JPH0457401A - High frequency antenna for traveling object identification device - Google Patents

Abstract

PURPOSE:To enhance the radiation efficiency by forming a radiation circuit with a foil printed circuit board, fitting the radiation circuit to a position via an air layer at a prescribed interval from a feeder circuit, coupling the radiation circuit and the feeder circuit electromagnetically and feeding the circuits. CONSTITUTION:A foil printed circuit board 6 is adhered to the inside of a case 10 of a responder of a traveling object identification device by using an adhesives and the radiation circuit 1 for the antenna is formed on the printed circuit board 6. Dielectric substrates 42, 43 made of a material such as a glass epoxy board is arranged to a position via an air layer 5 at a prescribed interval from the printed circuit board 6 and a ground base 7 is interposed between the boards 42, 43. A feeding circuit 2 of the antenna is formed on the board 42 by etching the metallic foil on the board 42. A circuit pattern of a transmission reception circuit 3 is formed by etching the metallic foil on the board 43. The circuit pattern of the transmission reception circuit 3 and a feeder of the feeding circuit 2 are connected by using a conductor wire 8 penetrated through the boards 42, 43.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a high-frequency antenna for a mobile object identification device, and in particular, to a high-frequency antenna used as a built-in antenna of a transponder attached to a mobile object. It is something that

[Prior Art] Conventionally, mobile object identification devices using microwaves have been put into practical use. This device emits microwaves to a transponder attached to a mobile object from an interrogator installed at a place where the mobile object passes, receives the microwaves with the transponder, modulates them, and retransmits them. This allows information specific to the transponder to be returned to the interrogator, or information is written from the interrogator to the memory of the transponder.

FIG. 3 shows the configuration of a transponder of such a mobile object identification device using microwaves. In the figure, 11 is a transmitting/receiving circuit board;
12 is an antenna board. The transmitter/receiver circuit board 11 includes
A transmitting/receiving circuit (not shown) is implemented. Further, a pattern of a rectangular radiating element 13 and a feeding line 14 is formed on the antenna substrate 12. The transmitting/receiving circuit of the transmitting/receiving circuit board 11 and the feed line 14 of the antenna board 12 are
A signal line connection is made by a conductor line 15 passing through 12. Regarding the material of the substrates 11 and 12, the transmitting/receiving circuit board 11 is made of a material with a relatively high dielectric constant, such as glass epoxy or ceramic, for the reason that the circuit can be made smaller and the radiation loss of the circuit can be reduced. A thin substrate was selected, and the antenna substrate 12 had a relatively low dielectric constant and a thick substrate, such as Teflon, for the reason that it had a large reception area and increased radiation efficiency.

[Problems to be Solved by the Invention] The above configuration has a problem in that the low dielectric constant substrate such as Teflon used for the antenna substrate 12 is extremely expensive. Furthermore, in order to increase the gain of the antenna, if an array antenna as shown in FIG. Electric wire 1
There was a problem in that the radiation of the array antenna 4 itself also increased, and the efficiency of the array antenna as a whole decreased.

The present invention has been made in view of these points, and its purpose is to provide a high-frequency antenna for a mobile object identification device that is highly efficient, compact, and inexpensive.

[Means for solving the problem] In the antenna for a mobile object identification device according to the present invention,
In order to solve the above problems, as shown in FIG. In a mobile object identification device including a transmitting/receiving circuit 3 for receiving data, a power feeding circuit 2 is configured on the back surface of a dielectric substrate 4 on which the transmitting/receiving circuit 3 is mounted, and is located at a position separated from the power feeding circuit 2 by an air layer 5 at a certain distance. Fixed foil printed circuit board 6
A radiation circuit 1 is configured on the top, and the power supply circuit 2 and the radiation circuit 1 are connected to each other.
It is characterized in that the two are electromagnetically coupled.

[Function] According to the present invention, as described above, the radiation circuit 1 is constituted by the foil-shaped printed circuit board 6, and the radiation circuit 1 is fixed at a position separated from the power supply circuit 2 by a certain distance of the air space 5, Since the radiation circuit 1 and the feeder circuit 2 are electromagnetically coupled to feed power, the ground plane 7 of the radiation circuit 1 is connected to the feeder circuit 2.
The air layer 5 and the dielectric substrate 42 forming the feeder circuit 2 are present between the radiation circuit 1 and the ground plane 7 . Here, since the relative dielectric constant of the air layer 5 is about 1, the radiation circuit 1 is the same as using a dielectric substrate with a lower dielectric constant than Teflon, and the radiation efficiency can be increased. .

In addition, in the present invention, since the radiation circuit 1 and the feed circuit 2 are electromagnetically coupled to feed power, the radiation circuit 1 and the feed circuit 2 can be configured on separate boards 6 and 42, The dielectric substrate 42 constituting the circuit 2 can be made thinner. Therefore, radiation loss from the feeder circuit 2 can be reduced.

[Embodiment] FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is an exploded perspective view of the same. In the figure, 10 is a case of a transponder of a mobile object identification device, and is made of a material such as a dielectric material through which radio waves can pass. A foil-like printed circuit board 6 is attached to the inside of the case 10 using an adhesive cap.
This printed circuit board 6 includes a radiation circuit 1 of the antenna. As the radiating circuit 1, a rectangular patch-shaped radiating element whose negative side is set to have a length approximately half the spatial wavelength is used. A dielectric substrate 42.4.3 is arranged at a position separated from the printed circuit board 6 by a certain distance of an air layer 5, and a ground plane 7 is interposed between the substrates 42.43. The substrate 42 is made of, for example, a glass epoxy substrate, and the feeding circuit 2 of the antenna is constructed by etching a metal foil (for example, copper foil) on the substrate 42. Here, since the radiating elements of the radiating circuit 1 are arranged in an array, the feeding lines of the feeding circuit 2 are also arranged in an array in correspondence with each radiating element. The substrate 43 is made of, for example, a glass epoxy substrate, and the circuit pattern of the transmitting/receiving circuit 3 is formed by etching metal foil (for example, silver foil) on the substrate 43. The circuit pattern of the transmitter/receiver circuit 3 and the feeder line of the feeder circuit 2 are connected by a conductor wire 8 penetrating the substrates 42, 43.

In this way, in this embodiment, the antenna radiation circuit 1 using the inexpensive foil-like printed circuit board 6 and the glass epoxy board 4 are constructed.
Power supply port obtained by etching 2! i
Since the antenna can be constructed using '82, it is possible to realize a significant cost reduction compared to the conventional example using a Teflon substrate.

[Effects of the Invention] As described above, in the present invention, in a high frequency antenna for a mobile object identification device, a feeding circuit is configured on the back side of a dielectric substrate on which a transmitting/receiving circuit is mounted, and the feeding circuit is located at a certain distance from the feeding circuit. The radiation circuit is constructed on a foil-shaped printed circuit board fixed at a position separated by an air layer, and the feeding circuit and the radiation circuit are electromagnetically coupled. Since an air layer with a low dielectric constant is arranged, higher radiation efficiency can be obtained than when using conventional Teflon substrates, etc., and the feeding circuit is configured on a separate substrate from the radiation circuit. This has the effect that radiation loss can be reduced and radiation efficiency of the antenna can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is an exploded perspective view of the same essential parts, and FIG. 3 is a perspective view of a conventional example. 1 is a radiation circuit, 2 is a power supply circuit, 3 is a transmitting/receiving circuit, 4 is a dielectric substrate, 5 is an air layer, and 6 is a printed circuit board.

Claims (1)

[Claims] (1) A mobile object identification device including a radiation circuit of an antenna, a feeding circuit for feeding power to the radiation circuit, and a transmitting/receiving circuit for transmitting or receiving a high frequency signal via the feeding circuit, in which a transmitting/receiving circuit is implemented. A feeding circuit is configured on the back surface of the dielectric substrate, a radiation circuit is configured on a foil-shaped printed circuit board fixed at a position separated from the feeding circuit by a certain distance of air space, and the feeding circuit and the radiation circuit are connected to each other. A high frequency antenna for a mobile object identification device characterized by being electromagnetically coupled.