JP2009253788A - Wireless communication unit and flowmeter equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication unit which has an antenna portion that can obtain a stable radiation pattern regardless of whether a good high-frequency ground is obtained for a power supply section of a wireless unit and can make the outer appearance of an apparatus on which the antenna portion is mounted as small as possible. <P>SOLUTION: In the wireless communication unit 10 equipped with a substrate 11 on which a wireless communication circuit (exemplified by a wireless circuit section/control section 13) is mounted, a non-ground dipole antenna consisting of two antenna elements 12a and 12b connected to the wireless circuit section/control section 13 is provided on the substrate 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication unit including a wireless communication circuit and an antenna, and a flow meter including the wireless communication unit.

  A wireless communication unit including an antenna and a wireless communication circuit (wireless unit) has been conventionally required to be miniaturized in order to be built in a flow meter such as a gas meter. Monopole antennas are useful in situations where the length of the antenna is sufficient and high-frequency grounding is solid, but when the antenna is made small, radio waves are not radiated efficiently even if power is supplied from the wireless unit. In addition, if the high-frequency ground is not firmly established between the power supply unit of the wireless unit and the antenna, the radiation characteristics of the antenna also become unstable.

In Patent Document 1, a shield plate that shields unnecessary radiation of an information processing board is provided inside an information terminal that communicates with a gas meter with a specific low-power radio wave, and a substantially dipole antenna (grounded dipole antenna) is provided between the antenna and the shield plate. A technique for reducing gain reduction by forming the antenna even when the antenna is reduced in size is disclosed. Patent Document 2 discloses a technique of embedding a linear λ / 2 dipole antenna in a resin outer casing of a gas meter.
JP 2002-374112 A JP-A-11-112223

  The technique described in Patent Document 1 uses a grounded dipole antenna, but cannot secure a high-frequency ground as compared with a non-grounded type, and the radiation characteristics of the antenna are unstable. Further, this technique is a technique for reducing the size of the antenna part, and is not a technique for determining how to embed an antenna part of a predetermined size in a device.

  In addition, as described in Patent Document 2, the technology in which the linear antenna is configured by a λ / 2 dipole antenna and embedded in the resin outer casing of the gas meter can further meet the demand for further miniaturization of the gas meter. However, it is difficult to incorporate this linear antenna in a miniaturized gas meter or to embed it in the outer casing. Further, in order to meet the demand for further miniaturization of such a gas meter, the distance between the antenna and the antenna feeder in the wireless unit cannot be gained. The radiation pattern becomes unstable.

  The present invention has been made in view of the actual situation as described above, and has an antenna portion capable of obtaining a stable radiation pattern regardless of whether the high-frequency ground of the power feeding portion of the wireless unit is good, and the antenna portion is It is an object of the present invention to provide a wireless communication unit capable of minimizing the external shape of the mounted device and to provide a flow meter equipped with the wireless communication unit.

  In order to solve the above-described problem, a wireless communication unit of the present invention is a wireless communication unit including a substrate on which a wireless communication circuit is mounted, and includes two antenna elements connected to the wireless communication circuit. An ungrounded dipole antenna is provided on the substrate.

  The flowmeter of the present invention is characterized by including the above-described wireless communication unit.

  According to the present invention, it is possible to obtain a stable radiation pattern at the antenna portion regardless of the quality of the high-frequency grounding of the power supply unit of the wireless unit, and to make the external shape of a device such as a flow meter equipped with the antenna portion as much as possible. It can be made smaller.

  Hereinafter, the wireless communication unit according to the present invention will be exemplified as being mounted on a flow meter. However, the present invention is not limited to the flow meter, and may be applied to other electronic devices such as a wireless fire alarm, a wireless gas leak alarm, and a handy terminal. May be installed. A wireless meter reading system and a security system can be constructed using these devices. In addition, as another electronic device which mounts the radio | wireless communication unit which concerns on this invention, it is not restricted to the apparatus used for the field | area regarding such a measurement. Further, the flow meter according to the present invention will be described below by taking a gas meter as an example, but it can be similarly applied to other flow meters such as a water meter.

  FIG. 1 is a diagram showing a configuration example of a gas meter according to the present invention, FIG. 2 is a block diagram showing details of a radio circuit unit / control unit in the gas meter of FIG. 1, and FIG. 3 is based on an antenna of the gas meter of FIG. It is a figure which shows a radiation pattern.

  A gas meter 1 illustrated in FIG. 1 includes a wireless communication unit 10. In the wireless communication unit 10, a wireless circuit unit / control unit 13 as an example of a wireless communication circuit is provided on a substrate 11. Further, in the present invention, small antenna elements 12 a and 12 b connected to the radio circuit unit / control unit 13 are also provided on the substrate 11 of the radio communication unit 10.

  In the wireless communication unit 10, an ungrounded dipole antenna is configured using the two antenna elements 12a and 12b. In this dipole antenna, the distance between the upper end of the antenna element 12a and the lower end of the antenna element 12b in FIG. 1 is formed with a length of about λ / 2 of the wavelength to be received or transmitted. This length may be determined according to the frequency band to be used. Thus, the wireless communication unit 10 forms a λ / 2 dipole antenna. Further, the dipole forming portions (the length corresponding to about λ / 2 described above) of the antenna elements 12a and 12b are not limited to a straight line as shown in FIG. Of course, it may be formed electrically with a length of about λ / 2 by inserting a coil or the like, or may be formed with a shorter length by sacrificing the state of reception / transmission.

  The formation of a non-grounded dipole antenna will be illustrated with reference to FIG. The wireless circuit unit / control unit 13 is supplied with power from the power supply unit 20 of the gas meter 1, and data transmission / reception is controlled by a control unit / meter interface unit 18 connected to a main control unit (not shown) of the gas meter 1. The radio circuit unit / control unit 13 includes the control unit / meter interface unit 18, a transmission circuit 16 that performs radio transmission, a reception circuit 17 that performs radio reception, and an antenna switching circuit 15 that performs radio transmission / reception switching. And.

  As the antenna elements 12a and 12b, for example, a small ceramic antenna or a pattern antenna printed on the substrate 11 may be employed. Since the impedance of the antenna elements 12a and 12b is normally 50Ω, it is necessary to perform impedance matching with the radio transmission / reception circuit including the transmission circuit 16 and the reception circuit 17 in order to use two antennas as an ungrounded dipole antenna. As shown in FIG. 2, a matching circuit 14 is inserted between the antenna switching circuit 15 of the wireless transmission / reception circuit and the two antenna elements 12a and 12b, and impedance conversion and circuit conversion for non-grounding are performed. Yes.

  With such a configuration, at the time of transmission, the control unit / meter interface unit 18 controls the antenna switching circuit 15 to switch to the transmission side, and outputs a transmission signal to the transmission circuit 16, and the transmission circuit 16 transmits the transmission. The signal is modulated and output to the antenna switching circuit 15, the modulated transmission signal is supplied to the antenna elements 12a and 12b via the matching circuit 14, and the antenna elements 12a and 12b radiate into the space as radio waves. On the other hand, at the time of reception, the control unit / meter interface unit 18 controls the antenna switching circuit 15 to switch to the reception side, and receives a reception signal received via the matching circuit 16 from the radio waves received by the antenna elements 12a and 12b. The receiving circuit 17 is controlled so as to demodulate, and the receiving circuit 17 executes demodulation processing and outputs the demodulated received signal to the control unit / meter interface unit 18.

  As described above, the radio communication unit 10 of the present invention is provided with the two antenna elements 12a and 12b connected to the radio circuit unit / control unit 13 so as to constitute a non-grounded dipole antenna. With the two antenna elements 12a and 12b, a stable radiation pattern can be obtained regardless of whether the high-frequency ground of the power feeding unit of the radio circuit unit / control unit 13 is good or bad. In addition, it can be expected that the antenna gain is increased by 3 dB as compared to a monopole antenna of the same size that is not firmly grounded at high frequency.

  Further, since the wireless communication unit 10 of the present invention is provided with such a non-grounded dipole antenna on the substrate 11 of the wireless communication circuit, that is, an antenna portion that requires a length is provided on the wireless circuit portion on the substrate 11. / Because the installation area of the control unit 13 is used, the outer shape of the gas meter 1 on which the antenna portion is mounted can be made as small as possible. That is, according to the present invention, it becomes easy to incorporate the λ / 2 dipole antenna in the miniaturized gas meter 1, and also when the wireless communication unit 10 built in the small gas meter 1 is miniaturized, as described above. In addition, it is not necessary to consider that sufficient high-frequency grounding is provided at the power feeding unit.

  Next, a preferable example of mounting the wireless communication unit 10 on the gas meter 1 will be described with reference to FIGS. The gas meter 1 becomes a gas meter with a built-in antenna for wireless communication by mounting the wireless communication unit 10.

  A substrate (wireless unit substrate) 11 built in the gas meter 1 is installed in a standing state in the same manner as the gas meter 1. At this time, the two antenna elements 12a and 12b to be mounted are arranged in the vertical direction at the end of the substrate 11 arranged at the lower part of the gas meter 1, as shown in FIG. In this case, the antenna elements 12a and 12b are arranged in the vertical direction, and the electric field surface radiation characteristic is vertical polarization. The vertically polarized radiation characteristics of the dipole antenna composed of two antenna elements at that time are as shown by radiation patterns 31 and 32 in FIG. 3, and the gas meter is installed on the wall of a house or the like, and at the time of communication Considering the holding position of a counterpart device such as a handy terminal, it can be said that a preferable radiation pattern is obtained. Thus, in the gas meter 1, it is preferable to install the board | substrate 11 so that the two antenna elements 12a and 12b may face a perpendicular direction.

  Although not shown, the two antenna elements 12a and 12b may be arranged in the horizontal direction, and in this case, the horizontal polarization is obtained. Such horizontal polarization is particularly useful for a flow meter installed on the ground such as a water meter.

It is a figure which shows one structural example of the gas meter which concerns on this invention. It is a block diagram which shows the detail of the radio | wireless circuit part / control part in the gas meter of FIG. It is a figure which shows the radiation pattern by the antenna of the gas meter of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gas meter, 10 ... Wireless communication unit, 11 ... Board | substrate, 12a, 12b ... Antenna element, 13 ... Wireless circuit part / control part, 14 ... Matching circuit, 15 ... Antenna switching circuit, 16 ... Matching circuit, 16 ... Transmission circuit , 17 ... receiving circuit, 18 ... control unit / meter interface unit, 20 ... power supply unit, 31, 32 ... radiation pattern.

Claims (2)

  A wireless communication unit including a substrate on which a wireless communication circuit is mounted, wherein a non-grounded dipole antenna including two antenna elements connected to the wireless communication circuit is provided on the substrate. Wireless communication unit.   A flow meter comprising the wireless communication unit according to claim 1.

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