JP2006166112A - Weak radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize the generation of interference radio waves to other radio communication systems or other radio communication channels, to secure sufficient reception radio wave strength even through an obstacle such as a wall, and to perform the short distance radio communication of a large capacity. <P>SOLUTION: In a weak radio communication system for transmitting and receiving radio signals based on a weak radio standard between a transmitter and a receiver, a distance between the transmitter and the receiver is set to be less than a distance used for radio wave strength stipulation of the weak radio standard, and the transmitter is provided with a radio wave transmission means for emitting transmission radio waves in the direction of the receiver and emitting them so as to have a focus between the transmitter and the receiver. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a weak wireless communication system that performs wireless communication using a weak wireless device in which an allowable value of radio field strength is defined by an electric field strength at a distance of 3 m.

FIG. 8 shows an example of a communication form of a conventional weak wireless communication system (Non-Patent Document 1). In the figure, the weak wireless device is configured to radiate radio waves isotropically from an antenna, and obtains a communication speed of about 10 kbps over a communication distance of 3 to 10 m using, for example, a narrowband wireless of 300 MHz band or lower. Such a weak wireless device does not require a license in order to use extremely weak radio waves, and is used for communication using a wireless tag, for example.
Supervised by Masayoshi Wakao, weak radio equipment / low-power radio equipment system design technology, published by Trikes, Inc., 1997, pp.101-107

  By the way, when trying to realize large-capacity wireless communication using the conventional weak wireless communication system shown in FIG. 8 between outdoors / indoors or indoor rooms separated by an obstacle such as a wall, There are challenges as shown.

  (1) A wide radio band is necessary to realize large-capacity radio communication, and it is assumed that a high radio frequency band of 320 MHz or higher is used, for example. However, when radio frequency radio waves of 320 MHz or higher are used in a weak radio communication system, the radio field strength tolerance becomes very small and the received radio field strength is insufficient.

  (2) As shown in FIG. 9, for example, when two or more sets of weak radios are arranged through a wall of about 30 cm and a plurality of radio communication channels are required for communication, Communication with each other is hindered because radio waves from the transmission antenna interfere with each other.

  The present invention minimizes the generation of interfering radio waves in other radio communication systems or other radio communication channels, and secures a sufficient received radio wave intensity even through obstacles such as walls, so that a large capacity short-range radio An object of the present invention is to provide a weak wireless communication system that enables communication.

  The present invention relates to a weak wireless communication system that transmits and receives a wireless signal based on a weak wireless standard between a transmitter and a receiver, and the distance between the transmitter and the receiver is used to define the radio field strength of the weak wireless standard. The transmitter is set to be less than the distance, and the transmitter includes a radio wave transmission unit that radiates the transmission radio wave in the direction of the receiver and radiates the focal point between the transmitter and the receiver.

  The radio wave transmission means includes an antenna that radiates a transmission radio wave and a radio wave lens, and is configured to vary the focal position of the transmission radio wave by adjusting the distance between the antenna and the radio wave lens.

  The radio wave transmission means includes an antenna that radiates transmission radio waves and a concave reflection plate, and is configured to vary the focal position of the transmission radio waves by adjusting the distance between the antenna and the concave reflection plate.

  The weak wireless communication system of the present invention can cause the receiver to receive almost all of the radio waves transmitted from the transmitter, thereby minimizing the generation of jamming radio waves for other radio communication systems or other radio communication channels. Can be suppressed. In addition, since the radio wave transmitted from the transmitter is focused between the transmitter and the receiver, it can be received by the receiver compared to the case where it is radiated isotropically from the transmitter as in the past. The radio wave intensity can be increased. Thereby, even when an obstacle such as a wall exists between the transmitter and the receiver, large-capacity communication can be performed.

  FIG. 1 shows a basic configuration of a weak wireless communication system of the present invention. In the figure, a weak radio 12 and a radio transmission / reception unit 14 are arranged on one side with a wall 11 in between, and a weak radio 13 and a radio transmission / reception unit 15 are arranged on the other side. Although it is assumed that radio waves are transmitted in both directions, for the sake of convenience, the weak radio device 12 and the radio wave transmission / reception unit 14 are used as transmitters, and the weak radio device 13 and the radio wave transmission / reception unit 15 are used as receivers. Description will be made assuming radio wave propagation from the unit 14 to the radio wave transmitting / receiving unit 15.

The features of the present invention are summarized in the following two points.
(1) The transmitter (radio wave transmission / reception unit 14) radiates the transmission radio wave toward the receiver (radio wave transmission / reception unit 15).
(2) The transmitter (radio wave transmission / reception unit 14) radiates the transmission radio wave so as to have a focal point between the transmitter (radio wave transmission / reception unit 14) and the receiver (radio wave transmission / reception unit 15). The definition of “focus” is “one point where radio waves gather”.

  According to the feature (1) of the present invention, almost all of the radio waves transmitted from the transmitter are received by the receiver, and almost no interference radio waves are generated with respect to other radio devices. Further, according to the feature (2) of the present invention, the radio wave transmitted from the transmitter is focused between the transmitter and the receiver, so that it is radiated isotropically from the transmitter as in the prior art. In comparison with the above, it is possible to increase the radio field intensity that can be received by the receiver. According to the feature (2) of the present invention, the transmitter radiates the transmission radio wave so as to have a focal point between the transmitter and the receiver. As a result, the transmitter of the feature (1) of the present invention transmits Radio waves are emitted in the direction of the receiver.

  Here, the advantage of the feature (2) of the present invention is divided into the case where the focal position of the radio wave transmitted from the transmitter is the midpoint between the transmitter and the receiver, the case close to the receiver, and the case close to the transmitter. This will be specifically described.

FIG. 2 shows a case where the focal position is the midpoint between the transmitter and the receiver. Here, when the received radio wave reaches the entire receiver (radio wave transmission / reception unit 15), the reception intensity is proportional to the square of the distance between the focal position and the receiver. Therefore, if the distance between the focal position and the receiver (radio wave transmission / reception unit 15) is X, and the distance between the focal position and the specified position of the radio wave intensity (3 m from the transmitter (radio wave transmission / reception unit 14)) is L, The ratio of the signal strength to the signal strength at the specified position is
20 ・ log (L / X)… (1)
It is expressed.

As shown in FIG. 2, if the distance between the transmitter (radio wave transmitter / receiver 14) and the receiver (radio wave transmitter / receiver 15) is 30 cm, the distance between the focal point and the receiver (radio wave transmitter / receiver 15) is 15 cm. The distance between the focal position and the specified position of the radio wave intensity (3 m from the transmitter) is 285 cm. At this time, the signal strength that the receiver can receive is higher than the signal strength at the specified position.
20 · log (285/15) ≒ 25.6 [dB]
It will be strong.

On the other hand, as shown in FIG. 3, in the case of the conventional configuration in which the transmission radio wave isotropically radiated from the transmitter, the radio wave intensity that can be received by the receiver is higher than the radio wave intensity at the specified position.
20 · log (300/30) = 20 [dB]
It will be strong. Therefore, when the distance between the transmitter and the receiver is the same (here, 30 cm), the radio wave intensity that can be received by the receiver according to the present invention can be increased by about 6 dB compared to the conventional configuration.

FIG. 4 shows a case where the focal position is closer to the receiver. Here, it is assumed that when the distance between the transmitter (radio wave transmitter / receiver 14) and the receiver (radio wave transmitter / receiver 15) is 30 cm, the focal position is shifted from the midpoint of the transmitter and receiver to the receiver side by 5 cm. is doing. In this case, radio waves are received by only a part of the receiver (radio wave transmitter / receiver 15). This state is equivalent to the radio field intensity when the receiver is received further 10 cm away from the transmitter so that the focal position is at the midpoint between the transmitter and the receiver. At this time, the signal strength that the receiver can receive is higher than the signal strength at the specified position.
20 · log (280/20) ≒ 22.9 [dB]
It will be strong. Even in this case, the radio wave intensity that can be received by the receiver according to the present invention can be increased by about 3 dB compared to the conventional configuration.

FIG. 5 shows a case where the focal position is closer to the transmitter. Here, it is assumed that when the distance between the transmitter (radio wave transmitter / receiver 14) and the receiver (radio wave transmitter / receiver 15) is 30 cm, the focal position deviates from the midpoint of the transmitter and receiver by 5 cm toward the transmitter. is doing. In this case, since the received radio wave reaches the entire receiver (radio wave transceiver 15), the radio wave intensity that can be received by the receiver is higher than the radio wave intensity at the specified position.
20 · log (290/20) ≒ 23.2 [dB]
It will be strong. Even in this case, the radio wave intensity that can be received by the receiver according to the present invention can be increased by about 3 dB compared to the conventional configuration.

Further, in the present invention, when the distance between the transmitter and the receiver is 1 m with respect to the same focal position as in FIG.
20 ・ log (290/90) ≒ 10.2 [dB]
Become stronger. On the other hand, in the conventional configuration as shown in FIG.
20 · log (300/100) ≒ 9.5 [dB]
Since it becomes stronger, the radio wave intensity of the present invention is slightly stronger.

  As described above, the radio wave intensity that can be received by the receiver is strongest (+6 dB) when the focal position of the transmitter radio wave is at the midpoint between the transmitter and the receiver (+6 dB). Even if the focal position is not at the midpoint between the transmitter and the receiver, the focal position exists between them, and the distance between the transmitter and the receiver is less than the distance (3 m) used for the radio field strength specification of the weak wireless standard. In this case, the weak wireless communication system of the present invention can receive a stronger radio wave than the conventional configuration.

  FIG. 6 shows a first embodiment of the weak wireless communication system of the present invention. In the figure, the radio wave transmission / reception units 14 and 15 have a configuration in which an antenna 21 is surrounded by a radio wave absorber 22 and a radio wave lens 23, and radio waves radiated from the antenna 21 are connected to an opposing radio wave lens via the radio wave lens 23. Propagate with focus in between. The focal position can be calculated from the shape and material of the radio wave lens 23 and the distance between the antenna 21 and the radio wave lens 23. For example, by adjusting the distance between the antenna 21 and the radio wave lens 23, the focal position of the transmission radio wave is determined. Can be changed. The radio wave radiated in the direction of the radio wave absorber 22 is absorbed and therefore does not leak outside.

  FIG. 7 shows a second embodiment of the weak wireless communication system of the present invention. In the figure, the radio wave transmission / reception units 14 and 15 are composed of an antenna 21 and a concave reflecting plate 24, and radio waves radiated from the antenna 21 only in the direction of the concave reflecting plate 24 are reflected by the concave reflecting plate 24 and face each other. Propagating with a focal point between the plates. The focal position can be calculated from the curvature of the concave reflector 24 and the distance between the antenna 21 and the concave reflector 24. For example, by adjusting the distance between the antenna 21 and the concave reflector 24, the focal position of the transmission radio wave is adjusted. Can be changed.

  In the first embodiment and the second embodiment, since two-way communication is assumed, the radio wave lens 23 or the concave reflecting mirror 24 is arranged on both sides, but one is received by the transmitter and the other is received. When used as a transmitter, it is sufficient if the radio wave lens 23 or the concave reflecting mirror 24 is disposed only in the transmitter.

The figure which shows the basic composition of the weak radio | wireless communications system of this invention. The figure which shows the case where a focus position is a middle point of a transmitter and a receiver. The figure which shows the case of the conventional structure where a transmission electromagnetic wave is radiated | emitted isotropic from a transmitter. The figure which shows the case where a focus position is near a receiver. The figure which shows the case where a focus position is near a transmitter. The figure which shows 1st Embodiment of the weak radio | wireless communications system of this invention. The figure which shows 2nd Embodiment of the weak radio | wireless communications system of this invention. The figure which shows an example of the communication form of the conventional weak radio | wireless communications system. The figure explaining the subject in a conventional structure.

Explanation of symbols

11 Wall 12 Weak radio (transmitter)
13 Weak radio (receiver)
14 Radio transceiver (transmitter)
15 Radio transceiver (receiver)
21 Antenna 22 Wave Absorber 23 Radio Wave Lens 24 Concave Reflector

Claims (3)

In a weak wireless communication system that transmits and receives wireless signals based on the weak wireless standard between a transmitter and a receiver,
The distance between the transmitter and the receiver is set to be less than the distance used for the radio field strength regulation of the weak wireless standard,
The weak radio communication system characterized in that the transmitter includes radio wave transmission means for radiating a transmission radio wave in the direction of the receiver and radiating the transmitter so as to have a focal point between the transmitter and the receiver. . The weak wireless communication system according to claim 1,
The weak radio communication system, wherein the radio wave transmission means includes an antenna that radiates a transmission radio wave and a radio wave lens, and is configured to vary a focal position of the transmission radio wave by adjusting a distance between the antenna and the radio wave lens. The weak wireless communication system according to claim 1,
The radio wave transmission means includes an antenna that radiates a transmission radio wave and a concave reflector, and is configured to vary a focal position of the transmission radio wave by adjusting a distance between the antenna and the concave reflector. system.

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