Telecommunications – Transmitter and receiver at separate stations – Distortion – noise – or other interference prevention,...
Reexamination Certificate
1998-06-29
2001-05-01
Chang, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Distortion, noise, or other interference prevention,...
C333S017300
Reexamination Certificate
active
06226496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio transmitting/receiving device, particularly to an antenna malfunction detecting system for detecting an abnormality in an antenna system which is connected to a radio transmitting/receiving device.
2. Description of the Related Art
A conventional antenna malfunction detecting system disclosed in, for example, the patent application laid-open No. Hei 6-296168, as shown in
FIG. 5
, relates to a radio transmitting/receiving device of an automobile telephone system. To detect an abnormality in an antenna, a circulator
17
is inserted between an output of a final-stage amplifier
16
and an antenna
3
. When there is an abnormality in the antenna, a reflected wave of an output signal of the final-stage amplifier
16
from the antenna is detected by a rectification circuit
21
. When the reflected wave is large as a result of comparison with a preset reference voltage (REF), the final-stage amplifier
16
is controlled by a control circuit
23
. Further, an alarm is given to a display circuit for indicating an occurrence of abnormality to a maintenance personnel.
Also, another conventional antenna malfunction detecting system is disclosed in the patent application laid-open No. Hei 5-136747, as shown in FIG.
6
. In this technology, a directional coupler
2
is inserted between a radio transmitter
1
and an antenna
3
. A traveling wave power from the radio transmitter
1
and a reflected wave power from the antenna
3
are detected and compared in a comparison circuit. Thereby, an increase of a reflected wave is detected, and an alarm is issued.
In the aforementioned conventional antenna malfunction detecting system for detecting a reflected wave, when there is a trouble in the antenna, the reflected wave occurring at a trouble point is detected. However, since a standing wave is generated between a reflection point and a wave source, the amplitude of the reflected wave varies depending on a position of a wave detector, and it might becomes maximum or minimum in accordance with the position of the wave detector for detecting the reflected wave. Therefore, the reflected wave cannot be detected precisely in some case. In this case, it is wrongly judged whether the antenna is normal or abnormal.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an antenna malfunction detecting system, which comprises a plurality of detectors for detecting voltage values of a standing wave, caused by a reflected wave occurring at a trouble point of an antenna system, at different detecting points, for obtaining precise detection result of malfunctioning.
An antenna malfunction detecting system according to the present invention comprises the following elements;
a circulator which is provided between a transmission final-stage amplifier and an antenna system for outputting a transmission wave having been input from the transmission final-stage amplifier to a first output to the antenna system, and outputting a reflecting wave generated at a trouble point of the antenna system and coming back from the first output to a second output;
a distributor being connected to the second output of the circulator for distributing the reflected wave to a plurality of outputs;
a plurality of detectors each connected to each output of the distributor respectively for detecting voltage values of a standing wave, caused by said reflected wave, at different detecting points each other; and
control circuit which receives each detection result of the plurality of detectors for judging abnormality of the antenna system by processing the received detection results.
Line length difference of each line between the distributor to each detector is ½
n
(where, n is positive integer) of a wavelength of radio signal being detected.
REFERENCES:
patent: 4584650 (1986-04-01), Kozuch
patent: 4799063 (1989-01-01), Hill
patent: 5079507 (1992-01-01), Ishida et al.
patent: 5408690 (1995-04-01), Ishikawa et al.
patent: 5471146 (1995-11-01), Krayeski et al.
patent: 5939953 (1999-08-01), Yogo et al.
patent: 5-136747 (1993-06-01), None
patent: 6-296168 (1994-10-01), None
Chang Vivian
McGuireWoods LLP
Mehrpour N.
NEC Corporation
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