Transmitter/receiver having an antenna failure detection system

Telecommunications – Transmitter – Measuring – testing – or monitoring of transmitter

Reexamination Certificate

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Details

C455S067700, C455S562100

Reexamination Certificate

active

06253067

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a transmitter/receiver having an antenna failure detection system and, more particularly, to a transmitter/receiver having an antenna failure detection system and preferably used in a base station of a mobile communication system.
(b) Description of the Related Art
An antenna failure detection system is generally used in a transmitter/receiver installed in a base station of a mobile communication system. An example of such an antenna failure detection system is described in JP-A-60-190037.
FIG. 1
shows the transmitter/receiver having an antenna failure detection system described in the publication mentioned above. The transmitter/receiver comprises a transmitting antenna
31
and a pair of receiving antennas
32
and
33
, a transmitter
37
for transmitting a down-signal toward a mobile station through the transmitting antenna
31
, a receiver
35
for receiving through the receiving antennas
33
and
32
an up-signal from a mobile station during a normal operation mode as well as a test signal during a test operation mode, a mobile test instrument
36
for transmitting/receiving a test signal for detection of an antenna failure, a coupler
34
for coupling transmitted signals from the mobile test instrument
36
with the transmitting/receiving antenna
31
and for coupling transmitted signals from the transmitter
37
with the transmitting antenna
31
, a control unit
38
for controlling the operation of the base station, and a test unit
39
for exchanging the base station between the normal operation mode and the test operation mode.
In the test operation, the test unit
39
changes the base station from a normal operation mode to a test operation mode. The mobile test instrument
36
transmits through the antenna
31
a test signal having a format and a frequency used by a mobile station in the normal operation mode. The receiver
35
receives the test signal through the receiving antennas
32
and
33
, and the control unit
38
compares the electric field of the received test signal against a reference which is equal to the electric field of the normal signals supplied from the base station without a failure in a normal operation mode, to thereby detect a failure of the base station. The test unit
39
displays an antenna failure based on the result of the comparison.
The transmitter/receiver having the mobile test instrument in addition to the transmitter and receiver, as described above, involves the problem of a large scale circuit for the base station. In addition, the number of service channels is reduced during the test operation mode because the test is conducted by using one of the service channels used in the normal communication.
JP-A-6-276166 describes another conventional antenna failure detection system in the base station, which comprises a pair of antennas
41
and
42
for receiving signals in a diversity receiving scheme, exchangers
43
and
44
disposed for antennas
41
and
42
, respectively, for exchanging between transmission and reception, a receiver
46
for receiving transmitted signals through antenna
41
for modulation, a receiver
47
for receiving a transmitted signal through antenna
42
for modulation, a peak detector
48
for detecting a peak electric field of the received signal supplied from the receiver
46
in a unit time length, a peak detector
49
for detecting a peak electric field of the received signal supplied from the receiver
47
in a unit time length, a comparator
50
for comparing both the peak electric fields to output a difference signal representing the difference between the peak electric fields, a failure indicator
51
for indicating occurrence of a failure based on the difference signal, and a transmitter
45
for transmitting data for transmission.
In operation, peak electric fields of the received signals from the receivers
46
and
47
operating in a diversity receiving scheme are detected by the peak detectors
48
and
49
, and compared against each other in the comparator
50
in a unit time length. If the difference between the peak electric fields exceeds a threshold value due to a failure of one of the antennas
41
and
42
, the comparator
50
identifies a failed antenna having a lower peak electric field. The failure indicator
51
outputs a failed signal based on the difference signal.
The conventional transmitter-receiver of
FIG. 2
has a problem in that a real time detection of antenna failure cannot be obtained if the base station has a dedicated receiving antenna and there is no mobile station in the service area of the base station during the test operation. This is because the base station uses a signal supplied from a mobile station which received the test signal in the service area of the base station, and the dedicated receiving antenna cannot be used for detection of reflected power by using the test signal.
In addition, the failure indicator
51
may judge a normal antenna as a failed antenna if the mobile station used for the test is fixed or stopped because the failure is judged based on the difference between both the electric field. In this case, one of the received electric fields may be larger at any time even if both the antennas are normal.
Further, if both the antennas failed at the same time, the failure detection cannot be obtained because the difference of the electric fields is judged based on the premise that the antenna detecting a larger electric field is normal and provides a reference value.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a transmitter/receiver having an antenna failure detection system which is capable of being formed as a small-scale circuit and detecting the antenna failure in a normal operation mode without reducing the number of service channels.
The present invention provides a transmitter/receiver comprising a transmitter, a transmitting antenna for transmitting a first signal supplied from the transmitter, a receiving antenna for receiving the first signal and a second signal from another station to deliver an antenna signal, a separator for receiving the antenna signal to separate the first signal and the second signal, a receiver for receiving the second signal from the separator, a detector for detecting the first signal to output a detected signal which is proportional to a coupling factor between the transmitting antenna and the receiving antenna, and a comparator for comparing the detected signal against a reference to output an antenna failed signal based on the result of the comparison.
In accordance with the transmitter/receiver of the present invention, an antenna failure can be detected from the first signal transmitted from the transmitter to another station, such as mobile station, in a normal operation mode, without reduction of the service channels of the transmitter/receiver.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.


REFERENCES:
patent: 4324002 (1982-04-01), Spilker, Jr.
patent: 5257407 (1993-10-01), Heinzelmann
patent: 5345601 (1994-09-01), Takagi et al.
patent: 5444862 (1995-08-01), Hibino
patent: 5471649 (1995-11-01), Rees et al.
patent: 5487176 (1996-01-01), Yoneyama
patent: 5574981 (1996-11-01), Ahonen
patent: 5684828 (1997-11-01), Bolan et al.
patent: 6018644 (2000-01-01), Minarik
patent: 60-190037 (1985-09-01), None
patent: 63-38337 (1988-02-01), None
patent: 1-115227 (1989-05-01), None
patent: 2-13021 (1990-01-01), None
patent: 6-276166 (1994-09-01), None

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