LC Tank Oscillator Switching for Flicker Noise Reduction
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Solution Overview
Problem
RF oscillators for wireless communication suffer from substantial flicker noise and parasitic capacitances, which reduce the tuning range and stability of frequency output in LC tank circuits.
Innovation Solution
The implementation of flicker noise reducing switches, comprising transistors and resistors, which selectively incorporate capacitance into the LC tank circuit to minimize noise and enhance frequency control, using a combination of P-type and N-type transistors with resistors to maintain transistors in the linear region and shield parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If small transistors are used to control voltages in LC tank circuit, then voltage control is improved, but flicker noise increases substantially
Solution Approach 1:
The patent introduces a buffer stage as an intermediary between the control voltage source and the LC tank circuit. This buffer stage isolates the control circuit from the resonant circuit, preventing direct interaction that causes flicker noise while maintaining effective voltage control. The buffer acts as a mediator that transfers control signals without allowing noise propagation.
Solution Approach 2:
The patent divides the oscillator circuit into separate functional stages: a control stage for voltage regulation and a resonant stage for frequency generation. By segmenting the circuit, the control functions are separated from the frequency-determining elements, allowing independent optimization of each stage without mutual interference and noise coupling.
2Measurement precision
If transistor size is reduced for voltage control, then control precision is improved, but parasitic capacitance increases
Solution Approach 1:
The buffer stage serves as an intermediary that decouples the control circuit from the resonant circuit, preventing parasitic capacitances from coupling between stages. This isolation allows small transistors to be used for precise control without their parasitic capacitances affecting the resonant frequency stability.
Solution Approach 2:
The patent extracts the control function into a separate buffer stage, removing the direct connection between control transistors and resonant elements. This extraction eliminates the harmful effect of parasitic capacitances by separating the control path from the frequency-determining path.
3Ease of operation
If switching capacitance is used for frequency tuning, then tuning range is reduced by parasitic capacitance, but frequency control is simplified
Solution Approach 1:
The buffer stage acts as an intermediary that isolates the switching capacitance control from the resonant circuit, minimizing the impact of parasitic capacitances. This allows for effective frequency tuning across a wider range by reducing the parasitic loading effect on the resonant elements.
Data Source
AI summary
Various systems and methods for implementing dynamic logic are disclosed herein. For example, some embodiments of the present invention provide LC tank circuits having an inductance and a capacitance. In addition, the circuits include a flicker noise reducing switch that is operable to selectively incorporate the capacitance such that an output of the circuit operates at a frequency based on a combination of the inductance and the capacitance.