JP2002111352A - Antenna of head set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a pattern on a dielectrics substrate by reducing the effects of the components and head proximity making the radiation characteristics curve flat. SOLUTION: A conductor pattern of pair configuration is provided close to, along, the outline of an upper part of a dielectrics substrate which is similar to the shape of the upper part of a case of a head set, with a long distance from an electroacoustic transducer near the center of the substrate. The conductor pattern of pair configuration is made arc-like or meander-line dipole antenna, or a folded dipole, with a feeder end provided at the center of the upper part of the dielectrics substrate whose dielectric constant is 5.0 or less at 2.5 GHz. Two dipole antennas may be parallel to each other as a transmission/reception antenna.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna used for a short-range wireless device, and more particularly, to a headset antenna.

[0002]

2. Description of the Related Art Generally, an inverted F-type antenna provided on a substrate or a chip antenna is generally used as an antenna for a conventional short-range wireless communication device. In any case, since a portion corresponding to the ground plane is required, there is a restriction on the arrangement. In the arrangement relationship with the small ground plane and the antenna, the antenna characteristics cannot be sufficiently ensured, or the antenna characteristics greatly change depending on whether or not a human body approaches.

When a chip antenna is arranged on a substrate inside a housing of a headset which is directly attached to an ear of a head, the thickness and width of a rectangular chip antenna are relatively large.
It cannot be placed near the outer shape of the board, and is easily affected by the metal part of the electro-acoustic converter placed near the center of the upper part of the housing. Further, the price of the chip antenna itself cannot be ignored.

[0004]

SUMMARY OF THE INVENTION An antenna having a dipole configuration in which a pattern is directly formed along the outer shape of a substrate in a housing of a headset of a short-range wireless communication device is mounted. Make the antenna less affected by the presence or absence of objects.

[0005]

The antenna of the headset according to the present invention has a dipole antenna formed of a pair of thin conductor patterns having a feed end in the upper center, and is mainly made of resin and has a dipole antenna of 2.4 GHz. It is disposed in close contact with a dielectric substrate having a relative dielectric constant smaller than 0.

In order to put a small headset on the ear,
The upper part of the housing of the headset is formed in an arc shape or mainly in an arc shape. In addition, since the circular electro-acoustic transducer that generates sound is placed near the center of the dielectric substrate, the main center line of the paired conductor pattern should be placed close to the upper outer shape of the dielectric substrate. Thus, the distance between the paired conductor pattern and the electroacoustic transducer can be increased.

When the main part of the upper part of the housing is arc-shaped, the conductor pattern of the pair is constituted by a main part with an arc-shaped curve, and its center line is close to the outer shape of the dielectric substrate. Be placed.

Alternatively, the paired conductor patterns are formed in a meander line shape. The main part of the meander line-shaped conductor pattern is arranged such that its center line is close to the outer shape of the dielectric substrate.

Alternatively, the main part is an arc-shaped parallel 2
In this curve, one side has a feeding end in the upper center, and the other side has a continuous shape without the feeding end to form a pair-shaped conductor pattern, which is arranged close to the outer shape of the dielectric substrate. 20
The dipole antenna has an impedance of about 0 ohm.

Alternatively, a main part is an arc-shaped curve,
Two types of paired conductor patterns having a meander line shape are arranged along the outer shape of the dielectric substrate with their respective center lines parallel to each other, and the two types of paired conductor patterns are provided with independent feeding ends.

When a dielectric substrate mainly composed of resin and having a relative dielectric constant at 2.4 GHz of 5.0 or less is used, a dielectric substrate composed of an epoxy resin and glass cloth is used. , And other electric components may be mounted.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings. FIG. 1 shows an embodiment of an antenna of a headset according to the present invention, in which a part of a housing of the headset is cut away. The headset is a device used for short-range wireless communication such as the Bluetooth standard and used by directly touching the ear of the head, and the headset shown in the embodiment of the present invention is a small one that is directly worn on the ear. is there. Of course, it has an electro-acoustic converter 2 for generating sound. The microphone 3 is mounted below the housing 1 of the headset, and electric components such as a wireless circuit are mounted on the dielectric substrate 4. By adopting a configuration in which it is sandwiched and fixed between the ears between the support portion 5 that is movable back and forth and the housing 1, the mountability to the ears is ensured while the size is reduced.

The paired conductor patterns 6 and 7 are formed along the outer shape of the upper part of the dielectric substrate 4. The paired conductor patterns 6 and 7 form a dipole antenna having feeding ends 8 and 9 at the upper center. When the main part of the upper part of the housing 1 is formed in an arc shape, the dielectric substrate 4 having the outer parts 10 and 11 in which the upper main part is in an arc shape is used in order to incorporate the upper part in the housing 1. The main portions of the conductor patterns 6 and 7 are formed in an arc-shaped curve along the vicinity of the outer shape of the dielectric substrate 4, and the relative permittivity at 2.4 GHz mainly composed of resin is 5.
It is arranged on a dielectric substrate 4 of 0 or less. Unlike the chip antenna, the thickness of the dipole antenna formed by the paired conductor patterns 6 and 7 can be almost ignored.
Even if the distance between the dielectric substrate 4 and the dielectric substrate 4 is small, there is no problem.

An arc-shaped outer shape 10 above the dielectric substrate 4;
An electro-acoustic converter 2 having a circular outer shape is arranged near the center 12 of the eleventh. It may be fixed to the surface of the dielectric substrate 4 opposite to the paired conductor patterns 6 and 7 or the inner surface of the housing 1. The distance between the magnetic circuit made of metal such as the circular yoke 13 of the electro-acoustic transducer 2 and the paired conductor patterns 6 and 7 is increased, and the paired conductor patterns are formed along the outer shape of the dielectric substrate 4. By arranging the dipole antennas 6 and 7, the influence of the electro-acoustic converter 2 can be reduced.

It is preferable that the electro-acoustic converter 2 has a function of vibrating at about 100 Hz in addition to a function of generating sound. In order to generate vibrations related to the human body, it is necessary to increase the diameter of the yoke 13 which is a magnetic circuit. Also in this case, the distance between the conductor patterns 6 and 7 and the yoke 13 can be increased, and interference with the yoke 13 can be reduced. As the electro-acoustic converter 2, it is also possible to use a device that generates sound using a piezoelectric element. Similarly, it is possible to increase the distance between the large-sized metal parts such as the electrodes and the case of the piezoelectric element and reduce the interference.

The housing 1 of the headset is attached to the ear by the support 5 and has an electro-acoustic converter 2 having a diameter of about 17 mm.
Is placed inside and the ear is applied to the ear, so that the upper dimension of the housing 1 needs to have a width of about 37 mm. The dielectric substrate 4 built in the vicinity of the housing 1 has an arcuate outer shape 10 at the top,
The radius of 11 is about 17 mm. When the feeding ends 8 and 9 are provided at the center upper portion of the dielectric substrate 4 and the main parts of the paired conductor patterns 6 and 7 are formed by arc-shaped curves.
The antenna length required to form an antenna having a dipole configuration corresponding to a half wavelength at 4 GHz can be configured so that the central angle of the whole is 180 degrees or less. The arrangement of the paired conductor patterns 6 and 7 along the outer shape of the dielectric substrate 4 reduces the influence of other electric components on the dielectric substrate 4 and reduces the mounting area for disposing the electric components. It will also be possible to secure a large amount.

The reason why the pair of conductor patterns 6 and 7 is used as a dipole antenna is that the dipole antenna does not require a ground plane and that stable characteristics can be obtained. It is important that the antenna of the headset has little interference with the metal yoke 13 of the electro-acoustic transducer 2 disposed close to the antenna, and that the characteristic change of the antenna due to the presence or absence of a human body is small.

When a headset is used for short-range wireless communication such as the Bluetooth standard, the antenna must have a radiation characteristic whose gain does not become extremely small in a specific direction. FIG. 2 shows a diagram comparing the radiation characteristics. FIG. 2A shows the radiation characteristics of a dipole antenna in which the main part of the embodiment shown in FIG.
Indicated by FIG. 2B shows the radiation characteristics of a standard dipole antenna in which the paired conductors are parallel. Both show the field strength of the figure eight pattern in a plane 360 degrees around the antenna where the lowest gain occurs. The dipole antenna composed of the conductor patterns 6 and 7 having a pair of arcs shown in the embodiment of FIG. 1 is arranged at a central angle of about 180 degrees, so that the maximum gain is higher than the radiation characteristic of the standard dipole antenna. Relatively low and gain dip relatively shallow. The maximum gain is -2.5 dBd, the difference between the maximum and minimum gains is reduced by about 7 dB, and the gain is leveled.

FIG. 3 is a partially cutaway view of another embodiment of the headset antenna of the present invention. Although shown in larger dimensions than the embodiment of FIG. 1, the housing 14 is about the same size as the housing of FIG. The main part of the upper part of the housing 14 is close to the inside of the arcuate shape 15, and the dielectric substrate 18 whose main part has the arcuate outer shapes 16 and 17 on the upper part is arranged. A pair of conductor patterns 19 and 20 having a meander line shape are arranged along the arcuate outer shapes 16 and 17 on the dielectric substrate 18. A meander line-shaped pair of conductor patterns 19,
The 20 arc-shaped center lines 21 and 22 are made close to and parallel to the arc-shaped outer shapes 16 and 17 of the dielectric substrate 18.

Arc-shaped outer shape 1 above dielectric substrate 18
The paired meander line-shaped conductor patterns 19 and 20 are arranged at positions away from the circular electro-acoustic converter 24 installed near the center 23 of the electro-acoustic converters 6 and 17. Yoke 25 of circular shape of vessel 24
Metal interference can be reduced. Further, the influence of the electric components of the dielectric substrate 18 and the mounting area for disposing the electric components can be increased.

A meander line-shaped conductor pattern 19;
20 has a shorter overall antenna length than the conductor patterns 6 and 7 having the arc-shaped curves in FIG. The entire antenna length is the length of the center lines 21 and 22 from the feeding ends 26 and 27 to the tips of the meander line-shaped conductor patterns 19 and 20. Meander line-shaped conductor patterns 19 and 20
The central angle of the antenna becomes 100 degrees or less, and the depth of the gain dip occurring in the radiation characteristic is between the standard dipole antenna and the dipole antenna having the arc-shaped curve in FIG. 1. Not as often as usual.

As shown in the embodiment of FIG. 1 or FIG. 3, the pair of conductor patterns 6, 7 and 19, 20 are brought into close contact with the dielectric substrates 4 and 18 so that the antenna length is shorter than in the free space. Can be shortened. But 2.
In the case of a dielectric substrate having a large relative dielectric constant of 4 gigahertz and 8.0 or more, shortening has progressed, and the resonance frequency of the dipole antenna formed by the meander line-shaped conductor patterns 19 and 20 of the embodiment of FIG. Impedance is 5
Since the impedance becomes much smaller than 0 ohm and the impedance of the feeding end is usually 50 ohm or more, reflection occurs.
In the case of a substrate having a relative permittivity of 5.0 or less, the impedance at the resonance frequency of the dipole antenna can be increased to 50 ohms or more by the balance between the degree of shortening and the meander line shape. Matching can be achieved. A dielectric substrate having a relative dielectric constant of 5.0 or more is generally a ceramic plate having a relative dielectric constant of 2.4 gigahertz and 8.0 or more or a substrate mixed with ceramic fine powder, which is expensive.

A half-wave dipole antenna composed of parallel paired conductors usually shows an impedance of about 75 ohms, and when the angle formed by the paired conductors is 90 degrees, it shows about 50 ohms. As the antenna length decreases, the radiation impedance decreases and the capacitive reactance increases. Therefore, the antenna is loaded with an inductive reactance and resonated at a target frequency. To do so, a pair of conductor patterns 1
The capacitive reactance and the inductive reactance are balanced by changing the pitch, width or line width of the meander line shapes 9 and 20. Increasing the relative permittivity of the dielectric substrate requires shortening the antenna length of the meander line-shaped pair of conductor patterns and increasing the capacitive reactance of the impedance due to the effect of the large relative permittivity.
At the target frequency, the capacitive reactance cannot be canceled by the inductive reactance due to the meander line shape.

FIG. 4 is a partially cutaway view of another embodiment of the present invention. A conductor pattern is formed by two curved lines 28 and 29 whose main parts are arc-shaped, and are arranged close to each other along the arc-shaped outer shape 31 of the dielectric substrate 30. The two curves 28 and 29 are electrically connected at the two tips 32 and 33. One of the arc-shaped curves 28 is continuous without providing a power supply end at the upper center, and the other arc-shaped curve 29 is provided with power supply ends 34 and 35 at the upper center. The overall antenna length is approximately the same as the half-wavelength dipole, forming a folded dipole antenna having feed ends 34 and 35 at the center.

A folded dipole antenna is a type of dipole antenna, and can make the impedance of the antenna a relatively large value of about 200 ohms. The radiation characteristics and the efficiency are almost the same as those of the half-wave dipole antenna. The reason why the impedance of the antenna is set to about 200 ohms is that the input / output impedance of the terminal of the transmission / reception circuit may be set to about 200 ohms, and to match this. Folded
The dipole antenna has advantages that the fractional bandwidth is slightly wider than the half-wavelength dipole antenna, and that it is easily matched with an unbalanced terminal.

FIG. 5 is a partially cutaway view showing another embodiment of the present invention. Two types of dipole antennas, a pair of conductor patterns 39 and 40 having a main part formed along the outer shape 38 of the dielectric substrate 37 and having a pair of arc-shaped curves and a pair of conductor patterns 41 and 42 having a meander line shape, are used. Are arranged with their center lines parallel. Each dipole antenna has independent feed ends 43, 44 and 45, 46, one of which is dedicated to serving as a transmitting or receiving antenna. The distance between the two types of dipole antennas may be greater than the range in which interference between the two antennas is allowed. In practice, the distance between the two closest types of conductor patterns 39, 40, 41, and 42 is set to 1.5 mm or more. I just need. The distance from the electro-acoustic converter 47 to the meander line-shaped conductor patterns 41 and 42 can be made relatively large.

An antenna used for short-range wireless communication such as the Bluetooth standard needs to perform transmission and reception. In the case where transmission and reception are performed alternately, a switching circuit for switching is required to connect the terminals of the antenna to the transmission circuit and the reception circuit. Through the switching circuit, not only loss of about 2 dB to 3 dB occurs, but also extra circuit cost and mounting area are required. If two types of antennas, transmission and reception, are arranged as in the embodiment of FIG. 5, no switching circuit is required. However, a circuit is generally required to prevent transmission radio waves from entering the receiving circuit from a nearby receiving antenna.

The antenna of the headset of the present invention is preferably a dielectric substrate mainly composed of resin and having a relative dielectric constant of 5.0 or less. As a result, in particular, a value in which the impedance of the meander line-shaped dipole antenna is approximated to 50 ohms can be selected, and even when the antenna length is shortened, the voltage standing wave ratio becomes a small value of 1.5 or less. It is preferable to use a dielectric substrate formed of an epoxy resin and glass cloth as the above-mentioned dielectric substrate.
A substrate having a relative dielectric constant of 4.4 at gigahertz was used.
The occurrence of defects at the terminal joints of the electric components due to the difference in the coefficient of thermal expansion is small.

The antenna of the headset of the present invention is a balanced type because it is a dipole antenna. In the embodiment of FIGS. 1 and 3 and FIG. 5, an antenna length that resonates at a half wavelength is selected, and the impedance is set to about 50 ohms. In order to reduce the reflection and improve the antenna efficiency, it is necessary to interpose a balanced-unbalanced converter when connecting to an unbalanced RF output terminal. As in the embodiment of FIG.
In a folded dipole antenna having an impedance of about 200 ohms, it is appropriate to connect to a balanced terminal, but even if it is connected to an unbalanced terminal, no major problem occurs.

When the antenna of the headset of the present invention is applied to the 2.4 GHz band, which is the Bluetooth standard for short-range wireless communication, the fractional bandwidth of the arc-shaped dipole antenna of the embodiment of FIG. Can be obtained. In the meander line-shaped dipole antenna of the embodiment of FIG. 3, a fractional bandwidth of about 3.6% can be obtained. It can meet the 3.3% bandwidth requirement of the Bluetooth standard. The fractional bandwidth indicates a ratio of a frequency width having a voltage standing wave ratio (VSWR) of 2.0 or less to a center frequency of the frequency width.

In the Bluetooth standard for short-range wireless communication, it is necessary to reduce transmission power as much as possible, and an efficient antenna is required. If the efficiency is high, the output can be suppressed and the signal level of the reception can be increased, which is advantageous for noise and can reduce the load on the reception circuit. The antenna of the headset according to the present invention has a thickness that is negligibly small and is arranged on the outer peripheral portion of the dielectric substrate, so that it does not hinder the arrangement of other components or substantially reduce the mounting area. Even if the antenna is shortened to some extent, it is longer than the chip antenna. Therefore, the antenna efficiency is relatively good even if the paired conductor wires are arranged non-parallel.

Although the arc-shaped curve and the meander line shape are used for the conductor pattern of the antenna of the present invention, an antenna in which the arc-shaped curve and the meander line shape are connected may be used.
In the present invention, it is added that the shape of the portion near the feeding end is defined as an arc shape or a meander line shape. Further, the arc-shaped curve is not defined by mathematical precision, but has a shape approximate to an arc.

[0033]

Since the antenna of the headset according to the present invention is configured as described above, it has the following advantages.

An antenna having a dipole configuration arranged in an arc shape can obtain a radiation characteristic having a smaller gain dip than an antenna having a parallel dipole configuration. Short-distance wireless communication such as the Bluetooth standard can easily cope with the need for gain leveling.

By forming a conductor pattern close to the outer shape of the dielectric substrate that is similar to the shape of the housing of the headset, the conductor pattern can be arranged away from the metal part of the electro-acoustic converter, and the electric components can be arranged. Mounting area can be increased. Further, since the dipole antenna can be formed in the same etching step as the conductor pattern for the circuit on the dielectric substrate, the cost of the antenna can be reduced.

By using an antenna having a dipole configuration, a ground antenna is not required, and a stable antenna characteristic with a small change depending on the presence or absence of the vicinity of the head can be obtained. Further, the antenna efficiency can be made relatively good, which is advantageous for reducing the transmission power.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an antenna of a headset according to the invention in a partially cut-away view.

FIG. 2 is a diagram comparing the radiation characteristics of the present invention and a standard dipole antenna.

FIG. 3 shows another embodiment of the antenna of the headset of the present invention in a partially cutaway view.

FIG. 4 shows another embodiment of the headset antenna of the present invention in a partially cutaway view.

FIG. 5 is a partially cutaway view of another embodiment of the headset antenna of the present invention.

[Explanation of symbols]

1, 14 Headset housing 2, 24, 36, 47 Electro-acoustic converter 4, 18, 30, 37 Dielectric substrate 5 Movable support 6, 7, 39, 40 Main part of circular arc Conductor pattern 8, 9, 26, 27, 34, 35, 43, 44, 45,
46 Feeding end 10, 11, 16, 17, 31, 38 Upper outer shape of dielectric substrate 13, 25 Circular yoke 19, 20, 41, 42 Meander line-shaped conductor pattern

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoichi Ito 16-2 Kimachi, Aoba-ku, Sendai, Miyagi F-term (reference) 5J046 AA04 AB13 PA07 QA02 5J047 AA04 AB13 EF05

Claims (7)

[Claims] 1. An antenna used for short-range wireless communication, wherein a dielectric substrate having a relative permittivity of 2.4 GHz and less than 5.0 is approximated to an inner shape of an upper portion of a headset housing. It is arranged close to the inside of the body, a circular electro-acoustic transducer is arranged near the center of the dielectric substrate, and a feeding end is provided at the upper center of the dielectric substrate along the outer shape of the dielectric substrate. An antenna of a headset, wherein a conductor pattern having a pair configuration is formed. 2. An antenna used for short-distance wireless communication, wherein the main part has an arc-shaped outer shape similar to the shape of the arc-shaped casing in the main part, and the electro-acoustic is located near the center of the dielectric substrate. 2. The headset antenna according to claim 1, wherein a transducer is arranged, and the pair of conductor patterns having a center line parallel to an outer shape of the dielectric substrate is arranged. 3. The headset antenna according to claim 1, wherein a main part of the antenna used for short-range wireless communication comprises the pair of conductor patterns formed by an arc-shaped curve. 4. The headset antenna according to claim 1, wherein said pair of conductor patterns is formed in a meander line shape in an antenna used for short-range wireless communication. 5. In an antenna used for short-range wireless communication, a main part is formed by connecting two arc-shaped parallel curves at two ends, and a feeding end is provided at the upper center of one of the curves. 3. The headset antenna according to claim 1, wherein a pair of conductor patterns is formed continuously at the upper center of the curve. 6. An antenna used for short-range wireless communication, wherein a main portion is composed of two conductor patterns having an arc-shaped curve and a meander line shape, and their center lines are arranged in parallel, and an independent feed is provided at the upper center. 3. The headset antenna according to claim 1, wherein the antenna has an end. 7. An antenna used for short-range wireless communication, wherein a substrate made of epoxy resin and glass cloth is used as the dielectric substrate.
7. The headset antenna according to items 6 to 6.