JP2000091841A - Omnidirectional antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ominidirectional antenna for transmitting and receiving circular polarization radio waves. SOLUTION: A calling signal with a long band modulated by a prescribed code is transmitted from an automobile side, and a key unit side device owned by a driver receives the calling signal, and transmits a response signal with a VHF band modulated by a prescribed code so that doorlock can be automatically controlled at the automobile side based on this response signal in this system. A calling signal transmitting part 48 at the automobile side and a calling signal receiving part 12 at the key unit side are constituted of pairs of antenna elements 48a, 48b, 12a, and 12b constituted of bar antennas (which can be compact loop antennas) arranged so that the central axes of the bars can orthogonally cross each other, and phase shifters 48a and 12c for feeding a power to each antennal element with a phase difference which is 90 deg.C. Thus, the transmitting part 48 and the receiving part 12 can operate as omnidirectional antennas for transmitting and receiving circular polarization with horizontal face omnidirectivity, and radio communication between the key unit and the automobile can be realized even when the user owning the key unit is present in any direction in the surrounding of the automobile.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an omnidirectional antenna formed by using a pair of antenna elements composed of a bar antenna or a small loop antenna.

[0002]

2. Description of the Related Art Conventionally, for example, in a car, a door can be locked / unlocked by a radio wave transmitted from a remote control key carried by a driver.
There is known a so-called keyless entry system (also called a radio key system).

A remote control key used in such a system includes a transmission circuit for generating a signal for door lock or unlocking by operating a push button by a user, and a signal from the transmission circuit to an automobile. And a transmission antenna for transmission toward the transmission.

In a keyless entry system, if the transmitting antenna built in the remote control key has directivity, the direction of the remote control key with respect to the automobile is adjusted in accordance with the directivity of the transmitting antenna, and then the push button is operated. Must. For this reason, it is desirable that the transmitting antenna incorporated in the remote control key be non-directional.

Therefore, conventionally, in order to improve the directional characteristics of a transmitting antenna incorporated in a remote control key, for example,
As disclosed in Patent Publication No. 2771735,
An antenna element consisting of a bar antenna in which a conductive wire is wound around a ferrite bar, and an antenna consisting of a conductive pattern formed in a long shape along a direction perpendicular to the central axis of the coil part of the antenna element (the axis of the ferrite bar). It has been considered to configure a transmission antenna using the elements.

[0006]

However, in the transmitting antenna disclosed in the above publication, the directional characteristics of each antenna element are simply synthesized, so that the directional characteristics can be improved. The overall directional characteristics cannot be made omnidirectional. Radio waves radiated from a bar antenna are circularly polarized waves, whereas linearly polarized radio waves are radiated from a long antenna element used for improving directivity characteristics. The transmitted radio wave is an elliptical polarization obtained by combining a circularly polarized wave and a linearly polarized wave, and the receiving device receiving the transmitted radio wave may not be able to receive the transmitted radio wave properly depending on the direction of the receiving antenna. There are also problems. Therefore, the above conventional measures cannot make the direction of the remote control key unnecessary.

The present invention has been made in view of such a problem, and has as its object to provide an omnidirectional antenna capable of radiating a circularly polarized radio wave in four directions around an antenna.

[0008]

According to the first aspect of the present invention, there is provided an omnidirectional antenna, comprising: a pair of antenna elements each composed of a bar antenna or a small loop antenna; The antennas are arranged such that the central axes of the coil portions of the elements are orthogonal to each other.
Power is supplied with a phase difference of 0 degrees.

That is, a bar antenna or a small loop antenna is a conductor (or a conductive pattern) constituting an antenna element.
Is formed in a coil shape of one or more turns, so that circularly polarized radio waves can be transmitted and received. As shown in FIG. 7, the directional characteristics of the directional characteristics are determined by the coil plane (XZ along the X axis and Z axis shown in FIG. 7) orthogonal to the central axis Y of the coil portion.
Plane), but has a so-called figure-eight characteristic centered on the antenna element in the direction of the central axis Y of the coil portion. Therefore, when a bar antenna or a small loop antenna is used alone and wireless communication is performed, the antenna element of the communication partner is positioned on the Y axis or the XZ plane shown in FIG. Must be adjusted as follows. FIG. 7 shows the directional characteristics of a bar antenna in which a conductive wire is wound around a ferrite bar in a coil shape.
The X axis represents a horizontal axis perpendicular to the center axis Y of the bar antenna, and the Z axis represents a vertical axis perpendicular to the center axis Y of the bar antenna.

However, in this embodiment, antenna elements having such characteristics are arranged such that the central axes of the coil portions of the antenna elements are orthogonal to each other, and these antennas are fed with a phase difference of about 90 degrees. Thus, the directional characteristics of the entire antenna have a donut shape having a cross-sectional shape of eight, which is a combination of the directional characteristics of eight shapes of each antenna element. For example, when a pair of bar antennas are arranged horizontally so that their central axes Y are orthogonal, the directional characteristics are as follows:
The figure-eight characteristic indicated by the dotted line in FIG. 7 is a directional characteristic obtained by rotating the figure-characteristic around the Z-axis, and becomes a horizontal omnidirectional. In this case, since the directional characteristics are obtained by combining the eight-character characteristics, sensitivity can be obtained in the vertical direction, and wireless communication is possible even if the antenna element of the communication partner deviates from the horizontal plane.

Also, the deviation of the electrical angle of the transmission radio wave from each antenna element caused by orthogonalizing each antenna element is canceled by feeding each antenna with a phase difference of about 90 degrees. According to the omnidirectional antenna, a circularly polarized radio wave can be radiated in all radiation directions.

Therefore, according to the omnidirectional antenna of the present invention, not only is the antenna element to be communicated with a receiving antenna capable of receiving circularly polarized waves, but also the receiving antenna can receive linearly polarized waves. Even a receiving antenna can receive radio waves without adjusting the antenna direction.

As described above, according to the omnidirectional antenna of the present invention, since a circularly polarized radio wave can be radiated in all directions, for example, a door lock / unlock in a keyless entry system of an automobile described in the prior art is disclosed. If the present invention is applied to a transmission antenna for transmitting radio waves for use, wireless communication between the remote control key and the vehicle-side device can be favorably performed without adjusting the direction of the remote control key on the driver side.

The bar antenna according to the present invention is a well-known bar antenna in which a conductor is wound in a coil shape around a rod (ie, a bar) made of a magnetic material such as ferrite. Is a known loop antenna in which the diameter of the loop is made sufficiently small with respect to the wavelength λ of the signal to be transmitted and received (specifically, λ / 12 or less). The small loop antenna is not limited to one in which a conductor (or a conductive pattern) forming an antenna element is wound in a coil shape, and a so-called coil antenna in which a conductor is wound a plurality of times in a coil shape may be used. it can.

When configuring the omnidirectional antenna of the present invention, the bar antennas may be combined with each other.
Small loop antennas may be combined, or a bar antenna and a small loop antenna may be combined.
When a small loop antenna is used as one of the antenna elements constituting the omnidirectional antenna of the present invention,
As described in claim 2, a small loop antenna is formed by coiling a conductor constituting an antenna element around a housing that houses a circuit board in which an electronic circuit for performing wireless communication via the omnidirectional antenna is housed. It is good to form by winding in a shape.

That is, in the small loop antenna, in order to increase the gain, the diameter of the loop is increased, and
It is desirable to form a coil antenna by winding the loop a plurality of times in a coil shape. However, if such an antenna element is configured as a single unit, the size of the communication device will increase. However, as described in claim 2, a small loop antenna is formed around a housing that houses a circuit board in which an electronic circuit for performing wireless communication using the omnidirectional antenna of the present invention is housed. For example, by integrating the electronic circuit and the antenna element, it is possible to form a small loop antenna having a large gain without increasing the size of the communication device. Also, since this small loop antenna is formed by winding a conductor around the housing, even if the number of turns of the conductor is increased,
This does not cause an increase in the size of the device, and this can also increase the gain.

On the other hand, when a bar antenna is used as one of the antenna elements, an electronic circuit for performing wireless communication with the bar antenna via the omni-directional antenna as described in claim 3 is provided. What is necessary is just to accommodate in the housing | casing which accommodates the built-in circuit board. That is, in this way, the electronic circuit and the antenna element can be integrated, and the communication device can be prevented from becoming large.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an entire configuration of a keyless entry system for a vehicle according to an embodiment to which the present invention is applied.

The keyless entry system of this embodiment is
A predetermined frequency (for example, 134 k
(Hz) is provided with an oscillator unit 4 for transmitting a calling signal obtained by modulating the signal with a preset calling key code, and when the calling signal from the oscillator unit 4 is received by the key unit 6 held by the driver, A function of transmitting a response signal obtained by modulating a signal of a predetermined frequency (for example, 300 MHz) in a VHF band with a preset response key code is provided. A function that detects that the driver having the key unit 6 approaches the vehicle 2 or that the driver has left the vehicle 2 and automatically controls the door lock according to the detection result. is there.

Then, in order to realize such a function,
On the key unit 6 side, a paging signal receiving section 12 for receiving a signal in a long wave band corresponding to the paging signal, a reception amplifier circuit 14 for amplifying a reception signal from the paging signal receiving section 12,
A signal detection determination for restoring a key code from the reception signal amplified by the reception amplification circuit 14 and determining whether the key code is a calling key code from the oscillator unit 4 corresponding to the key unit 6 When the circuit 16 and the signal detection determination circuit 16 determine that the restored key code is a call key code from the oscillator unit 4 corresponding to the key unit 6, a predetermined response key code is set. The key code generation circuit 18 generates the VH according to the key code generated by the key code generation circuit 18.
A VHF oscillation circuit 20 that generates the response signal by generating an F-band signal, and a response signal transmission unit 22 that transmits the response signal generated by the VHF oscillation circuit 20 to the vehicle 2 are provided. .

The oscillator unit 4 is provided on the vehicle 2 side.
A response signal receiving unit 32 for receiving a VHF signal corresponding to the response signal; a signal processing circuit 34 for processing a signal received from the response signal receiving unit 32 to recover a key code from the received signal; The key code restored by the signal processing circuit 34 is the key unit 6 corresponding to the vehicle 2.
It is determined whether or not the key code is a response key code from the key unit 6 corresponding to the vehicle 2.
And a door lock control device 38 for driving a door lock actuator 36 mounted on the automobile 2 to control the locked state of the door.

The door lock control device 38 includes a CPU,
The microcomputer comprises a microcomputer having a ROM, a RAM, and the like. For example, when the ignition key is not mounted on a key cylinder of the automobile 2, the oscillator unit 4 is operated to respond to a response signal from the key unit 6. When the ignition switch is mounted on the key cylinder, door lock control is performed based on the switch operation by the vehicle occupant or the traveling speed of the vehicle.

The door lock control performed by the door lock controller 38 based on a response signal from the key unit 6 is as follows.
For example, when the key code restored by the signal processing circuit 34 is a response key code from the key unit 6 corresponding to the vehicle 2, the driver and the driver receive the response signal received by the response signal receiving unit 32 from the reception level of the response signal. The relative distance to the vehicle is calculated, and when the calculated relative distance is equal to or less than the unlock determination distance and the relative distance is gradually shortened (in other words, when the driver having the key unit 6 approaches the vehicle, ), The door lock actuator 36 is driven to automatically release the door lock. Conversely, if the calculated relative distance gradually increases and the relative distance exceeds the lock determination distance (in other words, the lock distance). For example, when the driver with the key unit 6 moves away from the car), the door lock actuator 36 is driven to automatically lock the door.

Next, the oscillator unit 4 receives an operation command from the door lock control device 38 and transmits a call signal around the automobile 2. The oscillator unit 4 has a long wave band serving as a reference of the call signal. An oscillating circuit 42 for generating a signal operates in response to an operation command from the door lock control device 38, and generates a calling signal by modulating the signal from the oscillating circuit 42 with a preset key code for calling. The control circuit 44 includes a control circuit 44, an amplifying circuit 46 for amplifying the call signal from the control circuit 44, and a call signal transmitting unit 48 for transmitting the call signal amplified by the amplifier circuit 46.

According to the keyless entry system of this embodiment configured as described above, the door lock is released only by the driver holding the key unit 6 approaching the car,
Also, the door is automatically locked when the driver moves away from the car. For this reason, the driver does not need to operate the key unit to lock the door or release the door lock, and the usability can be improved as compared with the general keyless entry system described in the related art section.

By the way, in such a system, when the driver carrying the key unit 6 approaches the automobile 2, the calling signal transmitted by the calling signal transmitting section 48 in the oscillator unit 4 is transmitted to the key unit 6 side. Paging signal receiving unit 12
Must be reliably received. For this purpose, at least the ringing signal transmitting unit 4 on the oscillator unit 4 side is required.
It is necessary to make the directional characteristics when the radio wave 8 radiates radio waves non-directional on a horizontal plane.

Therefore, in the present embodiment, the call signal transmitting section 4
8 and the call signal receiving unit 12 are both omnidirectional antennas that are omnidirectional in the horizontal plane and can transmit and receive circularly polarized radio waves. Hereinafter, the omni-directional antenna forming each of the sections 48 and 12 will be described with reference to FIG.

As shown in FIG. 2, the call signal transmitting section 48
A pair of antenna elements 48a and 48b each composed of a ferrite bar antenna in which a conductive wire is wound around a ferrite bar are arranged such that the central axes of the antenna elements 48a and 48b are horizontal and orthogonal to each other. A call signal from the output amplifying circuit 46 is output (supplied) via a feed line to the other antenna element 48b.
Output (feed) the call signal from the output amplifying circuit 46 via the feed line and the phase shifter 48c provided on the feed line.
By doing so, each antenna element 48a, 48b can be fed with a phase difference of 90 degrees.

The paging signal transmitting section 48 thus configured
The directivity characteristics of each antenna element 48 are as shown in FIG.
a, and becomes non-directional on a horizontal plane along the central axis of 48b. For this reason, the car 2 transmits a call signal substantially uniformly around the entire periphery thereof, and the driver with the key unit 6 can call the key unit 6 no matter from which direction. It becomes possible to transmit a signal.
Further, since the radio wave transmitted from the calling signal transmitting unit 48 is a circularly polarized wave, the key unit 6 can receive the calling signal regardless of the direction in which the calling signal receiving unit 12 faces.

On the other hand, as in the case of the calling signal transmitting section 48, the calling signal receiving section 12 includes a pair of antenna elements 12 each composed of a ferrite bar antenna in which a conductive wire is wound around a ferrite bar.
a and 12b are arranged such that the axes of the antenna elements 12a and 12b are orthogonal to each other.
a, a reception signal from the antenna element 12a is input to the reception amplification circuit 14 through a feed line, and the reception element from the other antenna element 12b is
2b is input via the feed line and the phase shifter 12c provided on the feed line, the received signals from the antenna elements 48a and 48b are combined with a phase difference of 90 degrees, and the received signal is amplified. 14.

For this reason, in this embodiment, the key unit 6
The paging signal receiving section 12 which receives the paging signal also has the same directional characteristics as the paging signal transmitting section 48 and is capable of transmitting and receiving circularly polarized waves. Can more reliably receive the paging signal transmitted from.

Here, the phase shifter 48c is connected to the output amplifying circuit 4
6 is delayed (phase-shifted) so that the phase difference between the paging signals transmitted to the antenna elements 48a and 48b is 90 degrees, so that each of the antenna elements 48a,
The purpose of the present invention is to combine the radio waves radiated from 48b to make the directional characteristics of the calling signal transmitting section 48 non-directional, and to provide the present invention together with the feed line from the output amplifier circuit 46 to each of the antenna elements 48a and 48b. Function as power supply means.

The phase shifter 48c can be constituted by a passive circuit in which the amount of phase shift can be set by the amount of inductance of an inductive element such as a choke coil or the like. An active circuit including active elements such as a transistor and an IC, such as a delay circuit that cascade-connects and delays an input signal by a delay amount of each inverter, can also be used.

The phase shift amount of the phase shifter 48c may be set in consideration of a phase difference caused by a line length difference between feed lines from the output amplifier circuit 46 to the antenna elements 48a and 48b. Assuming that there is no line length difference in the feed line and no phase difference occurs in the feed line, a 90-degree phase shifter may be used as the phase shifter 48c.

Similarly to the phase shifter 48c, the phase shifter 12c receives signals from the antenna elements 12a and 12b from the reception amplification circuit 1c.
It functions as the power supply means of the present invention together with the power supply line 4 and may be configured in the same manner as the phase shifter 48c.
In FIG. 2, each antenna element 48a, 48b, 1
2a and 12b have capacitors C1, C2 and C, respectively.
3 and C4 are connected in parallel. Each of these capacitors C1 to C4 forms a resonance circuit together with each antenna element, and the resonance frequency of the resonance circuit is equal to the frequency of the call signal (134 kHz).
z), so that transmission and reception of the call signal can be performed well.

By the way, in the keyless entry system of this embodiment, the key unit 6 which has received the calling signal
On the vehicle side, the response signal transmitting unit 22 transmits a response signal in the VHF band, and on the automobile 2 side, the response signal is received by the response signal receiving unit 32 to control the door lock. It is desirable to use an omni-directional antenna for the 22 and the response signal receiving unit 32 as well. For this purpose, the present invention may be applied to these units, and an omnidirectional antenna configured in the same manner as the above-described paging signal transmitting unit 48 and paging signal receiving unit 12 may be used.

However, since the response signal transmitting section 22 and the response signal receiving section 32 transmit and receive signals in the VHF band having a short wavelength, in the present embodiment, the response signal transmitting section 22 on the key unit 6 side includes , A linear antenna formed of a conductive wire or a conductive pattern is used, and a reception antenna for television / radio reception mounted on the automobile 2 is used as the response signal receiving section 32 on the automobile 2 side. Like that.

In the response signal transmitting section 22, a linear antenna is used because the response signal has a short wavelength, so that even if a linear antenna is used as the transmission antenna, the antenna length may not be long. No, key unit 6
This is because the linear antenna is omnidirectional and there is no need to consider the directional characteristics.

In this embodiment, however, as shown in FIG. 4B, the response signal transmitting unit 22 is provided on a circuit board 6a in the key unit 6 by a pair of linear antennas 22a and 22b orthogonal to each other. By supplying power to these units at a phase difference of 90 degrees, the response signal transmitting unit 22 transmits a circularly polarized radio wave. This is so that the response signal transmitted from the key unit 6 can be received regardless of the direction in which the receiving antenna forming the response signal receiving unit 32 is oriented on the vehicle 2 side.

As shown in FIGS. 4 (a) and 4 (b), in the oscillator unit 4 and the key unit 6, the antenna elements 48a, which are bar antennas constituting the paging signal transmitting section 48 and the paging signal receiving section 12, respectively. 48b and 12
a, 12b, one of the antenna elements 48a, 12a
Are installed in the housings 4b, 6b of the units 4, 6 so that the central axes are orthogonal to the board surfaces through the holes formed in the circuit boards 4a, 6a of the units 4, 6, The other antenna elements 48b, 12b are fixed on the circuit boards 4a, 6a such that the central axis is parallel to the board surfaces of the circuit boards 4a, 6a of the units 4, 6. As a result, the call signal transmitting section 48 and the call signal receiving section 12 are housed in the housings 4b and 6b together with the other electronic circuit components constituting the units 4 and 6, and the wiring in the units 4 and 6 is performed. Work and the like can be simplified, and the size of each unit 4 and 6 can be reduced.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various embodiments can be adopted. For example, in the above embodiment, in the paging signal transmitting unit 48 and the paging signal receiving unit 12, the antenna elements 48a, 48b and 12a, 12b
Are all described as using a bar antenna with a ferrite bar conductor wound.For these antenna elements, use a small loop antenna whose loop diameter is sufficiently small for the wavelength λ of the signal to be transmitted and received. It is also possible to use a so-called coil antenna in which a loop of a small loop antenna is wound a plurality of times in a coil shape.

Then, for example, a pair of antenna elements 48a,
When both of the components 48b are composed of small loop antennas, as shown in FIG. 5 (a), a housing 4b for accommodating a circuit board 4a incorporating an electronic circuit component constituting the oscillator unit 4 is connected to a conducting wire. It is preferable to form a pair of small loop antennas whose winding central axes are orthogonal to each other by forming a bobbin shape that can be wound and winding a conductive wire around the bobbin shape. That is, in this case, the oscillator unit 4
A pair of antenna elements 48a and 48 composed of a small loop antenna (specifically, a coil antenna)
b can be formed, the oscillator unit 4 can be integrated with these antenna elements 48a, 48b, and the gain of each antenna element 48a, 48b can be increased.

Further, for example, of the pair of antenna elements 12a and 12b constituting the calling signal receiving section 12, one of the antenna elements 12a is constituted by a small loop antenna and the other antenna element 12b is constituted by a bar antenna. In this case, as shown in FIG. 5B, the antenna element 12b composed of a bar antenna is arranged on a circuit board 6a incorporating electronic circuit components constituting the key unit 6, and an antenna composed of a small loop antenna is formed. As for the element 12a, the housing 6b that houses the circuit board 6a is formed into a bobbin shape capable of winding a conductive wire, and the conductive wire is wound therearound so that the winding center axis is the center of the bar of the antenna element 12b. It is preferable to form a small loop antenna orthogonal to the axis.

Next, in the above embodiment, in the oscillator unit 4 and the key unit 6, the antenna element 48
The output amplifying circuit 46 for outputting a calling signal to the antenna elements a and 48b and the receiving amplifying circuit 14 for receiving and amplifying the received signals from the antenna elements 12a and 12b are common to the pair of antenna elements 48a, 48b and 12a and 12b, respectively. Has been described as being provided, but as shown in FIG.
For each of the antenna elements 48a, 48b and 12a, 12b, the output amplification circuits 46a, 46b and the reception amplification circuit 14
a and 14b may be provided. In this case, the phase shifters 48c and 12c do not necessarily need to be provided on the power supply path from the output amplification circuit or the reception amplification circuit to the antenna element, and as shown in FIG.
May be provided on the transmission path of the paging signal from the output amplifier circuit 46b to the output amplification circuit 46b, and on the transmission path of the reception signal from the reception amplification circuit 14b to the signal detection determination circuit 16.

In the above embodiment, the omnidirectional antenna of the present invention is described as being used for transmitting and receiving radio waves for door lock control between the vehicle 2 and the key unit 6 in the keyless entry system for a vehicle. However, the present invention is applicable to any wireless communication system that requires an omnidirectional antenna, such as a house locking system that locks and unlocks a door in a house or the like without using a key. Even in such a communication system, similar effects can be obtained by applying the same method as in the above embodiment.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an entire keyless entry system for a vehicle according to an embodiment.

FIG. 2 is an explanatory diagram showing a non-directional antenna constituting a calling signal transmitting unit and a receiving unit provided in a vehicle-side oscillator unit and a key unit, respectively.

FIG. 3 is an explanatory diagram illustrating directivity characteristics of an omnidirectional antenna included in a call signal transmitting unit and a receiving unit illustrated in FIG. 2;

FIG. 4 is an explanatory diagram showing an assembled state of an omnidirectional antenna to an automobile-side oscillator unit and a key unit.

FIG. 5 is an explanatory diagram illustrating another example of a state where the omnidirectional antenna is assembled to the vehicle-side oscillator unit and the key unit.

FIG. 6 is an explanatory diagram illustrating another configuration example of a power supply unit for an omnidirectional antenna assembled to a vehicle-side oscillator unit and a key unit.

FIG. 7 is an explanatory diagram illustrating directivity characteristics of a bar antenna.

[Explanation of symbols]

4 ... oscillator unit, 6 ... key unit, 4a, 6a ...
Circuit board, 4b, 6b ... housing, 12 ... calling signal receiving unit,
12a, 12b: antenna element, 12c: phase shifter, 48
... Paging signal transmitter, 48a, 48b ... Antenna elements, 4
8c: phase shifter.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2E250 AA21 BB38 CC20 HH01 JJ03 5J021 AA02 AA08 AA11 AB03 AB04 CA01 CA06 DB03 FA06 FA26 GA07 GA08 HA05 HA10 JA07 5J046 AA02 AA04 AA12 AA18 AB01 AB07 AB11 AB12 PA02 PA06 A02 TA03 TA03 AA18 AB01 AB07 AB11 AB12 EF04 FA09 FB12 FC06

Claims (3)

[Claims] 1. A pair of antenna elements comprising a bar antenna or a small loop antenna and arranged so that central axes of coil portions of the antenna are orthogonal to each other; An omnidirectional antenna, comprising: power supply means for changing and supplying power. 2. At least one of the pair of antenna elements forms an antenna element around a housing that houses a circuit board in which an electronic circuit for performing wireless communication via the omnidirectional antenna is housed. The omnidirectional antenna according to claim 1, comprising a small loop antenna formed by winding a conductive wire in a coil shape. 3. A bar antenna housed in a housing housing a circuit board in which an electronic circuit for performing wireless communication via the omnidirectional antenna is housed, among the pair of antenna elements. The omnidirectional antenna according to claim 1 or 2, wherein