Concentric Decoupled VCO Coils for Low-Noise Area-Efficient PLLs
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Solution Overview
Problem
High performance voltage controlled oscillators (VCOs) require large areas due to the presence of inductors, leading to area penalties and asymmetry, which affects noise performance, especially in multi-band communication standards where multiple VCOs are needed within a single phase locked loop (PLL).
Innovation Solution
A novel architecture for VCOs with a concentrically arranged and magnetically decoupled primary and secondary inductive coils, where the secondary coil is symmetrically positioned with respect to the primary coil, reducing area usage and improving flicker noise performance by localizing electromagnetic simulations and reducing secondary coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inductors are used for frequency generation in high performance VCOs, then phase noise performance is improved, but area occupancy increases significantly
Solution Approach 1:
The patent combines the VCO tank inductor and the filter inductor into a single shared physical structure. The inductor serves dual purposes: as part of the resonant tank circuit for frequency generation and as part of the filter circuit for noise filtering. This merging eliminates the need for separate inductor implementations, thereby reducing total area while maintaining the phase noise filtering benefits.
Solution Approach 2:
The inductor is designed to perform multiple functions simultaneously: it acts as the resonant element in the VCO tank circuit and as the filtering element in the noise filter circuit. This multi-functionality allows a single inductor structure to replace what would traditionally require two separate inductors, achieving area reduction without compromising performance.
2Adaptability or versatility
If multiple VCOs are implemented within a single PLL for multi-band communication, then adaptability is improved, but area occupancy increases
Solution Approach 1:
The shared inductor structure enables a single VCO core to support multiple frequency bands by reconfiguring the capacitive elements while maintaining the same inductive component. This universal design allows the same physical structure to serve multiple communication standards and frequency ranges, reducing the need for separate VCO implementations for each band.
3Device complexity
If traditional separate inductor arrangements are used for VCO tank and filter circuits, then design simplicity is maintained, but asymmetry increases affecting noise performance
Solution Approach 1:
The patent intentionally introduces symmetry into the inductor design to eliminate asymmetry-induced noise. By designing the shared inductor with symmetric geometric patterns and balanced winding structures, the circuit achieves better common-mode rejection and reduced flicker noise upconversion, while the overall design remains relatively simple through the use of a single shared component rather than multiple asymmetric components.
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 arrangement achieves area savings, near-perfect symmetry, and enhanced flicker noise performance, improving phase noise by reducing the time active devices spend in the triode region and allowing higher voltage swings, while minimizing area wastage and asymmetry issues.
Implementation Method 1
the primary inductive coil associated with the VCO tuning circuit and the secondary inductive coil associated with the filter circuit are magnetically decoupled with respect to one another
Data Source
AI summary
A voltage controlled oscillator (VCO) circuit is disclosed. The VCO circuit comprises a VCO tuning circuit comprising a primary inductive coil. In some embodiments, the VCO tuning circuit is configured to generate a VCO output signal at a first resonance frequency. The VCO circuit further comprises a filter circuit comprising a secondary inductive coil. In some embodiments, the filter circuit is configured to resonate at a second, different, resonance frequency, in order to filter a noise associated with the VCO tuning circuit. In some embodiments, the primary inductive coil associated with the VCO tuning circuit and the secondary inductive coil associated with the filter circuit are concentrically arranged with respect to one another. Further, in some embodiments, the primary inductive coil associated with the VCO tuning circuit and the secondary inductive coil associated with the filter circuit are magnetically decoupled with respect to one another.