Amplifiers – With amplifier bypass means
Reexamination Certificate
2000-08-09
2001-05-15
Pascal, Robert (Department: 2817)
Amplifiers
With amplifier bypass means
C330S149000
Reexamination Certificate
active
06232838
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a feed forward amplifier. Particularly, the present invention relates to a technique of being capable of improving the distortion removing effect by feed forward even when non-linear distortion of a main amplifier is compensated using an adaptive pre-distortion compensation method.
Recently, various feed-forward amplifiers are being developed. For example, according to the technique disclosed in JP-A-No. 284951/1998, the feed-forward amplifier includes a pre-distortion compensation circuit
3
, a variable attenuator
4
, a variable phase shifter
5
, and a main amplifier
6
, arranged in the listed order. The control circuit
19
controls the variable attenuator
4
and the variable phase shifter
5
to minimize the carrier component, or an input signal, in detected distortion components. The technique disclosed in the above publication can compensate distortions even if there are temperature variations.
A pre-distorter (pre-distortion compensator) is disposed on the main amplifier side of a distortion detection loop to relieve the burden of the auxiliary amplifier used in a feed-forward amplifier. The use of an adaptive pre-distorter (adaptive pre-distortion compensator) in an adaptive pre-distortion system, which can reduce non-linear distortion more than the pre-distorter, is being developed. The adaptive pre-distortion system is one of compensating non-linear distortions produced in amplifiers. According to this system, the characteristics reversed to characteristics of an amplifier are provided to an input signal. Thus, this pre-distortion system, which linearly operates an amplifier apparently, can adaptively deal with changes in characteristic of the amplifier due to changes in ambient environment.
However, there is the problem that when the adaptive pre-distorter is used to compensate non-linear distortion of the main amplifier, the vector modulator controlled by the adaptive pre-distorter may rather deteriorate the distortion decreasing effect by the feed forward.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-mentioned problems.
Moreover, the present invention is made to solve the above mentioned problems. The objective of the invention is to provide a technique of being capable of improving the distortion removing effect of a feed-forward amplifier even when non-linear distortion of a main amplifier is compensated using an adaptive pre-distorter.
In order to achieve the above-mentioned problem, the feed-forward amplifier comprises a first signal route having an amplifier; a second signal route for creating a signal having the same amplitude as that of a signal input to the first signal route and having a phase reversed to the phase of the input signal; wherein the feed-forward amplifier detects a distorted component of a signal amplified by the amplifier based on a signal passing through the first signal route and a signal passing through the second signal route, and removes the distorted component of the signal amplified by the amplifier based on the detected distorted component; a first vector modulator disposed in an input route of the amplifier, for varying an input signal of the amplifier; a second vector modulator disposed in the second signal route, for varying an input signal of the second signal route; and control means for controlling the first vector modulator to minimize distortion of the amplifier and controlling the second vector modulator to equalize a change in input signal of the amplifier due to the control to a change in input signal of the second signal route.
According to the present invention, the feed-forward amplifier can improve the distortion removing effect of the entire feed-forward amplifier by varying an input signal on the second signal route by the same degree as that of the input signal of the amplifier.
Moreover, the above-mentioned problem is solved by the feed-forward amplifier comprising a first signal route having an amplifier; a second signal route for creating a signal having the same amplitude as that of a signal input to the first signal route and having a phase reversed to the phase of the input signal; wherein the feed-forward amplifier detects a distorted component of a signal amplified by the amplifier based on a signal passing through the first signal route and a signal passing through the second signal route, and removes the distorted component of the signal amplified by the amplifier based on the detected distorted component; a first vector modulator disposed in an input route of the amplifier, for varying an input signal of the amplifier; a second vector modulator disposed in the second signal route, for varying an input signal of the second signal route; and control means for controlling the first vector modulator to minimize distortion of the amplifier and controlling the second vector modulator with the same amount as that of the above control.
A change in input signal of the amplifier is equalized to a change in input signal on the second signal route by controlling the second vector modulator with the same control amount as that of the first vector modulator.
Moreover, the above-mentioned problem is solved by a feed-forward amplifier comprising a first signal route having an amplifier; a second signal route for creating a signal having the same amplitude as that of a signal input to the first signal route and having a phase reversed to the phase of the input signal; wherein the feed-forward amplifier detects a distorted component of a signal amplified by the amplifier based on a signal passing through the first signal route and a signal passing through the second signal route, and removes the distorted component of the signal amplified by the amplifier based on the detected distorted component; a first vector modulator disposed in an input route of the amplifier, for varying the phase of an input signal of the amplifier; a second vector modulator disposed in the second signal route, for varying the phase of an input signal of the second signal route; and control means for controlling a phase change of the first vector modulator to minimize non-linear distortion of the amplifier and controlling the second vector modulator to the same phase change as that of the first vector modulator.
Moreover, the above-mentioned problem is solved by a feed-forward amplifier comprising a first signal route having an amplifier; a second signal route for creating a signal having the same amplitude as that of a signal input to the first signal route and having a phase reversed to the phase of the input signal; wherein the feed-forward amplifier detects a distorted component of a signal amplified by the amplifier based on a signal passing through the first signal route and a signal passing through the second signal route, and removes the distorted component of the signal amplified by the amplifier based on the detected distorted component; a first vector modulator disposed in an input route of the amplifier, for varying an input signal of the amplifier; a second vector modulator disposed in the second signal route, for varying an input signal of the second signal route; first detection means for detecting the waveform of an input signal of the first vector modulator; second detection means disposed for detecting the waveform of an output signal of the amplifier; means for outputting a difference between a waveform detected by the first detection means and a waveform detected by the second detection means; and control means for controlling the first vector modulator to minimize the difference and controlling the second vector modulator to equalize a change in input signal of the amplifier due to the control to a change in input signal of the second signal route.
Particularly, the first vector modulator comprises a variable attenuator and a variable phase shifter. The second vector modulator comprises a variable attenuator and a variable phase shifter.
Moreover, the first vector modulator is controlled in an adaptive pre-distortion system.
Accordi
NEC Corporation
Nguyen Patricia T.
Ostrolenk Faber Gerb & Soffen, LLP
Pascal Robert
LandOfFree
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