JP2010130593A - Compact transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a radiation pattern and radiation efficiency of a ground plane type antenna. <P>SOLUTION: A compact transmitter detects opening/closing of a window and wirelessly transmits a detection result. A ground plane type antenna 40 is disposed while separating an antenna lead wire 50, which is connected to one of feeding points, from a mounting surface of a cabinet as far as possible. A plurality of ground lead wires 54 are connected to the other feeding point, and the ground lead wires 54 are laid along a bottom surface of the cabinet and form a capacitor structure reducing antenna ground resistance in a gap with a metal conductor plate disposed at a side of the mounting surface. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a small transmitter with a built-in ground plane antenna structure that is mounted on a metal window frame of a window sash and wirelessly transmits detection information on opening / closing of a window.

  2. Description of the Related Art Conventionally, a wireless window opening / closing monitoring device that detects opening / closing of a window and transmits the alarm to a monitoring panel wirelessly is known. In such a window open / close monitoring device, the magnetic force of the magnet arranged on the window glass is detected by a magnetic sensing element such as a hall sensor, and when the detected magnetic force decreases, it is determined that the window is open / closed and an abnormality detection signal is warned. The alarm is transmitted wirelessly to the board. Also, the magnetic force of the magnet placed on the open / close lever of the crescent lock provided on the window is detected by another magnetic sensing element, and when the detected magnetic force decreases, it is determined that the crescent lock is open and an abnormal detection signal is transmitted wirelessly to the alarm panel. Alarm.

  The built-in antenna in the window open / close detector uses a frequency that complies with the standard of a specific low-power radio station, and the built-in antenna that cannot be large enough for the wavelength of the frequency to be used is a shortened type. In most cases, it takes a shape. The weaknesses of these antennas are affected by the surrounding environment where the antennas are installed, so that the performance of the antennas is greatly affected. Therefore, it is difficult to receive radio waves after the system is installed.

  That is, when the shape of the transmitter incorporating the antenna is less than the required antenna length, the antenna is electrically extended by connecting a loading coil to the antenna to be used. This cancels the capacitive reactance component X of the antenna of 1/4 wavelength or less, so that coils having reactance components -X having the same value and different polarities are connected in series, and the input impedance of the antenna is made to resonate only as a pure resistance, The coil is electrically extended to ¼ wavelength, and this coil is called a loading coil (also called “extension coil”).

  Further, in a small transmitter having a casing whose size is ¼ wavelength or less of the used frequency, a ground plane type antenna known as a ground antenna is often used. A ground plane type antenna is one in which one of the feeding points is connected to the antenna conductor and the other of the feeding points is connected to the ground. The antenna conductor is a quarter wavelength, and the ground is a perfect conductor plane. It can be considered that a quarter-wave image antenna exists, which is the same as a half-wave dipole antenna in free space.

The radiation efficiency η of the ground plane type antenna is determined by the radiation resistance Rr of the antenna conductor and the ground resistance Rg of the ground plane.
η = Rr / (Rr + Rg)
Given in. From this relationship, it is necessary to reduce the ground resistance Rg in order to increase the radiation efficiency of the antenna.

  However, when an antenna built in a small housing such as a window open / close detection device is operated as a ground plane type antenna, a sufficient ground area (earth area) cannot be secured. Is done. Especially when it is installed on a metal window frame, the antenna parameters change greatly due to the metal installed near the antenna, the radiation pattern of radio waves does not become circular, and the radiation efficiency deteriorates. is there.

It is an object of the present invention to provide a small transmitter having an antenna structure that improves the radiation pattern and radiation efficiency of a ground plane antenna.

The present invention relates to a small transmitter having a built-in ¼ wavelength ground plane antenna.
A housing having an open box shape opened at one end;
A metal conductor plate disposed on the bottom mounting surface side of the housing;
An antenna conductor connected to one of the feeding points and arranged away from the mounting surface side of the housing;
A plurality of ground conductors connected to the other of the feeding points and wired along the bottom surface of the housing to form a capacitor structure with the metal conductor plate;
It is provided with.

  Here, the antenna conductor has an antenna length less than ¼ wavelength, and a loading coil that electrically extends the antenna conductor to approximately ¼ wavelength is connected in series.

  The ground conductor forms a capacitor structure with the bottom of the casing interposed between the ground conductor and the metal conductor plate as a dielectric.

When a base plate made of a synthetic resin is placed on the bottom side of the casing following the metal conductor plate, and the casing is attached to a metal window frame, the ground conductor is located at the bottom of the casing interposed between the metal conductor plate. A capacitor structure is formed as a dielectric, and another capacitor structure is formed using a base plate interposed between the metal conductor plate and the metal window frame as a dielectric.

  According to the present invention, even in a small transmitter with a built-in ground plane antenna that cannot secure a sufficient ground plane for reasons such as being attached to a window frame, the ground conductor is attached to the bottom of the housing. A capacitor structure is formed between the antenna conductor and the metal conductor plate arranged on the mounting surface side by arranging the antenna conductors away from the mounting surface side of the housing and capacitively coupling it. The ground plane can be widened, the ground resistance can be reduced, and the radiation pattern and radiation efficiency of the antenna can be improved.

In addition, when attached to a metal window frame, another capacitor structure is formed between the metal conductor plate of the small transmitter and the metal window frame to ensure a wide ground plane including the metal window frame, The antenna radiation pattern and radiation efficiency can be improved.

  FIG. 1 is an explanatory view showing an installation state of a window opening / closing detection device as an example of a small radio according to the present invention. In FIG. 1, a window opening / closing detection device 10 of the present invention is fixed to a vertical frame of a window sash 12a, 12b of a sliding window to be monitored by a double-sided tape or a screw.

  On the upper side of the window opening / closing detection device 10, the window sash 12 a, 12 b is closed, and a window opening / closing detection magnet 14 is attached to the opposite position with double-sided tape, and the magnetic force from the window opening / closing detection magnet 14 is incorporated. It is detected by a Hall sensor as a magnetic sensing element.

  When the window sash 12a, 12b is opened, the magnetic force is reduced by the window opening / closing detection magnet 14 being separated from the window opening / closing detection device 10, and a detection signal indicating the opening of the window is detected by detecting the decrease in the magnetic force with a hall sensor. Sent to a monitoring device wirelessly to alert.

  The window open / close detection device 10 is arranged so that the lower end thereof is close to the crescent lock 16 provided on the window sash 12a, 12b, and the magnetic force of the crescent lock detection magnet 20 attached to the open / close lever 18 of the crescent lock 16 is lowered to the lower end. It is detected by another hall sensor built in the side.

  The crescent lock 16 locks the window sashes 12a and 12b at an operation position in which the opening / closing lever 18 is rotated in the illustrated vertical direction. At this time, the crescent lock detection magnet 20 is the hall sensor closest to the window opening / closing detection device 10. The magnetic force to be detected is maximized, and the locked state is detected.

  When the crescent lock 16 is unlocked by turning the opening / closing lever 18 downward, the magnetic force is reduced by the separation of the crescent lock detection magnet 20, and a detection signal indicating the unlocked state is detected by detecting the decrease in the magnetic force with a hall sensor. Sends a warning to the monitoring device by radio.

  FIG. 2 is an explanatory view showing a state where the cover member 24 is removed from the apparatus main body 22 in the window opening / closing detection apparatus 10 according to the present embodiment. On the upper part of the apparatus main body 22, there are a display unit 66 using red LEDs and green LEDs, a registration switch 70 for executing a threshold value registration process for determining the magnetic force detected by the lock detection hall sensor 48, and a cover member 24. A tamper switch 74 for detecting attachment / detachment is provided. Locking claws 25 and 27 are formed on the base sides on both sides of the apparatus main body 22, and the cover member 24 is fitted and fixed.

  The cover member 24 is detachable with respect to the apparatus main body 22, and a display window 57 is provided in the center of the front so that the display state of the display unit 66 of the apparatus main body 22 can be seen.

  FIG. 3 is an exploded view showing an embodiment of the window opening / closing detection apparatus according to the present invention. In FIG. 3, the window opening / closing detection device 10 according to the present embodiment includes an apparatus main body 22 and a cover member 24.

  The apparatus main body 22 is assembled from the bottom side, a base 30, a metal conductor plate 32, a bottom cover 34, a housing 36, a circuit board 38 including an antenna 40, and a main body cover 42, and a battery 44 is detachably provided. It is done. A conical magnetic current collector 26 is housed and fixed in the holder member 28 at an end portion of the cover member 24 located on the crescent lock side.

  A sensor board 45 is erected on the upper side of the circuit board 38, and a hall sensor 46 for detecting window opening / closing is disposed here. A crescent lock detecting hall element 48 is provided at the lower end of the circuit board 38. Further, a battery connector 37 is provided on the circuit board 38.

  FIG. 4 is an explanatory diagram showing details of the antenna structure in the present embodiment with respect to the circuit board 38 of FIG. In FIG. 4, an antenna 40 is a 1/4 wavelength ground plane type antenna, and an antenna conductor 50 is disposed on the upper left side of the circuit board 38. The antenna conductor 50 has a bent portion 50a formed in the middle thereof. The bent portion 50a is hung around and fixed to a groove formed at the upper left end of the housing 36 shown in FIG. The antenna lead wire 50 is disposed above the apparatus main body 22 with a distance above the mounting surface.

  The antenna length of the antenna conductor 50 is less than a quarter wavelength determined by the frequency used in accordance with the standard of the specific low-power radio station used in the present embodiment. In order to secure an antenna length of ¼ wavelength, a loading coil 52 is connected in series with the antenna conductor 50.

  For this reason, the feeding end 52 a of the loading coil 52 is connected to one of the final power points of the wireless transmission circuit mounted on the circuit board 38. The inductance component of the loading coil 52 is set so as to cancel the capacitive reactance component of the antenna conductor 50 and to have only the antenna pure resistance.

  In the present embodiment, four ground conductors 54 are connected to the other end of the power feeding point by the wireless transmission circuit mounted on the circuit board 38 by the power feeding end 54 a and extend in the direction opposite to the antenna conductor 50. The ground conductor 54 is routed along the bottom surface that is the inner side of the bottom plate 34 that is mounted on the lower side of the housing 36 in FIG. 3, and is placed between the metal conductor plate 32 in FIG. A capacitor structure is formed by sandwiching the bottom cover 34 as a dielectric.

  Due to the capacitor structure formed by the ground conductor 54, the bottom lid 34, and the metal conductor plate 32, the ground resistance Rg between the metal conductor plate 32 and the ground resistance Rg is widened. The radiation efficiency η of the antenna is improved along with the decrease in.

  Further, as shown in FIG. 1, the window opening / closing detection device 10 of the present embodiment is attached to a metal frame of a window such as an aluminum sash. As a result, the metal conductor shown in FIG. Another capacitor structure is formed between the plate 32 and the metal window frame to be attached, and a wide ground plane including the metal window frame is secured through the double capacitor structure.

  Further, when the window frame to be attached is made of wood, the ground plane can be secured by the capacitor coupling to the metal conductor plate 32 built in the apparatus, and the radiation efficiency of the antenna can be sufficiently enhanced even with the wooden window frame.

  FIG. 5 is an explanatory view showing the antenna radiation pattern according to the present embodiment in comparison with the conventional one. FIG. 5A shows an antenna radiation pattern according to the present embodiment. The antenna gain is increased by 20 dB compared to the conventional pattern of FIG. 5B (concentric circles indicate 10 dB), and the pattern shape is uniform in all directions. As a result, the antenna radiation efficiency is greatly improved.

  FIG. 6 is a block diagram showing a circuit configuration of the window opening / closing detection apparatus according to the present embodiment. In FIG. 6, a processor 60 provided as a control unit is a computer known as a one-chip microcomputer, and includes a CPU, ROM, RAM, AD conversion port, various input / output ports, etc. on one chip. In the embodiment, a nonvolatile memory 78 such as an EEPROM is externally attached.

  The magnetic force level detection signal from the window opening / closing detection magnet 14 provided on the window glass detected by the window opening / closing detection hall sensor 46 is amplified by the amplification circuit 62 and then applied to the AD conversion port 80 to be converted into a digitally converted magnetic force level (AD Conversion value) is taken into the processor 60 and converted into AD conversion data.

  The magnetic force level detection signal detected by the lock detection hall sensor 48 and detected by the crescent lock detection magnet 20 on the open / close lever 18 of the crescent lock 16 is also amplified by the amplifier circuit 64 and then applied to the AD conversion port 82 for digital conversion. The obtained magnetic force level (AD conversion value) is taken into the processor 60 and converted into AD conversion data.

  For the processor 60, a display unit 66, a frequency changeover switch 68, a registration switch 70, a test switch 72, a tamper switch 74, and a wireless transmission unit 76 including an antenna 40 are provided.

  The display unit 66 is provided with a two-color LED of a red LED and a green LED. For example, the red LED is lit when an abnormality is detected such as opening of a window or unlocking, and then the green LED is lit when normal operation is restored. To do. The frequency switch 68 selects any one of a plurality of usable channels prepared in advance for the wireless transmission unit 76.

  The registration switch 70 is used for setting a lock registration mode that is performed at the start of use of the window opening / closing detection device 10 of the present embodiment. As the test switch 72, a reed switch is used. When the test magnet is brought close to the test switch 72, the test switch 72 operates to transmit a test message from the wireless transmission unit 76 to the monitoring device. The tamper switch 74 is a switch that detects opening and closing of the cover member 24.

  The wireless transmission unit 76 is provided with a transmission circuit, and wirelessly communicates the monitoring state to the monitoring panel.

  The non-volatile memory 78 stores a window determination threshold value TH1 for window opening / closing detection obtained based on a magnetic force level acquired from the window opening / closing detection hall sensor 46 through measurement processing at the factory manufacturing stage of the apparatus.

  Further, the non-volatile memory 78 has a lock determination threshold value TH2 for detecting lock opening / closing obtained based on the magnetic force level acquired from the lock detection hall sensor 48 in the crescent lock registration process performed with the window opening / closing detection device 10 installed on the window. Is remembered.

  The processor 60 is provided with a registration processing unit 84, a window opening / closing monitoring unit 86, a lock monitoring unit 88, and a communication control unit 90 as functions realized by execution of a program by the CPU.

  As shown in FIG. 1, the registration processing unit 84 operates the open / close lever 18 of the crescent lock 16 to the unlocked position after the installation arrangement of the window open / close detection device 10, the window open / close detection magnet 14 and the crescent lock detection magnet 20 is completed. In this state, when the cover member 24 is removed and the registration switch 60 of the apparatus main body 22 is operated as shown in FIG. 2, the registration mode is set and the registration process is executed.

  In the registration process, the magnetic force level detected by the locking detection hall sensor 48 is acquired at a predetermined period, and compared with a predetermined effective level set in advance. Register, calculate a value lower by a predetermined ratio than the initially registered magnetic force level, register it in the nonvolatile memory 78 as a lock determination threshold TH2 for determining whether the crescent lock is unlocked, and monitor the lock of the crescent lock by the lock monitoring unit 88. Let it begin.

  In this case, the opening / closing lever 18 is returned to the unlocked position, the cover member 24 is opened, and the registration switch 70 is operated, so that the initial registration of the magnetic force level is performed again.

  The window open / close monitoring unit 86 compares the magnetic force level obtained from the window open / close detection hall sensor 46 with the window determination threshold TH1 read from the nonvolatile memory 78, determines whether the window is open or closed, and wirelessly transmits a message indicating the determination result. It transmits to the monitoring apparatus from the transmission part 76, and performs an alarm or alarm cancellation.

  The lock monitoring unit 88 compares the magnetic force level obtained from the lock detection hall sensor 48 with the lock determination threshold value TH2, and determines that the crescent lock is open when the lock determination threshold value TH2 or less is reached. An alarm is transmitted from the wireless transmission unit 76 to the monitoring device. In addition, the lock monitoring unit 88 wirelessly transmits a message to that effect to the monitoring device even when the lock monitoring unit 88 detects unlocking and returns to locking.

  In addition to the transmission of a message based on the judgments of the window opening / closing monitoring unit 86 and the lock monitoring unit 88, the communication control unit 90 transmits a regular notification message at regular time intervals.

  FIG. 7 is a flowchart showing the monitoring process of the present embodiment by the processor 60 of FIG.

  In FIG. 7, when the power is turned on by connecting the connector of the battery 44 with the field installation as shown in FIG. 1, the initialization process and the self-diagnosis process are executed in step S1. Proceeding to S <b> 2, data including a window determination threshold value TH <b> 1 for window opening / closing monitoring stored in the nonvolatile memory 78 is read.

  Subsequently, the process proceeds to step S3, where it is determined whether or not the lock monitoring registration mode is set. When the setting of the lock monitoring registration mode is determined by opening the cover member 24 and turning on the registration switch 70, the process proceeds to step S4. Locking monitoring registration processing including initial registration of the magnetic force level by the detection hall sensor 48 and registration of the lock determination threshold TH2 for detecting locking and unlocking of the crescent lock 16 is executed.

  Subsequently, in step S5, it is determined whether or not the monitoring cycle has reached a predetermined timing. If it is determined that the monitoring cycle has been reached, the process proceeds to step S6 to execute a low battery monitoring process for the battery 44. At this time, if the battery voltage drops below the specified voltage, a message indicating a low battery is wirelessly transmitted to the monitoring device to display a failure.

  Next, in step S7, a window opening / closing monitoring process is executed, and when a window opening or window closing is determined, a message indicating the contents is transmitted to the monitoring device. Furthermore, when the lock monitoring process is executed in step S18 and it is determined whether the lock is unlocked or the subsequent lock is closed, a message indicating the content is transmitted to the monitoring device. Subsequently, in step S9, it is determined whether the periodic notification time has elapsed, and if it has been determined, the process proceeds to step S10, and a periodic notification process for transmitting a periodic notification message to the monitoring device is performed.

  In the above embodiment, a window opening / closing monitoring device is taken as an example of a small transmitter, but other than this, any device that has an appropriate application and function and functions as a small transmitter that wirelessly transmits information from a built-in antenna. Therefore, the present invention can be applied to an appropriate apparatus as it is.

Further, the present invention includes appropriate modifications that do not impair the object and advantages thereof, and is not limited by the numerical values shown in the above embodiments.

Explanatory drawing which showed the installation state of the small transmitter by this invention Explanatory drawing which showed the state which removed the cover member from the apparatus main body about the small transmitter by this embodiment Explanatory drawing which showed the assembly / disassembly state of the small transmitter by this embodiment Explanatory drawing which showed the detail of the antenna structure in the small transmitter of this embodiment Explanatory drawing which showed the antenna radiation pattern by this embodiment in contrast with the past The block diagram which showed the circuit structure of the small transmitter by this embodiment The flowchart which showed the window opening / closing detection process of this embodiment by the processor of FIG.

Explanation of symbols

10: Window open / close detection devices 12a, 12b: Window sash 14: Window open / close detection magnet 16: Crescent lock 18: Open / close lever 20: Crescent lock detection magnet 22: Device main body 24: Cover member 36: Housing 40: Antenna 46: Window Open / close detection hall sensor 48: lock detection hall sensor 50: antenna conductors 50a, 54a: feeding end 52: loading coil 54: ground conductor 76: wireless transmission unit 84: registration processing unit 86: window opening / closing monitoring unit 88: locking monitoring Unit 90: Communication control unit

Claims (4)

In a small transmitter with a built-in ¼ wavelength ground plane antenna,
A housing having an open box shape opened at one end;
A metal conductor plate disposed on the bottom mounting surface side of the housing;
An antenna conductor connected to one of the feeding points and arranged away from the mounting surface side of the housing;
A plurality of ground conductors connected to the other of the feeding points and wired along the bottom surface of the housing to form a capacitor structure with the metal conductor plate;
A small transmitter characterized by comprising:
2. The small transmitter according to claim 1, wherein the antenna conductor has an antenna length less than ¼ wavelength, and a loading coil for electrically extending the antenna conductor to substantially ¼ wavelength is connected in series. A small transmitter characterized by.
2. The small transmitter according to claim 1, wherein the ground conductor forms a capacitor structure with a bottom portion of the casing interposed between the ground conductor and the metal conductor plate as a dielectric.
The small transmitter according to claim 1, wherein a base plate made of a synthetic resin is disposed on the bottom surface side of the casing following the metal conductor plate,
When the casing is attached to a metal window frame, the ground conductor forms a capacitor structure with the bottom of the casing interposed between the metal conductor plate and a dielectric, and the metal conductor plate and the metal window frame A small transmitter having a separate capacitor structure with the base plate interposed therebetween as a dielectric.

Images