Subthreshold-Biased Variable Gain Amplifier for Distortion Cancellation
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Solution Overview
Problem
Variable gain amplifiers in wireless communication devices generate distortion signals due to nonlinear signal transfer functions, which can cause deviations and disturb downstream components, and existing solutions fail to effectively compensate for these distortions.
Innovation Solution
A variable gain amplifier circuit that includes a biasing circuit providing a bias voltage above a threshold to activated amplifiers and a subthreshold biasing circuit providing a nonzero bias voltage below the threshold to non-selected amplifiers, allowing the non-selected amplifiers to generate distortion cancelling signals, thereby compensating for the distortions in the amplified output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple amplifiers are used to provide variable gain, then gain flexibility is improved, but distortion signals are generated due to nonlinear signal transfer functions
Solution Approach 1:
The patent applies distortion cancellation amplifiers that generate distortion signals opposite in phase to those produced by the main amplifiers. By converting the harmful distortion effect into a beneficial cancellation effect, the system maintains variable gain flexibility while reducing overall distortion in the output signal.
Solution Approach 2:
The distortion cancellation amplifiers are configured to preemptively generate counter-phase distortion signals that offset the nonlinear distortions before they significantly degrade the output signal quality. This preliminary anti-action approach prevents distortion accumulation throughout the signal chain.
2Object-generated harmful factors
If distortion cancellation amplifiers are added, then distortion reduction is improved, but device complexity increases
Solution Approach 1:
The patent integrates distortion cancellation amplifiers within the existing variable gain amplifier architecture, merging the distortion cancellation function with the gain control function. This consolidation reduces device complexity by sharing common components such as biasing circuits and signal paths between the main amplifiers and distortion cancellation amplifiers.
Solution Approach 2:
The amplifier circuit is designed so that the same amplifier blocks serve multiple functions: main amplifiers provide both gain and distortion generation, while distortion cancellation amplifiers provide both distortion cancellation and additional gain control. This multi-functionality reduces the total number of components needed.
Data Source
AI summary
This disclosure is directed to reducing output voltage distortions of Variable Gain Amplifiers (VGAs). A VGA may include a number of amplifiers each providing a portion of a total gain of the VGA. For example, a processing circuit may select one or more of the amplifiers of the VGA to provide the output signal with a selected gain. However, the selected amplifiers may provide amplified signals with one or more distortion signals when receiving a bias voltage. Systems and methods are described to reduce or cancel the distortion signals of the selected amplifiers by providing a subthreshold nonzero bias voltage (e.g., a weak voltage) to the remaining (e.g., non-selected) amplifiers of the VGA. For example, the non-selected amplifiers may receive the weak voltage to provide distortion signals with similar voltage amplitude and out of phase compared to the distortion signals of the selected amplifiers.