Varactor Capacitance Compensation for Input-Dependent Distortion
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Solution Overview
Problem
High precision radio-frequency and analog precision front-end circuits face limitations due to input-dependent capacitance, which causes distortion and is not effectively mitigated by minimizing input structures, especially in applications requiring 100 dB or higher dynamic range.
Innovation Solution
A capacitance compensation circuit using a combination of switches, varactors, and blocking capacitors with adjustable biasing circuits to precisely compensate for linear and parabolic voltage-dependent components of input capacitors, allowing for tunable capacitance to linearize the input node's capacitance characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If input structures are minimized to mitigate distortion effects, then distortion is reduced, but the solution is not practical for all applications and does not substantially eliminate distortion
Solution Approach 1:
The patent converts the harmful voltage-dependent capacitance effect into a beneficial compensation mechanism by using varactors to generate an equal and opposite capacitance variation, thereby linearizing the total input capacitance while maintaining necessary input structures
Solution Approach 2:
The patent introduces varactor-based compensation circuits as intermediary elements that mediate between the input signal and the voltage-dependent capacitance, providing a tunable compensation mechanism that works across different application scenarios
2Manufacturing precision
If varactors are used to compensate voltage-dependent capacitance, then capacitance linearization is achieved, but circuit complexity increases
Solution Approach 1:
The patent uses tunable varactor circuits that can be dynamically adjusted to match different input capacitance characteristics, providing precise linearization while allowing the circuit to adapt to different operating conditions rather than requiring fixed complex structures
Solution Approach 2:
The patent changes the electrical parameters of the compensation circuit by adjusting varactor bias voltages to match the specific voltage-dependent characteristics of different input capacitors, achieving precise compensation without requiring complex fixed structures for each case
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 solution effectively reduces or eliminates harmonic distortion by synthesizing a complementary capacitance characteristic, enhancing the spurious-free dynamic range and integral non-linearity of the system, thereby improving the overall performance of high precision circuits.
Implementation Method 1
compensating a polynomial voltage-dependent characteristic of capacitance
Implementation Method 2
plurality of blocking capacitors coupled between the plurality of switches and the plurality of varactors
Data Source
AI summary
A capacitance compensation circuit includes an input terminal, a plurality of switches coupled to the input terminal, a plurality of varactors coupled to the plurality of switches, and a plurality of blocking capacitors coupled between the plurality of switches and the plurality of varactors. The capacitance compensation circuit further includes a plurality of adjustable biasing circuits to precisely compensate for linear and parabolic voltage dependent components of an input or other capacitor. Two such circuits can be used with a single input terminal to compensate for both increasing and decreasing voltage dependent characteristics of a target capacitor.