JP2001308624A - Method of suppressing radio wave interference from radio frequency device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of suppressing radio wave interference from the radio frequency device, which can control the directivity of radio waves or the fluctuation of the output, by removing unwanted radio waves from a conductor, and having the conductor and setting an antenna at non-resonance state. SOLUTION: By mounting with the sensor signal input circuit 2 on the antenna built-in weak radio communication device is the common mode choke coil 3. The choke coil 3 interrupts unwanted electromagnetic waves from the sensor cable 4. The sensor cable 4 is fitted with the bifilar-wound curled code 6, which functions as the loading coil so as to prevent the sensor cable 4 and the transmission antenna 5 from resonating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio frequency device (for example, a radio device) having a transmitting antenna or a receiving antenna.
In particular, the present invention relates to a method for suppressing radio wave interference generated between a linear conductor disposed or electrically connected near the radio frequency device and an antenna.

[0002]

2. Description of the Related Art Conventionally, a radio frequency device having a transmission antenna or a reception antenna (transmission / reception antenna) (for example, in a radio device, a fixed or movable linear conductor (a wiring cord or a cable is widely used) near an antenna. Under such conditions, the linear conductor may resonate with a radio wave or emit unnecessary radio waves from the conductor.For example, in the case of a transmission antenna, the current excited in the conductor The directivity of the transmitting antenna changes, and at the same time, high-frequency energy, which is the source of radio waves generated inside the radio, propagates through the circuit and emits unnecessary radio waves from the conductor. The directivity of the receiving antenna changes due to the current excited in the conductor due to the received radio waves, and at the same time, some of the received radio waves that are amplified and leaked inside the radio are conducted. Is re-emitted as unwanted radio waves from. In this case, it is receiving the radio wave interference transmitted and received by the antenna, so that, in the receiving antenna,
The directivity of the antenna is disturbed, the sensitivity of the antenna is reduced, and the wireless communication is hindered. In particular, in a transmitting antenna, depending on the arrangement of conductors with respect to the antenna, the output of a main beam of radio waves and the like may increase significantly. At the time of output, a problem of exceeding the transmission output allowable value occurs.

[0003]

In order to solve such a problem, an upper limit value of the output of the main beam and the like is set at the stage of designing and manufacturing the radio device so that the output value becomes equal to or less than the allowable value of the Radio Law. Radios may be manufactured. However, even if an upper limit value is set for the output of the main beam or the like, the output in directions other than the direction in which the main beam is directed becomes relatively significantly higher or lower. Therefore, in a certain type of antenna, for example, an isotropic antenna that requires wireless communication in all directions, the radio wave output in the side lobe (direction other than the main beam) is low, so that wireless communication in that direction is not possible. Will be hindered. In particular, if a movable conductor (conductor) is installed near the antenna, the directivity and output of radio waves vary and vary depending on the arrangement of the conductor with respect to the antenna. In this case, since the movable conductor moves randomly during transmission and reception, it is difficult to predict a change in the arrangement state, and as a result, the directivity and output of the radio wave according to all the arrangement states of the conductor are grasped. It becomes extremely difficult, and it becomes difficult to cope with the above-mentioned communication disturbance.

As described above, in the prior art, the directivity changes due to the current excitation to the conductor, and unnecessary radio waves radiated from the conductor cause radio interference to lower the sensitivity of the antenna, as well as the main beam. Output exceeded the allowable value of the Radio Law. That is, even if an upper limit value is set for the output of the main beam or the like, the directivity and output of the radio wave vary irregularly and significantly depending on the arrangement of the conductors. For this reason, there arises a problem that the radio wave output also greatly increases and exceeds an allowable value specified by the Radio Law, or the radio wave output significantly decreases and an output required for wireless communication cannot be secured. In view of the above problems, the present invention suppresses fluctuations in directivity and output of radio waves caused by resonance of conductors with radio waves or emission of unnecessary radio waves from conductors, and can prevent communication failure due to radio wave interference. It is an object of the present invention to provide a method for suppressing radio wave interference.

[0005]

According to the first aspect of the present invention, in a radio frequency device having a transmitting antenna or a receiving antenna, a loading coil is provided on a linear conductor installed near the antenna. And That is, in the prior art, the directivity of radio waves fluctuated greatly up and down due to resonance between the conductor and the antenna, but in the present invention, by providing a loading coil on the conductor, the conductor and the antenna are To eliminate the resonance state.

According to the present invention, by attaching a loading coil (or a curl cord or the like) to the conductor, only the resonance length of the conductor with the radio wave can be changed without changing the length of the conductor itself. For this reason, the resonance state between the conductor and the antenna is eliminated, and the directivity of the radiated radio wave can be prevented from largely changing.

[0007] The loading coil can be attached to the conductor as it is, but may be manufactured by winding the conductor itself into a coil. In some cases, a curl code can be used instead of the loading coil, and this curl code can achieve the same suppression of radio wave interference as the loading coil. In particular, unintended radiating devices such as personal computers and information devices with built-in microcomputers and home appliances (which are not intended to emit radio waves but have built-in circuits that may emit radio waves) EMI (Electromagnetic Interference) parts for reducing radio waves radiated from the internal wiring or external wiring of unintentional radiation equipment, such as ferrite beads and ferrite cores. Alternatively, the wiring itself may be wound in a coil shape to function as a loading coil.

In general, when a conductor such as an electric wire cord is installed near an antenna, the conductor and the antenna become insulated by a parasitic element (conducting element) at a wavelength or frequency of a radiated radio wave due to a change in a positional relationship between the conductor and the shape of the conductor. Function as a wave or reflector). The loading coil according to the present invention suppresses the conductor from acting as a parasitic element, but the loading coil itself is widely used as an inductance loading antenna in the field of wireless communication. By using this loading coil, it is possible to shorten only the length of the antenna while keeping the resonance wavelength or the resonance frequency of the antenna unchanged.

However, the conventional loading coil is provided in a part of the antenna itself. On the other hand, the loading coil according to the present invention is provided not on the antenna but on the conductor provided near the antenna. If a ferromagnetic material such as a ferrite or an iron core is inserted into the loading coil, the size and performance of the coil can be reduced. Also, due to its electromagnetic properties, if the loading coil gets too close to the antenna,
Electromagnetic coupling occurs between the two, causing considerable damage to radio waves. In order to avoid this, it is necessary to keep the distance between them at a certain value or more so as to prevent electromagnetic interference.

In the present invention, a curl cord can be used instead of the loading coil. In this case, disconnection or the like can be prevented by the elasticity of the curl cord. At the same time, the mobility during use is improved, so that the usability of the wireless device is improved. This curl cord is preferably offset from the radio so that the performance as a loading coil is not impaired by its own elasticity and deformability. In the actual design, the design is performed by predicting the usage environment of the curl code. The number of turns, winding diameter, coating thickness, material, and the like are determined so that the performance of the curl cord is not impaired even if the curl cord is used in various conditions. The curl cord can be manufactured by the same manufacturing method as that of a type of cord used in a normal telephone or the like.

In general, unnecessary radio waves are radiated from a conductor portion other than an antenna of a radio frequency device, such as a radio device, which is an intended radiation device (a mobile phone, a transceiver, etc.). Also,
Unwanted radio waves are also emitted from unintended radiators including various electronic devices in the vicinity. When such an unnecessary radio wave is propagated to a conductor having a resonance length with the unnecessary radio wave, interference with a radio radio wave is caused due to a change in directivity, causing various obstacles. However, in the present invention, the provision of the choke coil prevents unnecessary radio waves from propagating to the antenna. That is, by connecting the choke coil to the conductor, leakage of current to the conductor can be prevented.

A choke coil is generally used as an EMI (electromagnetic interference) countermeasure product, and is divided into a normal mode choke coil and a common mode choke coil in view of its application range. A normal mode choke coil is used to block noise superimposed on a one-phase line. In the following embodiment, a two-phase common mode choke coil is used because the conductor is constituted by two parallel lines.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 is a perspective view showing the configuration of a weak radio device with a built-in antenna to which the method of the present invention is applied, and FIG. 2 is a perspective view showing the configuration of a conventional technique. The weak radio device with a built-in antenna according to the present invention is of a type in which an electric device such as a sensor is electrically connected to a radio device main body by a linear conductor, and converts data detected by the sensor into an electric signal. It transmits weak radio waves.
The loading coil may be independently connected to this linear conductor to serve both as the loading coil and the choke coil.However, if the shape of the loading coil does not suit the actual use environment, both the loading coil and the choke coil must be connected. It is more preferable to connect them in combination.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2, reference numeral 1 denotes a weak radio transmitter (transmitter) with a built-in antenna, which is a radio station that emits a remarkably weak radio wave specified in Article 4.1 of the Radio Law. ,
It is used in a system for attaching a urine leak detection sensor 9 used in the field of medical care and reporting the urine leak of a cared person by radio, and an internal circuit and a loop antenna are formed on a printed circuit board. I have. That is, the weak radio communication device 1 includes a sensor signal input circuit 2 to which a signal is input from a sensor, and a transmission antenna 5, and a radio wave radiated from the transmission antenna 5 is received by a receiver (not shown). Has become. One end of a two-phase common mode choke coil 3 is mounted on the sensor signal input circuit 2 of the weak radio communication device 1. The common mode choke coil 3 blocks propagation to the sensor cable 4 that emits unnecessary radio waves. FIG. 2 shows a state before the present invention is applied.

In the present invention, as shown in FIG. 1, one end of a curl cord 6, which functions as a loading coil, is connected to the other end of the common mode choke coil 3, and this curl cord 6 is bifilar wound. Work can be suppressed. Further, even if a later-described sensor cable 4 and curl code 6 itself move during transmission, the curl code 6 can be expanded and contracted to prevent disconnection. Furthermore, since the curl cord 6 has flexibility that can be bent, the care receiver wearing the curl cord 6 can use it safely and comfortably without feeling uncomfortable. In addition, curl code 6
By adjusting the number of windings, the winding diameter, the coating thickness, the material, and the like, not only the function as the loading coil but also the function as the common mode choke coil 3 can be achieved. That is, the intended purpose can be achieved only by the curl code 6.

Assuming that the curl cord 6 is in a contracted state, a double extended state, and a bent state,
The number of turns, winding diameter, coating thickness, material, etc., of the curl cord 6 should be checked so that the curl cord 6 is not impaired even if the curl cord 6 is used in any conceivable condition. Is determined. Curl code 6
Here, the number of turns is 25 turns, the outer diameter is 8 mm, and the outer diameter of the wire is 1.3 mm × 2.6 mm, and is covered with an elastomer resin.

At the other end of the curl cord 6, a jack 7 as a connection terminal is fixed.
The tip of a plug 8 as a connection terminal is detachably connected. The base end of the plug 8 is fixed to one end of a sensor cable (linear conductor) 4 having two parallel lines. The total length of the sensor cable 4 including the curl cord 6 is 45 cm, which is the same as the conventional product. If the curl code 6 is too close to the transmitting antenna 5, there is a risk of mutual interference in the electromagnetic field.
In contrast, the curl cord 6 is arranged at a distance of 7 cm. A sensing sensor 9 is attached to the other end of the sensor cable 4.

In the prior art, high-frequency energy is generated inside the weak radio transmitter 1 and unnecessary radio waves are generated, thereby disturbing the directivity of the radio waves. That is,
High-frequency energy is generated in an internal circuit of the weak radio transmitter 1, and the high-frequency energy is transmitted to the sensor signal input circuit 2.
Through the sensor cable 4 as a leakage current, and unnecessary radio waves are emitted from the sensor cable 4 to the surroundings. However, in the present embodiment, this can be favorably suppressed. In other words, unnecessary radio waves generated due to leakage current are:
It is cut off by the common mode choke coil 3 provided between the sensor cable 4 and the sensor signal input circuit 2 inside the weak radio transmitter 1, thereby causing interference between unnecessary radio waves and radio waves and a change in the electromagnetic field pattern due to the interference. Is suppressed.

In the prior art, a resonance state has occurred between the sensor cable 4 and the transmitting antenna 5. That is, a resonance state occurs between the sensor cable 4 and the transmission antenna 5 due to an excitation phenomenon by a radio wave. However, in the present embodiment, this can be favorably suppressed. That is, only the resonance wavelength of the sensor cable 4 can be changed by the curl cord 6 connected to the sensor cable 4 without changing the length of the sensor cable 4. Therefore, resonance between the sensor cable 4 and the transmitting antenna 5 and a change in directivity due to the resonance are suppressed.

In general, the length at which the antenna can radiate the radio wave most efficiently is one half of the wavelength of the radio wave of interest, but the length of the sensor cable 4 that efficiently resonates with the weak radio transmitter 1 is also It is about half the wavelength of the radio wave.
A sensor cable 4 that is about half the length of the radio wave
When installed near the transmitting antenna 5, the two 4 and 5 resonate with each other, and the sensor cable 4 functions as a parasitic element (a director or a reflector) of the transmitting antenna 5. In this case, the phase and the like of the current excited in the sensor cable 4 change only by a slight change in the distance and position between the two 4 and 5 or the shape of the sensor cable 4. A change in directivity occurs. For example, when the conductor functions as a director, it indicates that when the arrangement of the sensor cable 4 changes, the electric field intensity at the same reception point significantly increases or decreases as compared with the case of the transmission antenna alone.

Wavelength of radio wave of weak radio transmitter 1 95.
One half of 2 cm is about 47.6 cm. This substantially matches the length of the sensor cable 4 of 45 cm, and indicates that the sensor cable 4 easily functions as a parasitic element for the transmission antenna 5. Also, in the case of a movable conductor such as a sensor cable 4 attached to the human body,
When the care receiver wearing the weak radio transmitter 1 turns over or changes his / her posture, the arrangement of the sensor cable 4 always changes during transmission. Thus, each time the arrangement of the sensor cable 4 changes, the directivity of the radio wave radiated from the transmission antenna 5 changes. In particular, in a strong beam direction, the output may increase and violate the Radio Law. On the other hand, in a weak beam direction, the output may be insufficient and communication failure may occur.

When the sensor cable 4 was not attached, the electric field strength in the horizontal direction at a radius of 3 m from the weak radio transmitter 1 was about 400 μV / m. Depending on the arrangement, the maximum value in the horizontal direction is about 2,000 μV / m, and the minimum value is about 100 μV / m. This means that the electric field intensity in the same direction is increased by a factor of 5 as compared with the case where the sensor cable 4 is not attached, and exceeds the allowable value of the Radio Law. On the other hand, the minimum electric field intensity is reduced to one-fourth, and the radio wave output is weakened to a required value or less, which greatly impedes wireless communication.

In the present embodiment, the following effects are obtained by connecting the common mode choke coil 3 and the curl cord 6 to the sensor cable 4 in combination. That is, the electric field strength in this embodiment is 500 μV / max.
m, and a minimum of about 300 μV / m, during which the variation width is reduced to about one-tenth of the conventional range. The fact that the maximum electric field intensity is slightly less than 500 μV / m is equivalent to or less than the allowable value of the Radio Law, and the arrangement state of the sensor cable 4 is favorably within the allowable output range without any consideration under the actual use conditions. Can communicate wirelessly. If the curl code 4 is too close to the transmission antenna 5, the effect of the curl code 6 is not exhibited. However, in this practical cable arrangement, the curl code 6 and the transmission antenna 5 are separated by a predetermined distance. 6 can sufficiently exhibit the effect of suppressing radio wave interference.

In another embodiment, the following configuration can provide the same radio interference suppression effect as described above. (1) In the above embodiment, the weak radio transmitter is a receiver provided with a receiving antenna. (2) In the above embodiment, the sensor cable itself is wound in a coil shape, and this is used as a loading coil. (3) The number of sensor cable lines is not two, but is, for example, one or three or more.

The present invention is not limited to the above embodiment.
In the above-described embodiment, as an example of a weak radio device, a urine leak detection sensor used as a medical care product is described. However, for example, an acoustic device using weak radio, a lighting device, an electric heating device, and an information communication device may cause radio interference. It may be applied to the device in question. Further, instead of the common mode choke coil, a curl code having a similar role may be used, and this curl code suppresses mutual resonance between the sensor cable and the transmitting antenna and suppresses radiated radio waves from the sensor cable. The two roles of suppressing occurrence can be realized.

[0026]

As described above, according to the present invention, by connecting the loading coil to the conductor installed near the antenna, the conductor and the antenna can be brought into a non-resonant state. Further, in addition to the above effects, in the case where the choke coil is connected to the conductor, unnecessary radio waves radiated from the conductor can be removed, and radio interference can be suppressed. For this reason, there is an excellent effect that fluctuation and disturbance of the directivity and output of the radio wave caused by the change of the electromagnetic field can be suppressed well, and the communication failure can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the configuration of a weak radio device with a built-in antenna to which the method of the present invention is applied.

FIG. 2 is a configuration perspective view showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Weak radio communication device (transmitter) 2 Sensor signal input circuit 3 Common mode choke coil 4 Sensor cable (linear conductor) 5 Transmitting antenna 6 Curl cord (loading coil) 7 Jack 8 Plug 9 Sensor

Claims (8)

[Claims] A radio frequency device having a transmitting antenna or a receiving antenna, wherein the radio frequency device is disposed near the antenna.
A method for suppressing radio wave interference of a radio frequency device, comprising: providing a loading coil on a linear conductor having a resonance length of a radio wave generated from the radio frequency device, and suppressing the conductor from acting as a parasitic element. 2. A radio frequency device having a transmission antenna or a reception antenna, wherein a loading coil is connected to a linear conductor electrically connected to the radio frequency device and having a resonance length of a radio wave generated from the radio frequency device. A method for suppressing unnecessary radio waves radiated from the conductor and suppressing the conductor from functioning as a parasitic element. 3. A radio frequency device having a transmitting antenna or a receiving antenna, wherein a loading coil is connected to a linear conductor electrically connected to the radio frequency device and having a resonance length of a radio wave generated from the radio frequency device. And a choke coil provided to suppress unnecessary radio waves radiated from the conductor, and to suppress the conductor from acting as a parasitic element. 4. The method according to claim 1, wherein the loading coil is a curl cord connected to a conductor. 5. The method according to claim 1, wherein the loading coil is formed by winding a conductor itself in a coil shape. 6. A method for suppressing radio wave interference of unintentional radiating equipment, comprising providing a loading coil on external wiring of unintended radiating equipment and suppressing unnecessary radio waves radiated from the wiring. 7. A method of suppressing radio wave interference of an unintended radiating device, wherein a loading coil is provided on a wiring and an electronic circuit inside the unintended radiating device to suppress unnecessary radio waves radiated from the wiring and the electronic circuit. 8. The method according to claim 6, wherein an EMI (electromagnetic interference) countermeasure component such as a ferrite core or a choke coil is combined with the loading coil.