goes upward. 24 shows the frequency of the FM band in each of the antenna device 1 of FIG. 16 (without AM/FM capacity loading element 3 front upper cut) and the antenna device of FIG. 23 (with AM/FM capacity loading element 3 front upper cut). It is a characteristic diagram by simulation showing the relationship between the average gain. As shown in FIG. 24, when the front upper part of the AM/FM capacity loading element 3 is obliquely cut to increase the front-back distance between the upper part of the AM/FM capacity loading element 3 and the upper part of the Band III capacity loading element 8, FM The average gain in the frequency band decreases. Therefore, when cutting the AM/FM capacity loading element 3 and the Band III capacity loading element 8 in order to lengthen the distance in the front-rear direction, it is preferable to cut the lower part rather than the upper part.

According to this embodiment, the following effects can be obtained.

(1) Since the Band III capacitive loading element 8 has the top portion 8b or the top portion 8d, the area of the Band III capacitive loading element 8 should be increased at the same height as compared with the case where the top portion 8b and the top portion 8d are not provided. The average gain in the Band III frequency band of the antenna device 1 can be improved (FIGS. 8 and 11).

(2) The BandIII capacitive loading element 8 is erected on the metal base 19 and is connected to the opposite side of the erected portion 8a of the top portion 8b (an additional erected portion (in the same height range as the erected portion 8a) is erected). In the case of having an additional standing portion (capacity loading portion) connected to the right edge of the top portion 8b so as to face the installation portion 8a, compared to the case without the additional standing portion, the BandIII capacity loading element 8 Since the area becomes large, the average gain in the Band III frequency band can be improved (FIG. 9).

(3) The productivity of the Band III capacitive loading element 8 is higher than that in the case where the Band III capacitive loading element 8 is one sheet metal component having the top portion 8b (FIG. 6) and not one sheet metal component (FIG. 10).

(4) Since the L-Band element 16, the BandIII capacity loading element 8, and the AM/FM capacity loading element 3 are located in this order from the front to the back of the antenna device 1 (the third antenna, Since the two antennas and the first antenna are located in this order), it is possible to reduce the antenna gain and reduce the size (height).

(5) Since the band III capacitive loading element 8 and the AM/FM capacitive loading element 3 do not overlap in the front-back direction existence range (the front-back direction existence ranges of the first and second antennas do not overlap), The decrease in average gain can be suppressed (FIG. 18). Similarly, since the band III capacitive loading element 8 and the L-Band element 16 do not overlap in the front-back direction existence range (the front-back direction existence ranges of the second and third antennas do not overlap), the average gain of the BandIII frequency band of the antenna device 1 is obtained. Can be suppressed.

(6) Since the AM/FM helical element 5 is provided for reception of the AM and FM frequency bands and the Band III helical element 10 is provided for reception of the Band III frequency band, demultiplexing on the circuit is unnecessary. In addition, by adjusting the inductance of the AM/FM helical element 5 and the Band III helical element 10, it is possible to prevent an integer multiple of one resonance frequency from entering the other resonance frequency band, which is advantageous for high sensitivity.

(7) According to the LC circuit shown in FIG. 25, the coupling between the AM/FM capacitance loading element 3 and the Band III capacitance loading element 8 is suppressed, and the average gain drop in the FM frequency band can be suppressed. According to the capacitor C shown in FIG. 26, the coupling between the AM/FM capacitance loading element 3 and the Band III capacitance loading element 8 is suppressed, and the decrease in average gain in the AM and FM frequency bands can be suppressed.

Although the present invention has been described with the embodiment as an example, it will be understood by those skilled in the art that various modifications can be made to each component and each process of the embodiment within the scope of the claims. By the way. Hereinafter, modified examples will be described.

FIG. 27 is a perspective view of an antenna device 1A according to another embodiment of the present invention with the outer case 2 omitted. The antenna device 1A is different from that of the first embodiment in that the shape of the AM/FM capacity loading element 3 is changed to a meandering shape, and the AM/FM capacity loading element 3 is divided into two parts (the top part is separated. Point) and other points are the same. Even when the AM/FM capacitance loading element 3 has a shape as shown in FIG. 27, the same effect as that of the above-described embodiment can be obtained. Further, since the AM/FM capacity loading element 3 of the antenna device 1A is divided into left and right parts and the top has a space, the top of the AM/FM capacity loading element 3 is combined (the top does not have a space). Compared with the case of the configuration), the coupling between the Band III capacitance loading element 8 and the AM/FM capacitance loading element 3 is relaxed.

The Band III capacitance loading element 8, the Band III helical element 10, and the L-Band element 16 may be integrated by, for example, being provided on a single substrate. In this case, a band pass blocking filter (BEF) that blocks a signal in the L-Band frequency band between the portion corresponding to the Band III capacitive loading element 8 and the Band III helical element 10 and the portion corresponding to the L-Band element 16. It is desirable to insert.

When the L-Band frequency band is not used, the L-Band element 16 may be deleted. In this case, the absence of the L-Band element 16 is advantageous for downsizing. Also in this case, it is desirable that the Band III capacity loading element 8 and the AM/FM capacity loading element 3 are located in this order from the front for the above reason.

The LC circuit shown in FIG. 25 or the capacitor C shown in FIG. 26 may be omitted if it is unnecessary in design. Further, other than the LC circuit shown in FIG. 25 or the capacitor C shown in FIG. 26, any configuration may be used as long as it is a filter or the like that passes a signal in the Band III frequency band. The specific numerical values (frequency and angle), shape, and the like shown in the embodiments are merely examples, and can be appropriately changed according to required specifications.

1 Antenna Device, 2 Outer Case (Antenna Case), 3 AM/FM Capacitance Loading Element (First Capacitance Loading Element), 4 Holder, 4a BandIII Element Holding Part, 4b BandIII Substrate Holding Part, 5 AM/FM Helical Element, 6 AM/FM helical element holder, 7 AM/FM connection fitting, 8 BandIII capacity loading element (second capacity loading element), 9 BandIII substrate, 10 BandIII helical element, 11 BandIII helical element holder, 12 BandIII connection fitting, 13 pad, 14 AM/FM amplifier board, 15 AM/FM conductor plate spring, 16 L-Band element, 17 DAB amplifier board, 18 BandIII conductor plate spring, 19 metal base, 20 resin base, 21 seal member, 22 capture fastener, 23 bolt

Claims (6)

A first and a second antenna provided in a common case,
The first antenna has a first capacitive loading element, resonates in a first resonance frequency band,
The second antenna has a second capacitive loading element, and resonates in a second resonance frequency band higher than the first resonance frequency band,
An antenna device in which the second capacitive loading element is located in front of the first capacitive loading element. The antenna device according to claim 1, wherein the first and second capacitive loading elements do not have overlapping existing ranges in the front-rear direction. A third antenna provided in the common case,
The antenna device according to claim 1 or 2, wherein the third antenna resonates in a third resonance frequency band higher than the second resonance frequency band, and is located in front of the second capacitive loading element. The antenna device according to claim 3, wherein the first and second capacitive loading elements and the third antenna do not have overlapping existing ranges in the front-rear direction. The first antenna has a first helical element between the first capacitive loading element and a first feeding point,
The antenna device according to claim 1, wherein the second antenna includes a second helical element between the second capacitive loading element and a second feeding point. The antenna device according to claim 1, wherein both the first and second capacitive loading elements are sheet metal parts.

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