Distributed Active Transformer VCO Layout for Lower Phase Noise
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Solution Overview
Problem
Existing voltage controlled oscillators (VCOs) face challenges in reducing phase noise, particularly in wireless communications and other fields, where high phase noise limits frequency spectral efficiency and is difficult to address using silicon-based semiconductor technology.
Innovation Solution
A voltage controlled oscillator is designed with multiple oscillator cores magnetically coupled in series through a common inductive loop, providing a virtual AC ground and reducing resistance, which effectively decreases phase noise by increasing the amplitude of oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple oscillator cores are coupled in parallel, then phase noise is reduced, but device complexity and layout difficulty increase significantly
Solution Approach 1:
The oscillator is divided into multiple independent oscillator cores (first, second, third, and fourth oscillator cores) that are magnetically coupled in series through a common inductive loop. Each core operates semi-independently, allowing phase noise reduction through multiple cores while avoiding the layout complexity of parallel coupling. The series magnetic coupling architecture segments the signal path while maintaining compact integration.
Solution Approach 2:
The patent transitions from planar parallel coupling to three-dimensional magnetic coupling through a common inductive loop. The oscillator cores are arranged to couple magnetically through the loop, utilizing the vertical/dimensional aspect of magnetic field coupling rather than planar parallel connection. This dimensional change enables phase noise reduction without the layout complexity of parallel coupling.
2Ease of manufacture
If conventional VCO architectures are used, then circuit implementation is straightforward, but phase noise remains high and limits frequency spectral efficiency
Solution Approach 1:
Multiple oscillator cores are merged through magnetic coupling to a common inductive loop, combining their oscillation signals to reduce phase noise. The common inductive loop serves as a merging point for the magnetic fields of all four oscillator cores, achieving phase noise reduction while maintaining a unified circuit architecture that is manufacturable in silicon-based technology.
Solution Approach 2:
The patent changes the coupling parameter from electrical parallel connection to magnetic series coupling. This parameter change in the coupling mechanism allows the oscillator to achieve lower phase noise through the constructive combination of multiple cores' magnetic fields, while maintaining ease of manufacture through standard silicon-based semiconductor fabrication processes.
3Reliability
If oscillator cores are magnetically coupled in series through a common inductive loop, then phase noise is reduced by 6-9 dB, but the circuit requires virtual AC ground configuration
Solution Approach 1:
The second end of each inductive portion is coupled to a common voltage supply rail, which automatically provides the virtual AC ground reference needed for the magnetic coupling to function. This self-service configuration eliminates the need for additional active components or complex biasing circuits, as the power supply rail inherently serves as the AC ground reference for all oscillator cores.
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 configuration achieves a significant reduction in phase noise, demonstrated by a 6 dB to 9 dB gain in phase noise reduction, while also simplifying the circuit layout and eliminating the need for DC decoupling capacitors.
Implementation Method 1
the oscillator cores are coupled in series by electromagnetic induction, also known as inductive coupling, for example via a common inductive loop
Implementation Method 2
a second end of each of the first and second conductive portions of each of the oscillator cores being coupled to a same voltage supply rail, thereby providing a virtual AC ground at the second end of each of the first and second inductive portions
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present disclosure relates to a voltage controlled oscillator comprising a plurality of oscillator cores (C1 to C4) magnetically coupled in series.