Telecommunications – Transmitter and receiver at separate stations – Having measuring – testing – or monitoring of system or part
Reexamination Certificate
1997-12-29
2001-01-23
Le, Thanh Cong (Department: 2749)
Telecommunications
Transmitter and receiver at separate stations
Having measuring, testing, or monitoring of system or part
C455S121000, C455S129000, C455S115200, C455S226100
Reexamination Certificate
active
06178310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system, and, particularly, to a circuit for measuring voltage standing wave ratios (VSWR) of transmitting and receiving antennas in a base station.
2. Discussion of Related Art
VSWR of a transmitting/receiving antenna of a base station indicates that the ratio of the maximum value and minimum value of a standing wave is 1 in matching state, the standing wave being generated by interference of an incident wave and reflected wave when connecting a load impedance in a transmission line. If the standing wave does not equal to a characteristic impedance in a limited transmission line, some of the incident waves are reflected thereby to generate the reflected waves. The VSWR influences the performance of the transmitting/receiving antenna of the base station. Therefore, it is necessary to accurately measure the VSWR and implement the matching state.
FIGS. 1 and 2
are block diagrams respectively showing transmitting and receiving antenna VSWR measuring circuits of the base station. The forward path indicates a path through which signals are transmitted from the base station to the antenna. The reverse path indicates a path through which signals are transmitted from the antenna to the base station.
As shown in
FIG. 1
, the transmitting antenna VSWR measuring circuit includes: variable attenuators
12
and
15
coupled to a directional coupler
2
located next to the transmitting antenna
3
for attenuating radio frequency signals; diode detectors
13
and
16
respectively coupled to the variable attenuators
12
and
15
for converting the attenuated radio frequency signals into direct voltage; and voltage comparators
14
and
17
respectively connecting the diode detectors
13
and
16
to a measuring controller (not shown in the drawings) for comparing the converted direct voltage from the diode detectors
13
and
16
with threshold voltage and outputting the results of comparison to the measuring controller.
The following description relates to transmitting power and reflection power measuring procedures of the transmitting antenna VSWR measuring circuit of the base station in the conventional mobile communication system.
For the transmitting antenna transmitting power measuring procedure, the radio frequency signal which is received by the transmitting antenna
3
and passes the forward path or the directional coupler
2
is converted into the direct voltage by the diode detector
13
before being input to the voltage comparator
14
. The measuring controller controls analog working voltage of the variable attenuator
12
and detects the analog working voltage of the variable attenuator
12
when the output of the voltage comparator
14
is “HIGH” thereby to measure the transmitting power.
For the transmitting antenna reflection power measuring procedure, the radio frequency signal which is received by the transmitting antenna
3
and passes the reverse path of the directional coupler
2
is converted into the direct voltage by the diode detector
16
before being input to the voltage comparator
17
. The measuring controller controls analog working voltage of the variable attenuator
15
and detects the analog working voltage of the variable attenuator
15
when the output of the voltage comparator
17
is “HIGH” thereby to measure the reflection power. At this time, the VSWR of the transmitting antenna can be obtained using the measured transmitting power and reflection power.
As shown in
FIG. 2
, the receiving antenna VSWR measuring circuit
31
of the base station in the conventional mobile communication system includes: an amplifier
32
coupled to a directional coupler
22
located next to the receiving antenna
23
for amplifying a radio frequency signal, a local oscillator
33
coupled to the amplifier
32
for generating a signal of a predetermined frequency band and applying it to the amplifier
32
; a frequency mixer
34
for down-converting the radio frequency signal from the directional coupler
22
into an intermediate frequency (IF) signal; a local oscillator
36
coupled to the frequency mixer
34
for generating a signal of a predetermined frequency band and applying it to the frequency mixer
34
; and a receiving signal strength indicator
35
connecting the frequency mixer
34
to the measuring controller (not shown in the drawings) for converting the IF signal from the frequency mixer
34
into the direct voltage and outputting the result of conversion to the measuring controller.
The following description relates to receiving power and reflection power measuring procedures of the receiving antenna VSWR measuring circuit of the base station in the conventional mobile communication system.
For the receiving antenna receiving power measuring procedure, the radio frequency signal which is received by the receiving antenna
23
and passes the forward path of the directional coupler
22
is down-converted into the IF by the frequency mixer
14
before being input to the receiving signal strength indicator
35
. The receiving signal strength indicator
35
outputs the strength of the receiving signal converted into analog voltage to the measuring controller which measures the receiving power from the analog voltage.
For the receiving antenna reflection power measuring procedure, the signal which is sent from the local oscillator
33
via the directional coupler
22
is reflected by the receiving antenna
23
and input to the frequency mixer
34
after passing through the reverse path of the directional coupler
22
. The reflected signal is down-converted into the IF signal by the frequency mixer
34
and then converted into the analog voltage by the receiving signal strength indicator
35
, before being sent to the measuring controller. The measuring controller measures the reflection power from the analog voltage applied by the receiving signal strength indicator
35
. Therefore, the VSWR of the receiving antenna can be obtained using the measured receiving power and reflection power.
According to the transmitting and receiving antenna VSWR measuring circuits of the base station in the conventional mobile communication system, however, the transmitting power and receiving power of each frequency band cannot be measured in a multi-frequency allocation system, and the transmitting and receiving antenna VSWRs cannot be accurately measured when a noise signal exists in an adjacent frequency band.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a transmitting and receiving antenna VSWRs measuring circuit of a base station of a mobile communication system that substantially obviates one or more of the limitations and disadvantages of the related art.
An object of the present invention is to provide a transmitting and receiving antenna VSWRs measuring circuit of a base station in a mobile communication system, the circuit being implemented on a single board to measure transmitting and receiving antenna VSWRs of each frequency without influence of a noise signal in an adjacent frequency band.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure as illustrated in the written description and claims hereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, a transmitting and receiving antenna VSWRs measuring circuit of a base station in a mobile communication system comprises: transmitting and receiving antennas for transmitting and receiving a radio frequency signal of a predetermined frequency band in a mobile communication system; transmitting antenna VSWR measuring means for variable attenuating and detecting a transmitting signal received from the transmitting antenna a
Armstrong Darnell R.
Cong Le Thanh
Fleshner & Kim LLP
LG Information & Communications Ltd.
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