JPH0481897B2 - - 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 wireless transmitter is attached to security sensors, fire sensors, etc., or used to alert people to emergencies 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.

By the way, such a wireless transmitter has a configuration in which a transmitting circuit that transmits a predetermined high frequency signal is provided inside the transmitter to radiate radio waves.
Loop antennas are widely used because it is necessary to house the antenna within the main body.

However, in the case of a wireless transmitter provided with such a loop antenna, for example, like the wireless transmitter of the present invention described later, the first
Considering the case where it is used in the condition shown in the figure, the radio waves radiated from the loop antenna are horizontally polarized, so the antenna on the receiver side must be selected accordingly, which is a hassle. It was hot. Furthermore, even if the antenna on the receiver side is selected according to the antenna on the transmitter side, if the radio wave signal radiated from the transmitter side is reflected by an obstacle, the polarization component of the radio wave may be reversed. This often makes reception difficult.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
A simple method is used to radiate a polarization component that is different from the polarization component of the radio signal radiated from the antenna of the wireless transmitter, thereby making the radio signal radiated from the wireless transmitter side to the receiver side omnidirectional. The purpose is to provide a wireless transmitter with specific characteristics.

[Disclosure of transmission]

The present invention proposed to achieve the above object was arrived at as a result of intensive studies by the inventor, and includes forming an extra conductive pattern in the oscillation circuit section of the main body, and using this conductive pattern to connect the loop antenna to the main body. It is characterized by being configured to radiate a polarized wave component different from the polarized wave component of the radiated radio wave signal.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example of the use of a wireless transmitter attached to an external sensor such as a fire sensor.

A is a wireless transmitter of the present invention, which houses a U-shaped loop antenna inside its rectangular main body, and detects when a security signal such as a fire signal is sent from an external sensor (not shown). By driving the internal transmitting circuit, the original horizontally polarized wave is output from the loop antenna 104, and at the same time, another polarized wave different from the horizontally polarized wave component is output from the conductive pattern provided in the transmitting circuit. It is becoming more and more common. As a result, the radio waves radiated from the wireless transmitter A of the present invention exhibit so-called omnidirectional characteristics.

FIG. 2 is a diagram showing a specific structure of the wireless transmitter.

To explain the basic structure with reference to this figure, this wireless transmitter A has a battery case 103 that houses a battery as a driving source, converts a security signal received from an external sensor into a radio signal, and sends it to an antenna. A circuit board 100 forming a transmitting circuit section for radiating radiation from the circuit board 1
00, and a base body 101 that is placed over the base body 101.
The circuit board 100 is housed in a so-called two-piece outer shell consisting of a main body case 101 and a lid cover 102.

On the surface of the circuit board 100, there is a deep switch 100 for setting a house code, which will be described later.
c. Deep switch 100d for setting zone code and unit code, lid case 102
Tamper switch 1 that is turned on to make an emergency call when the is removed from the main body case 101.
00k, a coil 100a, a capacitor 100b, and a loop antenna 104 erected in a U-shape are mounted, and the rear end of the circuit board 100 is equipped with wiring for an external sensor (not shown). A connection terminal 100j for connecting is mounted.

In this example, after the circuit board 100 is housed in the base body 101, the battery case 103 is placed on the corresponding part of the circuit board 100, and the engaging portion (not shown) provided on the battery case 103 is assembled. ) by engaging the corresponding engaging portions (not shown) of the base body 101 so that the base body 101 and the lid case 102 can be detachably attached. It can be removed by engaging another engaging portion.

Therefore, the battery case 103 and the lid case 10
2 has a structure convenient for maintenance because it can be easily removed by hand without using any means such as screws.

Although not shown, a coil 100a and a trimmer capacitor 10 constituting an LC resonant circuit are also included.
It is advantageous if 0b is covered with an electromagnetic shield case made of a conductive material, since the oscillation frequency of the LC resonant circuit can be stably maintained.

FIG. 3 shows the configuration of a transmitting circuit section incorporated in the wireless transmitter.

This oscillation circuit section 10 includes a self-excited oscillation circuit section 11,
It is composed of 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 1 via the coupling capacitor C6.
After being amplified there, it is supplied to the loop antenna 104 of the antenna section 13.
is guided and radiated as radio waves.

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 at the intermediate tap Ao by the transistor Q2 for matching.

In addition, coil L2 and capacitors C5 and C8
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 a circuit board 10 to which the present invention is applied.
0, that is, a perspective view of a conductive pattern formed in the transmitting circuit section.

FIG. 5 shows a circuit board 1 shown corresponding to FIG.
00 is shown.

In the figure, the black area 14
However, the present inventors have determined that this is an extra part of the conductive pattern that radiates radio waves with a polarization component different from that of the loop antenna 104, and is a ground level pattern.

FIG. 5 shows the surface of the circuit board of the embodiment shown in FIG. 2 as it is, and each component shown in FIG. 2 is explained with a corresponding reference numeral in FIG. 5. .

It goes without saying that the present invention is equally applicable to portable transmitters with built-in sensors, in addition to the wireless transmitters attached to the external sensors described above.

FIG. 6 shows a perspective view of the present invention applied to a wireless transmitter with a built-in sensor.

This type of wireless transmitter A' has a reed switch 10 inside it, as shown in the enlarged view P.
0i and is used in conjunction with a permanent magnet. For example, if a permanent magnet is attached to a part of a door, and a wireless transmitter A' is installed in a corresponding door frame, the reed switch 100i will operate when the open/closed state of the door is detected. The wireless transmitter A′ detects the signal and transmits a security signal to the receiver (not shown).

The receiving device receives this signal and sends it to a host computer or the like, thereby activating necessary control equipment to take action.

Finally, experimental data conducted to demonstrate the effects of the present invention will be shown.

These figures show the results of an experiment conducted to confirm the polarized wave components radiated from an extra conductive pattern formed in the oscillation circuit section of the main body.

In both cases, measurements were taken at a height of 1.5 m above the ground, with a standard dipole antenna 3 m away from the transmitter. The transmission frequency is
The electric field strength measured at 310MHz is 0dBμV/m = 1μV/m.

Figures 7 and 8 are examples of using the same transmitter with a loop antenna placed horizontally on the ground, but with 28.2cm and 14.1cm lead wires connected to the ground, respectively, extended vertically instead of the conductive pattern. The measurement results are shown. A vertical dipole antenna was used on the receiving side.

As can be seen by comparing these figures, it can be seen that the longer lead wire has a stronger electric field strength with respect to the vertical antenna on the receiving side.

9 and 10 show the measured values of a vertical dipole antenna and b horizontal dipole antenna for the same type of wireless transmitter of the present invention in different lots. These measurement results are almost identical, indicating that transmitters of the same type exhibit the same characteristics, and all exhibit omnidirectional characteristics.

In FIGS. 11 and 12, the a-horizontal and b-vertical components were measured by changing the circuit pattern of an oscillator having a loop antenna placed horizontally on the ground.

The one in FIG. 11 shows an example in which a conductive pattern running horizontally from the oscillation circuit section to the power supply side is formed, and FIG. 12 shows an example in which a conductive pattern running vertically from the oscillation circuit section is formed.

It can be seen from the comparison between the two figures that a larger vertically polarized wave component is obtained when a vertical conductive pattern is formed with respect to a horizontally arranged loop antenna.

As explained above, by leaving an extra conductive pattern in the transmitting circuit section of a wireless transmitter, the present invention has a polarized wave component that is different from the polarized wave component radiated from the loop antenna originally provided in the transmitter. This is to obtain radio wave output of different polarized wave components, and in actual implementation, the shape of the conductive pattern formed is determined according to the circuit in consideration of radiation efficiency and the like.

〔Effect of the invention〕

According to the present invention, a polarized wave component different from that of the radio waves radiated by the loop antenna can be easily radiated, and therefore the radiation characteristics of the radio waves can be made omnidirectional, ensuring a wide transmission area. I can do it.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the usage state of the wireless transmitter of the present invention, Fig. 2 is an explanatory diagram of the structure of an installed type wireless transmitter used by additionally connecting an external sensor, and Fig. 3 is an explanatory diagram of the structure of the wireless transmitter housed inside the transmitter. FIG. 4 is an example diagram of a ground pattern formed on a circuit board according to an embodiment of the present invention, and FIG. 5 is a diagram showing the configuration of each circuit element constituting the transmitting circuit section. Figure 6 is an explanatory diagram of the structure of a wireless transmitter with a built-in sensor, and Figures 7 and 8 are electric field patterns showing the directional characteristics of the earth pattern formed on the circuit board, and are horizontal loop antennas. Figures 9a and 10b and 10a and 10b are diagrams showing the measurement of the electric field strength of a wireless transmitter that is an embodiment of the present invention. Figure 11 a, b and Figure 12 a, b are
FIG. 6 is a measurement diagram of electric field strength when conductive patterns running horizontally and vertically are formed on the power source of the transmitting circuit section, respectively. Explanation of symbols: A, A'... Wireless transmitter of the present invention, 104... Loop antenna, 10... Transmission circuit section, 100... Circuit board, 14... Extra conductive pattern.

Claims (1)

[Claims] 1. In a wireless transmitter that transmits a security signal in the form of a radio wave signal from a loop antenna provided in a main body transmitting circuit section, an extra conductive pattern is formed in the main body transmitting circuit section, and the conductive pattern is A wireless oscillator characterized in that the pattern is configured to radiate a polarization component different from the polarization component of the radio signal radiated from the loop antenna.