High-Frequency Gain Control Amplifier With Low Distortion Output
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Solution Overview
Problem
Conventional voltage controlled amplifiers suffer from harmonic and intermodulation distortion at the output for certain DC voltage control settings, limiting their effectiveness in gain variation of input signals.
Innovation Solution
A higher frequency signal is combined with the input signal and filtered to remove distortion, with its amplitude adjusted to control the gain of the input signal, utilizing a differential amplifier with optional nonlinear feedback elements to minimize distortion, and a predistortion function to offset nonlinearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional voltage controlled amplifier uses DC voltage control settings, then gain variation of the input signal is achieved, but harmonic and intermodulation distortion occurs at the output
Solution Approach 1:
The patent changes the control parameter from DC voltage to AC voltage at a frequency significantly higher than the input signal frequency. This parameter change allows gain control while avoiding the distortion problems associated with DC control settings in conventional amplifiers
Solution Approach 2:
The invention uses periodic AC voltage signals at a high frequency to control the amplifier's gain. This periodic control action enables continuous gain variation without the harmonic and intermodulation distortion that occurs with conventional DC control methods
2Object-generated harmful factors
If a higher frequency signal is combined with the input signal to control gain, then gain control with low distortion is achieved, but the higher frequency signal and its distortion components must be filtered out
Solution Approach 1:
The patent extracts and removes the high frequency control signal and its associated distortion components from the output using a filter. This extraction process separates the desired low frequency input signal from the unwanted high frequency components, achieving low distortion output
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in an output signal with very low distortion, as the higher frequency signal's distortion can be filtered out, providing controlled gain with minimal harmonic distortion, an improvement over traditional voltage controlled amplifiers.
Implementation Method 1
A filter is coupled to an output of the amplifier, which removes the higher frequency signal and or any distortion signals related to the higher frequency signal such as harmonics or intermodulation components
Data Source
AI summary
A gain control amplifier provides amplitude variation of an input signal that is coupled to the amplifier, by adding or combining a higher frequency signal that overdrives or distorts the amplifier to one or more degree(s), to provide the gain variation of the input signal. A predistortion circuit may be included to further reduce distortion of the input signal at the output of the amplifier.