Amplifiers – Combined with automatic amplifier disabling switch means
Reexamination Certificate
2000-02-28
2001-12-11
Mottola, Steven J. (Department: 2817)
Amplifiers
Combined with automatic amplifier disabling switch means
C330S151000
Reexamination Certificate
active
06329875
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power amplifier, a control method for such a power amplifier, and a communication equipment which are used mainly in a mobile communication system.
2. Related Art of the Invention
Recently, digital mobile communication system rapidly enters widespread use, and miniaturization of a communication terminal, and reduction of power consumption are advancing. As a successor to a currently used digital portable telephone, also a portable telephone using the CDMA (Code Division Multiple Access) system which can ensure a larger communication capacity is being developed. The CDMA system is described in detail in “CDMA HOSHIKI TO JISEDAI IDOTAI TSUSHIN SYSTEM” (Chap. 1, TRORIKEPSU SOSHO), and hence its detailed description is omitted.
Hereinafter, a power amplifier of the conventional art will be described with reference to
FIGS. 13 and 14
. FIG.
13
. is a diagram showing the configuration of power amplifier of the convention art. Referring to
FIG. 13
,
701
denotes an input terminal,
702
denotes a preamplifier,
703
denotes a postamplifier, and
704
denotes an output terminal.
FIG. 14
is a graph showing a consumed current, an amount of distortion, and an efficiency with respect to an output power of the power amplifier of the conventional art. In
FIG. 14
, the solid lines show variations of characteristics in the case where the initial currents are set to be similar to set values in a power amplifier of a conventional digital portable telephone of the TDMA system, and the broken lines show characteristics in the case where the initial currents of the preamplifier and the postamplifier shown in
FIG. 13
are set to be a half of the values.
Generally a power amplifier is controlled so that efficiency at maximum output becomes maximum. But in the CDMA portable telephone system, the power output is controlled in such wide range of exceeding 70 dB from maximum output in accordance with the distance between a telephone and a base station. Therefore it is demanded to satisfy high efficiency for whole power output range.
However as shown in
FIG. 14
, in the case where the initial currents are set to be similar to those in the TDMA system, the efficiency becomes poor because the consumed current at low output is large. On the contrary when the initial currents are half, the amount of distortion near maximum output becomes poor. Therefore the initial currents of the power amplifier are to be set as smallest within tolerable amount of distortion.
In this configuration, when the output power of the power amplifier is reduced, the efficiency is lowered and a current which is not actually necessary is consumed. In the CDMA system, particularly, the time period when transmission is performed at a power of a reduced level is longer than that when transmission is performed at the maximum power, and therefore the battery power is largely consumed, with the result that the talk time is shortened.
In order to improve the efficiency at the reduction of the output power, the initial current may be set to be close to that of Class B (the initial current is reduced in level). In this case, however, the distortion level is impaired. Therefore, the reduction of the initial current is limited.
SUMMARY OF THE INVENTION
The invention has been conducted in view of the problems of the power amplifier of the conventional art. It is an object of the invention to provide a power amplifier the efficiency of which is not impaired even in the CDMA system, and a control method for the power amplifier.
In order to solve the problems, the power amplifier of the present invention comprises: an input terminal; an output terminal; an N number of bypassable amplification circuits which are connected directly or indirectly in a sequential manner between said input terminal an d said output terminal; an impedance conversion circuit which is connected directly or indirectly between said amplification circuit of a final stage and said output terminal; and a bias control circuit which controls said amplification circuits,
each of said amplification circuits is configured by a high-frequency switch circuit, and an amplifier which is connected directly or indirectly to said switch circuit, and
said bias control circuit controls power source voltages of said amplifiers and controls status of said switch circuit.
A power amplifier of the present invention comprises: an input terminal; a first high-frequency switch circuit which can output a signal input to said input terminal while switching to two output terminals; a first amplifier which is connected directly or indirectly to one of said output terminals of said first high-frequency switch circuit; a second high-frequency switch circuit which is connected directly or indirectly to an output terminal of said first amplifier and another one of said output terminals of said first high-frequency switch circuit, and which can independently output two signals respectively input from said output terminals while switching to two output terminals; a second amplifier which is connected directly or indirectly to one of said output terminals of said second high-frequency switch circuit; an impedance conversion circuit which is connected directly or indirectly to another one of said output terminals of said second high-frequency switch circuit; an output terminal which is commonly connected directly or indirectly to an output terminal of said second amplifier and an output terminal of said impedance conversion circuit; and a bias control circuit which controls power source voltages of said first and second amplifiers and controls status of said switch circuit.
A power amplifier of the present invention comprises: an input terminal; a first high-frequency switch circuit which can output a signal input to said input terminal while switching to two output terminals; a first amplifier which is connected directly or indirectly to one of said output terminals of said first high-frequency switch circuit; a second high-frequency switch circuit which is connected directly or indirectly to an output terminal of said first amplifier and another one of said output terminals of said first high-frequency switch circuit, and which can independently output two signals respectively input from said output terminals while switching to two output terminals; a second amplifier which is connected directly or indirectly to one of said output terminals of said second high-frequency switch circuit; a third high-frequency switch circuit which is connected directly or indirectly to an output terminal of said second amplifier and another one of said output terminals of said second high-frequency switch circuit, and which can independently output two signals respectively input from said output terminals while switching to two output terminals; a third amplifier which is connected directly or indirectly to one of said output terminals of said third high-frequency switch circuit; an impedance conversion circuit which is connected directly or indirectly to another one of said output terminals of said third high-frequency switch circuit; an output terminal which is commonly connected directly or indirectly to an output terminal of said third amplifier and an output terminal of said impedance conversion circuit; and a bias control circuit which controls power source voltages of said first, second, and third amplifiers and controls status of said switch circuit.
A power amplifier of the present invention comprises: an input terminal; a first high-frequency switch circuit which can output a signal input to said input terminal while switching to two output terminals; a first amplifier which is connected directly or indirectly to one of said output terminals of said first high-frequency switch circuit; impedance switching means which is connected directly or indirectly to an output terminal of said first amplifier; a second high-frequency switch circuit which is connected directly or indirectly to another one of said output terminals of
Ishida Kaoru
Komatsu Naoki
Kosugi Hiroaki
Obara Toshio
Matsushita Electric - Industrial Co., Ltd.
Mottola Steven J.
Ratner & Prestia, PC
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