Predistorter Variable Capacitance for Amplifier Linearity
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Solution Overview
Problem
Amplifiers in communication systems face challenges in compensating for linearity due to the difficulty in simultaneously managing amplitude and phase distortions, which affects communication distance, quality, and standby time, and can result in amplifiers having large volumes, low gain, and narrow bandwidth.
Innovation Solution
A predistorter is used to compensate for the linearity of amplifiers by incorporating a capacitor and an impedance conversion circuit, which provides variable capacitance and includes a bipolar junction transistor (BJT) or field-effect transistor (FET) to adjust impedance, thereby addressing distortion issues without significantly altering the amplifier's original design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional amplifiers are used to amplify signals, then communication distance and quality are improved, but amplitude and phase distortions increase due to non-linear characteristics
Solution Approach 1:
The predistorter applies preliminary distortion to the input signal that is equal in magnitude but opposite in sign to the amplifier's non-linear distortion. This pre-distortion compensates for the amplifier's non-linearity, so that when the signal passes through the amplifier, the distortions cancel each other out, resulting in a linearized output signal with reduced amplitude and phase distortion.
Solution Approach 2:
The invention converts the harmful non-linear distortion characteristics of the amplifier into a beneficial property by deliberately introducing opposite distortion through the predistorter. The amplifier's inherent non-linearity, which was previously harmful, becomes predictable and可利用 for compensation purposes, transforming the harm into a benefit for achieving linear amplification.
2Object-generated harmful factors
If amplifier parameters are adjusted to reduce distortion, then linearity is improved, but amplifier volume increases and bandwidth decreases
Solution Approach 1:
The invention divides the amplifier system into two separate functional modules: a predistorter module that handles non-linear compensation and an amplifier module that provides power amplification. This segmentation allows each module to be optimized independently - the predistorter can be made compact with minimal impact on overall volume, while the amplifier maintains its required power output capabilities without needing excessive size reduction that would compromise performance.
Solution Approach 2:
The predistorter acts as an intermediary device between the signal source and the power amplifier. It prepares the signal by applying pre-distortion before the signal enters the amplifier, thereby eliminating the need for the amplifier itself to be redesigned or resized for linearity purposes. This intermediary approach allows the amplifier to maintain its original compact design while still achieving linear operation through the predistorter's compensation.
3Object-generated harmful factors
If amplifier parameters are adjusted to reduce distortion, then linearity is improved, but gain and bandwidth are reduced
Solution Approach 1:
The system is segmented into a predistorter for linearity control and a power amplifier for gain and bandwidth performance. This segmentation allows the power amplifier to operate at its optimal gain and bandwidth settings without compromise, while the predistorter handles the linearity correction separately, preventing any trade-off between distortion reduction and performance maintenance.
Solution Approach 2:
The predistorter serves as an intermediary that corrects signal distortion before the signal reaches the power amplifier. This allows the power amplifier to maintain its full gain and bandwidth capabilities without needing to reduce these parameters for linearity purposes, as the distortion compensation is handled independently by the predistorter in the signal path.
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
The predistorter effectively compensates for amplitude and phase distortions, reducing the need for large amplifier volumes and maintaining gain and bandwidth, thus improving the overall performance of communication systems.
Implementation Method 1
The predistorter comprises a first capacitor, a first bias input circuit and an impedance conversion circuit. The first capacitor has a first end coupled to a first node of the amplifier. The impedance conversion circuit is configured to perform an impedance conversion to provide a variable capacitance.
Data Source
AI summary
A predistorter has a first capacitor and an impedance conversion circuit. A first end of the first capacitor is coupled to a first node of the amplifier. The impedance conversion circuit is used to perform an impedance conversion to provide a variable capacitance. The impedance conversion circuit has a first bias input circuit and a bipolar junction transistor (BJT). The first bias input circuit is used to receive a first input bias. A base of the BJT is coupled to an output end of the first bias input circuit and a second end of the first capacitor, a collector of the BJT is floating, and an emitter of the BJT is coupled to a second node of the amplifier.