Amplifiers – Hum or noise or distortion bucking introduced into signal...
Reexamination Certificate
1999-07-01
2001-02-27
Mottola, Steven J. (Department: 2817)
Amplifiers
Hum or noise or distortion bucking introduced into signal...
C330S136000
Reexamination Certificate
active
06194964
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application entitled “Predistorter Having Automatic Gain Control Circuit and Method Therefor” earlier filed in the Korean Industrial Property Office on Jul. 7, 1998, and there duly assigned Serial No. 1998-27209.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a predistorter having an automatic gain control (AGC) circuit and method therefor and, in particular, to a simplified predistorter circuit which lacks a subtraction circuit typically found in a conventional predistorter, and includes an automatic gain controller (AGC) and method therefor.
2. Description of the Related Art
A predistorter is a circuit that minimizes an intermodulation distortion of a main amplifier. This is accomplished by estimating the intermodulation distortion in the main amplifier and adding the predistorted signal to the input signal of the main amplifier.
Referring to
FIG. 1
, a conventional predistorter comprises a harmonic generator
10
used for the predistortion, and a subtraction circuit
40
, which removes all but the spurious components among the signals being generated in the harmonic generator
10
, wherein the spurious components contribute to the linearization of the main amplifier. The subtraction circuit
40
aids in canceling the main carrier components being amplified in the harmonic generator
10
.
The subtraction circuit
40
receives the input signal via divider
5
and comprises an attenuator
50
, a phase shifter
60
, a combiner
52
and a divider
51
. The gain in the attenuator
50
and the phase shifter
60
is the same, and the phase is inverse, as compared to the gain and phase of the harmonic generator
10
.
A first variable attenuator
20
and a variable phase shifter
30
are used to optimize the resulting signal after canceling the main carrier components, thereby minimizing the intermodulation distortion of the main amplifier
80
.
However, practically speaking, the subtraction circuit
40
can not completely cancel the main carrier components. In addition, the subtraction is not performed when the frequency band is narrow and the frequency is changed.
As such, a problem occurs in that the gain of amplifier becomes unstable overall when the first variable attenuator
20
and variable phase shifter
30
are operated so as to minimize the intermodulation distortion of the main amplifier. Here, the gain of the overall amplifier is calculated as a gain derived from the predistorter and the main amplifier.
The gain of amplifier also becomes unstable overall because the spurious components power is that of a specific rate over the total signal.
SUMMARY OF THE INVENTION
A preferred embodiment of a predistorter of a high frequency amplifier in accordance with the present invention comprises: an automatic gain control circuit for controlling an overall gain of said high frequency amplifier so that there is no change in the overall gain of the high frequency amplifier when an output signal is changed as a result of comparing an input signal to the output signal of a main amplifier; and a variable attenuator being controlled by the automatic gain control circuit so that there is no change in an overall gain of the high frequency amplifier, thereby minimizing the change of gain of a combined signal; and a linearizer with a signal divider for dividing the input signal into a main-path signal and a sub-path signal, a phase shifter for delaying a phase of the main-path signal, a harmonic generator for generating harmonic signals using the sub-path signal, a second variable attenuator for attenuating an output of the harnonic generator, a variable phase amplifier for amplifying a phase of the output signal of the first variable attenuator, a combiner for combining an output signal of the variable phase amplifier with an output signal of the phase shifter, and a main amplifier for amplifying the combined signal.
A preferred embodiment of a method of predistortion using an automatic gain control circuit for a linearizer of a high frequency amplifier comprises the steps of: dividing an input signal into a main-path signal and a sub-path signal; delaying a phase of the main-path signal; generating harmonic signals with a harmonic generator, the harmonic signals being generated from the sub-path signal; regulating a phase and an amplitude of an output signal of the harmonic generator; combining the regulated output signal and the delayed main-path signal; amplifying and outputting the combined signal; comparing the input signal with the amplified combined output signal; and controlling an overall gain of the high frequency amplifier using the automatic gain control circuit when a change is detected in the amplified combined output signal, the change being detected during comparison with the input signal.
The step of controlling the overall gain of the high frequency amplifier comprises the steps of: minimizing a variation of a gain of the combined signal using the automatic gain control circuit to control a variable attenuator which attenuates said signal; and amplifying and outputting the combined signal so that an intermodulation distortion is suppressed, wherein the variation of the gain of the amplified combined output signal is minimized by the control of the automatic gain control circuit.
REFERENCES:
patent: 5770971 (1998-06-01), McNicol
patent: 5892397 (1999-04-01), Belcher et al.
patent: 5912588 (1999-06-01), Nummila
patent: 5963087 (1999-10-01), Anderson
patent: 5963090 (1999-10-01), Fukuchi
patent: 6002300 (1999-12-01), Herbster et al.
Dilworth & Barrese LLP
Mottola Steven J.
Samsung Electronics Co,. Ltd.
LandOfFree
Predistorter having an automatic gain control circuit and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Predistorter having an automatic gain control circuit and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Predistorter having an automatic gain control circuit and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2583082