JPH05327335A - Loop antenna - Google Patents

Abstract

PURPOSE:To change directivity even in the case of a single antenna or installing it in the fixed state by controlling a feeding switching circuit while composing the loop antenna of a conductor bar bent in the shape of a loop and the plural feeding switching circuits. CONSTITUTION:Feeding switching circuits A and B are composed of conductor bars T, and lines 1 and 2 and lines 1' and 2' are mutually switched by switches SW1 and SW2 while being interlocked. Then, the lines 1 and 2 and the lines 1' and 2' are switched by the switching operations of the feeding switching circuits A and B, the positions of feeder lines are changed, and the directivity of the antenna is changed. Therefore, even in the case of the single antenna or installing the antenna in the fixed state, the directivity can be changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop antenna having a structure in which electric power is fed between both ends of a conductor rod bent in a loop shape.

[0002]

2. Description of the Related Art FIG. 9 shows a loop antenna conventionally used as an antenna for portable or small-sized radio equipment. This antenna is composed of a conductor rod a bent in a loop shape and a tuning capacitor. It is composed of C ₁ , an impedance matching capacitance C ₂ , and feeding points B and B '. Here, since the conductor rod a bent in a loop has a certain inductance at an arbitrary frequency, a tuning capacitor C can be used as a method of tuning the conductor rod a to a desired frequency.
₁ is inserted in parallel with the inductance of the conductor rod a. However, in order to use the conductor rod B bent in a loop shape as an antenna, impedance matching needs to be performed, and therefore an impedance matching capacitance C ₂ is further inserted.

[0003]

Since the directivity of the antenna is determined by its shape, when a conventional loop antenna is used to change the directivity to take measures against multipath fading, a plurality of antennas are required. It is necessary to install. According to the present invention, it is possible to solve the above problems, and to provide a loop antenna that can change the directivity of a single antenna or a fixed antenna installation state. Is the purpose.

[0004]

In order to achieve the above object, according to the present invention, in a loop antenna in which the loop circumference is very short compared to the wavelength, a feeding point of a conductor rod bent in a loop shape. A loop antenna characterized by comprising a plurality of switching circuits to switch the, in place of the conductor rod, using a conductor foil on or in the dielectric substrate, Further, instead of the conductor rod, a conductor foil on or in the housing is used.

[0005]

The operation of the present invention will be described. Whether the antenna is a single antenna or the antenna is installed in a fixed state, the directivity of the antenna is changed by operating a plurality of feeding switching circuits provided in the antenna.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an external perspective view of the loop antenna of the present invention. This is a loop antenna composed of a conductor rod T bent in a loop shape and power supply switching circuits A and B. By controlling the power supply switching circuits A and B, the directivity of the antenna is set to 90. It changes once.

FIG. 2 shows an internal circuit diagram of the power supply switching circuits A and B. The lines 1 and 2 and the lines 1'and 2'constituted by the conductor rod T are connected to a mechanical switch SW ₁ and a mechanical switch SW. The switch SW ₂ performs a switching operation, and the mechanical switch SW ₁ and the mechanical switch SW ₂ operate in conjunction with each other. Here, in order to perform tuning and impedance matching, a tuning capacitor C ₁ and an impedance matching capacitor C ₂ are inserted in the lines 1 ′ and 2 ′ as compared with the conventional loop antenna shown in FIG. 9. It is the same.

By switching the lines 1 and 2 and the lines 1'and 2'by the switching operation of the power supply switching circuits A and B, the position of the power supply lines is changed to change the directivity of the antenna. In FIGS. 1 and 2, a, b and a ′, b ′ are power supply line terminals for the wireless devices (not shown) of the power supply switching circuit A and the power supply switching circuit B. Figure 3
Are electrically controlled by using the relays R ₁ and R ₂ instead of the mechanical switch SW ₁ and the mechanical switch SW _{2 in} the power supply switching circuits A and B.
FIG. 4 shows a circuit diagram for switching between 2 ′ and 2 ′. FIG. 4 shows power supply switching circuits A and B for switching the power supply lines of the antenna, a CPU for controlling the power supply switching circuits A and B, and power supply for transmitting an RF signal to the wireless device W. shows a circuit diagram of a loop antenna and a relay R ₃ Metropolitan selecting the side.

When the switching circuit A side is used as a power supply line, CP
The power supply switching circuit A selects the lines 1'and 2'by the control signal from U, and the power supply switching circuit B selects the lines 1'and 2 '.
Is selected. Since the power supply switching circuit A outputs the RF signal, the CPU controls the relay R ₃ to turn on the power supply switching circuit A and turn off the power supply switching circuit B in response to the control signal. The same operation as above is performed when the side is the power supply line.

The loop antenna shown in FIG. 5 has (X) (Y) (Z) shown in FIG. 6 in the three-dimensional directions x, y, z in the figure.
It has directivity as shown in. In the figure, Eφ represents a horizontal polarization component with respect to the directional characteristic plane, and Eθ represents a vertical polarization component. FIG. 7 shows the position of the feed line of the loop antenna shifted by 90 degrees from the position of FIG. 5, but at this time, the antenna moves in the three-dimensional directions x, y, and z in FIG. It has the directivity shown in Y) and (Z).

The present invention utilizes the phenomenon as described above, and the directivity of the loop antenna is changed by changing the feeding position while the loop antenna itself is installed in a fixed state. Although the loop antenna using the conductor rod bent in the loop shape has been described above, the conductor rod may be replaced by a conductor foil on the dielectric substrate or in the dielectric substrate, or on the casing or the casing. The inside conductor foil can be used.

[0012]

The present invention is constructed as described above and has the following effects. That is, by operating a plurality of power supply switching circuits, it is possible to efficiently and reliably change the directivity of a single antenna or a fixed antenna installation state. There are advantages.

[Brief description of drawings]

FIG. 1 is an external perspective view of a loop antenna of the present invention.

FIG. 2 is an internal circuit diagram of a power supply switching circuit.

FIG. 3 is a circuit diagram for switching lines by electrical control using a relay in a power supply switching circuit.

FIG. 4 is a circuit of a loop antenna including a switching circuit for switching the power supply line of the loop antenna, a CPU for controlling the power supply line, and a relay for selecting a power supply side for transmitting an RF signal to a wireless device. It is a figure.

FIG. 5 is an external perspective view of a loop antenna having directivity in a three-dimensional direction.

6 (X), (Y), and (Z) are diagrams showing the directivity in the three-dimensional directions of the loop antenna shown in FIG. 5, respectively.

7 is an external perspective view of the loop antenna at a position where the position of the power supply line is shifted by 90 degrees from the position of FIG.

8A, 8B, 8C, 8D, 8E, 8F, 8G, 8F, and 8G are diagrams showing directivity in three-dimensional directions of the loop antenna shown in FIG.

FIG. 9 is a plan view of a conventional loop antenna.

[Explanation of symbols]

T Conductor rod bent in a loop shape A, B Feeding switching circuit a, a'Feeding wire terminal for wireless device of feeding switching circuit b, b'Feeding wire terminal for wireless device of other feeding switching circuit

Claims (3)

[Claims] 1. A loop antenna having a very short loop circumference compared to a wavelength, comprising a plurality of switching circuits for switching feed points of conductor rods bent in a loop shape. A characteristic loop antenna. 2. The loop antenna according to claim 1, wherein a conductor foil on or in the dielectric substrate is used instead of the conductor rod. 3. The loop antenna according to claim 1, wherein a conductor foil on or in the housing is used instead of the conductor rod.