JPH1084209A - Antenna device and small radio device provided with the same - Google Patents

Abstract

(57) Abstract: The present invention facilitates tuning of a loop antenna used by being fixed to a necklace, and obtains stable communication quality without changing antenna characteristics even when worn on a human body. And a small radio device provided with the same. An inductance element (6) is connected in parallel to a loop antenna (2) attached to a necklace of a small wireless device (5) so that the loop opening surface is perpendicular to the surface of a human body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small radio device to be worn on a human body, and more particularly to an antenna device for improving antenna characteristics.

[0002]

2. Description of the Related Art As a conventional antenna device for a small radio device, an antenna in which a loop antenna is incorporated in a neck string is electrically insulated in a neck band 3 as shown in FIG. 1 of JP-A-1-241902. In some cases, the electric conductor 1 covered by the body 2 is used as a loop antenna.

[0003]

The resonance frequency f of a loop antenna is generally expressed by the following formula: f = 1 / [2π × (L × C) ^1/2 ] L: inductance of antenna, C: capacitance of tuning circuit You. With a loop antenna fixed to a necklace, the loop length is several tens of cm, the antenna inductance value is too large, and even if a small amount of stray capacitance is added, self-resonance occurs, and a desired value is obtained. It was difficult to tune by resonating at the frequency.

[0004] Further, since the necklace has flexibility, the shape of the loop antenna tends to change depending on the posture or movement of the wearer, and the antenna inductance changes, resulting in a change in the directivity and the like.
The antenna characteristic called antenna efficiency was apt to change, and the communication quality fluctuated greatly.

According to the present invention, in a loop antenna fixed to a necklace, the tuning range is widened by facilitating the tuning of the antenna, and the fluctuation of the antenna characteristics due to the change in inductance and capacitance caused by the influence of the human body is reduced.
An object of the present invention is to provide an antenna device and a small wireless device that can realize stable communication quality.

[0006]

In order to achieve the above object, an antenna device according to the present invention is fixed to a necklace and has a first
And an inductance element constituting a second loop antenna connected in parallel to the conductor. Further, the inductance element is characterized in that the loop opening surface is configured to be perpendicular to the human body surface when worn on the human body.

Further, the invention is characterized in that the inductance element is an air core coil. Also, a magnetic material is inserted into the loop of the air-core coil. The magnetic material is a ferrite material. Also,
The inductance element is formed of a loop-shaped metal plate.

[0008] Further, a small radio device of the present invention includes any one of the above antenna devices.

According to the antenna device of the present invention, as shown in the circuit diagram of FIG. 3, the main loop antenna 9 fixed to the necklace and the inductance element 10 are connected in parallel in a circuit. Can be reduced. For example, if both inductance values are the same, the inductance value becomes half as a whole. The antenna device includes capacitive elements 11, 12 such as chip capacitors.
The antenna tuning circuit and the impedance matching circuit are constituted by a and 12b, and are connected to the transmission / reception circuit 13 of the small radio. A loop antenna is built into the necklace, and the loop length is used radio wave (for example, VHF or UHF band frequency)
Even when the length of the loop antenna is longer than that of the wavelength and the inductance value of the loop antenna is increased, the antenna can be easily tuned by combining with the inductance element. Further, even when the antenna tuning circuit is combined with a variable capacitance element, a wide tuning frequency range can be secured.

Furthermore, when a magnetic material such as a ferrite material is inserted into the inductance element, the number of magnetic fluxes interlinking with the loop opening surface becomes twice the relative permeability of the ferrite, so that the inductance value becomes large and the main loop becomes large. The total inductance value with the antenna increases. When the operating frequency is relatively low, this configuration is effective because the larger the antenna inductance value, the easier it is to tune the antenna.

Further, when the inductance element is used as an auxiliary loop antenna, a large antenna gain is obtained by utilizing the image effect of the human body because the loop opening is oriented perpendicular to the human body. be able to. As shown in FIG. 4, when the loop antenna 15 is placed so that the loop surface is perpendicular to the human body surface 14, the current direction 17 of the image antenna 16 created by the influence of the human body and the actual antenna 15 The direction 17 of the flowing current is in phase. A synergistic effect between the actual antenna and the image antenna is obtained, and the antenna gain becomes larger than before mounting on the human body.

Further, since the auxiliary loop antenna does not change in shape and its antenna gain is relatively stable, it is possible to obtain a stable antenna gain as a whole even when the shape of the main loop antenna of the necklace changes. it can.

Further, since the directions of the magnetic fields of the main loop antenna and the auxiliary loop antenna are orthogonal to each other, there is an effect of polarization diversity. It is suitable for mobile communication because it can suppress occurrence.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the antenna device of the present invention will be described with reference to the drawings. In FIG. 1, a small radio 3
Is connected to a necklace 1 made of chemical fiber, synthetic resin, leather, or the like, so that the user can carry or use the small wireless device 3 around his or her neck. A loop antenna 2 made of a metal wire having high conductivity such as copper or a thin flexible substrate is formed inside the neck string 1. The loop antenna 2 may also be provided with a flexibility in order to make the neck string 1 flexible and enhance the mounting property. In the small wireless device 3,
An operation button 4 and a display window 5 for displaying information such as a liquid crystal panel are provided, and can be used for information terminals such as a pager, a radio, a liquid crystal television, and a clock.

FIG. 2 is a schematic perspective view illustrating the configuration of an embodiment of the antenna device according to the present invention, and is an example of the structure in the case of the small wireless device 3 shown in FIG. An air-core coil 6 is connected as an inductance element to the loop antenna 2 so as to be parallel to the circuit. The air core coil 6 is mounted so that the loop opening surface is perpendicular to the surface of the human body when the human body is worn in order to utilize the effect of the image antenna by the human body. In this example, an example of a four-turn coil is shown, but if a large inductance is required, the number of turns may be further increased. As a material of the air core coil 6, silver, copper, or the like having high conductivity is desirable. A display element 8 such as a liquid crystal panel is provided in the small wireless device main body 7 to disclose information.

FIG. 5 shows an example of measured data of the antenna directivity in the horizontal plane of the present antenna device. Dotted line 19 is the measurement result of the antenna alone, and solid line 20 is the measurement result when the antenna is worn on a human body. This example is data for vertical polarization, and is normalized by the maximum value of the antenna gain. It can be seen that even when the present antenna device is worn on a human body, the variation in antenna gain is small, and relatively stable antenna characteristics are exhibited. The directivity is also almost omni-directional, which is a desirable characteristic as a mobile communication antenna.

(Embodiment 2) FIG. 6 shows an embodiment of an antenna device according to the present invention, in which a ferrite material 23 is inserted into an air-core coil 22 as an inductance element connected in parallel to loop antennas 21a and 21b. It is. In order to increase the space utilization efficiency and reduce the size of the wireless device, the shape of the ferrite material may be changed to a square pillar or the like instead of a cylinder. If the frequency is up to about 150 MHz, the loss of ferrite is small, so that there is an effect that the antenna gain is increased by inserting the ferrite material. Radio unit 2
Reference numeral 4 denotes a display element 25 such as a liquid crystal panel.

(Embodiment 3) FIG. 7 shows an embodiment of the present invention, in which an auxiliary loop antenna 26 serving as an inductance element is formed of a single-turn loop-shaped metal wire and is formed on a side surface of a wireless device. It is. This embodiment has almost the same configuration as the example shown in FIG. 6, and the corresponding parts are denoted by the same reference numerals. The auxiliary loop antenna 26 is connected in parallel to the loop antennas 21a and 21b. When the operating frequency is relatively high, the present configuration is effective because a large inductance value is not required for tuning the antenna. The auxiliary loop antenna 26 is provided on the side surface of the wireless device main body 24 in order to secure an opening area as large as possible in the space inside the small wireless device case. The material of the auxiliary loop antenna 26 is desirably silver, copper, or the like having high conductivity. Also in this example, if a magnetic material such as a ferrite material is inserted in the loop plane of the auxiliary loop antenna 26, the antenna gain increases. A display device 25 such as a liquid crystal panel is formed in the wireless device main body 24.

(Embodiment 4) FIG. 8 shows an embodiment of the present invention, in which an auxiliary loop antenna 27 serving as an inductance element is formed of a wide metal plate. This embodiment has almost the same configuration as the example shown in FIG. 6, and the corresponding parts are denoted by the same reference numerals. The auxiliary loop antenna 27 is connected in parallel to the loop antennas 21a and 21b. Since the inductance value decreases as the width of the antenna plate increases, it is effective when the operating frequency is relatively high such as in the UHF band. The auxiliary loop antenna 2 is provided on a side surface of the wireless device main body 24 in order to secure an opening area as large as possible in the space inside the small wireless device case. The material of the auxiliary loop antenna 27 is desirably silver, copper, or the like having high conductivity. Also in this example, if a magnetic material such as a ferrite material is inserted in the loop plane of the auxiliary loop antenna 27, the antenna gain increases. A display device 25 such as a liquid crystal panel is formed in the wireless device main body 24.

(Embodiment 5) FIG. 9 shows an embodiment of the present invention, and shows a circuit configuration in a case where a small radio having an antenna device of the present invention has a receiving function. The antenna device 28 is connected to a receiving circuit 29 including an antenna tuning circuit. The receiving circuit 29 is connected to a VCO (voltage controlled oscillator) circuit 31 which is PLL-controlled by a synthesizer circuit 32. The signal amplified, filtered and demodulated by the receiving circuit 29 is decoded by the signal processing circuit 30 and enters the CPU 33. The CPU 33 drives the display means 34 such as a liquid crystal panel and the sounding means 35 such as a piezoelectric element and an electromagnetic buzzer in response to the input signal. In some cases, a speaker outputs an audio signal. CPU33
Is connected to input means 36 such as a mechanical switch and a sensor, and performs signal input such as operation mode switching and operation setting. Power is supplied to these components by a built-in primary battery, secondary battery, or the like.

In this embodiment, an example in which the small wireless device has a receiving function has been described. However, the effect of the antenna device of the present invention is effective even when the small wireless device has only a transmitting / receiving or transmitting function.

[0022]

Since the present invention is configured as described above, it has the following effects.

Since the main loop antenna fixed to the necklace and the inductance element are connected in parallel in circuit, the total inductance value can be reduced, and an antenna tuning circuit can be configured by combining with the capacitance element. , Can be easily tuned. Further, when combined with a variable capacitance element, the tuning frequency range can be set wide.

When the inductance element is configured as an auxiliary loop antenna, a large antenna gain is obtained by utilizing the image effect of the human body because the direction of the inductance element is configured to be perpendicular to the human body. Can be. In addition, since the antenna gain of the auxiliary loop antenna is relatively stable, even when the shape of the main loop antenna of the necklace changes, a stable antenna gain can be obtained as a whole.

Further, since the direction of the magnetic field is orthogonal to that of the main loop antenna, there is an effect of polarization diversity, the antenna directivity is improved, and the antenna becomes almost non-directional, so that the generation of a null point can be suppressed.

Further, if a magnetic material such as a ferrite material is inserted in the loop plane of the auxiliary loop antenna, a larger antenna gain can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a configuration of a small wireless device including an antenna device according to the present invention.

FIG. 2 is a schematic perspective view illustrating a configuration of the antenna device according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a circuit configuration of the antenna device according to the present invention.

FIG. 4 is an explanatory diagram showing the operation principle of the antenna device according to the present invention.

FIG. 5 is a graph showing the directivity of the antenna device according to the first embodiment of the present invention.

FIG. 6 is a schematic perspective view illustrating a configuration of an antenna device according to a second embodiment of the present invention.

FIG. 7 is a schematic perspective view illustrating a configuration of an antenna device according to a third embodiment of the present invention.

FIG. 8 is a schematic perspective view illustrating a configuration of an antenna device according to a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram illustrating a small radio device block configuration according to Embodiment 5 of the present invention;

[Explanation of symbols]

 1 ···· Necklace 2, 9, 21a, 21b · · · Main loop antenna 3 · · · · small radio 4 · · · operation buttons 5 · · · display window 6, 10 · ··· Inductance elements 7, 24 ··· Small radio unit 8, 25 ··· Display element 11 ··· Antenna tuning capacitance elements 12a and 12b ··· Capacitance element 13 ··· Transmission / reception circuit 14 ··· ..Human body surface 15 Loop antenna 16 Image antenna 17 Current flowing in loop antenna 18 Current flowing in image antenna 19 Antenna directivity of antenna alone 20 ··· Antenna directivity when worn on the human body 22 ··· Air core coil 23 ··· Ferrite material 26 ··· Auxiliary loop antenna 27 ··· Auxiliary loop antenna 28 ··· Antenna device 2 ··· Receiving circuit 30 ··· Signal processing circuit 31 ··· VCO circuit 32 ··· Synthesizer 33 ··· CPU 34 ··· Display means 35 ··· Sounding means 36 · ... Input means

Claims (7)

[Claims] 1. An antenna comprising: a conductor that is fixed to a necklace and forms a first loop antenna; and an inductance element that forms a second loop antenna connected in parallel to the conductor. apparatus. 2. The antenna device according to claim 1, wherein the inductance element is configured such that a loop opening surface of the inductance element is perpendicular to a human body surface when the human body is worn. 3. The antenna device according to claim 2, wherein said inductance element is an air core coil. 4. The antenna device according to claim 3, wherein a magnetic material is inserted into the loop of the air-core coil. 5. The antenna device according to claim 4, wherein said magnetic material is a ferrite material. 6. The antenna device according to claim 1, wherein the inductance element is formed of a loop-shaped metal plate. 7. A small radio device comprising the antenna device according to claim 1.