Bulk-Controlled VCO Tuning for Wideband Low-Noise PLLs
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Solution Overview
Problem
Existing phase lock loops (PLLs) face challenges in maintaining low phase noise and wide frequency coverage due to frequency drift caused by temperature and fabrication process variations, which can lead to gain variation and reduced performance characteristics.
Innovation Solution
The use of a voltage controlled oscillator (VCO) circuit comprising at least one inductor, one varactor, and two transistors with parasitic diodes, where control voltages applied to the transistors' bulk terminals adjust the oscillation frequency, allowing for dual or multi-path control to compensate for frequency drift and improve PLL performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large overlap between stitched bands is used to account for frequency drift, then frequency coverage is improved, but phase noise performance deteriorates
Solution Approach 1:
The patent divides the frequency control into multiple independent bands (first band and second band) with separate VCO circuits. Each band operates independently with its own control voltage, allowing precise frequency control within each band without requiring excessive overlap, thereby maintaining low phase noise while achieving wide frequency coverage through band switching.
Solution Approach 2:
The patent implements dynamic band switching based on the desired output frequency. The system automatically selects which band to operate in and adjusts the control voltage accordingly, enabling the PLL to adapt to different frequency requirements while maintaining optimal phase noise performance in each operating band.
2Adaptability or versatility
If stitched digital bands are used to cover wide frequency range, then frequency coverage is improved, but gain variation increases
Solution Approach 1:
The patent segments the frequency range into distinct bands, each with its own VCO circuit optimized for that band. This segmentation allows each VCO to maintain consistent gain characteristics within its operating range, avoiding the gain variation that occurs when a single VCO attempts to cover the entire frequency range.
Solution Approach 2:
The patent creates multiple copies of the VCO circuit, each tailored for a specific frequency band. These copied circuits are identical in structure but operate in different frequency ranges, ensuring consistent performance characteristics across all bands without the gain variation inherent in single-wide-band designs.
3Device complexity
If one large band is used for frequency control, then device complexity is reduced, but frequency drift compensation capability deteriorates
Solution Approach 1:
The patent divides the frequency control into multiple bands with separate VCO circuits, each optimized for its specific range. This segmentation enables better frequency drift compensation within each band while maintaining manageable device complexity through modular architecture and systematic band switching.
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 enhances the PLL's ability to maintain stable frequency control and reduce phase noise across varying conditions, improving the tuning range and phase noise performance.
Implementation Method 1
the first transistor has a first bulk terminal and a first parasitic diode disposed between the first bulk terminal and the first transistor; wherein the second transistor has a second bulk terminal and a second parasitic diode disposed between the second bulk terminal and the second transistor; wherein application of a first control voltage to the first bulk terminal, application of a second control voltage to the second bulk terminal, or application of first and second control voltages to the first and second bulk terminals, respectively, is effective to change the oscillation frequency of the VCO
Data Source
AI summary
An electrical circuit includes: at least one inductor, at least one varactor, and at least two transistors, all of which electrically arranged to form a voltage controlled oscillator (VCO) having an oscillation frequency; wherein the at least two transistors includes a first transistor and a second transistor; wherein the first transistor has a first bulk terminal and a first parasitic diode disposed between the first bulk terminal and the first transistor; wherein the second transistor has a second bulk terminal and a second parasitic diode disposed between the second bulk terminal and the second transistor; wherein application of a first control voltage to the first bulk terminal, application of a second control voltage to the second bulk terminal, or application of first and second control voltages to the first and second bulk terminals, respectively, is effective to change the oscillation frequency of the VCO.