Switched-Inductor VCO With Decoupled GM Cell for Multi-Band Q-Factor
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Solution Overview
Problem
Conventional voltage-controlled oscillators (VCOs) face challenges in maintaining a high Q-factor across multiple frequency bands and are difficult to implement in high-speed data converters due to limitations in inductance variability and noise performance.
Innovation Solution
A voltage-controlled oscillator (VCO) with a decoupled GM cell and a switched inductor configuration, incorporating a decoupling capacitor between the LC tank and the GM cell drain, allows for variable inductance adjustment through a transformer, maintaining a high Q-factor and enabling multi-band operation in a small area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a typical VCO with cross-coupled structure is used, then the basic oscillation function is achieved, but it is difficult to provide clock for high-speed data converters and maintain high Q-factor across multiple frequency bands
Solution Approach 1:
The patent implements a switched-inductor configuration that dynamically changes the inductance value of the LC tank based on the desired frequency band. By switching between different inductor values, the VCO can operate across multiple frequency bands while maintaining optimal Q-factor for each band, resolving the contradiction between adaptability and reliability.
Solution Approach 2:
The VCO is divided into functionally independent segments: a decoupled GM cell for oscillation generation and an LC tank for frequency determination. The decoupling capacitor isolates the GM cell from the LC tank, allowing independent optimization of each segment. This segmentation enables multi-band operation through inductor switching while maintaining high Q-factor in the LC tank.
2Adaptability or versatility
If inductance is made variable to support multi-band operation, then frequency range is expanded, but device area increases
Solution Approach 1:
The patent merges the inductance switching function with the existing VCO structure by using switches that can be integrated into the LC tank circuit. The switched-inductor configuration combines multiple inductors and switches in a compact arrangement that achieves multi-band operation without proportionally increasing the device area.
Solution Approach 2:
The patent utilizes the time dimension by switching inductors at different phases of the oscillation cycle. This temporal multiplexing allows a single physical structure to provide multiple inductance values, achieving multi-band operation without requiring all inductors to be simultaneously present, thus reducing area.
3Reliability
If decoupling capacitor is added between LC tank and GM cell drain, then Q-factor is maintained high, but device complexity increases
Solution Approach 1:
The patent extracts the decoupling function by adding a capacitor specifically between the LC tank and the GM cell drain. This extracted decoupling element isolates the noise and variability from the GM cell, allowing the LC tank to maintain high Q-factor independently. The added complexity is localized to a single capacitor and its associated connections.
4Productivity
If high-speed data converter is used, then signal processing performance is improved, but jitter performance requires better VCO
Solution Approach 1:
The patent converts the potential harm of GM cell noise and variability into a benefit by using the decoupling capacitor to isolate these disturbances from the LC tank. The GM cell can operate with higher gain and faster switching (benefiting speed) while the decoupling capacitor prevents these disturbances from degrading the oscillation quality (maintaining low jitter).
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 VCO design improves jitter performance and supports multi-band operation while occupying a smaller area, suitable for high-speed data converters.
Implementation Method 1
one or more decoupling capacitors inserted between the LC tank and one or more drain nodes of the GM cells
Implementation Method 2
The LC tank includes a variable capacitor and a switched inductor connected in parallel to the variable capacitor
Implementation Method 3
The LC tank includes a variable capacitor and a switched inductor connected in parallel to the variable capacitor
Implementation Method 4
A voltage-controlled oscillator (VCO) that may be implemented in a small area using a method of changing an inductance value by switching a mutual inductance change of a transformer
Data Source
AI summary
Disclosed are a voltage-controlled oscillator and an electronic device comprising same. A voltage-controlled oscillator according to an embodiment includes an LC tank and one or more GM cells connected to the LC tank. The LC tank includes a variable capacitor and a switched inductor connected in parallel to the variable capacitor. The GM cells include one or more decoupling capacitors inserted between the LC tank and one or more drain nodes of the GM cells.