JPH08335818A - Portable radio - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the antenna bandwidth reduction due to the miniaturization of portable radios with a built-in inverted F-shaped antenna,
Secure manufacturing margins to improve productivity and reduce costs. [Constitution] Element 1 of a built-in inverted F-shaped antenna
2 on the front side or the inner side of the radio housing 5 corresponding to
A wide band has been realized by fixing the conductive parasitic element 6 in which two surface portions are connected by a linear portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable wireless device such as a mobile phone or a car phone, and more particularly to a portable wireless device having a plate-shaped inverted F antenna built therein.

[0002]

2. Description of the Related Art With the miniaturization of portable radios such as mobile phones and car phones, miniaturization of antennas is required,
Plate-shaped inverted F-shaped antennas have become popular.

FIG. 5 is a plan view (A) and a side view (B) showing the structure of a flat inverted F antenna, and FIG. 6 is a characteristic example diagram thereof. In FIG. 5, 1 is an antenna element, 2 is a short-circuit surface, 3 is a ground plane, 4 is a feed line, and a is the length of the antenna element 1 and is set to a length of approximately λ / 4. b is the width of the antenna element 1, and d is the gap between the element 1 and the ground plane 3.

The horizontal axis of FIG. 6 shows the ratio of the gap d to the wavelength λ ₀ , and the width-length ratio of the antenna element 1 is As.
It is a characteristic example figure of radiation efficiency (eta) and bandwidth BW which set = b / a as a parameter.

However, this plate-shaped inverted F-shaped antenna also has problems with respect to its bandwidth, size, and structure when it is downsized. For example, in the case of a plate-shaped inverted F-shaped antenna built in for reception diversity of a digital cellular phone,
The length a = λ / 4 of the basic antenna element 1 is about 9
You need about cm. However, the volume of the current miniaturized mobile phone is about 150 cc, and the volume allowed for the built-in antenna is several cc. On the other hand, as shown in FIG. 6, in order to widen the bandwidth (BW), it is better to increase the gap d and increase As = b / a. Further, if the ground plane 3 is not sufficiently wide with respect to the element 1, the bandwidth becomes narrow.

[0006]

As described above, in the conventional portable telephone, the outer dimensions of the housing are first determined, and the RF portion (high frequency circuit portion) of the radio device, the logic portion, the battery, etc. are included therein. Since the remaining number cc after the arrangement is the volume allowed for the built-in antenna, the maximum values of the length a, the width b, and the gap d of the antenna element 1 are limited.
Therefore, in practice, it is difficult to set the length a of the antenna element 1 to λ / 4. Therefore, the antenna resonance frequency can be shortened by controlling the short-circuit surface, adding capacitance, or providing a dielectric in the gap to shorten the wavelength. Is designed to match the center frequency of the band. However, there is no improvement measure to widen the bandwidth without lowering the radiation efficiency, and as a result, the design margin (margin) for the product variation that usually must be taken into consideration during mass production design cannot be set, and the manufacturing specifications are extremely high. There are problems such as increased cost and poor productivity because the product is highly accurate to suppress product variations and the characteristics are secured through inspection and adjustment processes.

It is an object of the present invention to provide a portable radio device which improves cost reduction and productivity improvement by improving the decrease in bandwidth due to the miniaturization of the built-in antenna and ensuring a design and manufacturing margin. To do.

[0008]

The portable wireless device of the present invention comprises:
In a portable wireless device in which a plate-shaped inverted F-shaped antenna is built in an insulating casing, a low-loss conductor fixed to the front side or the inside of the casing corresponding to the antenna element of the plate-shaped inverted F-shaped antenna. It is characterized in that a parasitic element is provided.

Further, the parasitic element has a shape in which two surface portions are connected by a linear portion, and is fixed at a position where the central portion and the central portion of the antenna element are substantially opposed to each other. It is characterized by that.

[0010]

1 is a structural diagram showing an embodiment of the present invention,
(A) is a partially cut sectional view and (B) is a rear view. In the figure, a plate-shaped inverted F-shaped antenna serving as a built-in antenna is composed of an antenna element 1, a short-circuit surface 2, a ground plane 3, and a feed line 4, and the ground plane 3 also serves as a shield case for accommodating a radio circuit and electromagnetically shielding it. are doing. Reference numeral 5 is a plastic casing such as ABS resin, 6 is a parasitic element that forms an essential part of the present invention, and 7 is a battery.

The parasitic element 6 is made of a conductor such as a conductive tape or a conductive coating which has a low loss in the frequency band used.
A one-sided adhesive tape made of silver is used, and is attached to a position corresponding to the antenna element 1 of the built-in inverted F-shaped antenna on the front side or the inside of the housing 5 on the back surface of the wireless device. The shape is, as shown in FIG. 1 (B) and FIG.
It has a shape in which two rectangular surface portions whose inner corners are cut are connected by a narrow linear portion. As shown in FIG. 1 (B), when the parasitic element 6 is attached so that its center is substantially aligned with the antenna element 1 of the built-in antenna, the radiation efficiency is reduced without changing the antenna resonance frequency. Without increasing the bandwidth. The antenna resonance frequency becomes higher when the parasitic element 6 is shifted upward and stuck, and becomes lower when the parasitic element 6 is shifted downward and stuck. In addition, as shown in FIG. 2, since the surface portion is capacitive and the linear portion is inductive, the above-mentioned pasting position,
By experimentally obtaining and setting the area of the surface portion and the length and width of the line portion, it is possible to realize a wide band without changing the resonance frequency and the radiation efficiency.

FIG. 2 is a plan view showing a concrete example of the parasitic element 6 of the present invention, FIG. 3 is a characteristic example diagram showing the improvement of the bandwidth according to the present invention, and FIG. 4 is an example of radiation characteristic before and after the present invention is carried out. It is a figure. As can be seen from FIG. 3, the bandwidth when the reflection amount is −10 dB is higher than that of the conventional characteristic a by the parasitic element 6 of the present invention.
The characteristic b provided with is about 10% wider. Further, the characteristics a and b in FIG. 4 show characteristics when the direction of the portable radio device is changed by 90 °, and show that the characteristics do not change with and without the parasitic element 6, respectively.

[0013]

As described in detail above, by implementing the present invention, the bandwidth can be widened without affecting the resonance frequency of the built-in antenna and without degrading the radiation characteristic. The design and manufacturing margins can be increased, and the productivity can be improved.
Furthermore, the parasitic element 6 to be added has a low material cost and is easy to process, so that the cost can be reduced overall.

[Brief description of drawings]

FIG. 1 is a structural diagram showing an embodiment of the present invention.

FIG. 2 is a specific example diagram of a main part of the present invention.

FIG. 3 is a diagram showing an example of bandwidth improvement characteristics showing the effect of the present invention.

FIG. 4 is a diagram showing an example of radiation characteristics before and after implementation of the present invention.

[Explanation of symbols]

 1 Antenna Element 2 Short-circuited Surface 3 Ground Plane 4 Feeding Line 5 Housing 6 Parasitic Element 7 Battery

[Procedure amendment]

[Submission date] October 24, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a structural diagram showing an embodiment of the present invention.

FIG. 2 is a specific example diagram of a main part of the present invention.

FIG. 3 is a diagram showing an example of bandwidth improvement characteristics showing the effect of the present invention.

FIG. 4 is a diagram showing an example of radiation characteristics before and after implementation of the present invention.

FIG. 5 is a structural example diagram of a flat inverted F antenna.

FIG. 6 is a characteristic example diagram of a flat inverted F antenna.

[Explanation of reference numerals] 1 antenna element 2 short-circuited surface 3 ground plane 4 feeding line 5 housing 6 parasitic element 7 battery

Claims (4)

[Claims] 1. A portable wireless device in which a plate-shaped inverted F-shaped antenna is built in an insulating casing, wherein a low-frequency antenna fixed to the front side or the inside of the casing corresponding to the antenna element of the plate-shaped inverted F-shaped antenna. A portable wireless device comprising a parasitic element made of a lossy conductor. 2. The parasitic element has a shape in which two surface portions are connected by a linear portion, and is fixed at a position where a central portion of the parasitic element and a central portion of the antenna element substantially face each other. The portable wireless device according to claim 1, wherein: 3. The portable wireless device according to claim 1, wherein the parasitic element is a single-sided adhesive tape of a conductor. 4. The portable wireless device according to claim 1, wherein the parasitic element is a conductive paint.