Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Reexamination Certificate
2000-09-07
2003-05-20
Le, Thanh Cong (Department: 2684)
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
C455S084000
Reexamination Certificate
active
06567648
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for combining a transmitter and a receiver using a circulator and a method for canceling a transmission signal thereof, and more particularly, to a system for combining a transmitter and a receiver using a circulator and a method for canceling a transmission signal thereof, in which a transmission signal incoming to a receiver together with a reception signal is cancelled by generating a 180° phase inverted transmission signal with the same magnitude and delay time as those of the incoming transmission signal, to thereby improve an electrical separation degree of the transmitter and the receiver and simultaneously to reduce volume and cost thereof.
2. Description of Prior Art
In the case that a transmission/reception antenna is commonly used in various mobile communication and wireless communication base stations, relay systems or military communication devices, a conventional system for combining a transmitter and a receiver which is used for smoothly combining the transmitter and the receiver with the antenna uses an expensive component called a duplexer to combine the transmitter and the receiver, in which an electrical separation degree is sufficiently secured during combining the transmitter and the receiver owing to the electrical characteristics of the duplexer.
However, since the duplexer uses a number of dielectric resonators, an electrical loss of the duplexer is considerable. Since the transmission and reception bands are fixed in the duplexer, a pass band frequency is variable. In particular, the duplexer cannot be adapted in a secret conversation communication system which is used in a military communication device whose transmission/reception pass band is inverted frequently.
An example of a conventional transmitter/receiver combination circuit will be described in detail with reference to FIG.
1
.
The conventional transmitter/receiver combination circuit uses a duplexer
1
which is connected with an antenna
3
, in which a transmission band pass filter
1
a
and a reception band pass filter
1
b
for filtering a transmission signal Tx and a reception signal Rx, respectively are integrated into a single body. Here, a sufficient circuitry frequency separation feature can be obtained according to the performance of the respective band pass filters
1
a
and
1
b
of the duplexer
1
.
However, since the pass bands of the transmission/reception band pass filters
1
a
and
1
b
of the duplexer
1
are fixed in the transmitter/receiver combination circuit as described above, the fixed transmission/reception band pass filters
1
a
and
1
b
of the duplexer
1
block the transmission/reception bands in the case that the pass band is successively varied and the pass band is inverted, resulting in causing the duplexer not to be used in the transmitter/receiver combination circuit. Also, since the number of stages of the resonators in each band pass filter
1
a
or
1
b
of the duplexer increases, signal loss and cost increase due to insertion of dielectric resonators into the pass band.
Another conventional transmission/reception combination circuit shown in
FIG. 2
combines a transmitter and a receiver with a circulator
2
, in which an antenna
3
is connected to a first end of the circulator
2
in order to increase a separation degree and transmission and reception band pass filters
1
a
and
1
b
are connected to second and third ends, respectively.
The circulator
2
transfers a supplied signal without causing an electrical signal loss in an arrow direction of the circulator
2
, but has an electrical separation feature in an opposite direction of the arrow. The circulator
2
has a separation degree of 20 dB in general.
As described above, the circulator
2
has a merit capable of securing the separation degree of about 20 dB. However, a large power amplification of a transmission signal Tx is accomplished in a power amplifier (not shown) in a transmitter, then a harmonic component due to the amplification is removed in the transmission band pass filter
1
a
, and then the resultant signal is emitted toward the antenna
3
, while passing through the circulator
2
, in which case the high power transmission signal Tx from which 20 dB or so is attenuated in the circulator
2
is input to the receiver circuit from the circulator
2
together with the reception signal Rx.
Here, if a transmission signal Tx whose signal power is relatively strong is input to a low noise amplifier (not shown) of the receiver together with a reception signal Rx, the low noise amplifier does not perform a smooth operation and is in saturation state to thereby lose performance of the amplifier.
Thus, the separation degree of the 20 dB or so is considerably insufficient in view of stability of the transmission/reception communication system.
Finally, the conventional
FIG. 2
technology should add transmission and reception band pass filters
1
a
and
1
b
in order to supplement the insufficient frequency separation degree as in the
FIG. 1
technology. In this case, since the number of stages of the resonators in each band pass filter should be increased in order to obtain a sufficient separation band, a loss in the pass band occurs.
Further, since the pass bands of the transmission and reception band pass filters are fixed, the fixed transmission/reception band pass filters
1
a
and
1
b
of the duplexer
1
block the transmission/reception bands in the case that the pass band is successively varied and the pass band is inverted, resulting in causing the duplexer not to be used in the transmitter/receiver combination circuit.
SUMMARY OF THE INVENTION
To solve the prior art problems, it is an object of the present invention to provide a system for combining a transmitter and a receiver using a circulator and a method for canceling a transmission signal thereof, in which a transmission signal incoming to a receiver together with a reception signal is cancelled by generating a 180° phase inverted transmission signal with the same magnitude and delay time as those of the incoming transmission signal, in a transmission/reception common antenna system, to thereby improve an electrical separation degree of the transmitter and the receiver, to reduce a coupling loss and simultaneously to reduce volume and cost thereof.
It is another object of the present invention to provide a system for combining a transmitter and a receiver using a circulator and a method for canceling a transmission signal thereof, in which a high power transmission signal input to the receiver is efficiently cancelled in a transmission/reception common antenna system, and thus a low power variable filter can be used, to accordingly secure a sufficient separation degree between the transmitter and the receiver although a transmission/reception frequency band such as a secret conversation communication is inverted or changed.
It is still another object of the present invention to provide a system for combining a transmitter and a receiver using a circulator and a method for canceling a transmission signal thereof, which is included in the receiver and can greatly attenuate a noise signal level of a reception band which is generated from the transmitter and input to the receiver.
To accomplish the above object of the present invention, there is provided a transmitter/receiver combination system for combining a transmitter and a receiver into a single antenna in a wireless communication system, the transmitter/receiver combination system comprising: a circulator for receiving a transmission signal from the transmitter, transmitting the received transmission signal to an antenna without causing a signal loss, and transmitting a reception signal received from the antenna to other ends without causing a signal loss; and at least one transmission signal canceller for dividing the transmission signal input in an attenuated form as much as a predetermined magnitude via the circulator together with the reception signal into at least two
Ahn Dal
Kwak Won Jun
Park Jong Chul
Park Jun Seok
Yoon Chul Sang
Cong Le Thanh
Rosenberg , Klein & Lee
Telwave, Inc.
Trinh Tan
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