JP2000183630A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna system that can transmit/receive signals with three frequency bands or over while being resonated, whose antenna characteristic is not deteriorated, even when the system is made small and that obtains a prescribed bandwidth for the desired frequency band. SOLUTION: This antenna system consists of a 1st element section 16, where a loading circuit 12 is interposed in the middle of a helical element 10 and of a 2nd element section 32 whose rod element is placed close to the outside of the 1st element section 16 nearly in parallel and an end of the rod element, of which is capacitively coupled with a feeding point 20 of the 1st element section 16. A parallel resonance frequency of the loading circuit 12 is set to be an intermediate frequency between a 1st frequency band f1 and a 2nd frequency band f2, and the effective length of the 1st element section 16 is set nearly to be 1/4 wavelength with respect to the 1st and 2nd frequency bands f1, f2 respectively. The effective length of the 2nd element section 32 is set to nearly 1/4 to 1/2 wavelength with respect to the 3rd frequency band f3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device capable of transmitting and receiving signals of three or more predetermined frequency bands by resonating.

[0002]

2. Description of the Related Art Domestic TV broadcasts VHF (LOW), VH
In a conventional antenna device for in-vehicle use and for indoor desktop use for transmitting and receiving signals in three frequency bands of F (HIGH) and UHF, a monopole antenna having a physical length of about 1 m is commonly used. It had been. This is the lowest frequency of the three frequency bands, VHF (LO
W) is set to approximately １ ／ wavelength.

[0003]

The conventional antenna device occupies about 1 m and occupies a large space. Further, since the antenna device is long, there is a high risk of breakage such as breakage. It was strongly requested. Therefore, it is conceivable to simply reduce the size of the conventional antenna. However, simply reducing the size of the antenna tends to deteriorate the antenna characteristics such as the gain and the VSWR, and the bandwidth that can be transmitted and received with the predetermined antenna characteristics becomes narrow. However, there has been a problem that a sufficient bandwidth for transmission and reception cannot be secured in a desired frequency band, which has made practical use difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an antenna device which does not deteriorate antenna characteristics even if it is miniaturized and which can obtain a predetermined bandwidth with respect to a desired frequency band. Aim.

[0005]

In order to achieve the above object, an antenna device according to the present invention comprises a first element portion having a loading circuit comprising a parallel resonance circuit of a coil and a capacitor in an intermediate portion of a helical element, A second element portion, which is substantially parallel to the axial direction of the first element portion and is closely coupled to an outer side of the first element portion and capacitively couples a base end of the antenna element portion to a feeding point of the first element portion; The parallel resonance frequency of the loading circuit is set to an intermediate value between the first frequency band and the second frequency band higher than the first frequency band.
The effective length of the element section is set to approximately 1/4 wavelength for each of the first frequency band and the second frequency band, and the physical length of the second element section is set to the physical length of the first element section. And the effective length of the second element section is set to be approximately 1/1/3 of the third frequency band higher than the second frequency band.
The wavelength is set to 4 to 1/2 wavelength.

Also, a first element having a loading circuit comprising a parallel resonance circuit of a coil and a capacitor in an intermediate portion of the helical element, and an antenna element disposed at the axis of the first element or coaxially. A second element unit having a base end capacitively coupled to a feeding point of the first element unit, wherein the parallel resonance frequency of the loading circuit is set to a first frequency band and a second frequency band higher than the first frequency band. And the effective length of the first element section is set to be approximately 1 / l with respect to the first frequency band and the second frequency band, respectively.
The wavelength is set to four wavelengths, the physical length of the second element is shorter than the physical length of the first element,
The effective length of the element portion may be set to be approximately 1/4 to 1/2 wavelength with respect to the third frequency band higher in frequency than the second frequency band.

The physical length of the first element portion is
The wavelength may be set to 1/10 to 1/20 of the first frequency band.

[0008] Further, the antenna element portion may be constituted by a rod-shaped element.

Also, the coil of the loading circuit is
The helical element may be formed coaxially with the same winding diameter as the helical element.

[0010] The capacitive coupling of the second element portion may be configured such that the base end of the antenna element portion is disposed close to the feed point without being electrically connected in a direct current manner.

Further, the first element portion and the second element portion are both elastically deformable, and are made of an insulating resin having elasticity so as to integrally cover the first element portion and the second element portion. The cover may be formed by molding a bar on the book.

Further, the power supply point is provided with a duplexer for splitting a signal of a predetermined frequency band for each band, and an amplifier for amplifying the split and output signal is provided for each. Can also.

[0013]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a configuration diagram of a first embodiment of the antenna device of the present invention. FIG. 2 is a diagram illustrating the operation of the loading circuit. FIG. 3 is an equivalent circuit diagram. FIG. 4 is a VSWR characteristic diagram. FIG.
It is a gain characteristic diagram.

In FIG. 1, a helical element 10 made of a conductive metal wire having elasticity has a winding portion having the same winding diameter and a dense pitch on the same axis to form a coil 10a for a loading circuit 12. , This coil 10a
, Capacitors 14 are electrically connected in parallel. The loading circuit 12 is formed by the parallel resonance circuit of the coil 10a and the capacitor 14. And
The first element section 16 is constituted by the helical element 10 and the loading circuit 12 provided at an intermediate portion thereof.
In addition, a rod-shaped element as an antenna element portion 18 made of a conductive metal wire having elasticity is disposed near the outside of the helical element 10 and substantially parallel to the axial direction. The base end of the antenna element portion 18 is slightly separated from the feeding point 20 of the first element portion 16, is disposed close to the direct current electrically connected without being electrically connected, and is capacitively coupled by the stray capacitance 28. Then, a coaxial cable 22 is connected to the feeding point 20.
Is electrically connected to the outer conductor, and a ground wire 24 is electrically connected to the outer conductor near the feeding point 20. Further, the cover 26 is molded with an insulating resin having elasticity so as to integrally cover the whole of the first element portion 16 and the second element portion 32 so that the outer shape becomes a single rod shape.

The resonance frequency of the loading circuit 12 is, for example, VHF (L
OW) and the second frequency band f2 which is a higher frequency than this.
Is set to an intermediate value with VHF (HIGH). Therefore, as shown in FIG.
Acts as an inductance component on the first frequency band f1 and acts as a capacitance component on the second frequency band f2. As a result, the first element section 16
For the frequency band f1, 1 /
In addition to having an effective length of 4 wavelengths, it can also have an effective length of 1/4 wavelength for the second frequency band f2 due to the capacitance effect, and can resonate together as shown in FIG.

Further, since the antenna element portion 18 of the second element portion 32 is disposed close to the helical element 10, mutual coupling interference may occur and the bandwidth of the second element portion 32 may be reduced. . However, in the present invention, the base end of the antenna element 18 is connected to the feed point 2 by the stray capacitance 28.
Since the capacitance is capacitively coupled to 0, interference can be greatly reduced by the low frequency cutoff effect of the capacitive coupling, and the bandwidth can be maintained. The effective length of the second element section 32 is set to approximately １ ／ to 〜 of UHF as a third frequency band f3 having a higher frequency than the second frequency band f2.
The wavelength can be resonated as shown in FIG.
The physical length of the first element section 16 is, for example, about 2
50 mm. The physical length of the rod-shaped element as the antenna element portion 18 is, for example, 10
0 mm. The interval between the helical element 10 and the antenna element 18 is 5 to 10 mm, which is about 1/100 wavelength of the third frequency band f3. Further, the antenna element 18 forming the stray capacitance 28
The distance between the base end and the feeding point 20 is about 1 to 2 mm.

When the antenna characteristics of the antenna device having such a configuration were measured, as shown in FIG.
W), first frequency band f of VHF (HIGH), UHF
Good VSWR characteristics were exhibited for all of the first, second and third frequency bands f2 and f3. In addition, as shown in FIG. 5, the first frequency band f1, the second frequency band f2,
Good gain and sufficient bandwidth were obtained for any of the frequency bands f3.

By the way, the physical length of the first element section 16 is shortened as much as possible, so that 1/1 of the frequency to be resonated.
If the length is about 10 wavelengths, the antenna characteristics deteriorate. If the length is further reduced to about 1/20 wavelength, the antenna characteristics are significantly deteriorated, which is not practical. Therefore, in the present invention, as shown in FIG. 1, by taking measures such as interposing the loading circuit 12, deterioration of the antenna characteristics is suppressed, and the antenna characteristics are shortened as far as practically possible. Element part 16 is about 250
mm, achieving both the demand for miniaturization and the performance sufficient for practical use.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a configuration diagram of a second embodiment of the antenna device of the present invention. 6, the same or equivalent members as those shown in FIGS. 1 to 5 are denoted by the same reference numerals, and redundant description will be omitted.

In the second embodiment shown in FIG. 6, the antenna element 18 constituting the second element 32 is
The element portion 16 is disposed on the axis of the helical element 10, and the base end thereof is electrically connected to the power supply point 20 via a discrete component capacitor 30. In such a configuration, the outer shape can be made thinner than in the first embodiment, and the shape becomes axially symmetric with respect to the axis. Here, as in the second embodiment, the antenna element 18 is connected to the helical element 10.
In this case, mutual coupling interference easily occurs, and it is difficult to obtain a sufficient bandwidth. Therefore, it is not suitable for a frequency band requiring a wide band such as UHF, but can be used sufficiently for a frequency band having a relatively narrow bandwidth such as a cellular phone. In the second embodiment, capacitive coupling is performed by the discrete component capacitor 30, but it is needless to say that capacitive coupling may be performed by stray capacitance.

The antenna device according to the present invention is configured as described above, but it has VHF (LOW) and VHF (HIG).
H) and UHF are not limited to those applied to the first frequency band f1, the second frequency band f2, and the third frequency band f3, respectively. First, in the AM broadcasting frequency band, even if the conventional monopole antenna of about 1 m does not resonate, and does not resonate as in the present invention, even if the antenna device has a short physical length, the physical length of the antenna device is short. Can be received with a signal strength corresponding to In the FM broadcast frequency band, VHF (LOW) and the frequency band substantially match, and the first frequency band f1 can be shared. And DAB
The frequency band of BAND3 (digital, audio, broadcasting) is almost included in the frequency band of VHF (HIGH), and can share the second frequency band f2. In addition, 800MHz such as cellular phone
The band is close to the UHF frequency band and can share the third frequency band f3. In addition, by setting the bandwidth of the third frequency band f3 to be wide, it is possible to include a 1.5 GHz or 1.9 GHz telephone band. It should be noted that the third frequency band f3 is replaced with UHF, and a 1.5 GHz band or 1.9 GHz band is used.
It is also possible to set a band.

Therefore, the antenna device of the present invention can not only transmit and receive the signals in the three frequency bands described in the embodiment, but also can transmit and receive the signals in the four or more frequency bands by appropriate setting. is there. One example will be described with reference to FIG. In FIG. 7, the feed point 20 of the antenna device of the present invention is electrically connected to a duplexer 48 in which a low-pass filter 40, an FM band-pass filter 42, a DAB BAND3 band-pass filter 44, and a high-pass filter 46 are connected in parallel. Is done. And low-pass filter 4
0 outputs a signal in the AM broadcast frequency band, which is transmitted through the buffer amplifier 50 and the low-pass filter 52 to the AM broadcast frequency band.
/ FM output terminal 54. A signal in the FM broadcast frequency band is output from the FM band-pass filter 42, and is output to the AM / FM output terminal 54 via the FM amplifier 56 and the high-pass filter 58. Also, BA
The ND3 bandpass filter 44 outputs the BAND of DAB.
3 is output, and a BAND3 amplifier 60 is output.
Is output to the BAND3 output terminal 62 via Then, a signal in the L-band frequency band of the DAB is output from the high-pass filter 46 and output to the L-band output terminal 66 via the L-band amplifier 64. In FIG. 7, it goes without saying that a filter for splitting each frequency band by the splitter 48 is appropriately set according to a desired frequency band.

In the above embodiment, the second element 3
The coil element may be used instead of the rod-shaped element for the second antenna element portion 18. In the second embodiment, when a coil element is used as the antenna element section 18, it may be disposed coaxially with the helical element 10. Also, the loading circuit 12
Is not limited to the one composed of discrete components, and may be appropriately configured using a parallel two-wire cable or the like. Furthermore, in the embodiment, the coil 10a of the loading circuit 12 is connected to the helical element 10
Although the winding diameter is the same as that described above, the present invention is not limited to this, and it is a matter of course that the winding diameter may be reduced.

[0024]

As described above, since the antenna device of the present invention is constituted, the following special effects can be obtained.

In the antenna device according to the first aspect,
Since signals in three frequency bands can be transmitted and received while resonating, and their physical length can be shortened, they are suitable as a multi-frequency antenna for in-vehicle use or indoor desktop use. In particular, the bandwidth of the third frequency band having the highest frequency can be widened, which is suitable for receiving UHF requiring a wide band.

In the antenna device according to the second aspect, the same effect as that of the first aspect is obtained, and the second element portion is disposed in the helical element of the first element portion.
The outer shape can be made thinner and the appearance is excellent, and there is no direction for elastic deformation. But,
The bandwidth of the third frequency band tends to be narrow due to mutual coupling interference, which is suitable for transmission and reception of signals in a frequency band such as a telephone having a narrow bandwidth.

Since the physical length of the antenna device according to the third aspect is reduced, the antenna device is particularly suitable as a vehicle-mounted antenna device disposed outside the body.

Further, in the antenna device according to the fourth aspect, since the rod-shaped element is used as the antenna element portion, when the rod-shaped element is disposed outside the helical coil, the coil element is used as the antenna element portion. The outer shape of the entire antenna device can be made smaller than that of the antenna device.

In the antenna device according to the fifth aspect, the coil of the loading circuit can be manufactured by changing the pitch and the like on the same helical element with the same winding diameter and coaxially. It is easy to manufacture. In addition, since the components are formed in a series, the number of components can be reduced as compared with the case where components are formed separately.

Further, in the antenna device according to the sixth aspect, since the capacitive coupling at the base end of the antenna element portion is disposed close to the direct current without being electrically connected, a component as a capacitor is required. It is omitted, the number of parts is reduced, and the number of assembling steps is reduced, which is suitable for mass production.

Further, in the antenna device according to the seventh aspect, since the cover is molded so as to integrally cover the whole by molding, the number of assembly steps is small. Moreover, the insulating resin of the cover is also filled in the helical element, so that the strength against bending and the like is increased and the pitch of the helical element does not change,
Antenna characteristics become stable.

In the antenna device according to the eighth aspect, the antenna device of the present invention can be applied as an antenna of a desired number of frequency bands.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of an antenna device of the present invention.

FIG. 2 is a diagram illustrating an operation of a loading circuit.

FIG. 3 is an equivalent circuit diagram.

FIG. 4 is a VSWR characteristic diagram.

FIG. 5 is a gain characteristic diagram.

FIG. 6 is a configuration diagram of a second embodiment of the antenna device of the present invention.

FIG. 7 is a diagram illustrating that signals in a number of frequency bands can be transmitted and received by appropriate setting in the antenna device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Helical element 10a Coil 12 Loading circuit 14, 30 Capacitor 16 1st element part 18 Antenna element part 20 Feeding point 26 Cover 28 Floating capacitance 32 2nd element part 48 Duplexer 50 Buffer amplifier 56 FM amplifier 60 BAND3 amplifier 64 L band Amplifier f1 First frequency band f2 Second frequency band f3 Third frequency band

Claims (8)

[Claims] 1. A first element portion having a loading circuit comprising a parallel resonance circuit of a coil and a capacitor in an intermediate portion of a helical element, and is disposed substantially parallel to the axial direction of the first element portion and close to the outside thereof. A second element formed by capacitively coupling the base end of the antenna element to the feeding point of the first element;
And a parallel resonance frequency of the loading circuit is set to an intermediate value between a first frequency band and a second frequency band higher than the first frequency band, and the effective length of the first element unit is set to the first frequency band. Each of the first and second frequency bands is set to approximately 1/4 wavelength, the physical length of the second element portion is made shorter than the physical length of the first element portion, and the second An antenna device, wherein the effective length of the element section is set to be approximately 1/4 to 1/2 wavelength with respect to a third frequency band higher than the second frequency band. 2. A first element part having a loading circuit comprising a parallel resonance circuit of a coil and a capacitor in an intermediate part of a helical element, and an antenna element part arranged on the axis of the first element part or coaxially. A second element unit having a base end capacitively coupled to a feeding point of the first element unit, wherein the parallel resonance frequency of the loading circuit is set to a first frequency band and a second frequency band higher than the first frequency band. And the effective length of the first element portion is set to approximately １ ／ wavelength with respect to the first frequency band and the second frequency band, respectively, and the physical length of the second element portion is set. And the effective length of the second element portion is set to be approximately 1/4 to 1/2 with respect to the third frequency band having a higher frequency than the second frequency band. The feature is that the wavelength is set. Antenna device. 3. The antenna device according to claim 1, wherein the physical length of the first element portion is set to 1/10 to 1/20 wavelength of the first frequency band. Characteristic antenna device. 4. The antenna device according to claim 1, wherein said antenna element portion is constituted by a rod-shaped element. 5. The antenna device according to claim 1, wherein the coil of the loading circuit is formed coaxially with the same winding diameter as the helical element. 6. The antenna device according to claim 1, wherein the capacitive coupling of the second element portion is arranged close to the base end of the antenna element portion without direct current electrical connection to the feed point. An antenna device characterized by comprising: 7. The antenna device according to claim 1, wherein said first element portion and said second element portion are both elastically deformable, and said first element portion and said second element portion.
An antenna device, wherein a cover is molded into one rod-shaped body with elastic insulating resin so as to integrally cover an element portion. 8. The antenna device according to claim 1, further comprising: a splitter that splits a signal in a predetermined frequency band for each band at the feeding point, and outputs the split signal. An antenna device comprising: an amplifier for amplification;