JPH0524688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an improvement in a wireless transmitter that uses weak radio waves to transmit a security signal to a separately placed receiver.

[Background technology]

This type of transmitter is used attached to security sensors, fire sensors, etc., or to notify emergency situations such as when an elderly person who requires nursing care walks alone or when a sick person is separated from a caregiver. It is used.

Such a wireless transmitter is equipped with a transmitter circuit that generates a predetermined high-frequency signal, and modulates the high-frequency signal generated by the transmitter with an abnormal signal detected by a sensor, etc., and sends it to the antenna. The signal is transmitted from the unit to the receiver in the form of a radio wave signal.

For example, FIG. 7 shows a case where such a wireless transmitter is used as a portable device. When a sick person m is lying on a bed without a caregiver, the wireless transmitter a is placed next to the bed and the patient m is placed on the bed. When you leave the station for a walk, etc., carry wireless transmitter a with you, and in the event of an emergency, press the operation switch to send an abnormal signal to receiver b, and receive it. The device B side receives this abnormal signal, activates a notification means such as a housing information panel C, and notifies the nurse. Wireless oscillators have a self-excited oscillator circuit built into the main body, which consists of an LC resonant circuit that combines a coil and a capacitor, and are widely used because they have a simple circuit configuration and are inexpensive.

FIG. 8 explains the structure of a conventional portable wireless transmitter.The basic structure of this device is an upper case 20 provided with a push button switch 201.
The main body case 500 housing the circuit board is engaged with and integrally connected to the main body case 200.
A lid cover 300 is placed in a recess 203 formed in a part of the
The protruding pieces 300a of the two are engaged with each other. Lid cover 30
0 from the upper case 200, the lid cover is slid to release this engagement, and when the lid cover 300 is removed in this way, the battery accommodating portion formed in a part of the main body case 500 is removed. 202 (recess) and various operation switches 4
The structure is such that 00d and 400e are exposed.
When the main body case 500 and the lid cover 200 are disengaged, the circuit board 400 as shown in FIG. 9 is exposed.
0 is a coil 400a and a trimmer capacitor 400b that constitute a self-excited oscillation circuit as shown in the figure.
is mounted on the circuit board 400 in an exposed state as is the loop antenna 400c. Note that 401 is a display switch for setting the house code of the system, and when the operation switch 201 is operated, another circuit board (not shown) provided at a corresponding location on the lid cover 200 side is activated.
The transmitter circuit is activated by operating a switch on top.

However, in a device with such a self-excited oscillation circuit, the coil 4 constituting the LC resonant circuit
If another magnetic field or electric field exists near 00a, or if an object 600 with a different magnetic permeability such as a metal conductor is brought close to 00a as shown in FIG. 10, the magnetic flux φ generated by the coil 400a will change. The inductance of the LC resonant circuit may change, or the circuit board 400 may be exposed from the main body case 200 when carrying the wireless transmission base or during maintenance.
When a part of the human body is brought close to the LC resonant circuit,
There is a problem in that the oscillation frequency of the oscillation circuit section fluctuates due to changes in capacitance due to stray capacitance.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wireless oscillator having a highly reliable self-excited oscillation circuit whose oscillation frequency does not fluctuate due to the external environment.

[Disclosure of the invention]

The present invention proposed to achieve the above object,
In a battery-powered wireless oscillator that radiates a security signal in the form of a radio wave signal from a self-excited oscillating circuit section having an LC resonant circuit from an antenna, the oscillating circuit section constitutes an LC resonant circuit. Only the circuit elements that constitute the LC resonant circuit are mounted on the surface of the circuit board built into the main body of the wireless oscillator, and the other parts are mounted on the back side of the circuit board. It is characterized by a structure in which only the main body is covered with an electromagnetic shielding case.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 and 2 show the configuration of essential parts of the present invention, and FIG. 1 shows an example of a circuit board on which a self-excited oscillation circuit section is formed.

To explain with reference to the figure, 100 is an insulating substrate, on the surface of which is an LC resonant circuit that combines a coil and a capacitor (see 100a and 100b in Figure 4).A thin plate is punched out and bent downward into an arch shape. a loop antenna 104 formed by
0c, a deep switch 100d for setting the zone code and unit code, a switch 100e for operating the transmitting circuit when pressed by a push button 102a provided on the lid case 102, an LED 100f for lighting up to indicate the operating status of the transmitter, and a wireless transmitter. A battery case 103 (not shown in FIG. 1, see FIG. 4) for accommodating a battery that serves as a driving source for the
is mounted on the front surface of the insulating substrate 100 which serves as a circuit board, and other electronic components of the transmitting circuit necessary for operating the wireless transmitter are mounted on the back surface of the insulating substrate 100.

In such a structure, the feature of the wireless oscillator of the present invention is that the circuit elements of the LC resonant circuit constituting the above-described self-excited oscillation circuit, such as the coil 100.
A and the capacitor 100b are covered with a highly conductive electromagnetic shielding case, and in FIG. 1, a portion designated by reference numeral 105 is shown as this electromagnetic shielding. This shield case 105
is preferably connected to ground level.

Note that 105a is connected to coil 1 in the shield case.
Trimmer capacitor 100 coated with 00a
This is an operation hole for finely adjusting the capacitance of b.

FIG. 2 explains the principle of the electromagnetic shield of the present invention having such characteristics, and shows the coil 10.
0a is electromagnetically shielded by a shield case 105. It is well known that a high-frequency magnetic field is generated when a high-frequency current is passed through a coil, but in the present invention, the magnetic field generated by the coil has no effect on any external magnetic field or electric field that exists outside the shield case 105. Since the inductance of the LC resonant circuit can be kept constant at all times. In addition, the capacitor covered with the shield case 105 is also susceptible to external influences such as stray capacitance (it is well known from experience that when a part of the human body approaches a capacitor, the oscillation frequency fluctuates, (The difference between when the device is carried and when it is not carried may have an effect), and as a result, the oscillation frequency of the LC resonant circuit is maintained stably.

FIG. 3 is a circuit diagram showing in detail the self-exciting oscillation circuit section incorporated in the wireless oscillator.

The oscillation circuit section 1 includes a self-excited oscillation circuit section 11, a high frequency amplification section 12, and an antenna section 13.

The self-excited oscillation circuit section 11 includes a transistor Q1,
Resistors R1 and R2 and diodes D1 and D2 provide a temperature-compensated bias voltage, resistor R3 provides DC negative feedback, and a coil L determines the oscillation frequency.
1, a capacitor C1, a trimmer capacitor TC, and capacitors C3 and C4 that determine the amount of positive feedback to the base of the transistor Q1 in order to obtain stable oscillation.

Here, the trimmer capacitor TC is the coil L1
This is provided to finely adjust the resonant frequency of the LC resonant circuit composed of the capacitor C1 and the capacitor C1.

The oscillation output from the self-excited oscillation circuit section 11 having such a configuration is transmitted to the amplifier section 2 via the coupling capacitor C6.
The signal is supplied to the transistor Q2, where it is amplified, and then guided to the loop antenna 104 of the antenna section 13, where it is radiated as a radio wave.

In the antenna section 13, the loop antenna 1
04 is equivalent to one inductance, and a resonant circuit formed by this inductance and capacitor C7 is driven by the transistor Q2 at the intermediate tap _A0 point for matching.

In addition, coil L2 and capacitors C5 and C6
constitute a choke coil and a bypass capacitor, respectively, and prevent high frequency signals from going around to the power supply line.

FIG. 4 shows an exploded perspective view showing the structure of an embodiment of a wireless transmitter embodying the present invention.

This example diagram shows a portable wireless transmitter A, in which a circuit board that constitutes a transmitter circuit is housed in two parts: a main body base and a lid case.
It is formed into a so-called two-piece outer shell structure.

The circuit board includes, on the surface of an insulating substrate 100, a coil 100a and a trimmer capacitor 100b forming an LC resonant circuit, a loop antenna 104 with an intermediate tap portion formed by punching and bending a thin conductive plate, and a transmitter. Deep switches 100c and 100d for setting the house code, zone code, and unit code, a switch that drives the transmitter circuit operated by a push button switch 102a provided on the lid case 102 side, and a lighting display to indicate the operating status of the transmitter. (When the lid cover 102 is integrally connected to the main body case 101, the lighting state of the LED is visible through the corresponding through hole 102b of the lid cover 102.) A battery case 103 that accommodates a battery is provided.

In such a structure, the main body case 101 and the lid cover 102 have a pair of engaging portions 101a corresponding to the front and rear ends (the engaging portion on the lid cover side is hidden by the cover). ), and by matching the main body case 101 and the lid cover 102 and engaging their engaging portions, they are integrally combined. Insert the tip of a screwdriver into the provided operation hole (not shown) to release the engagement.
The coupling is easily removed, and the entire circuit board 100 is exposed as shown in FIG.

The battery case 103 mounted in the space at the rear of the circuit board 100
When housed in the main body case 101, the circuit board 1
It can be easily installed by engaging the recess 103b provided on the battery case 103 side with the engaging claw 101b protruding from the hole 100g and the missing part 100h of 00, and can be easily removed by releasing the engagement. It has a structure. Therefore, if the user releases the above-mentioned engagement, the main body case 10
1 and the lid cover 102 are easily removed, and the entire surface of the circuit board 100 housed inside is exposed, making it easy to replace the battery (not shown) and operate the deep switches 100c and 100d. Note that the set of protruding conductive pieces 103c provided on the portion of the circuit board 100 on which the battery case 103 is mounted is such that when the battery case 103 is mounted on the circuit board 100 as described above, Together with the conductive piece 103a provided in the groove, this constitutes a battery connection plate.

Further, in this figure, the electromagnetic shielding case 105 includes a coil 100a and a trimmer capacitor 100b.
When mounted at a predetermined location on the circuit board 100, the circuit elements constituting the LC resonant circuit are electromagnetically shielded.

According to the wireless oscillator of the present invention, the circuit elements such as the coil and capacitor that make up the LC resonant circuit are electromagnetically shielded by the shielding case, so do not bring conductive objects or hands close to these elements. Since the inductance and capacitance of the device do not change even when the device is in use, it can be used without becoming sensitive to environmental conditions.

Although the wireless transmitter of the present invention characterized by such a configuration is used as a wireless security system in cooperation with a receiver, it should not be limited to the portable wireless transmitter as described above. As mentioned at the beginning, it goes without saying that it can also be used as a stationary transmitter attached to a fire sensor or disaster prevention sensor.

FIG. 5 is a diagram showing the hardware configuration when applied to a portable wireless transmitter.

In the figure, 6 is an emergency signal generation circuit, which is activated when a push button switch 102a provided on the lid case 102 side is operated, and its output is input to a timer circuit 5, which generates timing pulses at preset time intervals. is generated. This timing pulse triggers the one-shot pulse generator 4, which intermittently drives the transmission ON/OFF circuit 3.

The signal code generator 2 is a house code setter 2.
1. In addition to the zone code setter 22 and unit code setter 23, the output from the supervisor setter 24 is received to generate necessary signals.

The output of the transmission ON/OFF circuit 3 provided after the one shot pulse generator 4 drives the signal code generation circuit 2 and the high frequency oscillation circuit section 1, and the output from the antenna 1.
04, a radio wave signal modulated at a predetermined frequency using a method such as the FSK method is radiated.

Finally, a case in which the wireless transmitter of the present invention is used as a portable transmitter will be described in more detail.

FIG. 6 shows an example of the configuration of a system used as a portable wireless transmitter A.

It is carried and used when a person who needs nursing care, such as an elderly person who walks alone or a sick person, is away from a caregiver. As already shown in the hardware configuration diagram of FIG. 5, the wireless transmitter A has a house code set in the wireless system, a zone code for distinguishing monitoring targets such as fire, crime prevention, and emergency.
The unit code assigned to each transmitter A can be set, and the seaper-vise function can be activated as needed.
It is also possible to set it to ON or OFF. Here, the supervision function is a function in which the receiver B side calls all the wireless transmitters A in the system individually and sequentially at predetermined time intervals to detect abnormalities in the wireless system. In the embodiment shown in FIG. 4, if the lid case 102 is removed from the base body 101, the deep switches 100c and 100d can be adjusted to all the settings described above.
This is possible by operating the operation piece.

When an emergency occurs for an elderly person walking alone or a sick person who is away from a caregiver, when the push button switch 102a of wireless transmitter A is pressed, an abnormal signal with a house code, zone code, and unit code is sent. It is generated in the circuit section and radiated from the antenna section in the form of a radio wave signal. The radio signal in this case is modulated using the FSK method, for example. on the other hand,
The radio wave signal radiated at this time is received by receiver B, subjected to necessary signal processing, and then sent to a host computer (not shown) or the like for necessary processing.

〔Effect of the invention〕

According to the wireless oscillator of the present invention, each circuit element of the LC resonant circuit constituting the self-excited oscillation circuit section is
Since it is covered with an electromagnetic shielding case, it is hardly affected by external magnetic fields or stray capacitance, and even when objects with different magnetic permeability are brought close together.
By changing the inductance of the LC resonant circuit,
In addition, the capacitance of the LC resonant circuit does not change even when a human body approaches it.
A stable oscillation frequency can be obtained and the reliability of the wireless oscillator can be improved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment showing the structure of a circuit board of a wireless transmitter to which the present invention is applied, Fig. 2 is a diagram explaining the principle of electromagnetic shielding, Fig. 3 is an example of the circuit configuration of the transmitting circuit section, Fig. 4 is an exploded perspective view of an embodiment in which the present invention is applied to a portable wireless transmitter, Fig. 5 is an example of the hardware configuration of the portable wireless transmitter, and Fig. 6 is an example of the use of the portable wireless transmitter. , Fig. 7 is a diagram of a basic usage example of a portable wireless transmitter, Fig. 8 is a structural explanatory diagram of a conventional portable wireless transmitter, and Fig. 9 is a structural explanatory diagram of a circuit board housed inside the transmitter. , FIG. 10 is a diagram showing a state in which there is no electromagnetic shield in the LC resonant circuit. (Explanation of symbols), A...Wireless transmitter, 1
...Self-excited oscillation circuit section, 100a... Coil (circuit element forming the LC resonant circuit), 100b...
...Trimmer capacitor (circuit element constituting the LC resonant circuit), 104...Loop antenna, 105...
...Electromagnetic shield case.

Claims (1)

[Scope of Claims] 1. A battery-powered wireless oscillator configured to radiate a security signal in the form of a radio wave signal from a self-excited oscillating circuit section having an LC resonant circuit through an antenna, comprising: the above oscillating circuit section; has a structure in which only the circuit elements constituting the LC resonant circuit are mounted on the surface of a circuit board built into the wireless oscillator body, and the other parts are mounted on the back surface of the circuit board,
and a wireless transmitter having a structure in which only the circuit elements forming the LC resonant circuit are covered with an electromagnetic shielding case.