JPH0221766Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a TV antenna for mobile objects used when a person riding in a moving object such as a train, a ship, a passenger car, or a car such as a bus tries to receive television. It is related to.

In a conventional antenna, a plurality of independent antennas each consisting of a radiator and a reflecting wall are installed around a central mast having an annular planar shape so that each radiator is located on the outer periphery. (for example, see Japanese Patent Publication No. 38-20009), the drawback is that increasing the length of the reflector in the direction perpendicular to the local direction increases bulk, reduces the number of antennas, and reduces omnidirectional performance. It was hot. On the other hand, if the length of the reflector is shortened, the bulk of the antenna can be reduced or the number of antennas can be increased, but this has the disadvantage that low band reception cannot be achieved.

Therefore, the present invention involves distributing the four radiators equally at 90 degrees, arranging the four support rods in a cross shape on their inner periphery, and aligning the axis of each support rod with the center feeder of each radiator. Correspond to the box position,
Furthermore, one end of each of the four support rods is connected to the radiator via a power supply box, and each other end (cruciform intersection) is electrically connected, thereby forming a support structure for the four radiators. In addition to functioning as a low-band reflector for each of the four radiators. The purpose of this is to be able to capture the target TV radio waves regardless of whether the moving object is facing east, west, south, or north, and to be able to capture the target TV radio waves even if the moving object is facing in the east, west, south, or north direction, and even if the moving object has such a function, the overall shape It is an object of the present invention to provide a television antenna for a mobile body which can be miniaturized, can capture the television radio waves with high sensitivity, and can keep the product price relatively low.

The drawings showing the embodiments of the present application will be described below. In FIGS. 1 to 3, reference numeral 1 indicates a bus as an example of a moving body, 2 indicates the roof of the bus, and 3 indicates a television antenna for the mobile body installed on the roof 2, respectively. In the antenna 3, 4a, 4b, 4c, and 4d are support rods, each made of a material with good conductivity and corrosion resistance, such as aluminum or stainless steel.
Further, each of them consists of a lying part 5 lying in a substantially horizontal state and an upright part 6, and is fixed to the roof 2 by a support 7. Also, these support rods 4a, 4
As clearly shown in FIG. 3, the elements b, 4c and 4d are arranged in a cross-shape as a whole by being oriented in directions different from each other by 90 degrees in the horizontal plane. The attached numbers a, b, c, and d are added to distinguish the four support rods from each other, and if there is no need to distinguish them in the specification and drawings, the attached numbers may be omitted. explain.
This also applies to the radiator and high-band reflector described later. Reference numeral 8 denotes a connector which electrically and mechanically connects the four support rods 4 together in a cross shape. 9a, 9b, 9c, and 9d are radiators, which include a power supply box 10 made of synthetic resin material and a radiator element 1 whose base is attached to the power supply box 10, similar to the radiators in well-known antennas.
It consists of 1. The power feeding box has the same structure as that of a well-known antenna, and serves as a fixture for mounting the radiator 9 on the upright portion 6 of the support rod 4. The mounting state is such that the local axis of each of the radiators 9a to 9d is in the same direction as the longitudinal direction of each recumbent portion 5 of the support rods 4a to 4d, respectively.
Therefore, the local directions of each of the radiators 9a to 9d differ from the local directions of adjacent radiators by 90° in the plane. Further, although a folded dipole is used as the radiating element 11 as an example, other configurations that are well-known or known in this type of antenna may be used. Reference numeral 12 denotes a power supply line, for example a coaxial cable, which is connected to the power supply section of the radiating element 11 in the power supply box 10 via a matching box 30 as shown in FIG. Note that the matching box 30 may be omitted if a power supply line having an impedance equal to the impedance of the power supply section of the radiating element 11 is used. 13 is a connector, and each radiating element 11
The free ends 11' of the two are mechanically connected to each other to obtain strength. Reference numeral 14 denotes a high-band reflector, which is fixed to the recumbent portion 5 of the support rod 4 by means similar to those used in well-known antennas. Next, in FIGS. 4 and 5 showing the support body 7 in detail, reference numeral 16 denotes a mounting base which can be fixed to the roof 2 with a set screw not shown. Reference numeral 17 is a standing rod fixed to the base 16, and its fixed state is reinforced by a reinforcing piece 18. Reference numeral 19 denotes a fastening device, which consists of two fastening elements 20, 20 of the same type, and these elements 20, 20 allow the support rod 4 to be fixed.
The supporting rod 4 is fixed to the upright rod 17 by sandwiching the recumbent portion 5 and the upper end of the upright rod 17 and further tightening bolts 21 and nuts 22. Note that 23 is an insulating tube interposed between the horizontal portion 5 of the support rod 4 and the fastening elements 20, 20, and 24 is an insulating collar that is attached to the bolt 21 at the portion where the bolt 21 penetrates the horizontal portion 5. in,
These are provided so as to cut off electrical continuity between the lying part 5 and the upright rod 17. For example, these are
It is formed using synthetic resin such as ABS resin.
Further, when the vertical rod 17 is made of an insulating material or other means for cutting off electrical continuity between the supporting rod 4 and the roof 2 is provided, the insulating cylinder 23 and the collar 2
4 may be omitted.

Next, in FIG. 6 showing the connector 13 in detail,
26, 26 are connecting elements made of insulating material such as ABS.
It is formed using a synthetic resin material such as resin.
These elements 26, 26 are joined to each other with the free ends 11' of the radiating elements 11 fitted into their recesses 26a, and the adjacent radiating elements 11 are tightened by tightening the screws 27 and nuts 28. The free ends 11' are mechanically connected to each other.

Next, in FIG. 7 showing the circuit connection of the above-mentioned antenna, 31 is a changeover switch, which is provided inside the bus 1, and connects each changeover terminal 31a to 31d to each radiator 9a to 9d, respectively, through a feed line 12. The common terminal 31e is connected to a television set provided inside the bus 1 via a power supply line 32.

With the above configuration, when the user wants to watch television inside the bus 1, the switch 31 is switched to the terminal 31a when the television radio waves arrive from the direction of arrow A in FIG. Then, the radiator 9a becomes connected to the television receiver. Therefore, in this state, the support rods 4b and 4d act as low-band reflectors and the reflector 14a acts as a high-band reflector for the radiator 9a, making it possible to receive TV radio waves from the direction of arrow A with good sensitivity. can. If the traveling direction of the bus 1 changes and the TV radio waves come from the arrow B direction, C direction, or D direction, the changeover switch 31 can be switched to the changeover terminals 31b, 31c, and 31d in sequence. good. Furthermore, when the direction of arrival of the radio wave is in the middle direction as shown by arrow E, the user may change the switch 31 while looking at the screen of the receiver to obtain the best screen.

Next, FIGS. 8 and 9 show the results of actual measurements of the directivity characteristics of the antenna having the above configuration, with one radiator (for example, 9a) in operation. Figure 8 shows the second part of the low band.
FIG. 9 shows the directivity characteristics of the sixth channel of the high band. In addition, the dimensions of each part of the antenna are circular diameter of 1700 mm (half wavelength of the lowest frequency of low band 90 MHz),
The length of the high band reflector 14 is 900 mm (half wavelength of the lowest frequency of the high band, 170 MHz)
It is.

Although the antenna described above is designed for all bands, the reflector 14 for high bands can be omitted if it is used exclusively for low bands. Further, in the case of a high band only, the reflector 14 may be omitted and the dimensions of each part may be designed for the high band. The dimensions of each part are as follows: Regardless of high band or low band, if the wavelength of the TV radio wave to be received is λ, the length of the lying part 5 of the support rod 4 is 0.27λ,
The length of the radiating element 11 in one radiator 9 is set to be a little less than four equal parts of the circumference with a radius of 0.27λ.

Next, FIGS. 10 and 11 show different embodiments of the present invention, and show a state in which the antenna having the above structure is formed into a two-stage stack and is mounted on a mast 33. The base of each support rod 4f is fixed to an annular fastener 34, and the fastener 34
is fixed to the mast 33 by known means.
Further, the signals from both antennas are mixed by a mixer 35. Furthermore, the spacing between the two antennas is the same as in the case of stacking ordinary antennas (for example, 1 to 1.5 m).

In this embodiment, parts that are functionally the same or equivalent to those in the previous embodiment are given the same reference numerals as in the previous embodiment with an alphanumeric letter "f", and redundant explanations are omitted.

As described above, in this invention, the four radiators 9 are arranged in a circular shape in which the local direction of each radiator 9 differs by 90 degrees in the plane from the local direction of the adjacent radiator. Therefore, when this is installed on a moving object such as a bus or ship to receive television, it is possible to receive television waves from any of the four directions around the moving object. This has the advantage that stable television reception can be achieved regardless of whether the TV is facing east, west, south, or north due to roads or shipping routes.

Moreover, in the present invention, since the four radiators 9 are arranged as described above, in order to support them, a support rod is placed inside the four radiators 9 arranged in a circular shape. 4 can be arranged to support those radiators 9. This means that the radiator 9, which is required to have a certain size due to the wavelength of the TV radio waves to be received, can be placed on the outermost side where it can have the longest dimension, and the planar installation of the antenna as a whole is This has the effect of reducing the area to the minimum necessary size, and this has the advantage of being usable in that it can also be installed on a relatively small moving body.

Furthermore, in the present invention, the four radiators 9 are arranged in a circular shape as a whole with the local direction different from the adjacent radiators by 90 degrees as described above, and each radiator 9 is arranged in a circle inside them. The four support rods 4 supporting the respective radiators 9 are arranged on the local axis of each radiator 9 to have a cross-shaped planar shape, and are electrically connected at the center. On the radiator side, there is a power supply box 1 for each radiating element 11.
are connected in an electrically insulated state with 0 interposed therebetween,
These cross-shaped support rods 4 of course serve as supports themselves, but the two support rods 4a and 4c and 4d and 4b on each coaxial line each serve as a long reflector. It has the feature that each of the four radiators 9, 9, 9, 9 acts as a low band reflector.

Four support rods 4 arranged in a cross shape like this
a, 4b, 4c, and 4d not only serve as support rods, but also serve as long-dimension low-band reflectors at the maximum dimension within the circle surrounded by the four radiators 9a, 9b, 9c, and 9d. Four radiators 9a, 9b, 9c, 9d
has the advantage of not only being unaffected by the two radiators on both sides, but also being completely electrically separated from the radiators on the opposite side, resulting in excellent low-band reception characteristics. Moreover, the overall shape consists of two low-band antennas 4a, 4c and 4d, each having a long dimension.
and 4b, they are four radiators 9
It has the advantage that it fits within the circular area surrounded by a, 9b, 9c, and 9d, and the overall planar shape is small. On top of that are four support rods 4a, 4b, 4c, 4
The number of parts can be reduced by the fact that d has two long-dimension low-band antennas 4a and 4c and 4d and 4b, which is effective in reducing costs.

[Brief explanation of drawings]

The drawings show an embodiment of the present application, and FIG. 1 is a front view showing how the antenna is installed on a moving object;
Fig. 2 is a perspective view of the same, Fig. 3 is a plan view, Fig. 4 is a perspective view of the support, Fig. 5 is an exploded view of the same, Fig. 6 is an exploded view of the connecting part, and Fig. 7 is a circuit connection diagram. , FIG. 8 and FIG. 9 are directional characteristics diagrams, FIG. 10 is a perspective view showing a different embodiment, and FIG. 11 is a circuit connection diagram. 1... moving body, 9... radiator, 4... support rod.

Claims (1)

[Scope of utility model registration request] In a television antenna 3 installed on top of a moving body so as to be able to receive television waves coming from all four directions around the moving body, each of the antennas 3 is capable of receiving television waves. Consisting of four radiators 9 and four support rods 4 supporting each of the radiators 9, each of the four radiators 9 has a radiator arranged on both sides of the power supply box 10. The element 11 is formed in an arc shape, and the four radiators 9 are arranged in a circular shape in which the local direction of each radiator 9 differs by 90 degrees in the plane from the local direction of the adjacent radiator 9, and each The free ends 11' of the radiating elements 11 in the radiator 9 are mechanically connected to the free ends 11' of the adjacent radiating elements 11 in an electrically insulated state, while each of the support rods 4 has the circular shape. One of the four radiators 9 is arranged on the local axis of each radiator 9, and the planar shape is cross-shaped, and the radiator side of each support rod 4 is One end portion is fixed to a power feeding box 10 of each of the radiators 9 to support each radiator 9, and each of the support rods 4 is attached adjacent to the radiator 9 that it supports. Reflectors 4d and 4 for the low band of the radiator
A television antenna for a mobile object, characterized in that it is made of a conductive material so as to function as 4a and 4c, and each other end is electrically and mechanically connected to another support rod at the center. .