Telecommunications – Transmitter and receiver at same station – With transmitter-receiver switching or interaction prevention
Reexamination Certificate
1997-12-10
2001-05-22
Trost, William G. (Department: 2683)
Telecommunications
Transmitter and receiver at same station
With transmitter-receiver switching or interaction prevention
C455S015000, C455S126000, C455S067150, C455S082000, C370S280000, C370S278000, C370S282000
Reexamination Certificate
active
06236840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a transmission output detecting circuit used in a radio transmitter-receiver of a TDD (time-division duplexing) communication system, and particularly relates to such a transmission output detecting circuit in which loss of transmission power is eliminated when transmission output is detected.
2. Description of the related art
In mobile stations and base stations for mobile communication adopting a TDD communication system, the level of transmission power is changed adaptively so as to keep reception in the respective stations in the optimum level. For such a purpose, each of radio transmitter-receivers of these stations has a circuit for detecting its transmission output.
As shown in
FIG. 4
, a conventional radio transmitter-receiver of a TDD communication system having a transmission output detecting circuit has an antenna
1
, an antenna filter
2
for restricting a signal band, a TDD switch
3
for switching connection between transmission and reception, a reception system constituted by a reception first-stage amplifier (reception top amplifier)
7
for amplifying a reception signal, a reception first mixer
8
for mixing an oscillation signal of a local oscillator
12
with the reception signal so as to convert the reception signal into a first intermediate frequency signal, an amplifier
9
for amplifying the first intermediate frequency reception signal, a reception second mixer
10
for converting the output of the amplifier
9
into a second intermediate frequency signal, and a demodulator
11
for demodulating the second intermediate frequency reception signal to a base band signal, a transmission system constituted by a modulator
6
for modulating a transmission signal, a transmission mixer
5
for mixing the oscillation signal of the local oscillator
12
with the modulated transmission signal so as to convert the transmission signal into a radio frequency signal, and a transmission power amplifier
4
for amplifying transmission power, and a transmission output detecting circuit belonging to this transmission system and constituted by a directional coupler
13
for making a portion of the transmission signal branch out, and a detector
14
for diode-detecting the branching transmission signal.
The TDD switch
3
of this radio transmitter-receiver is a high-frequency switch which is constituted by an FET, an PIN diode or the like, and performs switching between transmission and reception at a high speed in response to a control signal applied thereto. In a receiving period, a signal received through the antenna
1
is inputted to the reception top amplifier
7
through the antenna filter
2
and the TDD switch
3
, and demodulated to a base band signal by the system constituted by the reception first mixer
8
, the amplifier
9
, the second mixer
10
, and the demodulator
11
.
On the other hand, in a transmitting period, a transmission signal modulated by the modulator
6
is converted into a radio frequency signal by the transmission mixer
5
, amplified by the transmission power amplifier
4
, and then transmitted from the antenna
1
through the TDD switch
3
and the antenna filter
2
.
At that time, a part of the output of the transmission power amplifier
4
is branched out by the directional coupler
13
, and performed diode-detection by the detector
14
, so that the transmission output is detected. The level of the transmission power is adjusted by this detection output.
Instead of providing the directional coupler, a part of the transmission output may be simply extracted by capacity coupling.
In a conventional transmission output detecting circuit, however, a part of transmission output is extracted through a directional coupler or a capacity coupling connected to the output of a transmission power amplifier, so that a loss is caused in the transmission power and it becomes necessary to amplify the transmission power correspondingly.
Specifically, the detector
14
requires a power of about 10 dBm at maximum in accordance with the relationship between the detection sensitivity and the dynamic range of the detection circuit. Accordingly, measures are taken such that allowing for such a loss, the output is increased correspondingly in the power amplifier
4
, or in the case of a comparatively middle or small power radio station the transmission power of which is 20 dBm or less, the transmission output extracted by the directional coupler
13
is amplified by an amplifier
15
before the transmission output is detected by the detector
14
as shown in
FIG. 5
, since the insertion loss is increased by the increase of the coupling factor of the directional coupler.
In either case, the conventional transmission output detecting circuit has a problem that its current consumption is increased at the time of transmission, and its circuit configuration is complicated.
SUMMARY OF THE INVENTION
In order to solve the foregoing problems, it is an object of the present invention to provide a transmission output detecting circuit in which transmission power can be detected by a simple circuit configuration without increasing a transmission current.
The transmission output detecting circuit of the present invention is provided with a detecting means for detecting a transmission output on the basis of leakage power of a TDD switch in a transmitting period.
It is therefore possible to detect transmission output without making transmission power branch out, while preventing the power consumption from increasing.
In order to achieve the above object, according to an aspect of the present invention, provided is a transmission output detecting circuit for use in a radio transmitter-receiver of a TDD communication system having a TDD switch for connecting a transmission system to an antenna system in a transmitting period and for connecting a reception system to the antenna system in a receiving period; comprising a detection means for detecting transmission output on the basis of leakage power of the TDD switch in the transmitting period. Accordingly, it is possible to detect the transmission output without making transmission power branch out.
Preferably, a switch means is provided for supplying the detection means with, only in the transmitting period, an output of a first-stage amplifier of the reception system into which the leakage power of the TDD switch is inputted. The leakage power to be detected is amplified by the first-stage amplifier of the reception system. Accordingly, it is not necessary to provide newly another amplifier for detecting the transmission output.
Preferably, the switch means is constituted by a single-pole double-throw switch synchronizing with the TDD switch so as to supply the output of the first-stage amplifier of the reception system to a next-stage circuit of the reception system in the receiving period, and supply the output of the first-stage amplifier of the reception system to the detection means in the transmitting period. The next-stage circuit of the reception system and the detection means are selected alternately by this single-pole double-throw switch.
Preferably, the switch means is constituted by two single-pole single-throw switches synchronizing with the TDD switch so as to supply the output of the first-stage amplifier of the reception system to a next-stage circuit of the reception system in the receiving period, and supply the output of the first-stage amplifier of the reception system to the detection means in the transmitting period. These two single-pole single-throw switches synchronize with each other so as to function as one single-pole double-throw switch.
Preferably, the switch means is constituted by a single-pole single-throw switch inserted to a branch path branching-out from a connection path between the first-stage amplifier and a next-stage circuit of the reception system and synchronized with the TDD switch so as to turn off in the receiving period while turn on in the transmitting period to thereby supply out the outpu
Aihara Yukichi
Sasaki Fujio
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
Perez-Gutierrez Rafael
Trost William G.
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