JP2002368536A - Antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain matching so that broad band characteristics at every antenna are maintained by excluding the interaction between a plurality of antenna elements to the utmost. SOLUTION: The antenna is provided with: two antenna elements 22 and 24 which are arranged in parallel and have a different object frequency band; and a matching circuit 25 for matching the antenna elements after securing isolation between the two antenna elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device having a plurality of antenna elements mounted thereon and installed on, for example, a roof of a vehicle.

[0002]

2. Description of the Related Art Recently, a PDC (Personal Di) has been developed.
digital cellular) or CDMA (Co
de Division Multiple Access
ss: code division multiple access) system, PHS (Person)
2. Description of the Related Art Various types of mobile phones such as an al Handyphone System (simplified mobile phone system) are widely and widely used, and among them, it is possible to select one of two systems such as a PDC system and a PHS system for making a call. Some of them are compatible with multiple methods.

In a mobile phone of this type which can use a plurality of systems, a target frequency band differs for each system, so that a plurality of antennas corresponding to each system must be prepared.

However, when a portable telephone compatible with such a plurality of systems is used in a vehicle such as a passenger car, it is generally used such that the portable telephone is installed on, for example, a roof of the vehicle and connected to the portable telephone. A plurality of external antennas must be prepared for each system.

[0005] However, in vehicles such as passenger cars, GPS (Global Position) for FM radio, AM radio, and navigation devices, in addition to mobile phones.
(Singing System: Global Positioning System) An antenna is required for each receiver and the like, and it is desirable that the number of antennas to be installed be as small as possible.

Therefore, a common antenna device corresponding to two frequency bands is considered. It is considered that the antenna device basically has a configuration as shown in FIG.

FIG. 1 exemplifies an element configuration of such an antenna device. Here, a first antenna element 12 of, for example, 1.8 [GHz] band for a first frequency band is provided at a feeding point 11. Connected to the first antenna element 12 as a second frequency band, for example, 900 [MHz].
The second antenna element 14 for the same frequency band is connected via the choke coil 13 of the band.

As described above, the two antenna elements 12 and 14 having different target frequency bands are connected to the choke coil 13.
It is configured to be connected in series while separating via
The effective antenna element length in the 1.8 [GHz] band is the length L1 of the first antenna element 12 itself, and the effective antenna element length in the 900 [MHz] band is the first antenna element 12, the choke coil 13, and the second antenna element. Is set to have a length L2 obtained by combining the antenna elements 14 of FIG.

[0009]

However, the two antenna elements 12 and 14 connected in series cannot be completely separated from each other by the choke coil 13, and actually, the two antenna elements 12 and 14 cannot be separated. Will affect each other.

[0010] To prevent such interference between antennas, matching may be considered. However, it is extremely difficult to perform a design in which mutual effects are completely taken into consideration, and a matching circuit is required at the output of the antenna. However, it is difficult to achieve accurate matching due to the frequency relationship between the antenna elements.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to minimize the influence between a plurality of antenna elements and to perform matching so that each antenna has a wide band characteristic. An object of the present invention is to provide an antenna device that can be used.

[0012]

According to the first aspect of the present invention,
It is characterized by comprising a plurality of antenna elements arranged in parallel and having different target frequency bands, and a matching circuit for matching the antenna elements after isolating the plurality of antenna elements.

With this configuration, it is possible to completely eliminate the influence between a plurality of antenna elements and to easily perform matching over a wide band for each antenna.

According to a second aspect of the present invention, in the first aspect of the present invention, at least one of the plurality of antenna elements having a shorter element length and the matching circuit are included, and the other antenna elements It is characterized by further comprising an antenna casing made of a dielectric, which is provided with an element.

According to this structure, in addition to the operation of the first aspect of the present invention, installation and handling are facilitated by having an antenna casing which includes an antenna element having a short element length and a matching circuit. Not only that, the antenna casing itself made of a dielectric material can be used as a part of the antenna element by forming the antenna casing itself into a shape that matches the antenna element, thereby reducing the size of the antenna element and the antenna casing. Can contribute.

According to a third aspect of the present invention, in the second aspect, the antenna element contained in the antenna casing is top-loaded.

With such a configuration, in addition to the effect of the invention described in claim 2, the antenna casing can be made smaller and smaller.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic element configuration of an antenna device. A first antenna element 22 of, for example, 1.8 [GHz] band for a first frequency band is provided at a first feeding point 21. On the other hand, a second antenna element 24 of, for example, 900 [MHz] band is connected to the second feeding point 23 for the second frequency band, and a matching circuit 25 is connected to each of the feeding points 21 and 23. Connected.

The matching circuit 25 is configured to perform isolation using an isolator between the antenna elements 22 and 24 connected in parallel and to perform matching independently for each element. In each of the antenna elements 22,
The output from 24 is sent to a tuner (not shown).

FIGS. 2 and 3 show frequency characteristics obtained by the antenna device having the configuration shown in FIG.

FIG. 2 shows frequency characteristics of the first antenna element 22 in a range from 1.7 [GHz] to 1.9 [GHz] centering on 1.8 [GHz]. 2 (1) is a Smith chart, and FIG. 2 (2) is a corresponding VSWR. As shown in the figure, the VSWR is set to 2.0 or less over the entire frequency band described above, and it can be seen that the band can be widened.

On the other hand, FIG. 3 shows 800 [M] centered on 900 [MHz] in the second antenna element 24.
Hz] to 1000 [MHz] (= 1.0 [GHz])
FIG. 3A shows a Smith chart, and FIG. 3B shows a corresponding VSWR.
It is. As shown in the figure, about 840 [MHz] to 10
It can be seen that the VSWR is set to 2.0 or less over 00 [MHz], and broadband can be generally realized.

Next, a mounting example of the vehicle roof antenna device according to the present embodiment will be described with reference to FIG. The figure shows an antenna body 31 installed and fixed on the roof of a vehicle.
FIG. 4 (1) is a top view of the antenna body 31, and FIG. 4 (2) is a top view of the antenna body 31 and the antenna mast 32 mounted on the antenna body 31. It is a side view of the mast 32, and is attached with the left direction in the figure facing the front of the vehicle.

Here, a 1.8 GHz band DCS1800 (Digital) is used as an antenna of a portable telephone.
Cellular System 1800) and 90
0 [MHz] band GSM (Global System)
for Mobile communication
n) In addition to having two antenna elements, 1.5
It is assumed that a total of five antenna elements of a 7542 [GHz] navigation GPS antenna element, an AM radio antenna element, and an FM radio antenna element are provided.

Thus, the antenna body 31 is constructed by disposing an antenna cover 34 made of a dielectric material such as ABS resin on the rubber pad 33 on the bottom surface.

A bolt 35 for mounting and fixing the antenna body 31 to the vehicle roof is formed on a lower surface of the rubber pad 33 which is in contact with the vehicle roof, and various conductors 36 to 39 are led out from the bolt 35. You.

The power supply plug 40, radio jack 41, telephone plug 42, and G
A PS plug 43 is connected. The power plug 40 is connected to a power supply device (not shown), and the radio jack 41 is connected to the same AM / FM.
The radio, the telephone plug 42 is connected to the mobile phone, and the GPS plug 43 is connected to the GPS unit.

The rubber pad 33 and the antenna cover 34
In addition to the matching circuit 25 shown in FIG. 1, a GPS antenna 44 and a D
A CS1800 antenna 45 is provided.

Of these, the antenna 45 for the DCS1800
Is about 40 when the effective antenna length is λ / 4 (λ = wavelength).
In order to minimize the height of the antenna cover 34 as a housing while maximizing the antenna length of [mm], the antenna height is about 15 [mm] by top loading.

In addition to this point, the inner cover of the antenna cover 34 made of a dielectric material is formed so as to fit the top loading portion of the antenna 45 for the DCS1800 so as to be fitted therein. By using the confronting portion 34 as a part of the antenna element, the size of the antenna 45 for the DCS1800 can be further reduced while obtaining sufficient radiation characteristics, thereby reducing the size of the antenna cover 34 itself. Has contributed.

On the other hand, the antenna mast 32 mounted on the antenna cover 34 constituting the antenna body 31 as shown by an arrow A includes the GSM antenna 47, the AM radio antenna 48, and the FM radio antenna 49. The antenna elements are arranged in parallel and externally connected as a single antenna rod, and their effective antenna lengths are indicated by L11 to L13 as shown in FIG. And

In a matching circuit (not shown) provided in the antenna cover 34, the GPS antenna 44 and the DC
Antenna 45 for S1800, Antenna 47 for GSM, A
M radio antenna 48 and FM radio antenna 4
Nine nine antenna elements having different target frequency bands are arranged in parallel, isolation between the elements is taken, and the matching point is appropriately adjusted for each. As a result, mutual influence between antennas is completely eliminated, and matching can be easily achieved over a wide band for each antenna.

In addition, the present invention is not limited to the above-described embodiment, and can be variously modified and implemented without departing from the gist thereof.

Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiments, at least one of the problems described in the column of the problem to be solved by the invention can be solved and the effects described in the column of the effect of the invention can be solved. In a case where at least one of the effects described above is obtained, a configuration in which this component is deleted can be extracted as an invention.

[0036]

According to the first aspect of the present invention, it is possible to completely eliminate the influence between a plurality of antenna elements and to easily achieve matching over a wide band for each antenna.

According to the second aspect of the present invention, in addition to the effects of the first aspect of the present invention, installation and handling are provided by having an antenna casing which includes an antenna element having a short element length and a matching circuit. Not only makes it easier
By forming the antenna casing itself made of a dielectric material into a shape conforming to the antenna element that contains the antenna casing, the antenna casing can be used as a part of the antenna element, thereby contributing to downsizing of the antenna element and the antenna casing.

According to the third aspect, in addition to the effect of the second aspect, the antenna casing can be made smaller and smaller.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic element configuration of an antenna device according to one embodiment of the present invention.

FIG. 2 is a diagram showing frequency characteristics of the first antenna element according to the embodiment.

FIG. 3 is a diagram showing frequency characteristics of a second antenna element according to the embodiment.

FIG. 4 is a diagram showing a mounting example of the vehicle roof antenna device according to the embodiment;

FIG. 5 is a diagram illustrating a configuration example of a shared antenna device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Feeding point 12 ... 1st antenna element 13 ... Choke coil 14 ... 2nd antenna element 21 ... 1st feeding point 22 ... 1st antenna element 23 ... 2nd feeding point 24 ... 2nd antenna element Reference Signs List 25 matching circuit 31 antenna body 32 antenna mast 33 rubber pad 34 antenna cover 35 bolts 36 to 39 lead wire 40 power plug 41 radio jack 42 telephone plug 43 GPS plug 44 GPS antenna 45 DCS1800 Antenna for 47 47 Antenna for GSM 48 Antenna for AM radio 49 Antenna for FM radio

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5J021 AA13 AB02 CA04 CA06 FA32 HA05 HA10 JA03 5J046 AA02 AA07 AB06 MA09 RA03

Claims (3)

[Claims] A plurality of antenna elements arranged in parallel and having different target frequency bands, and a matching circuit for matching each antenna element after isolating the plurality of antenna elements. An antenna device characterized by the above-mentioned. 2. An antenna casing comprising at least one antenna element having a shorter element length and a matching circuit among the plurality of antenna elements, and further comprising a dielectric material, wherein the antenna casing is provided with other antenna elements. The antenna device according to claim 1, wherein: 3. The antenna device according to claim 2, wherein the antenna element contained in the antenna casing is top-loaded.