Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
2000-08-22
2003-04-22
Vuong, Quochien (Department: 2681)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S115200, C455S117000, C455S126000, C330S129000
Reexamination Certificate
active
06553213
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an output power detecting circuit of transmitter and particularly to an output power detecting circuit of transmitter which restrains, when an output signal level of a transmitter increases, a detected voltage output from an output power detecting circuit from increasing exponentially and from exceeding the dynamic range of a control unit.
2. Description of the Related Art
In general, a mobile communication system such as a hand-held telephone system or the like realizes communications between a base station installed at the fixed area and mobile stations respectively provided at moving vehicles or the like. In this case, since distance between the base station and mobile station in which the communication is established changes from time to time, the level of transmitting signal which is transmitted from the mobile station and is received to the base station, namely the field intensity of the receiving radio-wave at the base station changes to a large extent depending on the position of the mobile station at the time of communication and the normal communication is disabled in some cases between the base station and mobile station depending on the position of the mobile station. In view of avoiding such phenomenon, in the mobile communication system such as hand-held telephone system, the base station monitors the signal level transmitted from the mobile station at the time of communication between the base station and mobile station. When such signal level is lower or higher than the normal level range, the base station transmits a transmitting level instruction (TX-AGC) signal (hereinafter, referred to as TX-AGC signal) in the constant period, for example, in every period of 1.25 ms to the mobile station in order to indicate increase or decrease of the transmitting signal level. Upon reception of the TX-AGC signal, the mobile station increases or decreases the transmitting signal level depending on the content of instruction of TX-AGC signal in order to realize normal communication between the base station and mobile station.
Here,
FIG. 2
is a block diagram illustrating an example of structure of the mobile station used in the mobile communication system of the related art.
As illustrated in
FIG. 2
, a mobile station is composed of a signal transmitting system
20
T, a signal receiving system
20
R and a transceiver system
20
C. In this case, the signal transmitting system
20
T comprises an isolator
22
, a power amplifier (PA)
23
, a drive amplifier (DA)
24
, a signal mixer (MIX)
25
, a TX-AGC amplifier (TX-AGC AMP)
26
, a modulator (MOD)
27
, a digital-analog converter (D/A)
28
and an output power detecting circuit
29
and these structural elements
22
to
29
are connected as illustrated in FIG.
2
. The signal receiving system
20
R comprises a low noise amplifier (LNA)
30
, a signal mixer (MIX)
31
, a band-pass filter (BF)
32
, an RX-AGC amplifier (RX-AGC AMP)
33
, a demodulator (DEM)
34
, a low-pass filter (LF)
35
and a digital-analog converter (D/A)
36
and these structural elements
30
to
36
are connected as illustrated in FIG.
2
. Moreover, the transceiver system
20
C comprises a duplexer
21
, a control unit (CPU)
37
and a transmitting/ receiving antenna
38
and these structural elements
21
,
37
,
38
are connected as illustrated in FIG.
2
.
The mobile station used in the mobile communication system of the related art comprising the structural elements explained above almost operates as explained below.
In the case where communication is performed between a mobile station and the base station, the transmitting signal from the mobile station is formed as the transmitting base-band signal in the control unit
37
and this base-band signal is supplied to a modulator
27
and is then converted to the modulation signal in the frequency higher than the base-band signal. The modulation signal obtained is amplified in the TX-AGC amplifier
25
to be the signal level depending on the TX-AGC signal supplied from the control unit
37
through the digital/analog converter
28
and is then mixed in the frequency with a local oscillation signal in the signal mixer
25
and is converted to a high frequency signal. This high frequency signal is amplified up to the predetermined level in the drive amplifier
24
and is then amplified up to the level suitable for the transmitting signal in the power amplifier
23
. The amplified high frequency signal is supplied as the transmitting signal to the duplexer
21
via the isolator
22
and is then supplied to the transmitting/receiving antenna
38
from the duplexer and finally transmitted as the radio-wave signal from the antenna
38
.
Meanwhile, the receiving signal in the mobile station is supplied, when the radio-wave signal transmitted from the base station is received by the transmitting/receiving antenna
38
, to the duplexer
21
and it is then supplied to the low noise amplifier
30
from the duplexer
21
and then amplified to have the predetermined signal level. The amplified receiving signal is mixed in the signal mixer
31
with the local oscillating signal to become the frequency-mixed signal. Thereafter, the frequency-mixed signal is then supplied to the band-pass filter
32
and only the intermediate frequency signal is extracted from the frequency-mixed signal. The extracted intermediate frequency signal is amplified up to the predetermined level in the RX-AGC amplifier
38
and the amplified intermediate frequency signal is supplied to the demodulator
34
to be demodulated into the base-band signal to become the receiving base-band signal. The receiving base-band signal obtained is supplied to the control unit
37
through elimination of unwanted frequency element in the low-pass filter
35
and is then supplied to an application circuit not illustrated from the control unit
37
.
At the time of starting the communication between the mobile station and base station, the TX-AGC signal is supplied to the mobile station from the base station in the constant period, for instance, in every period of 1.25 ms to designate the signal level to be transmitted from the mobile station. The mobile station supplies, upon reception of the TX-AGC signal transmitted thereto with the transmitting/receiving antenna
38
, this TX-AGC signal to the control unit
37
through the signal receiving system
20
R like the receiving signal. The control unit
37
generates a digital TX-AGC signal depending on the supplied TX-AGC signal and the detected voltage from the output power detecting circuit
29
. This digital TX-AGC signal is then supplied to the digital-analog converter
28
for the digital-analog conversion, the analog gain control voltage obtained is supplied to the TX-AGC amplifier
26
, thereby signal gain of the TX-AGC amplifier
26
is set to the value determined by the analog gain control voltage, namely to the value instructed with the TX-AGC signal.
Moreover, a part of the transmitting signal obtained at the output of the power amplifier
3
is supplied to the output power detecting circuit
29
. The output power detecting circuit
29
detects the transmitting signal supplied to form a detection voltage corresponding to the transmitting signal and compares this detection voltage with the reference voltage to generate the detection voltage indicating the result of comparison and then supplies the detection voltage to the control unit
37
. The control unit
37
arithmetically processes the detection voltage supplied to generate the digital TX-AGC signal in order to control the gain of the TX-AGC amplifier
26
. This digital TX-AGC signal is supplied to the TX-AGC amplifier
26
via the digital-analog converter
28
. Thereby the gain of the TX-AGC amplifier
26
is controlled as explained above.
Moreover, the control unit
37
arithmetically processes the receiving base-band signal level to generate the digital RX-AGC signal for controlling the gain of the RX-AGC amplifier
33
. This digital RX-AGC signal is s
Alps Electric Co. ,Ltd.
Beyer Weaver & Thomas
Vuong Quochien
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