JPH06260949A - Radio equipment - Google Patents

Abstract

PURPOSE:To protect an electronic equipment from the static electricity and also prevent the undesired radiation in a limited space without deteriorating the antenna gain by using an antenna which doubles as a shielding case. CONSTITUTION:A multilayer printed board 2 includes four layers where a 2nd layers is used as a circuit blocking ground 12 and a 3rd layer face antenna 13 respectively. Meanwhile the circuit elements 21 and 22 are provided on a 1st layer face and a 4th layer face respectively. Most of parts provided on one of both sides of the board 2 are covered by a U-shaped antenna doubling as a shielding case 1. The antenna 1, an antenna adjusting trimmer capacitor 3, and the inner layer antenna 13 are connected together in series and form an electrical loop. Then the ground 12 is connected to the antenna 13 at one of both ends of the board 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a radio device with an antenna,
In particular, it relates to a wireless device with a loop antenna.

[0002]

2. Description of the Related Art In conventional radio equipment with an antenna,
Increasing the gain of the antenna was very important in the design. In order to obtain a relatively high antenna gain, it is advisable to put out a protruding antenna such as a monopole antenna outside the housing.

However, the protrusions in such a radio device have been a cause of deteriorating portability. The use of an extendable antenna improves portability, but there is a problem that communication is not possible during extension. The inverted F-type antenna, which is often used in recent years for mobile phones and the like, is an antenna with relatively good characteristics that ensures portability and gain.

However, this inverted F type antenna also has a drawback. It is an electric field type antenna. As we know, the electromagnetic wave near the human body has a higher magnetic field component than an electric field component. Therefore, the electric field type antenna having a high antenna gain has a significant decrease in the gain when brought into close contact with or close to the human body.

In recent years, wristwatch type devices, which were said to be the ultimate communication devices, have come into the market. For a wristwatch type wireless device, a magnetic field type antenna such as a loop antenna is often used as an antenna for the above reason. As the name implies, this is a loop-shaped antenna and can be roughly classified into an all-wavelength loop antenna that matches at one wavelength and a minute loop antenna that hardly reaches all wavelengths. The small loop antenna theoretically exhibits omnidirectional characteristics, is small, and is often used in wristwatch-type communication devices and the like.

[0006]

However, as we all know,
The antenna gain of the small loop antenna is determined by the size of the loop, that is, the opening area and the width of the loop antenna, and the larger the gain, the better.

However, as the size of wireless devices has decreased, parts have been mounted at high density, and the places where antennas can be obtained have been limited. Further, if a large component such as a crystal or a SAW filter is provided in the direction of cutting the magnetic flux of the loop antenna, it interferes with the magnetic flux, resulting in a decrease in antenna gain. In addition, many communication devices are usually shielded to prevent damage or malfunction due to external factors such as static electricity, and to prevent unnecessary radio waves generated internally. , The decrease of the antenna gain was more remarkable in the smaller devices.

[0008] In such a limited space, it has been desired to develop a wireless device which does not deteriorate the characteristics.

[0009]

In a wireless device using a loop antenna, a multilayer substrate is used as a printed circuit board for wiring an electronic circuit, and a U-shaped band-shaped shield case is covered so as to surround the electronic circuit. A case is connected to a printed circuit board, and one or more layers of the inner layer of the multilayer board and the shield case are connected via a capacitor to form a loop, and a high frequency circuit of a wireless circuit is connected to the loop. .

[0010]

With these configurations, the dedicated shield case also functions as an antenna, and the magnetic flux of the loop antenna is never blocked by the shield case as in the conventional radio device with a loop antenna. Since it becomes a loop antenna that is maximally effective, an antenna with high gain can be realized.

Further, since the ground of the internal high-frequency circuit and the antenna are separated in the multilayer substrate, it is possible to prevent high-frequency current from flowing into the high-frequency circuit. In this way, it is possible to realize the shield case type antenna that obtains the maximum gain inside the device and also exhibits the shield effect.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an example of a perspective view of the present invention. 1 is an antenna also serving as a shield case, 2 is a multilayer printed circuit board, 3 is a trimmer capacitor for antenna adjustment, and 21 is a circuit element.

The multilayer printed board 2 is a four-layer board in the embodiment. The antenna that also serves as a shield case reduces electrostatic damage and unnecessary radiation on the printed circuit board.
Shield related circuit blocks. In the embodiment, most of the components on one surface (top surface in perspective view) of the printed circuit board 2 are shielded by the U-shaped antenna / shield case. The material of the shield case is iron or copper, which is plated with gold, nickel, or the like, which has high-frequency characteristics.

FIG. 2 shows a connection diagram relating to the antenna of the present invention. 1 is an antenna also serving as a shield, 3 is a trimmer capacitor for antenna adjustment, 12 is a ground for a circuit block, 1
Reference numeral 3 is an inner layer antenna provided on the printed circuit board, and 20 is a circuit block excluding the antenna.

In the embodiment, the circuit block ground 12 uses the second layer. In addition, the inner layer antenna 13
Uses the third layer in the examples. The antenna adjustment trimmer capacitor 3 is for adjusting the resonance frequency of the antenna. In the embodiment, it has a variable capacitance of 3 pF.

The GND for the circuit block and the inner layer antenna are
It is connected at one end of the printed circuit board 2. The reason for this is that if the inner layer antenna and the ground potential of the circuit become equal, the high frequency current of the loop antenna flows to the high frequency portion in the circuit block, causing abnormal oscillation or unstable operation.

Next, a sectional view of the present invention is shown in FIG. 1 is a loop antenna also serving as a shield, 2 is a printed circuit board, 3 is an antenna adjusting trimmer capacitor, 11 is a one-layer surface of the printed circuit board, 12 is a two-layer surface of the printed circuit board, 13 is a three-layer surface of the printed circuit board, and 14 is a four-layered circuit board of the printed circuit board. It is a layer surface.
Reference numeral 21 is a circuit element on the first layer surface, 22 is a circuit element on the fourth layer surface, and 30 is a through hole.

In the embodiment, the two-layer surface 12 is used as the ground of the circuit block and the three-layer surface 13 is used as the inner layer antenna. And the antenna 1 which also serves as a shield case,
Antenna adjustment trimmer capacitor 3 and printed circuit board 3
The inner layer antenna on the layer surface is connected in series to electrically draw a loop, and the resonance frequency in the embodiment is 430 MHz.
Is.

The signal terminal and the ground terminal of the high frequency input / output portion of the circuit block are respectively connected to the printed circuit board 3.
A shield antenna type loop antenna is formed by connecting via a through hole to each of two points at which the characteristic impedance of the inner layer antenna on the layer surface is 50 ohms.

[0020]

As described above, by using the present invention,
It is possible to overcome various problems that were the conventional drawbacks. This is shown below. There is no possibility that the shield case cuts off the magnetic flux of the loop antenna, resulting in a significant reduction in the gain of the loop antenna as in the conventional wireless device.

Further, since it is possible to realize an antenna that effectively utilizes the space inside the equipment, it is possible to realize an antenna with extremely high gain. Further, protection against static electricity and shielding for preventing unnecessary radiation can be performed at the same time without deteriorating the antenna gain.

Further, since the antenna and the shield case are integrated, the weight can be reduced. As described above, the effect of the present invention increases as the device becomes smaller, and is extremely effective for a wristwatch type wireless device and the like.

[Brief description of drawings]

FIG. 1 is an example of a perspective view of the present invention.

FIG. 2 is a connection diagram relating to the antenna of the present invention.

FIG. 3 is a sectional view of the present invention.

FIG. 4 is an example of a perspective view of a conventional wireless device.

FIG. 5 is an example of a cross-sectional view of a conventional wireless device.

[Explanation of symbols]

 1 Antenna Used as Shield Case 2 Multilayer Printed Circuit Board 3 Trimmer Capacitor for Antenna Adjustment 4 Conventional Antenna 5 Conventional Shield Case 6 Conventional Printed Circuit Board 11 1st Layer Surface of Printed Circuit Board 12 Circuit Block Ground 13 Inner Layer Antenna on Printed Circuit Board 14 4 layer surface of printed circuit board 20 Circuit block excluding antenna 21 Circuit element on 1 layer surface 22 Circuit element on 4 layer surface 30 Through hole

Claims (1)

[Claims] 1. In a wireless device using a loop antenna, a multilayer board is used for a printed circuit board for wiring an electronic circuit, and a U-shaped band-shaped shield case is covered so as to surround the electronic circuit of the wireless device, and the shield is provided. A case is connected to a printed board, one or more layers of the inner layer of the multilayer board and the shield case are connected via a capacitor to form a loop, and a high frequency circuit of a wireless circuit is connected to the loop. Wireless equipment.