Multi-Injection LC Tank VCOs for Low Phase Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Voltage controlled oscillators (VCOs) in communication systems suffer from phase noise, which interferes with desired signals and reduces receiver sensitivity by mixing with undesired channels, especially when the phase noise bandwidth exceeds the channel separation.
Innovation Solution
The implementation of multi-injection LC tank VCOs with parallel or series coupled transformers and phase-locked loops to combine oscillating output signals, reducing phase noise through signal-to-noise ratio improvement and using three winding transformers for compact multi-band VCOs to maintain low phase noise across various frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-injection LC tank VCO is used, then the device complexity is low, but the phase noise is high which reduces receiver sensitivity
Solution Approach 1:
The VCO is divided into multiple independent injection paths, each with its own signal source injecting into the LC tank at different points. This segmentation allows the output signal to be composed of multiple coherent signals that collectively reduce phase noise while maintaining the basic LC tank structure, thus improving receiver sensitivity without excessive complexity increase
Solution Approach 2:
Multiple output signals from different injection paths are combined through a composite output mechanism. The merging of these coherent signals results in constructive interference that enhances the signal-to-noise ratio and reduces overall phase noise, directly addressing the receiver sensitivity issue while using a unified output interface
2Reliability
If multiple VCOs are used to reduce phase noise, then the phase noise is reduced, but the device complexity and size increase
Solution Approach 1:
A single LC tank circuit serves multiple functions by accepting injections from multiple sources at different points. This multi-functional approach allows one VCO structure to achieve the phase noise reduction效果 that would traditionally require multiple separate VCOs, thereby reducing device complexity and size while maintaining improved phase noise performance
Solution Approach 2:
Multiple injection paths are nested within a single LC tank structure, with each injection path containing its own signal source and coupling mechanism. This nesting allows multiple functional elements to be integrated into one compact unit, achieving low phase noise without proportionally increasing device size or complexity
3Adaptability or versatility
If the VCO output spectrum has wide phase noise bandwidth, then the frequency tuning range is flexible, but the undesired channels interfere with desired channels at baseband
Solution Approach 1:
The injection signals are introduced at specific localized points within the LC tank circuit, creating different local impedance conditions that shape the phase noise spectrum. By carefully selecting injection points and their coupling strengths, the phase noise power spectral density is redistributed to concentrate energy within the desired channel bandwidth while suppressing out-of-band noise that would cause channel interference, thus maintaining frequency tuning flexibility
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 proposed solution significantly reduces phase noise in VCOs, enhancing signal purity and receiver sensitivity while maintaining cost, size, and power efficiency, and allows for reliable operation across multiple frequency bands.
Implementation Method 1
multi-injection LC tank VCOs with parallel or series coupled transformers to combine oscillating output signals
Implementation Method 2
phase-locked loops to combine oscillating output signals, reducing phase noise through signal-to-noise ratio improvement
Data Source
AI summary
A voltage controlled oscillator (VCO) with low phase noise and a sharp output spectrum is desirable. The present disclosure provides embodiments of LC tank VCOs that generate output signals with less phase noise compared with conventional LC tank VCOs, while at the same time limiting additional cost, size, and/or power. The embodiments of the present disclosure can be used, for example, in wired or wireless communication systems that require low-phase noise oscillator signals for performing up-conversion and/or down-conversion.