Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
1998-12-21
2001-05-08
Maung, Nay (Department: 2744)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S091000, C455S115200
Reexamination Certificate
active
06229995
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to transmitters for radio communication systems and, in particular, to a high efficiency power control device capable of reducing noise, current consumption and the generation of spurious signals in a radio transmitter.
2. Description of the Related Art
In a radio communication system, a terminal apparatus and a base station apparatus include a power amplifier for amplifying a low power signal to a high power signal. A CDMA (Code Division Multiple Access) or PCS (Personal Communication System) phone deals with both very low power signals and very high power signals.
FIG. 1
is a block diagram illustrating a conventional transmitter for a terminal apparatus such as the CDMA or PCS phone. An IF (Intermediate Frequency) filter
110
receives a modulated IF input transmission signal S
IF
and filters the IF transmission signal. An IF amplifier
120
amplifies the IF transmission signal, and an IF filter
130
filters an output of IF amplifier
120
. A mixer
140
mixes an output of IF filter
130
with a local oscillation frequency generated from a local oscillator
150
to generate an RF (Radio Frequency) signal. An RF filter
160
filters the mixed signal to detect the RF signal. A drive amplifier
170
amplifies the RF signal in order to obtain a power signal for driving a power amplifier
190
. An RF filter
180
filters an output of drive amplifier
170
. The power amplifier
190
amplifies the filtered RF signal. A duplexer
220
switches an antenna
230
to a transmitting part or a receiving part. An isolator
210
, which is connected between an output node of power amplifier
190
and an input node of duplexer
220
, transfers an output of power amplifier
190
to duplexer
220
without attenuation in order to prevent transmission distortion from a reflected wave. An automatic power controller (APC)
200
connected between drive amplifier
170
and power amplifier
190
automatically controls a gain of power amplifier
190
.
It is to be appreciated that the above structure has numerous deficiencies, particularly with respect to a linear system having a large difference between the maximum power level and the minimum power level. For example, power amplifier
190
is always driven, irrespective of whether or not the transmission power is high or low. As a result, the current consumption of the transmitter is increased. Further, since the power amplifier has variable input/output characteristics according to an applied voltage, it is difficult to obtain optimal power amplifying efficiency when the applied voltage is changed by power control. Moreover, it is difficult to control a negative voltage of GaAs FETs (Field Effect Transistors) used for the power amplifier. Additionally, it is difficult to reduce noise and the generation of spurious signals in the transmitter.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a power control device capable of increasing power amplifying efficiency and reducing noise, current consumption and the generation of spurious signals in a radio transmitter.
To achieve the above and other objects, there is provided a power control device in a transmitter of a radio communication system. The transmitter has a drive amplifier, a power amplifier and a duplexer. The power control device includes: a divider for dividing an output of the drive amplifier into first and second power signals at a same rate; a switching element for transferring the second power signal to the duplexer in response to a first control signal, and wherein the power amplifier is enabled in response to a second control signal; and a control signal generator for generating the first and second control signals, wherein said control signal generator activates the first control signal to enable the switching element and inactivates the second control signal to disable the power amplifier when the transmitter transmits a low power signal, and said control signal generator inactivates the first control signal to disable the switching element and activates the second control signal to enable the power amplifier when the transmitter transmits a high power signal.
Further, the power control device may include an isolator having an input node operatively coupled to the power amplifier and the switching element and an output node operatively coupled to the duplexer. The isolator transfers outputs of the power amplifier and the switching element to the duplexer without attenuation to prevent transmission distortion from a reflected wave.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
REFERENCES:
patent: 5152004 (1992-09-01), Vaisanen et al.
patent: 5438684 (1995-08-01), Schwent et al.
patent: 5530923 (1996-06-01), Heinonen et al.
patent: 5661434 (1997-08-01), Brozovich et al.
patent: 5909643 (1999-06-01), Aihara
patent: 6078794 (2000-06-01), Peckham et al.
Dilworth & Barrese LLP
Maung Nay
Samsung Electronics Co,. Ltd.
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