JP2009278172A - Radio communication unit and flowmeter with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication unit of a diversity reception system which is made to function by a plurality of antenna elements and one radio unit. <P>SOLUTION: The radio communication unit includes the plurality (shown by two lines) of antenna elements 12a and 12b, and one radio communication circuit (radio transmission and reception part/control part) 13 connecting them. The radio communication circuit 13 includes a switching means for switching the antenna element to be used between the two antenna elements 12a and 12b, a measuring means for measuring electric field strength by radio waves induced in the respective elements 12a and 12b, and a comparison means for comparing the measured electric field strengths of the respective antenna elements. The switching means executes the switching of the elements 12a and 12b depending on the intermittent drive cycle of the radio communication circuit 13, and executes the switching of the antenna elements as needed so as to perform reception using the antenna element of the higher electric field strength on the basis of the results of comparison in the comparison means. <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.

  2. Description of the Related Art 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 incorporated in various devices including a flow meter such as a gas meter.

  With regard to such a wireless communication unit, Patent Document 1 discloses that a shield plate that shields unnecessary radiation of an information processing board is provided inside an information terminal that communicates with a gas meter using a specific low-power wireless radio wave. There has been disclosed a technique for reducing a gain reduction even if the antenna is made small by forming an antenna (grounded dipole antenna). Further, Patent Document 1 operates in the same manner as an L-type dipole antenna in which an antenna and a shield plate are configured in a vertical direction by a configuration in which the axial direction of the longitudinal portion of the shield plate and the antenna are arranged substantially perpendicularly in the same plane. It is described that the antenna can be configured as a polarization diversity antenna having vertical and horizontal polarization components.

  Patent Document 2 also includes a gas meter with a built-in wireless communication unit and a piping pipe connected to the gas meter and serving as a gas flow path. The wireless communication unit is connected to a part of the piping pipe at a desired frequency. A technique for configuring a diversity antenna by resonating is disclosed.

  By the way, a gas meter is often installed in a meter box or a pipe shaft in an apartment house, and in a general house, it is often installed in a place with a poor view from the table such as near the kitchen. . When a wireless unit and an antenna are attached to a gas meter installed in such an environment and wireless meter reading is performed, wireless communication between the opposing wireless automatic notification device, etc. propagates while radio waves are reflected on surrounding buildings. Therefore, multipath occurs.

  In the multipath, the radio wave reflected between the gas meter and the wireless automatic notification device is strengthened or weakened, resulting in unstable wireless communication, and the electric field strength necessary for wireless communication may not be obtained.

There is a diversity antenna system as an effective means for this multipath. In mobile communication, two combinations of antennas and radio receivers are prepared, and antennas are installed according to the strength of the changing radio waves by installing antennas at regular intervals. A method of switching the system is adopted.
JP 2002-374112 A JP-A-11-112223

  However, incorporating two systems of antennas and wireless receivers similar to mobile communications in a gas meter has many problems in terms of space, cost, power consumption, and the like.

  The present invention has been made in view of the actual situation as described above, and provides a radio communication unit of a diversity reception system that functions with a plurality of antenna elements and one radio unit. The purpose is to provide an on-board flow meter.

  In order to solve the above-described problem, a wireless communication unit of the present invention includes a plurality of antenna elements and one wireless communication circuit connected to the plurality of antenna elements, and the wireless communication circuit is used. Switching means for switching the antenna elements to be switched between the plurality of antenna elements, measurement means for measuring the electric field strength caused by the radio wave induced in each of the plurality of antenna elements, and the measurement of each antenna element measured by the measurement means Comparing means for comparing electric field strengths, wherein the switching means performs switching of the antenna element in accordance with an intermittent drive cycle of the wireless communication circuit, and based on a result of comparison by the comparing means. Switch antenna elements as necessary to receive using the strongest field element Is obtained by means executes.

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

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to comprise the radio | wireless communication unit of a diversity reception system so that it may function by several antenna elements and one radio | wireless unit.

  Hereinafter, the wireless communication unit according to the present invention will be exemplified as being mounted on a flow meter, but not limited to a flow meter, for example, a wireless fire alarm, a wireless gas leak alarm, a handy terminal, a wireless automatic notification described later You may mount in other electronic devices, such as an apparatus. 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 wireless meter reading system in which a gas meter incorporating a wireless function and a wireless automatic notification device are combined. A wireless meter reading system illustrated in FIG. 1 includes n wireless built-in gas meters 1-1, 1-2,... 1-n (hereinafter described as gas meters 1) and wireless meter reading for each gas meter 1. And a wireless automatic notification device 2.

  The wireless automatic notification device 2 is connected to a telephone line or a PHS line. Here, each gas meter 1 is often installed in a place surrounded by a building such as a pipe shaft or a meter box in each room such as a housing complex. In addition, the wireless automatic notification device 2 is often installed at places where the radio wave is transmitted through the building while reflecting off the gas meter 1 such as a common area on the first floor of an apartment house or the like.

  In this way, when radio waves propagate while reflecting in a building or the like between the gas meter 1 and the wireless automatic notification device 2, the multipath fading in which the radio waves reflected through various paths are strengthened or weakened. Occurs. Even if the electric field strength is sufficient for wireless communication between the gas meter 1 and the wireless automatic notification device 2, wireless communication may not be possible if radio waves cancel each other out due to multipath and are extremely attenuated.

  Therefore, in the present invention, a diversity reception system is adopted as a multipath improvement measure. However, since the electric field strength frequently changes in mobile communication in an automobile or the like, a plurality of antennas are frequently switched while constantly monitoring the strength of radio waves. And the wireless automatic notification device 2, there is no need to frequently switch a plurality of antennas.

  Therefore, the wireless communication unit according to the present invention employs the configuration and control described below. FIG. 2 is a schematic view showing an example of a gas meter equipped with a wireless communication unit according to the present invention. An example in which the gas meter 1 illustrated in FIG. 2 is applied to the wireless meter reading system in FIG. 1 will be described. Hereinafter, although the number of antenna elements will be described as two, a plurality of antenna elements may be used.

  The gas meter 1 illustrated in FIG. 2 is a gas meter with a built-in wireless communication antenna equipped with the following wireless communication unit 10. The wireless communication unit 10 includes two antenna elements 12a and 12b and one wireless communication circuit connecting the antenna elements 12a and 12b, and the two antenna elements 12a and 12b are connected to one wireless communication circuit. A method of switching and connecting 12b is adopted. This wireless communication circuit is exemplified by a wireless transmission / reception unit / control unit 13 provided on a substrate (wireless unit substrate) 11.

  In the gas meter 1 of FIG. 2, a wireless unit substrate 11 is mounted on the lower portion, and antenna elements 12 a and 12 b are disposed at both ends thereof. As the antenna elements 12a and 12b, a linear antenna such as a ceramic antenna or a printed pattern antenna is mounted on the wireless unit substrate 11, but the two antenna elements are about λ / 4 to λ / 2 so that the correlation becomes as small as possible. Need to be separated. Of course, it may be formed in a length of about λ / 4 to λ / 2 by inserting a coil or the like, or may be formed in a shorter length by sacrificing the state of reception / transmission. .

  FIG. 3 is a block diagram showing details of the wireless communication unit in the gas meter of FIG. With reference to FIG. 3, the detail of the above-mentioned radio | wireless communication unit 10 is demonstrated. The wireless transmission / reception 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 transmission / reception 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 transmission / reception switching that switches between radio transmission / reception. A circuit 15 and an antenna switching circuit 14 connected to the antenna elements 12a and 12b and switching the antenna element to be used between the antenna elements 12a and 12b are provided. The antenna switching circuit 14 is an example of switching means for switching the antenna element to be used between the two antenna elements 12a and 12b.

  With such a configuration, at the time of reception, the control unit / meter interface unit 18 performs switching control so that the transmission / reception switching circuit 15 performs radio reception, and the antenna is received from the radio wave received by one of the antenna elements 12a and 12b. The reception circuit 17 is controlled so as to demodulate the reception signal received through the switching circuit 14 and the transmission / reception switching circuit 15, and the reception circuit 17 executes a demodulation process so that the received signal after demodulation is controlled / meter interface unit. 18 is output. Here, which antenna element is used for reception is determined by the control unit / meter interface unit 18 as described later, and is executed by controlling the antenna switching circuit 14.

  On the other hand, at the time of transmission, the control unit / meter interface unit 18 performs switching control so as to wirelessly transmit to the transmission / reception switching circuit 15 and outputs a transmission signal to the transmission circuit 16, and the transmission circuit 16 outputs the transmission signal. The signal is modulated and output to the antenna switching circuit 14 via the transmission / reception switching circuit 15, the modulated transmission signal is fed to one of the antenna elements 12a and 12b, and one of the antenna elements 12a and 12b is in the space. Radiates as. Which antenna element radiates is determined by the control unit / meter interface unit 18 as described later, and is executed by controlling the antenna switching circuit 14.

  The control unit / meter interface unit 18 in the present invention compares the field strength of each antenna element measured by the measurement unit with the measurement unit that measures the electric field strength caused by the radio wave induced in each of the two antenna elements 12a and 12b. And a comparison means. Then, the control unit / meter interface unit 18 uses an antenna as necessary so that reception is performed using the antenna element having the strongest electric field strength (the stronger of the two) based on the comparison result of the comparison unit. The antenna switching circuit 14 is controlled to execute element switching. Such a switching function realizes reception by the diversity reception method in the wireless communication unit 10. In other words, the wireless communication unit 10 receives the radio wave transmitted from the opposing wireless automatic notification device 2 or the like, measures the strength of the radio wave induced in the two antenna elements 12a and 12b, and has the higher electric field strength level. The antenna element can be switched to. Further, at the time of transmission, the antenna elements may be switched as necessary so that transmission is performed using the antenna element with the stronger electric field strength as a result of comparison by the comparison means at the time of reception.

  And the control part / meter interface part 18 in this invention controls the antenna switching circuit 14 so that switching of an antenna element may be performed according to the intermittent drive period of the radio | wireless transmission / reception part / control part 13. FIG. Here, the intermittent drive cycle of the wireless transmission / reception unit / control unit 13 is a cycle for intermittently exploring whether radio waves are not emitted (that is, whether there are radio waves to be received). The intermittent drive cycle set in the interface unit 18 is indicated.

  The intermittent drive cycle and switching of the antenna element corresponding to the intermittent drive cycle will be described with reference to FIGS. 4 and 5 are diagrams illustrating timing examples of the diversity antenna switching operation in the wireless transmission / reception unit / control unit of FIGS. 2 and 3, and FIG. 4 is a timing example of the standby operation in the wireless transmission / reception unit / control unit. FIG. 5 shows an example of the timing of the receiving operation in the radio transmitter / receiver / control unit on the gas meter side when a call (radio transmission) is made from the opposite wireless automatic notification device side. 6 and 7 are flowcharts for explaining an example of the antenna switching operation of FIG. 5 based on the standby operation of FIG.

  First, as illustrated in FIG. 4, the control unit / meter interface unit 18 of the gas meter 1 controls the transmission / reception switching circuit 15 and the reception circuit 17 so as to be driven with a period T set therein, and the reception circuit 17. Repeats intermittent drive according to the drive control. Here, the period T includes a period T1 received by the antenna element and a period T2 until the next reception. The control unit / meter interface unit 18 determines the start and end points of the period T1 for each period by the receiving circuit 17. To drive control. At that time, the control unit / meter interface unit 18 controls the antenna switching circuit 14 so that the two antenna elements 12a and 12b are alternately switched in accordance with the period T as shown in FIG. I do.

  More specifically, this receiving operation will be described. First, the control unit / meter interface unit 18 controls the antenna switching circuit 14 so that it is received by the antenna element 12a (hereinafter referred to as the first antenna), and the transmission / The reception switching circuit 15 and the reception circuit 17 are controlled to perform a standby operation for the period T1 with the first antenna, and whether or not the activation signal I is received with the first antenna is present or not from the reception circuit 17 (Step S1). The activation signal I indicates a signal indicating its own station ID (ID of the wireless automatic notification device) received from the radio wave transmitted from the wireless automatic notification device 2. If it is received in step S1 (in the case of YES), that is, if there is a call (wireless transmission) from the opposing wireless automatic notification device 2, the process proceeds to step S10.

  In the case of NO in step S1, the control unit / meter interface unit 18 waits for the elapse of the period T2 from the end of the period T1, and by the same control, the antenna element 12b (hereinafter referred to as the second antenna) only for the period T1. A standby operation is performed, and it is further determined whether or not the activation signal I is received by the second antenna (step S2). In the case of NO in step S2, that is, in the state where there is no call (wireless transmission) from the opposed wireless automatic notification device 2, the intermittent drive is continued by returning to step S1.

  On the other hand, in the case of YES in step S2, that is, when there is a call (wireless transmission) from the opposing wireless automatic notification device 2, the control unit / meter interface unit 18 receives the activation signal II. Is determined (step S3). Here, as illustrated in FIG. 5, the activation signal II transmitted from the wireless automatic notification device 2 side is usually a signal following the activation signal I, for example, a signal indicating the ID of the slave unit (gas meter 1). Point to. Further, following the activation signal II, data such as a signal requesting an integrated value and a signal requesting a test call is transmitted.

  If YES in step S3, the data following the activation signal II is received with the second antenna remaining (step S9), and the process ends. At this time, reception by the second antenna is maintained until data communication is completed, and switching to the first antenna is not performed. In addition, after the process of step S9 (and later-described steps S7, S8, S14 to S16) is completed, the intermittent standby operation may be temporarily stopped and the control unit / meter interface unit 18 may start a series of operations again. 6 and 7 are shown on the premise of FIG. 6, but the flow may automatically return to step S <b> 1 after the end in FIGS. 6 and 7.

  In the case of NO in step S3, the control unit / meter interface unit 18 causes the reception circuit 17 to measure the electric field strength (RSSI value) for a certain period of time while receiving the second antenna, receives the measurement value (step S4), and then Then, switching to the first antenna causes the receiving circuit 17 to measure the electric field intensity for a certain period of time and receives the measured value (step S5). As described above, the reception circuit 17 receives the activation signals I and II from the transmission radio wave of the wireless automatic notification device 2 at the intermittent reception, and the electric field strength is constant when the activation signal II matches the own station ID of the gas meter 1. Time measurement is performed, and then the electric field strength is measured for a certain time by switching to another antenna.

  Then, the control unit / meter interface unit 18 compares these measured values to determine whether or not the measured value of the first antenna is equal to or greater than the measured value of the second antenna (step S6). In the case of NO in step S6, the data is switched to the second antenna and data following the activation signal II is received (step S7), and the process is terminated. If YES in step S6, the data following the activation signal II is received with the first antenna (step S8), and the process ends. Note that the flow in the case of NO in step S3 is also shown in the lower timing of FIG.

  In this way, the control unit / meter interface unit 18 compares the electric field strength measured with the currently used antenna element with the electric field strength measured with another antenna element, and switches to the antenna element with the stronger radio wave. The following data part is received. Note that when the activation signal II is received without receiving the activation signal I during intermittent reception, antenna switching is not performed.

  Further, as briefly described in step S9, also in steps S7 and S8, after the activation signal II is received, the electric field strength is measured, the electric field strength is compared, and the antenna element selection switching operation is executed. The selected antenna element is maintained until the operation is completed. Here, the predetermined communication refers to transmission of a request message including an activation signal from the wireless automatic notification device 2 to the gas meter 1, transmission of a response message from the gas meter 1 to the wireless automatic notification device 2, and wireless automatic notification device 2 To the transmission of the end message to the gas meter 1. Here, the reason why the antenna is switched every predetermined communication is that the change in the electric field level due to the multipath is slow because of the fixed communication, and it is not necessary to frequently switch the antenna elements.

  If YES in step S1, the process proceeds to step S10 as described above to determine whether or not the activation signal II has been received, and the processes in steps S11 to S16 are executed based on the determination. The processes in steps S10 to S16 are processes in which the processes in steps S3 to S9 described above and the first antenna and the second antenna are interchanged, and will be briefly described.

  In the case of YES at step S10, data following the activation signal II is received with the first antenna (step S16), and the process is terminated. In the case of NO in step S10, the control unit / meter interface unit 18 causes the receiving circuit 17 to measure the electric field intensity for a certain period of time while maintaining the first antenna, receives the measured value (step S11), and then the second antenna. And the receiving circuit 17 measures the electric field strength for a predetermined time and receives the measured value (step S12). Then, the control unit / meter interface unit 18 compares these measured values and determines whether or not the measured value of the second antenna is equal to or larger than the measured value of the first antenna (step S13). If NO in step S13, the first antenna is switched to receive data following the activation signal II (step S14), and the process ends. If YES in step S13, the data following the activation signal II is received with the second antenna remaining (step S15), and the process ends.

  As described above, by adopting the diversity reception method and executing switching according to such intermittent drive cycle, one unit built in the gas meter 1 is used for wirelessly measuring the gas meter 1 installed in an apartment house or the like. With this wireless communication circuit and two antenna elements, a space-saving, low-cost, diversity reception system that does not require frequent antenna switching can be constructed, and stable wireless communication that is resistant to the influence of the surrounding environment can be expected.

  In the above description, the antenna switching operation when a call is made from the wireless automatic notification device 2 to the gas meter 1 (a request message including an activation signal is wirelessly transmitted) has been described. There is also a case where a call is made (a request message including an activation signal is wirelessly transmitted) to the automatic automatic notification device 2. In this case, two antenna elements and one wireless communication circuit are mounted on the wireless automatic notification device 2 side, and a call (request including an activation signal) is made from the gas meter 1 by switching and controlling the two antenna elements. It is possible to switch to an antenna element having a higher electric field strength by receiving a message (wireless transmission). The activation signal I transmitted from the gas meter 1 is a signal indicating the ID of the gas meter 1, and the activation signal II transmitted from the gas meter 1 usually indicates a signal indicating the ID of the master unit (the wireless automatic notification device 2). . Further, following the activation signal II, various information data such as an integrated value requested from the parent device and information indicating a test call are transmitted.

  In this way, not only on the gas meter 1 side, but also on the wireless automatic notification device side, a diversity reception system incorporating two antenna elements and one wireless communication circuit enables bidirectional and multipath wireless communication. Communication is possible.

It is a figure which shows the structural example of the wireless meter-reading system which combined the gas meter which incorporated the wireless function, and the wireless automatic notification apparatus. It is the schematic which shows an example of the gas meter carrying the radio | wireless communication unit which concerns on this invention. It is a block diagram which shows the detail of the radio | wireless communication unit in the gas meter of FIG. It is a figure which shows the example of a timing of the diversity antenna switching operation in the radio | wireless transmission / reception part / control part of FIG.2 and FIG.3, and is a figure which shows the example of a timing of the standby operation in a radio | wireless transmission / reception part / control part. FIG. 4 is a diagram illustrating a timing example of diversity antenna switching operation in the wireless transmission / reception unit / control unit of FIG. 2 and FIG. 3, and wireless transmission / reception on the gas meter side when there is a call (radio transmission) from the opposite wireless automatic notification device side It is a figure which shows the example of a timing of the receiving operation in a part / control part. FIG. 6 is a flowchart for explaining an example of the antenna switching operation of FIG. 5 based on the standby operation of FIG. 4. It is a flowchart following FIG.

Explanation of symbols

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

Claims (3)

A plurality of antenna elements and one wireless communication circuit connecting the plurality of antenna elements;
The wireless communication circuit includes a switching unit that switches an antenna element to be used between the plurality of antenna elements, a measuring unit that measures electric field strength caused by a radio wave induced in each of the plurality of antenna elements, and the measuring unit. A comparison means for comparing the measured electric field strength of each antenna element;
The switching means performs switching of the antenna element according to the intermittent drive cycle of the wireless communication circuit, and uses the antenna element having the strongest electric field strength based on the result of comparison by the comparing means. A radio communication unit that performs switching of an antenna element as necessary so as to receive data.   The wireless communication unit according to claim 1, wherein the number of the antenna elements is two.   A flow meter comprising the wireless communication unit according to claim 1.

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