JPH1032424A - Parasitic antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parasitic antenna with less coupling loss. SOLUTION: This antenna 2 is composed of first and second antennas 21 and 22 and a power feeding line 23 for connecting them. The first antenna 21 is electrostatically coupled in a close state to the antenna 11 of a radio equipment 1. That is, in the case that the radio equipment 1 functions as a transmitter, a current supplied to the antenna 11 is made to flow to the parasitic antenna 2 through the electrostatic coupling. On the other hand, in the case that the radio equipment 1 functions as a receiver, radio waves sent from the other radio equipment are received by the parasitic antenna 2, thus a voltage is induced and the current made to flow by the induction of the voltage is supplied to the radio equipment 1 through the electrostatic coupling. Also, since the first antenna 21 and the antenna 11 of the radio equipment 1 are orthogonal with each other, they do not interfere with the radiation impedance of each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parasitic antenna used for extending a communication range of a radio having no feed line, such as a specific low-power radio station, and more particularly, to a parasitic antenna such as a whip antenna. The present invention relates to a parasitic antenna suitable for use in a wireless device having a linear antenna.

[0002]

2. Description of the Related Art The specified low-power radio station is defined by the Radio Law as "having no power supply line and grounding device" (Article 49-14 of the Radio Equipment Regulations). in this way,
Conventionally, there is a device as shown in FIG. 7, for example, as a device for extending the communication range of a wireless device that cannot use a power supply line and a grounding device.

In FIG. 1, reference numeral 1 denotes, for example, a radio of a specified low power radio station, and this radio 1 has a linear whip antenna 11, for example. And this radio 1
A parasitic antenna 2 having two linear, for example, whip antennas 21 and 22 is provided in addition to the antenna 11 of FIG. This parasitic antenna 2 is composed of the two antennas 2
One ends of the first and the second 22 are connected to each other via a feed line 23. Then, the two antennas 21 and 22
, For example, the first antenna 21 is
The antennas 11 are arranged in a state of being substantially parallel to the antennas 11, that is, extending in the same direction, and at a predetermined interval d.

[0004] Each of the antennas 21 and 22 constituting the parasitic antenna 2 has the same effective length L as the antenna 11 of the wireless device 1. The feed line 23 that couples the antennas 21 and 22 to each other is formed by, for example, a coaxial cable.

In the configuration shown in FIG. 7, it is assumed that, for example, an electromagnetic wave (hereinafter referred to as a radio wave) due to a radiated electric field is emitted from the antenna 11 of the wireless device 1. When the radio wave is emitted from the antenna 11 of the wireless device 1 as described above, the radio wave is once received by the first antenna 21 of the parasitic antenna 2, whereby the first antenna 21 has Voltage V is induced.

[0006]

(Equation 1)

In the equation 1, E is a radiated electric field [V / m] received by the first antenna 21, and L is an effective length [m] of the first antenna 21.

[0008] The current flowing when the voltage V is induced in the first antenna 21 is supplied to the second antenna 22 via the power supply line 23. As a result, a radio wave is generated from the second antenna 22 by the radiated electric field,
Fired in the air.

Contrary to the above, a radio wave transmitted to the radio device 1 from another radio device (not shown) can be received via the parasitic antenna 2.
That is, once the radio wave transmitted from the above another wireless device is
The signal is received by the second antenna 22 of the parasitic antenna 2. As a result, the voltage V represented by the above equation 1 is induced in the second antenna 22. Then, the current that flows when the voltage V is induced is supplied to the first antenna 21 via the power supply line 23. As a result, a radio wave due to the radiated electric field is emitted from the first antenna, and this radio wave is
The signal is received by the antenna 11 of the wireless device 1.

That is, according to the configuration shown in FIG. 7, by using the parasitic antenna 2, a state substantially equivalent to extending the antenna 11 of the wireless device 1 can be formed. 1 can be extended. Further, even when the wireless device of the communication partner is in a space where radio waves are shielded, or is out of the range of radio waves, for example, the second antenna 22 of the parasitic antenna 2 is arranged where necessary. By doing so, communication with the other party's wireless device becomes possible.

As described above, the parasitic antenna 2
The first antenna 21 is provided substantially parallel to the antenna 11 of the wireless device 1 because each of the antennas 11, 21
This is for efficiently receiving the radio waves emitted by the radiated electric field of each other. That is, each of the antennas 11, 21
Since a radio wave emitted from a linear antenna like this is a plane wave along the extension direction of the antenna, in order to efficiently receive it with a similar linear antenna, It may be extended in the direction along. For example, a horizontally-polarized radio wave is emitted by an radiated electric field from an antenna installed horizontally with respect to the ground, so that the antenna on the receiving side is installed horizontally to receive this efficiently. Similarly, a vertically polarized radio wave is emitted from an antenna that is installed vertically to the ground, so the antenna on the receiving side must be installed vertically to receive it efficiently. I do.

In order to increase the output of the entire apparatus shown in FIG. 7, that is, to increase the radio wave (radiation electric field intensity) emitted from the second antenna 22 of the parasitic antenna 2, the first
It is necessary to increase the voltage V induced in the antenna 21 of FIG. In order to realize this, as can be seen from Equation 1 above, the first antenna 21 is
The intensity E of the radiated electric field received from the antenna 1 may be increased, and for that purpose, the first antenna 21 may be brought closer to the antenna 11 of the wireless device 1 (the distance d may be reduced). This is because the radiated electric field strength E is inversely proportional to the distance d between the antenna 11 of the wireless device 1 and the first antenna 21. As described above, by reducing the distance d between the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2, the output of the entire device of FIG. 7 can be improved, and the entire device can be improved. The receiving sensitivity is also improved.

By the way, in the configuration shown in FIG. 7, it is known that the impedance Z of the antenna 11 of the wireless device 1 is generally expressed by the following equation (2).

[0014]

(Equation 2)

In the equation (2), the “effective constant” is an inherent impedance such as a conductor loss and an inductance of the line itself forming the antenna 11. The “radiation impedance” is an impedance corresponding to a radio wave being radiated from the antenna 11 into space. The “mutual radiation impedance” refers to the antenna 11
When two or more antennas including
This is the impedance caused by each antenna interfering with its respective radiation impedance.

Normally, when no other antenna such as the first antenna 21 exists in the vicinity of the antenna 11 in the vicinity of the antenna 11, the radio wave is efficiently radiated from the antenna 11. That is, it is designed that the [mutual radiation impedance] in the above equation (2) hardly exists. Therefore, the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2
Too close to each other, the mutual radiation impedance increases, and the output impedance of the antenna terminal (terminal to which the antenna 11 is connected) of the wireless device 1 and the antenna 1
Matching with the impedance of 1 cannot be achieved. Thereby, the antenna 11 of the wireless device 1
The coupling loss between the antenna and the first antenna 21 increases, the output efficiency of the wireless device 1 decreases, and the radio wave (radiated electric field intensity) emitted from the second antenna 22 of the parasitic antenna 2
Is weakened.

Therefore, in the configuration as shown in FIG. 7, the radiated electric field strength E is increased by bringing the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2 close to each other, and the mutual radiation impedance is increased. It is necessary to determine the distance d between the antennas 11 and 21 in consideration of the balance with the increase in the coupling loss between the antennas 11 and 21 due to the increase in the distance. For example, when the operating frequency f of the wireless device 1 is f = 430 MHz, which is one of the frequencies used in the specific low-power wireless station, by setting the interval d to d = about 10 cm, The coupling loss can be suppressed to a minimum of about 10 dB. At this time, a radio wave (radiation electric field) emitted from the second antenna 22
The maximum strength is obtained. At this time, the receiving sensitivity of the entire apparatus also becomes maximum. Note that the distance d is set to d = 10 cm.
Even if the value is increased or decreased from the above value, the coupling loss only increases, and does not become smaller than the value of 10 dB.

[0018]

However, in the above prior art, the distance d between the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2 is set to d = 10 cm, so that Although the coupling loss between the antennas 11 and 21 can be minimized, the coupling loss of 10 dB is hardly a small value. In particular, as in this example, the radio 1
In the case of a specific low-power radio station with a small output,
The coupling loss of 10 dB is a very large value. Therefore, despite the use of the parasitic antenna 2 to extend the communication range of the wireless device 1, there is a problem that the effect cannot be sufficiently exhibited.

Accordingly, an object of the present invention is to provide a parasitic antenna capable of extending the communication range of the wireless device 1 by further reducing the coupling loss.

[0020]

In order to achieve the above object, according to the present invention, a first antenna provided close to an antenna of a wireless device includes:
A second antenna connected to the first antenna via a feed line, wherein the first antenna is electrostatically coupled to an antenna of the radio, and the first antenna is
Antenna and the antenna of the wireless device are configured to avoid mutual interference with the respective radiation impedances of the respective antennas, that is, in a state where the respective antennas are hardly affected by the mutual radiation impedance described above. It is characterized by having.

That is, it is generally known that three electric fields, namely, a radiated electric field, an induced electric field, and a static electric field exist around an antenna emitting a radio wave. Of these three electric fields, the radiated electric field is inversely proportional to the distance from the antenna, the induced electric field is inversely proportional to the square of the distance from the antenna, and the static electric field is inversely proportional to the cube of the distance from the antenna. It has been known. Therefore, as the distance from the antenna becomes shorter, the induced electric field becomes larger than the radiated electric field, and the electrostatic field becomes larger than the induced electric field.

Therefore, the first aspect of the present invention intends to realize signal transmission between a radio device and a parasitic antenna by utilizing the above-mentioned electrostatic field, which increases dramatically as the distance from the antenna decreases. Is what you do. That is,
The antenna of the wireless device and the first antenna of the parasitic antenna are brought close to each other. This allows the first antenna to be placed in a very strong electrostatic field caused by the antenna of the radio, for example when the radio is functioning as a transmitter. Conversely, if the radio is functioning, for example, as a receiver, the radio's antenna can be placed in a very strong electrostatic field created by the first antenna. Thus, by placing the antenna of the wireless device and the first antenna close to each other and in a very strong electrostatic field, the two can be strongly electrostatically coupled.

In the state where the antenna of the wireless device and the parasitic antenna (first antenna) are electrostatically coupled as described above, for example, it is assumed that the wireless device now functions as a transmitter. In this case, a current (high-frequency current) is supplied from the wireless device to the antenna, and this current flows to the first antenna, that is, the parasitic antenna via the electrostatic coupling. After that, it flows to the second antenna via the feeder line, and the second antenna emits a radio wave.

On the other hand, when the wireless device functions as, for example, a receiver, radio waves transmitted from another wireless device are:
First, the signal is received by the second antenna of the parasitic antenna. As a result, a voltage is induced in the second antenna, and a current that flows due to the induction of the voltage flows to the antenna of the wireless device via the power supply line, the first antenna, and the electrostatic coupling, whereby the radio wave is transmitted to the wireless device. Will be received by

That is, in the above-described conventional technique, the radio waves are transmitted and received by the radiated electric field between the antenna 11 of the wireless device 1 and the parasitic antenna 1 (the first antenna 21). According to the first aspect of the present invention, a current flowing in one of the antenna of the wireless device and the parasitic antenna is supplied to the other via the above-described electrostatic coupling, instead of transmitting and receiving a radio wave.

The first antenna and the antenna of the wireless device are configured so as not to mutually interfere with their radiation impedance. Therefore, although these antennas are close to each other, they are hardly affected by the mutual radiation impedance described above.

According to a second aspect of the present invention, in the parasitic antenna according to the first aspect, the first antenna and the antenna of the wireless device are linear, and the first antenna is It is characterized by being provided in a state substantially orthogonal to the antenna of the wireless device. In this way, by making the first antenna orthogonal to the antenna of the wireless device, even if a radio wave due to a radiated electric field is emitted from one of these antennas, it is difficult to receive this radio wave by the other antenna. That is, the influence of the mutual radiation impedance can be reduced.

As the linear antenna here, there is a so-called monopole antenna (unipole antenna) such as a whip antenna.

According to a third aspect of the present invention, in the parasitic antenna according to the second aspect, the first antenna is arranged such that a center of an effective length of the first antenna is substantially equal to an effective length of an antenna of the wireless device. It is characterized by being provided so as to cross the center.

In other words, experiments have shown that by crossing the center of the effective length of the first antenna and the center of the effective length of the antenna of the radio, the coupling loss between the antennas can be minimized. Obtained.

According to a fourth aspect of the present invention, there is provided the parasitic antenna according to the first, second or third aspect, wherein a supporting means for supporting the first antenna is provided in the wireless device. It is.

That is, the first antenna of the parasitic antenna is supported by the wireless device via the support means. Therefore, this first antenna, and eventually the parasitic antenna,
This is equivalent to connecting directly to the radio.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a parasitic antenna according to the present invention will be described with reference to FIGS. 1 to 4. FIG.

Before describing the details of the present embodiment, first, a point of interest (technical idea) of the present invention will be described with reference to FIG. The figure shows a Hertz dipole (small dipole) that is fundamental when considering an antenna.
FIG. 3 is a view showing a state where the apparatus is placed in a free space. In the figure, it is known that the electric field strength E ₀ [V / m] generated by the Hertz dipole 3 at an arbitrary point P is the sum of three electric fields, a radiated electric field, an induced electric field, and an electrostatic field. The electric field is represented by the following equation (3).

[0035]

(Equation 3)

Here, I is the current [A] flowing through the dipole 3, L ₀ is the effective length [m] of the dipole 3, λ
Is the wavelength of the current [m], d ₀ is the distance from the dipole 3 to the point P (m). Θ is ΔPOX
(X is an axis passing through the center O of the dipole 3 and perpendicular to the extension direction of the dipole 3.), t is time [s], and c is the propagation speed of radio waves [m / s]. .

From _equation (3), the radiated electric field (first term) is inversely proportional to the distance d ₀ from the dipole 3, the induced electric field is inversely proportional to the square of the distance d ₀ , and the static electric field is the distance d _0.
Is inversely proportional to the cube of. Therefore, as the distance d ₀ from the dipole 3 becomes shorter, the induced electric field becomes larger than the radiated electric field, and the electrostatic field becomes larger than the induced electric field. This relationship is also established between the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2 shown in FIG.

Therefore, in order to simply express the above equation (3), the common part of each term in the equation (3) is put together into one coefficient A as shown in the following equation (4).

[0039]

(Equation 4)

Then, this equation 4 is substituted into the above equation 3, and
Summarizing this, the above equation (3) is simply expressed as in the following equation (5).

[0041]

(Equation 5)

Here, the distance d ₀ in Expression 5 is replaced with the distance d between the antennas 11 and 21 in FIG. 7, and the distance d is, for example, d = 1.
The values [m], 0.1 [m], and 0.01 [m] are substituted. Then, as the wavelength λ in Equation 5, for example, a wavelength corresponding to a frequency of f = 430 MHz, which is one of the frequencies f used in the specific low power radio station, that is, λ = c / f = (3 × 10 ^{−). 8} ) / (430 × 10) ≒ 0.
A value of 70 [m] is substituted. Then, a calculation result obtained by substituting each of these values into Equation 5 is
It is shown in Table 1.

[0043]

[Table 1]

As is clear from Table 1, when the antennas 11 and 21 are apart from each other, for example, when the distance d is d = 1 [m], the radiated electric field, the induced electric field and the static electric field are generated. Among them, the radiated electric field is the largest. Then, as the distance d becomes shorter, the induced electric field becomes larger than the radiated electric field, and the electrostatic field becomes larger than the induced electric field. Then, in a state where the antennas 11 and 21 are close to each other, for example, the distance d is d = 0.01.
In the state [m], the electrostatic field is the largest of the three electric fields, and its value is orders of magnitude larger than other radiated electric fields and induced electric fields.

Therefore, the present invention focuses on the fact that the electrostatic field is increased by orders of magnitude as described above by bringing the antennas 11 and 21 closer to each other. It is intended to be combined.
Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1A shows a schematic configuration of the present embodiment. As shown in the figure, this apparatus is different from the conventional apparatus shown in FIG. 7 in that the distance d between the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2 is larger than that in FIG. The antennas 11 and 21 are made to be orthogonal to each other while making the antennas closer together by making them even narrower. The distance d is, for example, d = 5 [mm]. Other configurations are the same as those in FIG. 7 described above, and therefore, the same portions are denoted by the same reference numerals and detailed description thereof will be omitted.

That is, since the antenna 11 of the wireless device 1 and the first antenna 21 of the parasitic antenna 2 are close to each other,
For example, when the wireless device 1 functions as a transmitter, the first antenna 21 is placed in a very strong electrostatic field generated by the antenna 11 of the wireless device 1. On the contrary, when the wireless device 1 functions as a receiver,
The antenna 11 of the wireless device 1 will be placed in a very strong static electric field generated by the first antenna 21. As described above, by placing the antennas 11 and 21 close to each other and in a very strong electrostatic field,
Both can be firmly electrostatically coupled to each other.

Thus, in a state where the antenna 11 of the wireless device 1 and the parasitic antenna 2 (first antenna 21) are electrostatically coupled, for example, the wireless device 1 now functions as a transmitter. Suppose you have In this case, from the wireless device 1,
A current (high-frequency current) is supplied to the antenna 11, and the current flows to the first antenna 21, that is, the parasitic antenna 2 via the above-described electrostatic coupling. After that, it flows to the second antenna 22 via the power supply line 23, and the second antenna 22 emits a radio wave.

On the other hand, when the wireless device 1 functions as a receiver, for example, a radio wave transmitted from another wireless device (not shown) is first transmitted to the second antenna 22 of the parasitic antenna 2.
Received at. As a result, a voltage is induced in the second antenna 22, and a current flowing due to the induction of the voltage flows to the antenna 11 of the wireless device 1 via the power supply line 23, the first antenna 21, and the above-described electrostatic coupling. As a result, the radio wave is received by the wireless device 1.

As described above, according to the present embodiment, currents are generated in the antenna 11 and the first antenna 21 of the wireless device 1 by performing communication, respectively. Feeding each other through a bond.

Further, although the antenna 11 and the first antenna 21 of the wireless device 1 are close to each other, they are orthogonal to each other. This radio wave is difficult to be received by the antennas 21 and 11 facing each other. That is, the antennas 11 and 21 do not interfere with each other with respect to their radiation impedances, that is, are hardly affected by the mutual radiation impedance described above. Therefore, even if the antennas 11 and 21 are provided close to each other, the coupling loss does not become extremely large unlike the related art, and the output efficiency and the reception sensitivity of the wireless device 1 do not decrease.

Here, FIG. 1B shows the intersecting positional relationship between the antenna 11 of the wireless device 1 and the first antenna 21.
In the figure, x is the distance from the tip of the antenna 11 of the wireless device 1 to the intersection with the first antenna 21 and y
Is the distance from the tip of the first antenna 21 to the intersection of the wireless device 1 with the antenna 11. When the output efficiency of the wireless device 1 was measured by changing the distances x and y by an experiment, when x was changed while y was constant, x became half the effective length L of the antenna 11 (x = L / 2). )
Maximum efficiency was obtained. On the other hand, when y was changed while x was constant, the maximum efficiency was obtained in the point that y became half of the effective length L of the first antenna 21 (y = L / 2). That is, when both x and y are set to half the effective length L of each of the antennas 11 and 21, that is, each of the antennas 11 and 2
When each center of the effective length L of the
Was obtained that the output efficiency was highest. Also in the present embodiment, the antennas 11 and 21 are provided in such a manner that the centers of the respective effective lengths L cross each other so that the maximum output efficiency is obtained.

By the way, as described above, the antenna 11 of the wireless device 1 and the first antenna 21 are electrostatically coupled, but in order to realize this electrostatic coupling, the antenna 11 and the antenna 21 must be connected to each other. Requires a capacitance. In the present embodiment, a capacitance is generated at a portion sandwiched between the antennas 11 and 21, that is, at a portion where the two intersect, and the electrostatic coupling is realized by the capacitance. Conversely, of the antennas 11 and 21 that do not intersect each other, for example, the first antenna 21,
The shaded portion in FIG. 1B is a portion that does not contribute to the capacitance. Therefore, instead of the first antenna 21, for example, by providing a small electrode having the same area as the above-mentioned crossing portion in the vicinity of the antenna 11 of the wireless device 1, the above-described capacitance is generated. Coupling can be achieved.

However, the first antenna 21 has a function of realizing the above-mentioned electrostatic coupling, and also has a function of the second antenna 22.
And more specifically, has a function of matching the output impedance of the antenna terminal 24 to which the second antenna 22 is connected with the impedance of the second antenna 22. Therefore, if, for example, the small electrode or the like is provided in place of the first antenna 21, impedance matching with the second antenna 22 cannot be obtained, thereby providing sufficient output efficiency and reception sensitivity. Is not obtained. Therefore, the first antenna 21 plays a very important role of realizing electrostatic coupling with the antenna 11 of the wireless device 1 and matching impedance with the second antenna 22. I have.

As described above, according to the present embodiment, by bringing the antenna 11 of the wireless device 1 and the second antenna 21 close to and orthogonal to each other, the two are firmly electrostatically coupled to each other, They are configured so that they are hardly affected by mutual radiation impedance. Therefore,
The coupling loss between the antennas 11 and 21 can be made smaller than that of the above-described conventional technology.
With the configuration shown in (1), the coupling loss can be suppressed to 3 dB. This value of 3 dB is much smaller (1/5) than the value of 10 dB in the above-mentioned conventional technology.
It is. Therefore, the intensity of the radio wave emitted from the second antenna 21 can be much higher than before, and
The receiving sensitivity of the wireless device 1 is also greatly improved. Therefore, there is an effect that the communication range of the wireless device 1 can be extended far more than before. This technique is particularly effective when a low-output device such as a specific low-power radio station is used as the radio 1.

Further, this technique is very effective when the wireless device of the communication partner is, for example, in a space where radio waves are shielded, or when it is out of the radio wave range. For example, a case where the wireless device of the other party is in a space where radio waves are shielded will be described with reference to FIG.

That is, in the figure, the radio 1 is, for example, a stationary type, and for example, two portable radios 3, 4 are provided in a space different from the space where the radio 1 is installed. Is arranged. And a space where the wireless device 1 is grounded;
The space where the portable wireless devices 3 and 4 are arranged is shielded so that radio waves do not mutually propagate. In such a case,
The second antenna 22 of the parasitic antenna 2 is
By arranging the antenna 11 in the space where the radios 4 are installed, a state equivalent to extending the antenna 11 of the radio 1 to the space where the radios 3 and 4 are arranged is formed. , And the wireless devices 3 and 4 can be communicated.
Also, as shown in the figure, even if there are a plurality of wireless devices 3 and 4 of the other party, and even if the plurality of wireless devices 3 and 4 are arranged in a wide range, a book having a wider communication range than the conventional one is provided. According to the embodiment, radio waves can be sufficiently transmitted and received between the wireless device 1 and each of the wireless devices 3 and 4.

FIGS. 4A and 4B show another example of the present embodiment. FIG. 4A is a front perspective view of the wireless device 1 and FIG. 4B is a rear perspective view thereof. This radio 1 has a first antenna 2
1 is provided with a support fitting 25 for supporting the wireless device 1.

That is, the first antenna 21 is attached to the rear surface of the wireless device 1 by the support bracket 25 in a state in which the first antenna 21 is close to the antenna 11 of the wireless device 1 and both are orthogonal to each other. This makes it possible to form a state equivalent to the case where the first antenna 21 and thus the parasitic antenna 2 are directly connected to the wireless device 1. Therefore, it is very convenient when storing the wireless device 1 or carrying the wireless device 1 together with the parasitic antenna 2. The support fitting 25 is easily detachable from the wireless device 1.

In FIG. 4, the first antenna 2
Although the first antenna 21 is formed in an L-shape, the first antenna 21 and the antenna 11 of the wireless device 1 do not interfere with each other's radiation impedance, and they are electrostatically coupled to each other. If so, the first antenna 21 may have a shape like the above-mentioned L-shape other than the linear shape.
Further, not only the first antenna 21 but also an antenna other than a linear antenna may be used for the antenna 11 and the second antenna 22 of the wireless device 1.

In the present embodiment, a case has been described where the present technology is applied to a specific low-power radio station, but this means that the present technology is particularly effective for a specific low-power radio station. It is. Therefore, the present technology can be applied to wireless stations (apparatuses) other than the specified low-power wireless station.

The linear antennas forming the antenna 11 of the wireless device 1 and the antennas 21 and 22 of the parasitic antenna 21 include, for example, those shown in FIG. That is, as shown in the figure, the antenna 11 (21, 22) is formed by extending a spirally formed conducting wire 12 in a substantially straight line as a whole, and covering this with, for example, an insulating sheath 13. is there. In addition, the thing of only the conducting wire 12 which is not covered with the outer cover 13 is also included in the linear antenna.

Further, as shown in FIG. 6, the feed line 23 forming the parasitic antenna 2
A matching circuit 26 may be provided on the side of the antenna 22. By providing this matching circuit 26, the antenna terminal 2
4 and the impedance of the second antenna 22 can be adjusted more delicately and with high accuracy, and the communication range can be further extended.

[0064]

According to the parasitic antenna of the first aspect of the present invention, by bringing the first antenna close to the antenna of the radio, the static electric field in which these antennas influence each other is increased. By placing each antenna in a strong electrostatic field in this way, the two are firmly electrostatically coupled to each other. Then, even when the antennas are close to each other, the antennas are configured to be hardly affected by the mutual radiation impedance. Therefore, the coupling loss between the antennas can be made smaller than that of the above-described related art, and thus, there is an effect that the communication range of the wireless device can be extended as compared with the related art. This technique is particularly effective when using a low-output radio such as a specific low-power radio station.

According to the second aspect of the present invention, the first
When the antenna of the wireless device and the antenna of the wireless device are linear antennas, the influence of the mutual radiation impedance is suppressed by making these antennas orthogonal to each other. Therefore, when the first antenna and the antenna of the wireless device are linear, the same effects as those of the first aspect can be obtained.

According to the third aspect of the invention, the center of the effective length of the first antenna and the center of the effective length of the antenna of the wireless device intersect with each other to reduce the coupling loss between the antennas. The smallest. Therefore, there is an effect that the communication range of the wireless device can be further extended.

According to the fourth aspect of the present invention, by attaching the first antenna to the wireless device via the support means, a state equivalent to directly connecting the parasitic antenna to the wireless device is formed. Can be. Therefore, there is an effect that it is very convenient when storing or carrying the wireless device.

[Brief description of the drawings]

1A and 1B are diagrams showing an embodiment of a parasitic antenna according to the present invention, in which FIG. 1A is a schematic configuration diagram showing a use state of the parasitic antenna, and FIG. It is the figure which expanded the coupling | bond part with an antenna.

FIG. 2 is an explanatory diagram of a Hertz dipole which is a basis of the embodiment.

FIG. 3 is a diagram showing an application example of the embodiment.

FIG. 4 is a diagram showing another example of the embodiment, and FIG.
FIG. 3B is a front perspective view of the wireless device, and FIG.

FIG. 5 is a diagram showing another form of each antenna in the embodiment.

FIG. 6 is a diagram in which a matching circuit is provided in the embodiment.

FIG. 7 is a schematic configuration diagram showing a use state of a conventional parasitic antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radio 2 Non-feed antenna 11 Antenna 21 1st antenna 22 2nd antenna 23 Feeding line

Claims (4)

[Claims] A first antenna provided in proximity to an antenna of a wireless device; and a second antenna connected to the first antenna via a feeder line. An antenna is electrostatically coupled to the antenna of the wireless device, and the first antenna and the antenna of the wireless device are configured to avoid mutual interference with respective radiation impedances of the antennas. A parasitic antenna characterized in that: 2. The wireless communication system according to claim 1, wherein the first antenna and the antenna of the wireless device are linear, and the first antenna is provided substantially orthogonal to the antenna of the wireless device. A parasitic antenna according to claim 1. 3. The wireless communication device according to claim 2, wherein the first antenna is provided so that a substantially center of an effective length thereof intersects a substantially center of an effective length of the antenna of the wireless device.
Parasitic antenna according to 1. 4. The parasitic antenna according to claim 1, wherein a supporting means for supporting the first antenna is provided in the wireless device.