JPH0440102A - Antennas and small portable radios - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small portable radio device, particularly to an antenna structure.

[Prior Art] Conventionally, as shown in FIGS. 4 and 5, which are conventional examples, a metal plate constituting a loop antenna 21 is simply bent into a loop shape, and end portions 23 and 24 are attached to a substrate 22. Generally, it is fixed at .

Further, as shown in FIG. 6, which is an equivalent circuit diagram, a resonant circuit consisting of a variable capacitance capacitor 32 connected in parallel with a coil 31 representing the loop antenna 21 is constructed, and its resonant frequency is adjusted to the radio signal. By matching the transmitting and receiving frequencies, a constant sensitivity of the transmitter and receiver is obtained.

[Problems to be solved by the invention] In small portable radio devices that transmit and receive high frequencies, the influence of the antenna on the sensitivity is particularly large. T-type antennas are used.The size of these antennas is quite small compared to the wavelength of the frequency to be transmitted and received, so the gain of the antenna is small, and the inductance of the antenna is large, so the Q of the antenna circuit is A high Q means that the frequency characteristic of the antenna circuit itself is narrow band. Therefore, if the resonant frequency of the antenna circuit shifts for some reason, the gain of the antenna will drop significantly. This will result in

In addition, although the inductance of the antenna increases, the transmission and reception frequency is high, so the resonant frequency of the resonant circuit formed by the capacitor connected in parallel with the antenna must also be increased. Must be a small value.

When an object such as a human body comes close to the antenna,
Capacitance is generated, and its amount reaches several pF. Since this capacitance is isometrically connected in parallel to the resonant circuit, the difference with the value of the capacitor becomes so small that it cannot be ignored.This increases the resonant frequency of the resonant circuit. This, combined with the fact that Q is high as mentioned earlier, may result in a significant decrease in the sensitivity of the small portable radio.

SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna that eliminates the above-mentioned problem, that is, a shift in the resonance frequency due to the proximity of an object such as a human body to the antenna, and provides a constant gain at all times.

Another object of the present invention is to provide a small portable radio device that is equipped with the antenna of the present invention and can always transmit and receive data with constant sensitivity.

[Means for Solving the Problems 1] The antenna of the present invention is an antenna for transmitting and receiving radio wave signals, and the antenna includes two outer metal plates, one inner metal plate, and two electrically insulating plates. It has a multilayer structure consisting of plates, the two outer metal plates are located on the surface of the antenna, the two electrically insulating plates are located inside them, and the one metal plate is located inside them. The inner layer metal plate is in a positional relationship such that it is sandwiched, and one end of the inner layer metal plate is
It is connected to a signal input/output terminal of an antenna circuit including the antenna, another end is connected to a ground terminal of the antenna circuit, and both of the outer layer metal plates are connected to the ground terminal of the antenna circuit. It is characterized by

Further, a small portable radio device is constructed which is characterized by being equipped with such an antenna.

[Example 1] Fig. 1 is a longitudinal sectional view of an antenna of the present invention viewed from the aperture direction.

The outer metal plate 1 is grounded at its end 4.5. Further, the inner layer metal plate 2 has an end 4 as a signal extraction side terminal and an end 5 as a ground III terminal.

The outer layer JE plate 1 and the inner layer metal plate 2 are crimped together with an insulating plate 3 interposed therebetween. In this way, the antenna in the form of a loop antenna is installed on the substrate 6.

FIG. 2 is a perspective view of the antenna of the present invention.

At the tip of the inner metal plate 2 at the end 4, there is an end connecting pawl 7. As a result, the connection with the board 6 is established, and a radio wave signal is transmitted to the board 6 for human output.

FIG. 3 is an equivalent circuit diagram of an antenna circuit including the antenna of the present invention. The coil 11 represents the inductance of the loop antenna constituted by the inner metal plate 2, and the contact 16 corresponds to the end 4 and the contact 17 corresponds to the end 5. A variable capacitance capacitor 12 is connected between contacts 16 and 17, and forms a resonant circuit together with coil 11.

Radio signals matching the resonant frequency of this resonant circuit are transmitted and received via the antenna circuit. Reference numeral 15 represents a connection terminal to the high frequency amplifier circuit section, 18 represents a capacitor, and 14 represents a ground.

Now, the characteristics of the antenna of the present invention are shown below.

In FIG. 3, the capacitor 13 is connected when a human body is nearby,
This represents the capacity generated between the outer case and the outer case. It can be seen that both terminals of the capacitor 13 are grounded. That is, since the antenna surface of the present invention is grounded, even if any object approaches, its capacitance will be grounded and the resonant frequency of the antenna circuit will not change.

Furthermore, the radio signal receiving means in the loop antenna uses changes in the magnetic flux of the radio signal.

According to the well-known Maxwell's equations, the left side of the equation represents the electromotive force in the loop antenna, and the right side represents the temporal change in the magnetic flux linking the aperture of the loop antenna.

Therefore, no matter what object is near the loop antenna, if there is a change in magnetic flux or if there is no metal object that closes the aperture direction, an electromotive force will be generated. Since the outer layer metal plate 1 is not placed in a position where it closes the opening surface direction, it does not affect the electromotive force of the antenna.

FIG. 4 is an example of a conventional antenna. Further, FIG. 5 is a perspective view of a conventional antenna, and FIG. 6 is an antenna circuit diagram using the conventional antenna. Coil 31 represents the inductance of loop antenna 21 , contact 36 corresponds to end 23 and contact 37 corresponds to end 24 . Contact point 36
A variable capacitor 32 is connected between and 37.
Together with the coil 31, it constitutes a resonant circuit. Radio signals matching the resonant frequency of this resonant circuit are transmitted and received via the antenna circuit. Reference numeral 35 represents a connection terminal to the high frequency amplifier circuit section, 38 represents a capacitor, and 34 represents a ground.

When a conventional antenna is used, since the loop antenna 21 is made of a good electrical conductor such as metal, a capacitance such as the capacitor 33 is isometrically inserted when a human body or the like approaches. There is no problem if the value of this capacitor 33 is negligibly smaller than the value indicated by the variable capacitor 32. However, in an antenna circuit that transmits and receives high frequencies, if the same loop antenna is used, the inductance will not change. Therefore, it is difficult to achieve resonance at the target frequency unless the capacitance inserted in parallel is made small. Therefore, the value of the variable capacitor 32 must be made small, and then it becomes susceptible to the influence of the capacitor 33. As a result, the resonant frequency shifts.

With the antenna of the present invention, the above-mentioned problem cannot occur in principle. This is because, as shown in FIG. This is because there is no possibility that it will be connected to 11.

FIG. 7 is a diagram showing another embodiment of the antenna of the present invention.

In this example, the position of the end portion 4.5 is slightly shifted to the center.

Fig. 8 is an external view of a small portable radio device equipped with an antenna according to the present invention. In the antenna of the present invention, in order to reduce the volume inside the main body 41, most of the parts are glued together, but since the adhesive surface of the antenna is on the outer layer metal plate 1 side, the resonant frequency of the antenna circuit may be shifted. There isn't.

Information data is displayed on the display section 42. Further, the information is expressed in audio by the speaker 46.

Further, various operations can be performed using the switch 43.

The main body 41 is fixed to a belt of pants or the like using a chain 44 and a retaining ring 45 to prevent the main body 41 from falling.6 Figure 9 shows the antenna of the present invention when it is incorporated into an arm-mounted small portable type+I device. FIG.

In FIG. 9, an example is shown in which an antenna is incorporated into an arm band 58 having a means for attaching to the arm, since this is a radio device to be carried while attached to the arm.

A main body 51 has a radio, and an inner metal plate 53 used as a loop antenna is connected thereto. The outer layer metal plate 52 has a structure in which the inner layer metal plate 53 is sandwiched therebetween with an insulating plate 54 interposed therebetween. Outer layer metal plate 52
is grounded within the main body 51.

The buckle 55 is a means for connecting the arm band 58, and the outer layer metal plate 52 and the inner layer metal plate 53 are connected to the main body 51.
It has means for electrically connecting so that it forms a loop when viewed from above.

In the case of the arm-worn type, the arm 56 of the human body is always close to the antenna, as shown in FIG. In addition, the main body 5
1, the outer circumferential side of the wrist band 58 may also come close to the human body or other objects. These effects can be largely eliminated because the outer layer metal plate 52 always faces outward.

The arm-worn type is always close to the human body, so it is expected that the influence of the human body will be large, but by using the antenna of the present invention, the antenna circuit's resonance frequency can be prevented from shifting, and sensitivity can always be maintained at a constant level. It has the feature of being able to send and receive data.

FIG. 10 is an external view of a small wrist-mounted portable radio device equipped with the antenna of the present invention. Information data is displayed on the main body 51 in which the antenna is incorporated in the wrist band 58 by a display section 63. Further, the information is expressed in audio by the speaker 65. Further, various operations can be performed using the switch 64.

[Effects of the Invention] As described above, the antenna of the present invention has the effect of preventing a shift in the resonant frequency of the antenna circuit caused by an object such as a human body coming close to the antenna.

Further, it is characterized by being equipped with the antenna of the present invention.
Small portable radios can always transmit and receive with constant sensitivity even when they are carried.

The present invention is extremely effective as a means for solving the inherent difficulties of small portable radio devices that transmit and receive high frequencies.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the antenna of the present invention viewed from the aperture direction. FIG. 2 is a perspective view of the antenna of the present invention. FIG. 3 is an equivalent circuit diagram of an antenna circuit including the antenna of the present invention. FIG. 4 is an example diagram of a conventional antenna. FIG. 5 is a perspective view of a conventional antenna. FIG. 6 is an antenna circuit diagram using a conventional antenna. FIG. 7 is a diagram showing another embodiment of the antenna of the present invention. FIG. 8 is an external view of a small portable radio device equipped with the antenna of the present invention. FIG. 9 is a longitudinal sectional view of the antenna of the present invention incorporated into a small portable radio device worn on the wrist. FIG. 10 is an external view of a small wrist-mounted portable radio device equipped with the antenna of the present invention. Outer layer metal plate...Inner layer section I! : Plate... Insulating plate... End... Board... End connection tab... Coil 12 ・ ・ ・ 13 ・ ・ ・ l 4 ・ ・ ・ l 5 ・ ・ ・ 16, 17 18 ・・ ・ 21 ・ ・ ・ 22 ・ ・ 23, 24 ・ 3 l ・ ・ ・ ・ 32 ・ ・ ・ ・ 33 ・ ・ ・ ・ 34 ・ ・ ・ ・ 35 ・ ・ ・ ・ 36, 37 ・ 38 ・ ・ ・ ・ 41・ ・ ・ ・ 42 ・ ・ ・ ・ 43 ・ ・ ・ ・ 44 ・ ・ ・ ・ ・Variable capacitor ・Capacitor ・Ground ・Connection terminal ・Contact capacitor ・Loop antenna ・Board end coil variable capacitance capacitor Capacitor ground connection terminal Contact capacitor Main body display switch holder 45...Retaining ring 46...Speaker 51...Main body 52...Outer layer metal plate 53...Inner layer Metal plate 54... Insulating plate 55... Buckle 56... Human arm 58... Arm band 63... Display section 64... ...Switch 65...Speaker applicant Seiko Epson Co., Ltd. agent Patent attorney Kisanbe Suzuki (1 person) '4-3+
Nahama, 71η ≠? 1 draw

Claims (2)

[Claims] (1) In an antenna for transmitting and receiving radio wave signals, the antenna has a multilayer structure consisting of two outer layer metal plates, one inner layer metal plate, and two electrically insulating plates, and the above-mentioned two
two outer layer metal plates are located on the surface of the antenna,
The two electrically insulating plates are located inside the two electrically insulating plates, and the one inner metal plate is sandwiched between the two electrically insulating plates, and one end of the inner metal plate is connected to the antenna. The outer layer metal plate is connected to a signal input/output terminal of an antenna circuit including the antenna circuit, and another end thereof is connected to a ground terminal of the antenna circuit, and both of the outer layer metal plates are connected to the ground terminal of the antenna circuit. Features an antenna. (2) A small portable radio device comprising the antenna according to claim 1.