JPH02190006A - Antenna system - Google Patents

Abstract

PURPOSE:To constitute a beam direction switch type antenna system with two dipole antennas or 1/4 wavelength monopole antennas and to miniaturize the antenna system by selecting the length of a coaxial cable so that the impedance when viewing the cable from an input terminal of an antenna not energized is equivalently short-circuited. CONSTITUTION:When an SPDT(Single Pole double throw) switch 4 is switched to the position of a radiator 1a, the length of the coaxial cable at the side of a radiator 1b is selected so that the feeding point of the radiator 1b is short- circuited equivalently and since the radiator 1b acts like a reflector when the interval of the two radiators is selected properly, the antenna beam is directed forward. When the SPDT switch 4 is thrown to the position of the radiator 1b conversely and the length of the coaxial cable at the side of the radiator 1a is regulated similarly as above, the radiator 1a acts like a reflector and the antenna beam is directed backward. Thus, the small sized beam direction switching type antenna system constituted with only two half length antennas or 1/4 wavelength monopole antennas is obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is used in, for example, train radio. The present invention relates to a beam switching type antenna device.

[Conventional technology]

Fig. 4 is a diagram showing a conventional antenna device.
, (2a) and (2b) are reflectors, (3) is a coaxial cable, and (4) is a switch, in which a 5PDT switch is used.

Next, the operation will be explained. In fig.

The combination of the radiator (1a) and the reflector (2a) constitutes a so-called two-element Yagi array antenna, and when power is supplied to the radiator (1a), a beam is radiated forward.

Furthermore, another set of Yagi array antennas consisting of a radiator (2a) and a reflector (2h) are arranged back to back, and the 2 radiators (la), (2a) and 5 PDT switches (4) are connected using a coaxial cable (3). By switching the connection L and the 5PDT switch, it is possible to configure an antenna device that can switch the beam direction in two directions: forward and backward.

[Problem to be solved by the invention]

Since the conventional antenna device is constructed as shown below, it requires two radiators and two reflectors, and the overall size of the antenna is also large.

This invention was made to solve the problems described in 1-., and an object thereof is to obtain a small beam direction switching type antenna device.

[Means to solve the problem]

The antenna device according to the present invention arranges two half-wavelength dipole antennas or 174-wavelength monopole antennas in parallel, connects them to Sui Nochi with a coaxial cable, and when the switch is switched to one antenna side,
The length of the coaxial cable is set so that the impedance seen from the feeding point of the other antenna to the switch side is equivalently short-circuited.

In the antenna device of the present invention, when one of the half-wavelength antennas or the quarter-wavelength antenna is excited by Sui-Sochi, the other antenna can be operated with the reflector. Therefore, a beam direction switching type antenna can be configured with only two antennas, and the antenna device can be made smaller.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure ↓5, (la), (111) is a radiation P5 consisting of a half-wavelength dipole antenna or a 1.74-wavelength monopole antenna. (3) is a coaxial cable, (4) is a switch, and this embodiment shows a 5PDT switch.

In Figure 1, the 5PDT switch (4) is connected to the radiator (
Consider the case where the switch is made to the la) side. At this time, the radiator (
The radiator (1
By setting the length of the coaxial cable on the b) side and choosing the spacing between the two radiators appropriately, the radiator (lb) acts as a reflector, so the beam in Figure 2 [as shown in (5)] The antenna beam points forward. Conversely, switch the 5PDT switch (4) to the radiator (11) side and turn the radiator (1a) on.
If the length of the side coaxial cable is adjusted in the same way, the radiator (la) will act as a reflector, and the antenna beam will be
It faces rearward as shown in beam 2 (6) in FIG. Therefore, depending on the configuration of J-, a half-wave antenna or 174
FIG. 2 is a diagram showing another embodiment of the present invention, in which a beam direction switching type antenna device can be constructed using only two wavelength monobolite antennas. In the figure, since a transfer switch is used as the switch (4) and one terminal of the switch is grounded, the influence of radio wave leakage due to the isolation of the switch can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, the length of the coaxial cable is set so that the impedance seen from the input end of the antenna on the non-power feeding side is equivalently short-circuited. Beano, a direction-switchable antenna device can be configured with two single antennas,
It has the effect of being smaller than conventional ones.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an antenna device according to one embodiment of the present invention, FIG. 2 is a diagram showing another embodiment of the invention, FIG. 3 is a diagram showing a radiation pattern of the antenna device according to the present invention, and FIG. FIG. 4 is a diagram showing a conventional antenna device. In the figure, (la) and (lb) are radiators consisting of half-wavelength dipole antennas or 174-wavelength monopole antennas, and (2a) and (2b) are reflectors. (3) shows the coaxial cable, (4) shows the Swiss-Sochi pattern, (5) shows the beam 1 pattern, and <6> shows the beam 2 turn. Note that the same reference numerals in the four figures indicate the same or corresponding parts. Figure Figure Figure Front σ Rear 6: Beam 2 pattern

Claims (2)

[Claims] (1) In an antenna device consisting of a half-wavelength dipole antenna or quarter-wavelength monopole antenna, a switch, and a coaxial cable, two half-wavelength dipole antennas or quarter-wavelength monopole antennas are arranged in parallel, and the switch as one SPDT (Singl
e Pole double throw) switch, and when the switch supplies power to one antenna, the impedance between the switch and the antenna when viewed from the input end of the antenna on the side that is not being supplied with power is equivalently almost short-circuited. An antenna device characterized by having a set length of a coaxial cable. (2) In an antenna device consisting of a half-wave dipole antenna or quarter-wave monopole antenna, a switch, and a coaxial cable, two half-wave dipole antennas or quarter-wave monopole antennas are arranged in parallel, and the switch One transfer switch is used as a switch, and one terminal of the switch is grounded.
Connect the coaxial cable between the switch and the antenna so that when power is supplied to one antenna by the switch, the antenna on the side that is not being supplied with power is connected to the ground, and the impedance seen from the input end to the switch side is equivalently almost a short circuit. An antenna device characterized by having a set length.