JPH02170702A - Plane antenna - Google Patents

Abstract

PURPOSE:To stabilize receiving sensitivity even when the moving direction of a moving body is frequently changed by providing >= two signal line take-out positions, and taking out an output from the position where prescribed conditions are excellent. CONSTITUTION:A core 21 of a coaxial cable 20 is connected to a right marginal part of a central conductor 13, and a housing 22 of the coaxial cable 20 is connected to an external conductor 11 positioned near the right side of the central conductor 13. On the other hand, a core 31 of a coaxial cable 30 is connected to the marginal part of the lower part of the central conductor 13, and a housing 32 of the coaxial cable 30 is connected to the external conductor 11 positioned near the lower part of the central conductor 13. Thus the take-out positions of the coaxial cables 20 and 30 are provided at the right and lower edges of the central conductor 13, and the output is taken out from the position where the prescribed conditions (the intensity or phase of the received signal) are excellent. Thus, the receiving sensitivity is stabilized even when the moving direction of the moving body is frequency changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plane antenna installed on a horizontal portion (N root, trunk lid, etc.) of a vehicle body surface, such as an automobile.

[Prior Art] For antennas for mobile objects such as automobiles, antennas with few protrusions are required for reasons such as eliminating wind noise and improving appearance.
Antenna is preferred.

Incidentally, one type of plain antenna is a slot antenna, which is an antenna in which a part of the conductor is cut out in a circular shape (generally, cuts are made at equal intervals).

In other words, in the slot antenna, a closed circle slot is provided between the center conductor and the outer conductor, the core wire of the coaxial cable is connected to the periphery of the center conductor, and the jacket of the coaxial cable is connected to the outer conductor. However, the received signal is guided from the coaxial cable. The radiation pattern of the conventional device has a shape that destroys the figure-8 characteristic.

[Problems to be Solved by the Invention] However, in the conventional device described above, the directivity (sensitivity changes) depending on the connection position (signal extraction position) of the coaxial cable, and the sensitivity changes when the direction of movement of a moving object such as a car changes. If the direction of movement changes frequently, there is a problem in that the sensitivity changes frequently, and when receiving radio etc., it is difficult to hear.

[Means for Solving the Problems] The present invention provides a circular slot antenna with two or more signal line extraction positions, and outputs the output from a position where predetermined conditions are favorable.

[Function] The present invention provides two or more signal line extraction positions,
Since the output is extracted from a position where the predetermined conditions are favorable, the reception sensitivity is stable even if the moving direction of the moving object is frequently changed.

[Example] FIG. 1 is an explanatory diagram showing one embodiment of the present invention.

In the circular slot antenna lo, a central conductor 13 is provided at the center of an outer circumferential conductor 11, and a closed circle slot 12 is provided between the outer circumferential conductor 11 and the central conductor 13. Note that the shaded portion in FIG. 1 indicates a conductor portion.

In addition, the core wire 21 of the coaxial cable 20 is connected to the right side peripheral edge of the central conductor 13 in the figure, and the outer jacket 22 of the coaxial cable 20 is connected to the outer peripheral conductor 11 located near the right side of the central conductor 13.
is connected.

On the other hand, the core wire 31 of the coaxial cable 30 is connected to the peripheral edge of the lower part of the central conductor 13 in the figure, and to the outer peripheral conductor 11 located near the lower part of the central conductor 13.

A jacket 32 of a coaxial cable 30 is connected.

The core wire 23 at the other end of the coaxial cable 20 and the core wire 33 at the other end of the coaxial cable 30 can be switched by a switch 40.

Furthermore, a detection means (not shown) is provided, and this detection means detects the strength or phase of the received signal and switches the switch 4o so as to select a coaxial cable with a good strength or phase.

Note that the length should be approximately the same as one wavelength of the received signal.
The length of one circumference of the closed circle slot 12 is set, and the entire circular slot antenna 10 is made of a thin film, and this thin film antenna is used by being attached to a plastic trunk of an automobile or the like.

Next, the operation of the above embodiment will be explained.

The embodiment shown in Figure i1 is pasted on the plastic trunk of a car, etc., and broadcast signals are received. In this case, first,
Assume that the switch 4° is connected to the core wire 33 on the coaxial cable 30 side as shown in FIG. 1, and the strength of the received signal is above a predetermined level.

At this time, when the moving direction of the car changes and the strength of the received signal via the coaxial cable 30 becomes less than a predetermined value, the detection circuit detects the decrease in signal strength, and the control means (not shown) After that, if the strength of the signal passing through the coaxial cable 20 decreases, the switch is switched to the coaxial cable 30, and the above operation is repeated.

In the above explanation, switch 4 is
0 is provided, but in reality, the signal extraction position is electronically selected as follows.

In other words, a diode is connected to the core wire 23 of the coaxial cable 20, and a bias is applied to this diode in the forward direction and the reverse direction. For example, when bias is applied in the forward direction,
Signals are allowed to pass through the coaxial cable 2o. Further, a diode is connected to the core wire 33 of the coaxial cable 30 in the same manner as described above, and by changing the way the bias is applied, passing or blocking of the received signal is selected.

Further, the coaxial cable 20.3o is preferably set very short, and for example, the diode is preferably installed near the top of the closed circle slot 12. In this way, transmission loss is reduced. .

Of course, the diode may be installed at a location other than directly above the closed circle slot 12, and the signal extraction position may be electronically selected using a method other than the above.

In the above description, the switch 40 is automatically switched, but it may also be switched manually.

In the above embodiment, the core wires 21.31 of the coaxial cable 20.30 are connected to the edge of the center conductor 13, but this is because the received current is connected to the center conductor 13, especially in the case of the FM frequency band. This is because the flow concentrates on the edge of the 13th edge.

Further, in the above embodiment, the shape of the closed circle slot 12 is rectangular, but it may be square, circular, or oval.In general, it is more efficient to make the closed circle slot circular. Good.

Furthermore, although the coaxial cables 20 and 30 are taken out at the right end and bottom end of the central conductor 13, they may be set at the left end and top end of the central conductor 13. It may be provided in more than one place.
In this case as well, the output is extracted from a position where the predetermined conditions (strength or phase of the received signal) are favorable.

[Effects of the Invention] According to the present invention, even if the moving direction of the moving object is changed frequently,
This has the effect of stabilizing reception sensitivity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention. 10...Circle slot antenna, 11...Outer conductor, 12...Closed circle slot, 13...Center conductor, 20.30...Coaxial cable. 40...Switch.

Claims (3)

[Claims] (1) A plane antenna characterized in that, in a circle-shaped slot antenna, two or more signal line extraction positions are provided, and the output is extracted from the position where predetermined conditions are favorable. (2) The plain antenna according to claim (1), wherein the predetermined condition is the strength or phase of a received signal. (3) The plane antenna according to claim (1), wherein one of the two or more take-out positions is selected electronically.