JP2867205B2 - VHF and UHF common antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
HF high band and UHF band signals can be appropriately received, and small VHF and UHF
It relates to a common HF antenna.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of television receivers,
It is becoming popular to mount this in a car, and there is a demand for a small antenna for receiving television broadcasts.

Therefore, as an example of a conventional antenna,
A monopole antenna or a dipole antenna set to have an effective length appropriate for an appropriate broadcast frequency (for example, VHF high band) of a television broadcast is used. However, television broadcasts use VHF low band (90-108M
Hz), a VHF high band (170 to 222 MHz), and a UHF band (470 to 770 MHz). The antenna has a high antenna gain for one band whose effective length is appropriately set. , But only a low antenna gain is obtained for other bands. Therefore, there is a problem that good reception characteristics cannot be obtained for all three bands.

[0004] Other examples of antennas that solve this problem include VHF low band, VHF high band, and UHF.
There is a type in which three monopole antennas or dipole antennas each having an appropriate effective length are provided for each of the three bands, and the antenna outputs are combined by a combining circuit and supplied to a television receiver.

[0005]

In the case of using three monopole antennas or dipole antennas as described above, in order to obtain good antenna characteristics, the interval between antenna elements must be determined by the frequency to be received. They must be set apart by more than half a wavelength. This is because the reception characteristics are significantly deteriorated even if the effective length is appropriate due to the inter-element interference effect. Therefore, if the distance between the antenna elements is set to be large, the reception characteristics can be satisfied, but the size becomes large, which is unsuitable for use in vehicles.

The present invention has been made in view of the above circumstances, and has been made in consideration of the VHF low band, the VHF high band, and the UH
An object of the present invention is to provide a small VHF and UHF common antenna which can satisfactorily receive any of the F bands.

[0007]

In order to achieve the above object, a VHF and UHF common antenna according to the present invention has a VH
1/4 of the frequency between F low band and VHF high band
In the middle of the main monopole element having a wavelength length, VH
A parallel resonance circuit that resonates at a frequency between the F low band and the VHF high band is interposed in series, and is parallel to the base end of the main monopole element and spaced apart by 1/4 wavelength of the UHF band frequency. A sub-monopole element having a length is provided, a base end of the main monopole element is connected to a center conductor of a coaxial cable, and a base end of the sub-monopole element is connected to a ground conductor and an outer conductor of the coaxial cable. Connected and configured.

A plurality of the main monopole elements are provided so as to be relatively different in arrangement direction, and any one of the received signals respectively obtained by the plurality of antennas is selected by a switching device. May be.

Further, a plurality of antennas may be provided at different positions, and one of the received signals obtained by each of the plurality of antennas may be selected by a switching device.

[0010]

The main monopole element in which a parallel resonance circuit is interposed in the middle portion has resonance points above and below the resonance frequency of the parallel resonance circuit. Therefore, these two resonance points are V
By setting so as to be within the HF low band and the VHF high band, good antenna characteristics can be obtained for the VHF low band and the VHF high band. Also, since the sub-monopole element having a quarter wavelength of the UHF band is disposed parallel to and spaced apart from the base end of the main monopole element, the sub-monopole element and the corresponding main monopole element are arranged. The base end of the pole element acts as a quarter-wave impedance transformer for the UHF band, the output impedance of the main monopole element is low for the UHF band, and the reflection characteristics for the UHF band are improved. The receiving characteristics are improved.

If a plurality of main monopole elements are provided in different arrangement directions, the received signal can be switched as appropriate to act as a directional diversity antenna.

[0012] If a plurality of arrangement positions are provided apart from each other, the reception signals can be appropriately switched to act as a space diversity antenna.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. FIG. 1 shows the VHF and UH of the present invention.
FIG. 2 is a configuration diagram of an F-shared antenna, and FIG.
FIG. 3 is a graph of the frequency versus standing wave ratio of the HF and UHF shared antennas, and FIG. 3 is a configuration diagram of a directional and space diversity antenna using the VHF and UHF shared antennas of FIG.

In FIG. 1, VHF low band and VHF
A main monopole element 10 having a length L ₁ substantially at an intermediate frequency of a high band, for example, about 波長 wavelength of 140 MHz;
, A parallel resonance circuit 12 having a resonance frequency between the VHF low band and the VHF high band, for example, 140 MHz, is interposed in series. The parallel resonance circuit 12 is formed by connecting an inductance element 14 and a capacitance element 16 in parallel. The length of the base end portion of the main monopole element 10 below the parallel resonance circuit 12 is, for example, approximately 波長 wavelength of the substantially center frequency of the UHF band, and the tip end portion above the parallel resonance circuit 12 is For example, it is formed of a telescopic rod antenna.

The base end of the main monopole element 10 has a length L ₂ which is parallel to the main monopole element and spaced apart by a distance D and has a length L ₂ which is about １ ／ wavelength of the center frequency of the UHF band. A pole element 18 is provided.

Further, the base end of the main monopole element 10 is
It is connected to the center conductor 20a of the coaxial cable 20. The base end of the sub-monopole element 18 is connected to the coaxial cable 20.
Of the ground conductor 22
Connected to.

[0017] In such a configuration, acts on inductive parallel resonant circuit 12 to the VHF low-band, the effective length of the main monopole element 10 is longer than the length L _1. Further, the parallel resonance circuit 12 acts capacitively with respect to the VHF high band, and the effective length of the main monopole element 10 is set to the length L _1.
It will be shorter. As a result, the main monopole element 1
0 has two resonance points in the VHF low band and the VHF high band, and good reception characteristics can be obtained for both bands. Here, the sub-monopole element 18 is short for the VHF band and does not significantly affect the antenna characteristics for the VHF band.

The sub-monopole element 18 and the base end of the main monopole element 10 in which the sub-monopole element 18 is parallel to the UHF band function as a quarter-wave impedance transformer. Therefore, by appropriately setting the distance D between the main monopole element 10 and the sub-monopole element 18 and the thickness of these elements, the output impedance at the base end of the main monopole element 10 with respect to the UHF band is sufficient. Is reduced to
Matching with the coaxial cable 20 can be obtained, and good reception characteristics can be obtained for the UHF band. The output impedance of the main monopole element 10 without the sub-monopole element 18 is high with respect to the UHF band. Although the signal cannot be input to the element 20, the metamorphic action of the sub-monopole element 18 reduces the output impedance of the main monopole element 10 to achieve matching, and the reflection characteristics are greatly improved.

FIG. 2 shows the length L ₁ of the main monopole element 10.
Is 450 mm, the cylindrical diameter of the element is 6 mm, the length L ₂ of the sub-monopole element 18 is 110 mm, the cylindrical diameter of the element is 6 mm, and the distance D between the main monopole element 10 and the sub-monopole element 15 is 15 mm. 5 is a graph of the frequency versus standing wave ratio of the VHF and UHF shared antennas of the present invention set in FIG. 5, and a good standing wave ratio is obtained in all three bands of the VHF low band, the VHF high band, and the UHF band. .

If the VHF and UHF antennas of the present invention as described above are mounted on a moving body such as a car, the magnitude of the received signal greatly changes due to the effects of fading and the like as the moving body travels. Easy to do. Therefore, a diversity antenna is used to reduce such fading. FIG. 3 shows a directional and space diversity antenna according to the present invention shown in FIG.
This is configured by using four F shared antennas. VH
F and UHF shared antennas 50, 50, 50, 50
Two pairs are provided, each pair being configured to be relatively swingable at the base end of the antenna, and these two pairs are disposed on the moving body with a distance S therebetween. In addition, four VHF and UHF
The coaxial cables 20, 20, 20, 20 of the common antennas 50, 50, 50, 50 are all connected to a switching device 60, and the switching device 60 causes the respective VHF and U
One of the received signals output from the HF shared antennas 50, 50, 50, 50 is selected and provided to the television receiver.

In this configuration, the VHF and UHF common antennas 50, 50, 50, 50 are swung to appropriately set the _two relative angles θ ₁ , θ ₂ , so that antennas having different directivity directions can be obtained. Act as a combined directional diversity antenna. In addition, the two sets are arranged on the moving body at an interval S, thereby acting as a space diversity antenna.

In the description of the above embodiment, the resonance frequency of the parallel resonance circuit 12 is set to 140 MHz. However, the present invention is not limited to this, and the resonance may be performed at any frequency between the VHF low band and the VHF high band.

[0023]

As described above, since the VHF and UHF antennas of the present invention are constituted, the following special effects are obtained.

In the VHF and UHF shared antenna according to the first aspect, the VHF low band and the VH
Good reception characteristics can be obtained in any of the three bands of the F high band and the UHF band. In addition, the distance between the main monopole element and the sub-monopole element is small, so that a slim and small antenna can be obtained, which is suitable for mobile objects.

The VHF and UHF according to claim 2
The shared antenna acts as a directional diversity antenna, and can reduce fading.

Further, the VHF and UHF shared antenna according to the third aspect functions as a space diversity antenna, and can reduce fading.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a VHF and UHF shared antenna of the present invention.

FIG. 2 is a graph of frequency versus standing wave ratio of the VHF and UHF shared antenna shown in FIG.

FIG. 3 is a configuration diagram of a directivity and space diversity antenna using the VHF and UHF shared antenna of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main monopole element 12 Parallel resonance circuit 18 Submonopole element 20 Coaxial cable 20a Center conductor 20b Outer conductor 22 Ground conductor 50 Common antenna for VHF and UHF 60 Switching device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-181305 (JP, A) JP-A-62-201514 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01Q 5/00-11/20

Claims (3)

(57) [Claims] 1. A parallel resonance circuit that resonates at a frequency between a VHF low band and a VHF high band at an intermediate portion of a main monopole element having a length of 1/4 wavelength of a frequency between a VHF low band and a VHF high band. Are arranged in series, and a sub-monopole element having a length of 1/4 wavelength of the frequency of the UHF band is arranged at a distance in parallel with the base end of the main monopole element, and the main monopole element is provided. VHF and UH wherein a base end of a pole element is connected to a center conductor of a coaxial cable, and a base end of the sub-monopole element is connected to a ground conductor and an outer conductor of the coaxial cable.
F common antenna. 2. A plurality of VHF and UHF common antennas according to claim 1, wherein said main monopole elements are disposed in a relatively different arrangement direction, and one of received signals respectively obtained by said plurality of antennas. A VHF and UHF shared antenna, wherein one is selected by a switching device. 3. A plurality of VHF and UHF antennas according to claim 1 which are arranged at different positions, and one of received signals respectively obtained by the plurality of antennas is selected by a switching device. VH characterized by comprising
F and UHF common antenna.