JPH0685511U - Transmitting / receiving antenna device for weak radio waves - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to minimize fluctuations in the received electric field level in the traveling direction of a mobile unit when performing communication by a weak radio wave between a fixed station and a mobile station. [Structure] The transmission / reception antenna device 30 for weak radio waves includes a radio wave shielding enclosure 36 surrounding the antenna body 26. The enclosure 36 has a function of giving directivity so that only the radio waves radiated from the portion of the wireless communication line 16 facing the antenna body 26 reach the antenna body 26. For this reason, radio waves of opposite phases on different propagation paths are not received, and fluctuations in the received electric field level of the antenna body 26 are reduced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention utilizes a weak radio wave that is not restricted by the Radio Law between a fixed-line transceiver and a wireless communication line consisting of a spiral open coaxial cable, and uses information such as images, data, and audio signals. The present invention relates to an improvement of a weak radio wave transmission / reception antenna device which is connected to a transmitter / receiver on the side of a mobile station and is connected to a radio communication line to transmit and receive such information for two-way communication.

[0002]

[Prior art]

 As shown in FIG. 4, this type of antenna device is provided with an antenna main body 26 composed of a short spiral open coaxial cable 28 used facing the wireless communication line 16 composed of the spiral open coaxial cable 18. ing. The spiral open coaxial cable 18 of the wireless communication line 16 is connected to the transceiver 24 on the fixed station side by the coaxial cable 22, and the antenna main body 26 is mounted on the mobile body and is mounted on the mobile body by the coaxial cable 32. It is connected to 34.

In the spiral open coaxial cable 18, the width and pitch of the spiral slit 18a are set so that the transmission loss and the coupling loss have an optimum relationship with respect to a predetermined length. Moreover, the distance between the wireless communication line 16 and the antenna body 26 is limited to about one wavelength or less so that communication can be performed at a weak radio wave level.

[0004]

[Problems to be solved by the device]

 However, this weak transmitter / receiver antenna device of the prior art was used on the premise that the electric field strength was 15 μV / m or less at a distance of 100 m from the radio equipment, which is a condition of the weak radio wave level in the old Radio Law. However, if the electric field strength is 500 μV / m or less and the frequency is 322 MHz or less at a distance of 3 m from the radio equipment, which is a condition of the weak radio wave level in the New Radio Law, the transmission output level is significantly limited. Therefore, stable communication could not be performed. In particular, in the spiral open coaxial cable 18 which is a wireless communication line, the electric wave w is radiated in all directions through the spiral slit 18a arranged on the surface thereof, but the received electric field of the antenna device on the mobile station side is As shown in Fig. 4, the levels are not constant in the traveling direction of the moving body due to the interference of the opposite phase radio waves generated by the difference in the radio wave paths. Therefore, the electric field strength distribution is as shown in Fig. 5. It fluctuates greatly.

An object of the present invention is to avoid the above-mentioned drawbacks, to minimize the fluctuation of the received electric field level in the traveling direction of a moving body, and to perform stable communication by a weak electric wave, which is a transmitting / receiving antenna for weak electric waves. To provide a device.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a weak radio wave equipped with an antenna body composed of a short spiral open coaxial cable used facing a wireless communication line composed of a long spiral open coaxial cable. It is an object of the present invention to provide a transmission / reception antenna device for weak radio waves, characterized in that the transmission / reception antenna device for radio waves is provided with a radio wave shielding enclosure that surrounds the antenna body and provides directivity in the radio wave transmission and reception direction.

[0007]

[Action]

 In this way, when the antenna body is surrounded by the radio wave shielding enclosure, only the radio waves radiated from the line section facing the antenna body will reach the antenna body due to this enclosure, and the radio waves of opposite phases on different radio wave paths will be received. Since the noise disappears, the fluctuation of the received electric field level of the antenna body becomes small. Therefore, the intensity distribution of the received electric field does not fluctuate in the traveling direction of the moving body, and stable communication can be performed.

[0008]

【Example】

 An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a mobile radio communication between a fixed station 12 and a mobile station 14 using a transmitting / receiving antenna device 10 for weak waves according to the present invention. An example of application of a communication system for performing is shown. The wireless communication line 16 on the fixed station side is composed of, for example, a long spiral open coaxial cable 18 having a length of about 10 to 300 m. One end of the spiral open coaxial cable 18 is terminated by a non-reflective terminating resistor 20 and the other end. Is connected to a transceiver 24 on the fixed station side via a coaxial cable 22. The width and pitch of the spiral slit 18a of the spiral open type coaxial cable 18 are set so as to optimize the transmission loss and the coupling loss with respect to the length thereof.

The transmitting / receiving antenna device 10 for weak radio waves according to the present invention includes an antenna body 26 used to face the wireless communication line 16, and the antenna body 26 is composed of a short spiral open coaxial cable 28. One end of the spiral open type coaxial cable 28 is terminated by a reflectionless termination resistor 30, and the other end is connected to a transmitter / receiver 34 on the mobile station side via a coaxial cable 32. In order to transmit and receive at a weak radio wave level between the fixed station 12 and the mobile station 14, the spiral open type coaxial cable 28 on the side of the mobile station 14 uses the radio wave used for the spiral open type coaxial cable 18 on the side of the fixed station 12. They are separated by less than half wavelength.

The antenna device 10 of the present invention includes a radio wave shield enclosure 36 that surrounds the antenna body 26 and provides directivity in the radio wave transmission / reception direction. The enclosure 36 is provided so that the radiated radio wave w is received only from the portion where the antenna body 26 faces the wireless communication line 16 in order to enhance the directivity of the received radio wave.

As already mentioned, when the wireless communication line 16 is composed of a long spiral open coaxial cable 18 of about 10 to 300 m, the received electric field level at a position apart from this line by a certain distance is , But not in the longitudinal direction, but fluctuates greatly. The width and pattern of this variation depend on the length of the cable, the width and pitch of the spiral slit 18a, other characteristics of the cable and the distance from the cable, and it is difficult to theoretically calculate this. . However, this fluctuation occurs because there are multiple propagation paths from the spiral slit 18a on the cable surface to the reception point of the radio waves radiated, and the phases of the radio waves reaching the reception point are different and interfere with each other. It is known to occur in.

When the antenna body 26 is surrounded by the radio wave shielding enclosure 36, only the radio waves emitted from the line portion facing the antenna body 26 by the enclosure 36 reach the antenna body 26. For this reason, radio waves having opposite phases of different propagation paths are not received, and fluctuations in the received electric field level of the antenna body 26 are reduced. Therefore, the intensity distribution of the received electric field does not fluctuate in the traveling direction of the moving body, and stable communication can be performed. Therefore, without installing a special RF amplifier in the antenna device 10 and the transmitter / receiver system, bidirectional transmission of information such as images, data and voice at a stable weak radio wave level between the fixed station 12 and the mobile station 14. Can be communicated to.

FIG. 2 shows that two antenna devices 10A and 10B according to the present invention are arranged side by side in the longitudinal direction, and these two antenna devices 10A and 10B are used to connect between a fixed station 12 and a mobile station 14. This shows a communication system that performs bidirectional communication at a weak radio wave level, and the two antenna devices 10A and 10B have exactly the same structure. It is connected to a bidirectional distributor 38 via different coaxial cables 32A and 32B, and this distributor 38 is connected to a transceiver 34 on the mobile station 14 side.

The lengths of the coaxial cables 32A and 32B are different because the phases of the received radio waves of the antenna devices 10A and 10B differ due to the distance D between the centers of the antenna devices 10A and 10B. This is for adjustment. The distributor has a function of synthesizing the reception radio waves of the antenna devices 10A and 10B and distributing the transmission radio waves of the mobile 14 stations. As described above, by using the two antenna devices 10A and 10B, it is possible to effectively double the received electric field level on the mobile station 14 side as compared with the case where the antenna device 10 is used. Therefore, the distance between the antenna devices 10A and 10B and the wireless communication line 16 can be increased.

Similar to FIG. 2, FIG. 3 shows a communication system for performing two-way communication at a weak radio wave level between a fixed station 12 and a mobile station 14 by using two antenna devices 10 A and 10 B according to the present invention. As shown, the two antenna devices 10A and 10B are not arranged side by side in the longitudinal direction, but are arranged concentrically around the axis of the wireless communication line 16 on the fixed station 12 side. Is different.

When the two antenna devices 10A and 10B are arranged concentrically with the axis of the wireless communication line 16 as the center, the reception radio waves of the two antenna devices 10A and 10B are not out of phase with each other. The received electric field level on the mobile station 14 side can be effectively doubled as in the case of the embodiment of FIG. 2 except that it is not necessary to adjust the length of the coaxial cable. The arrangement of this embodiment is effective when the two antenna devices cannot be installed in the longitudinal direction of the line due to the size limitation of the moving body.

In the above description of the embodiment, the received electric field level on the mobile station side was described, but the same applies when the radio wave radiated from the mobile station side to the fixed station side is received on the fixed station side. Level improves. In addition, if the frequency bands are appropriately separated, two-way communication can be performed using a plurality of radio waves.

[0018]

[Effect of device]

 According to the present invention, as described above, since the radio wave is transmitted and received between the antenna body and the line portion facing the antenna body by enclosing the antenna body with the radio wave shielding enclosure, as described above, Enables stable two-way communication with weak radio waves, so that the radio waves radiated between the fixed station and the mobile station are converted to surface waves. An economical communication system can be provided without improving the characteristics of the device.

[Brief description of drawings]

FIG. 1 is a system diagram of a mobile wireless communication system according to a first application example using a transmitting / receiving antenna device for weak radio waves according to the present invention.

FIG. 2 is a system diagram of a mobile radio communication system according to a second application example using the transmitting / receiving antenna device for weak radio waves according to the present invention.

FIG. 3 is a cross-sectional view of a main part of a mobile wireless communication system according to a third application example using the weak radio wave transmission / reception antenna device according to the present invention.

FIG. 4 is a system diagram of a mobile wireless communication system of an application example using a conventional antenna device.

5 is a distribution diagram of a received electric field level in the communication system of FIG.

[Explanation of symbols]

 10 Transmission / reception antenna device for weak radio wave 10A Antenna device 10B Antenna device 12 Fixed station 14 Mobile station 16 Wireless communication line 18 Spiral open coaxial cable 18a Spiral slit 20 Non-reflective terminal resistance 22 Coaxial cable 24 Transceiver 26 Antenna body 28 Spiral type Open coaxial cable 30 Non-reflective terminating resistor 32 Coaxial cable 34 Transceiver 36 Radio wave shield enclosure 38 Distributor

Claims (1)

[Scope of utility model registration request] 1. A transmission / reception antenna device for weak radio waves, comprising: an antenna main body composed of a short spiral open coaxial cable used facing a wireless communication line composed of a long spiral open coaxial cable. A weak transmission / reception antenna device for a weak electric wave, which is provided with a radio wave shielding enclosure for providing directivity in a radio wave transmission / reception direction.