Amplifiers – Hum or noise or distortion bucking introduced into signal...
Reexamination Certificate
2000-01-26
2001-11-06
Pascal, Robert (Department: 2817)
Amplifiers
Hum or noise or distortion bucking introduced into signal...
C330S151000
Reexamination Certificate
active
06313702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase correction amplifier for correcting a phase characteristic, and a feed-forward amplifier using the above phase correction amplifier, which can be applied to a transmitting power amplifier used, for example, in a radio base station.
2. Description of the Related Art
A power amplifier used for a transmitting apparatus in a mobile radio communication system has a structure in which an amplification is performed within a linear area of an amplification characteristic in order to realize low signal distortion. In this case, however, there is a problem in which this structure has a low power efficiency.
Accordingly, in actual use of the power amplifier, an operation area of the amplification is extended until an output of the power amplifier reaches in the vicinity of a saturation area in order to improve the power efficiency. In this case, when a peak envelope power (i.e., an instantaneous power) of an input signal becomes large, the signal distortion also becomes large.
For example, in a power amplifier used in a PDC (Personal Digital Cellular) system for collectively amplifying and transmitting signals on a plurality of channels, the signal distortion at mutual modulation becomes large compared to amplification of the transmitting signal on a single channel. In a CDMA (Code Division Multiple Access) system, since the peak envelope power becomes large due to coincidence of phases in carrier wave when using large multiplexed codes.
Conventionally, there are known many structures to compensate for the signal distortion in the power amplifier. For example, a pre-distortion type distortion compensator, a feed-forward type amplifier consisting of a distortion extraction loop and a distortion eliminating loop, etc., have been known.
Accordingly, the present invention relates to an improvement of the feed-forward type amplifier by correcting the phase characteristic of a phase correction amplifier.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a phase correction amplifier which can correct a phase characteristic thereof and can be applied to a transmitting power amplifier used, for example, in a radio base station.
Another object of the present invention is to provide a feed-forward amplifier using the above phase correction amplifier.
In accordance with a first aspect of the present invention, there is provided a phase correction amplifier including: a GaAs field effect transistor; and a Si field effect transistor or a Si bipolar transistor; wherein the GaAs field effect transistor and the Si field effect transistor or the Si bipolar transistor are cascade-connected each other.
In accordance with a second aspect of the present invention, there is provided a phase correction amplifier including: a GaAs field effect transistor; and a Si field effect transistor or a Si bipolar transistor; wherein the GaAs field effect transistor and the Si field effect transistor or the Si bipolar transistor are cascade-connected each other through a variable attenuator.
In accordance with a third aspect of the present invention, there is provided a feed-forward amplifier including: a distortion extracting loop consisting of a main amplifier signal path and a linear signal path in order to distribute a transmission signal; a directional coupler for receiving an output signal through the main amplifier signal path and an output signal through the linear signal path; a distortion eliminating loop consisting of a sub-amplifier signal path and a linear signal path in order to input an output signal from the directional coupler; and a power compositor for receiving an output signal through the sub-amplifier signal path and an output signal through the linear signal path, and coupling both the output signals.
In a preferred embodiment, each of the main amplifier and the sub-amplifier is constituted by a phase correction amplifier comprising a GaAs field effect transistor, and a Si field effect transistor or a Si bipolar transistor, wherein the GaAs field effect transistor and the Si field effect transistor or the Si bipolar transistor are cascade-connected each other through a variable attenuator.
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Fujitsu Limited
Nguyen Khanh V.
Pascal Robert
Rosenman & Colin LLP
LandOfFree
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