VCO Resonant Circuit Layout for Flicker Phase Noise Reduction
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Solution Overview
Problem
Modern communication systems face challenges in reducing phase noise, particularly flicker noise, in voltage-controlled oscillators (VCOs) used in wireless communication networks, which affects signal quality and stability.
Innovation Solution
The introduction of a common mode resonant high impedance at two times the oscillating frequency in the VCO's resonant circuit, achieved by coupling a variable capacitive element between the inductor's center tap and a reference voltage, reduces flicker noise by shifting the flicker corner frequency from hundreds of kHz to tens of kHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional VCO resonant circuits are used, then the circuit structure is simple, but phase noise (flicker noise) is high
Solution Approach 1:
A common-mode resonant circuit is introduced as an intermediary element coupled to the differential resonant circuit. This common-mode resonant circuit acts as a mediator that generates high impedance at twice the oscillation frequency, thereby suppressing flicker noise without requiring fundamental changes to the existing differential VCO structure.
Solution Approach 2:
The patent modifies the resonant circuit parameters by adding a common-mode resonant circuit with specific inductance and capacitance values. This common-mode resonant circuit is designed to resonate at twice the oscillation frequency, creating high impedance that filters flicker noise. The parameter optimization includes selecting L_cm and C_cm values that achieve the desired resonant frequency while maintaining circuit simplicity.
2Object-affected harmful factors
If flicker noise is reduced by traditional methods, then phase noise improves, but power consumption increases
Solution Approach 1:
The patent converts the typically harmful even harmonics and common-mode signals into a beneficial filtering mechanism. By allowing the common-mode resonant circuit to naturally resonate at twice the oscillation frequency, it creates high impedance that inadvertently filters flicker noise. This approach uses the circuit's natural behavior rather than fighting against it, reducing power consumption compared to active filtering methods.
3Measurement precision
If the oscillating frequency is increased, then signal quality improves, but flicker corner frequency remains high
Solution Approach 1:
The patent addresses the flicker corner frequency issue by introducing a new dimension to the frequency domain analysis. The common-mode resonant circuit creates high impedance at twice the oscillation frequency, effectively adding a frequency transformation dimension. This allows the VCO to achieve low flicker corner frequency regardless of the oscillation frequency, decoupling signal quality from flicker noise performance.
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 effectively minimizes phase noise in VCOs, enhancing signal-to-noise ratio and stability by creating a common mode resonant high impedance, thereby improving the performance of VCOs in wireless communication systems.
Implementation Method 1
generating a common mode resonant high impedance at two times an oscillating frequency of the oscillating signal
Data Source
AI summary
Certain aspects of the present disclosure provide methods and apparatus for reducing phase noise in voltage-controlled oscillators (VCOs). One example VCO generally includes a first resonant circuit comprising an inductor and a first variable capacitive element coupled in parallel with the inductor; and a second variable capacitive element coupled to a center tap of the inductor and further coupled to a reference voltage, wherein the center tap of the inductor is further coupled to a voltage source.