Amplifiers – Combined with automatic amplifier disabling switch means
Utility Patent
1999-07-02
2001-01-02
Mottola, Steven J. (Department: 2817)
Amplifiers
Combined with automatic amplifier disabling switch means
C330S053000, C330S151000
Utility Patent
active
06169449
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a transmission power control circuit for use in a transmitter and, in particular, to a transmission power control circuit which is included in a transmitter used in a code division multiple access (CDMA) system.
Heretofore, proposal has been made in Japanese Unexamined Patent Publication Nos. Hei 7- 336243 (namely, 336243/1995), Hei 8-222963 (namely, 222963/1996), and Hei 5-83041 (namely, 83041/1993) about a wide variety of transmission power control circuits which can be used in a CDMA system which has a base station and a plurality of mobile stations communicable with the base station. This is because transmission power is controlled in each mobile station of the CDMA system in response to a control signal sent from a base station. To this end, the transmission power control circuit is usually included in the transmitter of each mobile station and must cope with a variation over a very wide range, such as 70 dB.
More specifically, the transmission power control circuit disclosed in Hei 5-83041 (will be simply referred to as Reference) mentioned above has a power amplifier circuit which includes a FET as an amplifying element and a gate bias circuit for controlling a gate bias of the FET. With this structure, it is possible to reduce electric power on low power transmission not only by control a drain bias of the FET but also by varying the gate bias of the FET. In this event, electric power consumption can be decreased by reducing an electric current caused to flow through the FET on the low power transmission within a predetermined output range.
However, it is to be noted that such a reduction of the electric power consumption can be established only within the predetermined output range. In other words, such a power reduction can not be realized when an output level becomes lower than the predetermined output range. This is because the power amplifier which includes the FET must keep a linear characteristic and can not reduce an idle current to zero on the low power transmission.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a transmission power control circuit which is capable of controlling transmission power over a very wide range.
It is another object of this invention to provide a transmission power control circuit of the type described, which can be effectively used in a CDMA system.
It is still another object of this invention to provide a method of controlling transmission power over a very wide range by using a circulator.
A transmission power control circuit to which this invention is applicable has a circuit input terminal and a circuit output terminal. According to this invention, the transmission power control circuit comprises a first transmission circuit which has a first input terminal and a first output terminal, a second transmission circuit which has a second input terminal and a second output terminal, a circulator which has a first circulator port connected to the first output terminal, a second circulator port connected to the circuit output terminal, and a third circulator port selectively connected to the second output terminal and which circularly transmits an electric signal from a selected one of the second and the third circulator ports to the first circulator port, and a switch circuit which selectively connects the circuit input terminal to the first and the second transmission circuits to selectively supply the electric signal to the first and the third circulator ports.
In operation, the first transmission circuit has an output impedance and the electric signal is sent from the third circulator port to the second circulator port through the first circulator port in dependency upon the output impedance when the switch circuit selects the second transmission circuit to supply the electric signal to the third circulator port through the second transmission circuit.
Herein, the first transmission circuit may include a power amplifier for amplifying the electric signal while the second transmission circuit may include a bypass circuit which does not amplify the electric signal. In this event, it is possible to vary a gain of the transmission power control circuit over a wide range by selecting the power amplifier and the bypass circuit. Moreover, the circulator serves to avoid attenuation of the electric signal sent from the bypass circuit.
REFERENCES:
patent: 3992669 (1976-11-01), Dades
patent: 4056785 (1977-11-01), Swan
patent: 4305043 (1981-12-01), Ho et al.
patent: 4910478 (1990-03-01), Koyama
patent: 5909643 (1999-06-01), Aihara
patent: 0 735 668 A1 (1996-10-01), None
patent: 5-83041 (1993-04-01), None
patent: 7-336243 (1995-12-01), None
patent: 8-222963 (1996-08-01), None
Mottola Steven J.
NEC Corporation
Scully Scott Murphy & Presser
LandOfFree
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