JPS61220501A - Antenna for portable inductive radio equipment - Google Patents

Abstract

PURPOSE:To attain close coupling with an inductive line by mounting an antenna coil of an inductive radio equipment onto a safety helmet or a shoulder belt of a worker. CONSTITUTION:The antenna coil 8 is separated from an inductive radio equipment 9 and fixed to a side face of a helmet 7 and connected to the inductive radio equipment 9 by a coaxial cable 10. The antenna coil 8 is arranged at the height of the helmet 7 to bring the coil near the inductive line arranged to the ceiling of a building or its vicinity normally and close coupling is attained. Further when the antenna coil 8 is arranged to the shoulder belt, since the human body gives a height, the close coupling of same degree is attained. In arranging the two antenna coils 8 to the helmet 7 so that the maximum sensitivity is made orthogonal, stable reception is attained regardless of the attitude of the worker.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an antenna for a portable induction radio, and particularly to one in which the antenna coil is mounted independently from the radio and its housing.

(Prior Art) Conventionally, as an antenna for a portable radio device, a conductor rod with an electrical length of λ/4 of the operating frequency (A is the wavelength) or an integral multiple thereof is attached to the main body of the radio device, or is carried over the shoulder. It is often used by standing upright at the shoulder position of the belt.

This method is used to transmit radio waves into a wider space or to effectively derive the radio wave energy in the space, and is used when the communication range is relatively wide.

On the other hand, guided radio systems are widely used when the communication range is limited to a specific location or when communication is limited to inside a building.

As shown in Fig. 3, this inductive radio system uses a pair of conductor lines 1 and 2 to transmit a signal in a relatively low frequency band, such as LF (low frequency 30 kHz to 300 kHz) or MF (medium frequency 300 kHz to 300 kHz). MHz) frequency band No. 3 as a carrier, which is modulated with various information signals and transmitted between the portable radio device 3 and base device 4 that move along the conductor line, or between these portable radio devices. This is a place where you can communicate with others. The antenna used in such a portable radio device is generally a coil having the required inductance by winding a conducting wire 6 around a core 5 of ferromagnetic material such as ferrite, as shown in Fig. 4(a). When these devices are attached to a portable radio device, they are either mounted inside the induction radio device 3 as shown in FIG. 3(b), or attached to the outside of the upper end of the device as shown in FIG. 3(c).

(++i problem that the invention seeks to solve) However,
In recent years, these radio devices have become smaller and more compact, and in order to improve the work efficiency of the person carrying them, it has become possible to use them by storing them in a chest jacket or attaching them to a waist belt.

However, the above-mentioned guide lines 1 and 2 are usually installed at a higher place than the human body, such as on the ceiling of a building or near the ceiling, and the induced magnetic field from the guide lines is proportional to the square of the distance from this. Attenuate. Therefore, with the antenna coil and its mounting method used in the conventional induction radio as described above, it is not only difficult to connect it to the guidance line installed high overhead, but also makes it difficult to attach the induction radio to the waist belt. When used while attached to the human body, not only does the antenna efficiency decrease due to the shadow of the human body, but also the directivity of the coil is unidirectional, so it may be completely affected by changes in the worker's posture. It also had drawbacks such as communication failure.

(Means for Solving the Problems) The present invention has been made in order to eliminate the drawbacks of the conventional induction radio as described above, and the antenna coil of the induction radio can be used for example in safety helmets, etc. The antenna coil can be attached to the shoulder of the belt or fixed to the shoulder of the belt to obtain the combined directivity of the antenna.

(Function) Since the present invention is configured as described above, the antenna coil is always located at the highest part of the human body, and the connection between the antenna coil and the guide line installed at a high place can be maintained tightly. In addition, it is possible to combine the overall directivity characteristics of multiple antenna coils with different directivity to make them omnidirectional, so the coupling between the antenna and the guide line can be achieved regardless of the worker's posture. It can always be kept stable.

(Example) The present invention will be described in detail below based on an illustrated example.

FIG. 1 is a side view showing an embodiment of the present invention.

In the figure, reference numeral 7 denotes a helmet, and an antenna coil 8 is fixed to the side surface of the helmet, and an induction radio device 9 is connected to the helmet by a coaxial cable 10.

With this configuration, the antenna coil can always be located at the highest part of the human body even when the induction radio main body 9 is placed in a chest pocket or attached to a waist belt.

Furthermore, as shown in FIG. 2, the present invention provides two antenna coils on both sides of the helmet 7, fixes one vertically and the other horizontally, and inputs and outputs the input and output signals from both of them through a matching circuit 11. The configuration may be such that the signals are combined and connected to the radio device via the coaxial cable 10.

By doing this, the directivity of each antenna coil is usually maximized in the X-axis direction and has the lowest sensitivity in the y-axis and X-axis directions, as shown in FIG. 4(a). However, according to the above embodiment, the combined directivity can be made to have the same sensitivity in two orthogonal directions.

Furthermore, although not shown, a third antenna coil may be fixed to the rear or front of the helmet so as to have directivity in a direction different from that of the other antenna coils, so as to obtain a composite directivity of these three antenna coils. It is possible to realize an antenna that has directivity that is uniform over three-dimensional spaces such as up and down, left and right, and front and rear.

Furthermore, the present invention is not limited to the above-mentioned example, and the antenna coil may be made independent from the main body of the radio, fixed at a predetermined position as necessary, and connected to the front radio by a feeder line. Any method may be used.

(Effect of the invention) Since the present invention is configured as explained above,
This is effective in creating a highly efficient and stable antenna suitable for portable induction radio equipment.

[Brief explanation of drawings]

Fig. 1 is a side view showing one embodiment of the present invention, Fig. 2 is a side view showing another embodiment, Fig. 3 is a diagram showing the principle of inductive radio, and Fig. 4(a) is a diagram of the antenna coil. A diagram showing the direction of the magnetic field,
Figures (b) and (c) are diagrams illustrating an example of mounting a secondary x14 antenna coil. 1 and 2... Conductor line, 3 and 9... Portable induction radio, 5'... Core, 6... Coil, 7... Helmet, 8... Antenna coil, 10... ·coaxial cable. Figure 3 (l) Figure 4 (Q) Figure □y (C)

Claims (2)

[Claims] (1) In a portable induction radio, at least the antenna coil is made independent from the radio and attached to a safety helmet or a shoulder belt, so that the communication medium and the antenna An antenna for portable induction radio equipment characterized by maintaining a tight coupling with the coil. (2) A plurality of the antenna coils are provided, and the antenna coils are mounted so that their directivity directions are different from each other to obtain a composite directivity characteristic.
) portable induction radio antenna.