Amplifiers – Hum or noise or distortion bucking introduced into signal...
Reexamination Certificate
2000-02-24
2001-08-07
Pascal, Robert (Department: 2817)
Amplifiers
Hum or noise or distortion bucking introduced into signal...
C330S151000, C455S063300, C375S296000
Reexamination Certificate
active
06271723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distortion compensating device for compensating for a third-order distortion produced by an amplifier, and more particularly to a distortion compensating device which comprises a four-terminal power distributor connected to a third-order distortion generator and a phase adjuster for a size reduction.
2. Description of the Related Art
It has been known in the art that an amplifier generates high-order distortions when the amplifier amplifies a signal. Particularly, it is known that a third-order distortion generated by the amplifier adversely affects the signal processing performed by the amplifier. If a signal having a certain frequency which is inputted to the amplifier is referred to as a fundamental signal, then the amplifier generates a third-order distortion depending on the fundamental signal, the third-order distortion having a frequency different from the frequency of the fundamental signal.
One way of compensating a third-order distortion generated by an amplifier is to generate a distortion-compensating third-order distortion at a stage preceding the amplifier and cancel out the third-order distortion generated by the amplifier with the distortion-compensating third-order distortion. A distortion compensating device for generating such a distortion-compensating third-order distortion may combine a third-order distortion generated by a phase adjuster, for example, with a linear signal in an appropriate phase relationship and output the combined signal to a subsequent amplifier. Another distortion compensating device may comprise a third-order distortion generator and a wide-band phase unit.
However, the conventional distortion compensating devices are large in scale and cannot be reduced in size because they have two separate signal processing systems, e.g., a signal processing system for processing an inputted fundamental signal and a signal processing system for generating a third-order distortion, and a separate combiner for combining output signals from the two signal processing systems, i.e., a fundamental signal and a third-order distortion signal.
The conventional distortion compensating devices need a wide-band LNA (Low Noise Amplifier) for amplifying a third-order distortion because a large signal loss occurs when the third-order distortion is generated. The conventional distortion compensating devices also require a complex external control circuit and a memory circuit for storing control information because a highly accurate control process is necessary for generating a third-order distortion suitable for distortion compensation.
For the above reasons, there has been a demand for the development of a distortion compensating device that can be reduced in size and has a low power requirement.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a distortion compensating device having a relatively small size, for compensating for a third-order distortion produced by an amplifier.
Another object of the present invention is to provide a distortion compensating device having a reduced power requirement.
To achieve the above objects, there is provided in accordance with the present invention a distortion compensating device for compensating for a third-order distortion generated by an amplifier, comprising a power distributor having a first terminal for supplying an input signal to be inputted to an amplifier or being supplied with an input signal from an amplifier, a second terminal, and a third terminal, a third-order distortion generator connected to the second terminal for generating a third-order distortion having an amplitude for canceling out a third-order distortion generated by the amplifier depending on the supplied input signal, and a phase adjuster connected to the third terminal for adjusting the phase of the input signal to set the phase difference between the input signal and the third-order distortion generated by the third-order distortion generator to a phase difference for canceling out the third-order distortion generated by the amplifier, the power distributor having a fourth terminal for combining and outputting the third-order distortion generated by the third-order distortion generator and the input signal whose phase is adjusted by the phase adjuster.
Since the distortion compensating device has four-terminal power distributor associated with the third-order distortion generator and the phase adjuster, the distortion compensating device may comprise a coupler unit having such a coupler, and can be reduced in size. Specific examples for setting up the amplitude of the third-order distortion generated by the third-order distortion generator and also setting up the phase difference to be adjusted by the phase adjuster will be described later on with reference to preferred embodiments of the present invention.
If the first terminal supplies the input signal to be inputted to the amplifier, then the distortion compensating device is positioned at a stage preceding the amplifier and supplies the input signal from the first terminal to the amplifier. If the first terminal is supplied with the input signal from the amplifier, then the distortion compensating device is positioned at a stage following the amplifier and is supplied with the input terminal outputted from the amplifier from the first terminal. At any rate, the distortion compensating device generates the third-order distortion for canceling the third-order distortion generated by the amplifier thereby to compensate for the third-order distortion generated by the amplifier.
The distortion compensating device may be used to compensate for third-order distortions generated by more than one amplifier. For example, the distortion compensating device may be arranged to compensate for third-order distortions generated by either a plurality of amplifiers preceding the distortion compensating device or a plurality of amplifiers following the distortion compensating device. Alternatively, the distortion compensating device may be arranged to compensate for a third-order distortion generated by at least one amplifier preceding the distortion compensating device and a third-order distortion generated by at least one amplifier following the distortion compensating device.
In order for the distortion compensating device to compensate for third-order distortions generated by a plurality of amplifiers, the distortion compensating device generates a third-order distortion capable of canceling the sum of the third-order distortions generated by the amplifiers. The principles of the present invention are therefore applicable to the compensation for a third-order distortion generated by a single amplifier or third-order distortions generated by plural amplifiers.
The principles of the present invention are applicable to various fields where the third-order distortion generated by an amplifier is to be compensated for. For example, the distortion compensating device according to the present invention may be incorporated in a communication unit of a portable telephone system for compensating for a third-order distortion generated by an amplifier in the communication unit, or a communication unit of a W-CDMA system for compensating for a third-order distortion generated by an amplifier in the communication unit. The communication unit may comprise a base station or a terminal.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.
REFERENCES:
patent: 4157508 (1979-06-01), Hecken
patent: 5304944 (1994-04-01), Copeland et al.
patent: 5850305 (1998-12-01), Pidgeon
patent: 6081159 (2000-06-01), Kim et al.
patent: 6122085 (2000-06-01), Bitler
Ito Hidefumi
Nagano Terufumi
Okubo Yoichi
Sera Yasuo
Suto Masaki
Choe Henry
Kokusai Electric Co. Ltd.
Pascal Robert
Wenderoth , Lind & Ponack, L.L.P.
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