JPH08213832A - Antenna for mobile radio system - Google Patents

Abstract

PURPOSE: To reduce the deterioration in a basic characteristic of an antenna owing to the effect of a human body by connecting 1st and 2nd metallic boards with a metallic wire and providing a cable through which a feeding signal is supplied to attain a small size and light weight antenna mounted easily on the human body. CONSTITUTION: The antenna has antenna elements 2-4 made of a metallic board. The element 2 and a 1st conductor wire 8a are connected via a capacitor 5 and the element 4 and a conductor wire 8b are connected. The antenna element 2 is formed by a conductive pattern made of a metal such as copper and silver on an upper side of a thin dielectric board 1 and the area of the side is a×b. The elements 2, 3 are fixed at an interval t1 with a metallic wire 6. The element 4 is connected to an edge of the element 3 electrically. An insulation board 10 whose thickness is t2 is placed under the electrode 3. Three slits 7 are formed in the inside of the element 2 to form a meander line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile radio antenna. In particular, the present invention relates to a small mobile radio antenna which is attached to the shoulder of a human body and is suitable mainly for use in mobile radio.

[0002]

2. Description of the Related Art In recent years, demand for mobile communication using a wireless device such as a mobile phone is rapidly increasing. A planar small and thin antenna may be used for these radios. Conventionally, a plate-shaped inverted F antenna has been used as a small antenna for mobile phones. The structure of such an antenna is, for example, “T. Taga and K. Tsunekawa:“ Perform-
ance Analysis of a Built-in Planar Inverted F Ante
nna for 800MHz Band Portable Radio Units, "IEEE Tr
ans., vol. SAC-5, no. 5, pp.921-929 (1987) "and" Japanese Patent Application No. 2-250655 ". Since the plate-shaped inverted F antenna is small and can transmit and receive both horizontal and vertical polarized waves, it is suitable for a mobile phone used in multiple propagation paths.

[0003]

However, in the above-mentioned prior art, since the plate-shaped inverted F antenna is installed on the radio housing, the antenna and the human body are close to each other when the mobile phone is used.
There is a drawback that the gain is significantly reduced. In addition, the plate-shaped inverted F antenna functions as an antenna by connecting to a radio housing having a ground plane that is sufficiently larger than the antenna, so only the antenna can be installed away from the radio. There wasn't. As a result, there is a limit to downsizing the wireless device, and it has not been possible to downsize the wireless device so that the user is not bothered to carry the wireless device at all. As described above, it is particularly inconvenient for a person who always works to carry a wireless device to use a conventional wireless device which is not sufficiently miniaturized.

The inventors of the present invention have separated the antenna of the radio from the radio main body and made only the antenna of the human body, for example, to reduce the size and weight of the conventional radio having a plate-shaped inverted F antenna. I studied how to fix it on the shoulder. This method is mainly used at a frequency of about 150 MH.
When the antenna of the wireless device of z is separated from the main body, the impedance of the antenna becomes extremely large and a good matching state cannot be maintained, and it is impossible to attach and use the antenna only to the human body. Also another 1
One of the major technical challenges was the significant reduction in antenna gain due to mounting the antenna on the human body.

As a result of further research, the inventors have found that the above problem can be solved by connecting the coaxial cable and the antenna element via a trimmer capacitor. Regarding a significant reduction in antenna gain, (1) insert an insulating plate between the human body and the antenna element, (2) connect a third antenna element to the antenna element, and (3) attach the antenna. It has been found that the problem can be solved by setting the orientation of the antenna with respect to the human body in an optimum direction when the antenna is mounted on the shoulder of the human body. With respect to the above problems, a technique for improving the characteristics of the antenna when using the antenna in such a method and an invention for stably mounting the antenna on the human body have been completed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a mobile radio antenna separated from the radio main body in order to sufficiently miniaturize the radio main body.

Another object of the present invention is to provide a mobile radio antenna which is small and lightweight so that it can be easily mounted on the human body. Another object of the present invention is to provide a mobile radio antenna in which the deterioration of the basic performance of the antenna such as impedance and gain due to the influence of the human body is extremely small even when mounted on the human body.

Another object of the present invention is to provide a mobile radio antenna which can be stably mounted on a portion relatively less affected by the human body (for example, on the shoulder).

[0009]

In order to achieve the above object, a mobile radio antenna of the present invention is provided with a first metal plate and a first metal plate facing each other. A second metal plate electrically connected to the plate; a third metal plate standing on the second metal plate and electrically connected to the second metal plate; An insulating plate provided in close contact with the metal plate, a first conductive wire connected to the first metal plate via a capacitance, and a second conductive wire connected to the third metal plate. And a cable for supplying a power supply signal to the first metal plate and the third metal plate.

In the mobile radio antenna having the above structure, the first metal plate and the second metal plate are connected via a metal wire, and the first metal plate and the second metal plate are connected to each other. It is preferable to have fixing means for fixing the metal plates to each other.

In the mobile radio antenna having the above structure, it is preferable that the first metal plate has a slit. Further, in the mobile radio antenna having the above configuration,
The shape of the first metal plate is preferably a meander line shape.

In the mobile radio antenna having the above structure, the cable is a coaxial cable, the first conductive wire is an inner conductor of the coaxial cable, and the second conductive wire is an outer conductor of the coaxial cable. Is preferred.

Further, in the mobile radio antenna having the above structure, when the mobile radio antenna is installed on the shoulder of the human body, the first antenna is provided on the arm side.
It is preferable that the metal plate and the second metal plate are connected to each other via a metal wire, and the third metal plate is provided on the arm side.

In the mobile radio antenna having the above structure, it is preferable that the capacitance is a variable capacitor. Further, in the mobile radio antenna having the above structure, it is preferable that a dielectric is filled between the first metal plate and the second metal plate.

In the mobile radio antenna having the above structure, the first metal plate has a length of 65 mm or less and a width of 6 mm.
It is preferably 5 mm or less. Further, in the mobile radio antenna having the above configuration, the distance between the first metal plate and the second metal plate is preferably 30 mm or less.

In the mobile radio antenna having the above structure, the thickness of the insulating plate is preferably 30 mm or less.

[0017]

The mobile radio antenna of the present invention is constructed as described above, and the first metal plate, the second metal plate and the third metal plate function as antenna elements for transmitting and receiving radio waves. Also, the first metal plate and the third metal plate are connected to a cable, and can be connected to the radio device main body via this cable. This allows the antenna to be separated from the radio body. An insulating plate is provided in close contact with the second metal plate, which allows the antenna to be electrically separated from the human body when the antenna is attached to the human body. As a result, even when the antenna is installed close to the human body, the change in impedance and the deterioration in gain can be extremely suppressed. Further, since the antenna element can be supplied with power via the capacitor, the matching state of the antenna can be made extremely excellent although the ground plane is not required.

Further, according to the preferable construction of the mobile radio antenna in which the first metal plate and the second metal plate are fixed by the metal wire and the fixing means, the antenna is deformed even when the antenna is mounted on the human body. It is possible to suppress deterioration of the antenna characteristics due to.

Further, according to the preferable configuration in which the first metal plate has the slit, it is possible to increase the peripheral length with respect to the size of the metal plate which is the antenna element. Since the circumference of the metal plate corresponds to the resonance frequency of the antenna, the size of the metal plate for a specific frequency can be further reduced by providing the slit.

Further, according to a preferred construction of the mobile radio antenna in which the shape of the first metal plate is a meander line shape, it is possible to further increase the peripheral length with respect to the size of the metal plate. Therefore, the size of the metal plate for a specific frequency can be further reduced. As a result, the size of the first metal plate can be made extremely small, and the antenna can be more easily attached to the human body. In addition, the distance between the first metal plate and the second metal plate is greatly reduced, which makes it easier to attach the antenna to the human body.

Further, according to the preferable structure in which the mobile radio antenna is connected to the main body by the coaxial cable, it is possible to receive and transmit stable electromagnetic waves with less noise picked up.

When the mobile radio antenna is installed on the shoulder of a human body, the first metal plate and the second metal plate are connected to each other via a metal wire on the arm side and on the arm side. According to the preferable configuration in which the third metal plate is provided, the impedance change and the gain deterioration can be further reduced even when the antenna is installed close to the human body.

Further, in the mobile radio antenna, according to a preferable configuration in which the capacitance is a variable capacitor or a dielectric is filled between the first metal plate and the second metal plate, the variable capacitor is added to the capacitance. By properly adjusting the capacity of the variable capacitor by using the antenna, the characteristics of the antenna can be improved. Further, the antenna can be installed close to the human body, and even in this case, the change in impedance and the deterioration in gain can be further reduced.

In the mobile radio antenna, the first metal plate has a length of 65 mm or less and a width of 65 mm or less,
Alternatively, the distance between the first metal plate and the second metal plate is 3
According to a preferable configuration in which the thickness of the insulating plate is 0 mm or less, or the thickness of the insulating plate is 30 mm or less, the antenna becomes smaller.

The most important feature of the present invention is that an insulating plate is provided in close contact with the antenna element and that a third metal plate is connected to the antenna element. As a result, the antenna can be made compact and lightweight suitable for wearing on the human body, and even when the antenna is installed close to the human body, the change in impedance and the deterioration in gain can be suppressed to an extremely small level.

Further, another important feature of the present invention is that when the antenna is installed on the shoulder of the human body, the connection point between the first and second metal plates is on the arm side opposite to the head. This makes it possible to further reduce the change in impedance and the deterioration in gain when the antenna is installed close to the human body.

As described above, the antenna of the present invention can be attached separately from the radio device, and one side of the antenna element can be reduced to about 65 mm or less, and an extremely high gain can be obtained when attached to a human body. The resulting antenna has been realized.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a mobile radio antenna according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a first embodiment of a mobile radio antenna according to the present invention. The antenna of this embodiment has an antenna element 2 which is a first metal plate, an antenna element 3 which is a second metal plate, and an antenna element 4 which is a third metal plate.
The antenna element 2 and the first conductive wire 8a are connected via the capacitor 5, and the antenna element 4 and the conductive wire 8b which is the second metal wire are connected.

The antenna element 2 is formed on the upper surface of the thin dielectric substrate 1 by a conductive pattern of copper, silver, conductive paste or the like, and the area is a (vertical length) × b. (Horizontal length). The antenna element 2 and the antenna element 3 are fixed and held at a distance t ₁ by a spacer (capacity) 5 which is a fixing means. The antenna element 2 and the antenna element 3 are electrically connected to each other by a metal wire 6 at points near the corners.

The dielectric substrate 1 is made of glass epoxy in this embodiment. The substance used for the dielectric substrate 1 may be any substance having a dielectric property, and it is preferable to use a substrate having a high relative dielectric constant because the size can be reduced, but the substance is not limited to a specific substance.

The antenna elements 4 are electrically connected to each other at the edges of the antenna element 3.
The antenna elements 3 and 4 are installed substantially vertically. An insulating plate 10 having a thickness of t ₂ is installed under the antenna element 3 so as to be in close contact therewith.

The antenna of the present embodiment has the first conductive wire 8a.
And a coaxial cable 8 having an inner conductor that is the outer conductor and an outer conductor that is the second conductive wire 8b. The coaxial cable 8 is a cable for supplying a power feeding signal to the antenna elements 2 and 4. The inner conductor 8a of the coaxial cable 8 is connected to the antenna element 2 via a trimmer capacitor 9 which is a variable capacitor for impedance matching of the antenna, and the outer conductor 8b is connected to the antenna element 4. As the trimmer capacitor 9, a capacitor (capacity) having an appropriate capacity may be used.

As shown in FIG. 1, the antenna element 2 has three slits 7, 7, 7 formed inward from one edge of the element. The shape in which the plurality of slits 7, 7, 7 are formed in the antenna element 2 and the antenna element 2 meanders is called a meander line shape. The resonance frequency of the antenna is the antenna element 2
The perimeter is approximately λ / 2, which is approximately determined by the perimeter. Here, λ is the wavelength of the used frequency. However, the resonance frequency is an approximate value, so an accurate value is obtained by experiment. Λ / 2 for antennas without slits
Is about (2a + 2b). Therefore, the slit 7 serves to lengthen the circumference of the antenna element 2 and lower the resonance frequency of the antenna. That is, since the perimeter of the antenna element 2 and the resonance frequency of the antenna are inversely proportional, if the dimensions a and b of the antenna element 2 are the same, forming the slit 7 lowers the resonance frequency. However, the presence / absence, shape and number of slits are arbitrary.

As in the present embodiment, a plurality of slits 7, 7, 7 are formed in the antenna element, and the antenna element 2 is formed in a meander line shape in a meandering shape, whereby the perimeter of the antenna element can be further extended. It is possible to significantly reduce the resonance frequency. Since the perimeter of the antenna element determined by the used frequency can be realized by using the antenna element having a smaller surface, the antenna can be further downsized.

Next, an antenna which can obtain an extremely high gain when mounted on a human body, a technique for improving the characteristics of the antenna when this antenna is used, and a technique for stably mounting the antenna on the human body The technique will be clarified by describing the following examples.

FIG. 2 is an explanatory view showing a state in which the antenna 21 shown in FIG. 1 is worn on the shoulder of the user 22. As shown in FIG. 2, the antenna 21 includes a radio 23
Are connected by a coaxial cable. By making the structure of the antenna as in this embodiment, the size of the antenna can be reduced to a size suitable for shoulder mounting, so that it does not disturb the user 22.

FIG. 3 is a diagram showing measured values of the voltage standing wave ratio (VSWR characteristic) of the mobile radio antenna of the present invention.
In FIG. 3, reference numeral 31 is a line showing measured values when the antenna is mounted on the shoulder of the human body as shown in FIG. 2, and 32 is a line showing measured values when the antenna is placed in free space. The size of the antenna element 2 used for the measurement is a = b = 50 m
m, the distance between the antenna elements 2 and 3 is t ₁ = 10 m
m, and the thickness of the insulating plate 10 is t ₂ = 10 mm. The number of slits 7 is 18, and the length of the meander line antenna element 2 is 900 mm. The measurement frequency range is 135 to 185 MHz.

As shown by the solid line 31 in FIG. 3, it can be seen that a good matching state is obtained when the device is worn on the shoulder and the resonance frequency is 159 MHz. The frequency bandwidth with a voltage standing wave ratio (VSWR) of 2 or less is 5 MHz (specific bandwidth = 3%). The matching state of the antenna changes depending on the distance between the metal wire 6 and the feeding point of the coaxial cable 8 and the value of the trimmer capacitor 9. By appropriately selecting these values, a good matching state can be obtained.

Further, as shown by the dotted line 32 in FIG. 3, the deterioration of the VSWR characteristics in the free space is small and 159 MHz.
It can be seen that the VSWR at is 1.6. This suggests that the change in the VSWR characteristics due to the mounting condition of the antenna on the shoulder or the individual difference is small.
Therefore, the mobile radio antenna of this embodiment can obtain a very good matching state, although it does not require a ground plane.

FIG. 4 is a graph showing the directivity of the antenna. The dimensions of the antenna are the same as the dimensions of the antenna used for the measurement in FIG. The directivity of the antenna was measured by mounting the antenna on the left shoulder as shown in FIG. The measurement frequency is 159 MHz. The directivity was measured based on a standard dipole antenna.

In FIG. 4, a solid line 41 indicates the vertical polarization directivity in the horizontal plane (XY plane) of the mobile radio antenna of the present invention, and a dotted line 42 indicates the direction when a conventional whip antenna of about 170 mm is attached to the chest. Showing sex. Reference numeral 43 shows the human body seen from above, and the X direction in the figure shows the front direction of the human body. The whip antenna is attached to the left chest. As can be seen from FIG. 4, the maximum radiation level is −11 dBd for the mobile radio antenna of the present invention and −19 dBd for the whip antenna.

As can be seen from these directivities, it is understood that the mobile radio antenna of this embodiment can obtain an extremely high gain as compared with the conventional whip antenna. When the antenna of this embodiment is worn on the human body, it is desirable to mount the antenna on the shoulder in order to obtain good antenna characteristics. However, the antenna is mounted stably on the shoulder and the antenna characteristics are good. In order to keep the above, it is desirable that the size of the surface of the antenna element 2 is 65 mm or less in the length a and 65 mm or less in the width b. Length a and width b are each 65 mm
If it exceeds, it becomes too large, which makes it inconvenient when it is worn on the human body, and a great deal of discomfort occurs. Also, the antenna element 2
The distance t ₁ between the antenna element 3 and the antenna element 3 is preferably 30 mm or less. The thickness of the insulating plate is 30mm
The following is desirable. If the distance t ₁ between the antenna elements and the thickness of the insulating plate exceed 30 mm, the size becomes large compared to the improvement of the effect, which is inconvenient for carrying.

As described above, the three technical inventions described below largely contribute to the fact that the mobile radio antenna of the present invention exhibits a high gain when it is attached to a human body. Next, these will be described in order. In this embodiment, a dielectric glass epoxy substrate having a thickness of 0.8 mm is used as the dielectric substrate 1, and the distance t ₁ between antenna elements is t ₁ = 10.
The mobile radio antenna of FIG.

The first is the insertion of the insulating plate 10. Figure 5
Is a mobile radio antenna of the present invention.
Thickness t of the insulating plate 10 adhered to the element 2₂ By horizontal
It is a figure which shows the change of the maximum gain in a surface. t₂ = 0 is
Although there is no insulating plate, the gain at this time is −
Very low at 17 dBd. However, with an insulating plate attached, t
₂ Is increased, t₂ Gain increases rapidly up to = 3 mm
And t₂ == 10 mm, the value is about -11 dBd. This
Insert the insulating plate 10 between the antenna and the human body
This prevents the gain deterioration when the antenna is attached to the human body.
The problem is greatly improved. It is used for the insulating plate 10.
As long as the substance has an insulating property,
A material with a large specific resistance is preferable for forming a mold, but
It need not be limited to the substance.

The second is an antenna element (metal plate) 4
Is the addition of. The mobile radio antenna of the present invention radiates radio waves using a magnetic current formed in the opening around the antenna element 2 as an equivalent wave source. Further, in the present invention, a metal plate is installed in the opening to intentionally obstruct the emission of radio waves in a specific direction, thereby greatly changing the gain when the human body is attached. By installing the metal plate 4 adjacent to the metal wire 6 as in the embodiment shown in FIG.
The gain improvement of Bd was obtained.

The third is the installation direction of the antenna. When the antenna is mounted on the shoulder, the antenna can be installed in various directions, but the present invention has a large gain when installed in one specific direction as compared to when installed in another direction. I'm taking advantage of it. That is, when the antenna is mounted on the shoulder and the metal wire 6 and the metal plate 4 are installed on the arm side opposite to the head as shown in FIG. 2, the gain is installed on the head side. It is about 5 dBd larger.
Thus, when the antenna is mounted on the shoulder of the human body, the problem of gain deterioration is greatly improved by setting the orientation of the antenna with respect to the human body in the optimum direction. Also, FIG.
In the above, the case where the antenna is installed on the left shoulder is shown, but it is also possible to install it on the right shoulder. In that case, the installation positions of the metal wire 6 and the metal plate 4 may be on the opposite side of FIG.

By the above-mentioned three technical inventions, an antenna which can obtain an extremely high gain when mounted on a human body has been realized. FIG. 6 shows a second mobile radio antenna according to the present invention.
2 shows the configuration of the embodiment of FIG. Second shown in FIG.
Among the members of the embodiment, the members having the same functions as the members of the first embodiment have the same reference numerals as those used in the first embodiment.

In the embodiment shown in FIG. 6, a dielectric 11 is filled between the antenna elements 2 and 3. By doing so, the resonance frequency of the antenna can be lowered, and thus the antenna can be further downsized. The substance used for the dielectric body 11 of the present embodiment is not limited to a particular substance as long as it has a dielectric property.

In the above description of the embodiments, the antenna elements have the same shape and are all described as squares, but the shape of the antenna elements is not necessarily square.
For example, it may be rectangular or circular.

[0051]

According to the present invention, since the antenna element can be extremely miniaturized by using the capacitance, a mobile radio antenna separated from the radio main body is provided in order to sufficiently miniaturize the radio main body. It becomes possible to do. Also, by using the variable capacitor, the matching state of the antenna can be made extremely good even though it does not have a ground plane.

Further, according to the mobile radio antenna of the present invention, it is possible to provide a mobile radio antenna which is small and lightweight so that it can be easily mounted on the human body.
Further, even when mounted on the human body, it is possible to suppress deterioration of the basic performance of the antenna such as impedance and gain due to the influence of the human body to an extremely small level.

Further, since the antenna of the present invention can be made small and have a low profile, it can be stably mounted on a portion (for example, on the shoulder) that is relatively unaffected by the human body. In addition, the antenna of the present invention can be filled with a dielectric between two antenna elements, and can be further downsized, and an antenna that can be easily worn on the shoulder can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of a mobile radio antenna of the present invention.

FIG. 2 is a perspective view showing a state in which the mobile radio antenna shown in FIG. 1 is worn on a user's shoulder.

FIG. 3 is a VSW of the mobile radio antenna shown in FIG.
It is a figure which shows R characteristic.

FIG. 4 is a radiation characteristic diagram of the mobile radio antenna shown in FIG.

5 is a diagram showing a change in gain depending on the thickness of an insulating plate of the mobile radio antenna shown in FIG.

FIG. 6 is a perspective view showing a second embodiment of the mobile radio antenna of the present invention.

[Explanation of symbols]

 1 Dielectric Substrate 2 Antenna Element (First Metal Plate) 3 Antenna Element (Second Metal Plate) 4 Antenna Element (Third Metal Plate) 5 Spacer (Capacity) 6 Metal Wire 7 Slit 8 Coaxial Cable 8a 1st Lead wire 8b Second lead wire 9 Variable trimmer capacitor 10 Insulating plate 11 Dielectric

Claims (11)

[Claims] 1. A first metal plate, a second metal plate provided opposite to the first metal plate and electrically connected to the first metal plate, and the second metal plate. A third metal plate standing on the plate and electrically connected to the second metal plate; an insulating plate provided in close contact with the second metal plate; and a first metal plate A first conductive wire connected via a capacitor and a second conductive wire connected to the third metal plate are provided, and a power supply signal is supplied to the first metal plate and the third metal plate. A mobile radio antenna having: 2. The first metal plate and the second metal plate are connected via a metal wire, and the first metal plate and the second metal plate are fixed to each other. The mobile radio antenna according to claim 1, further comprising fixing means for 3. The first metal plate has a slit,
The mobile radio antenna according to claim 1. 4. The mobile radio antenna according to claim 1, wherein the first metal plate has a meander line shape. 5. The cable according to claim 1, wherein the cable is a coaxial cable, the first conductive wire is an inner conductor of the coaxial cable, and the second conductive wire is an outer conductor of the coaxial cable. The mobile radio antenna according to any one of claims 1. 6. When installed on the shoulder of a human body, the first metal plate and the second metal plate are connected via a metal wire on the arm side, and the third metal plate is installed on the arm side. Claim 1 provided
The mobile radio antenna according to any one of items 1 to 5. 7. The mobile radio antenna according to claim 1, wherein the capacitance is a variable capacitor. 8. The mobile radio antenna according to claim 1, wherein a dielectric is filled between the first metal plate and the second metal plate. 9. The first metal plate has a length of 65 mm or less and a width of 65 mm or less.
An antenna for mobile radio according to item. 10. The mobile radio antenna according to claim 1, wherein a distance between the first metal plate and the second metal plate is 30 mm or less. 11. The mobile radio antenna according to claim 1, wherein the insulating plate has a thickness of 30 mm or less.