Tapped-Inductor Oscillator Layout for Low-Noise, Low-Power VCOs
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Solution Overview
Problem
Designing voltage-controlled oscillators (VCOs) that meet the demands for smaller size, lower cost, and higher frequency while maintaining noise performance and power requirements is challenging, especially as semiconductor devices shrink and RF frequencies increase, leading to decreased supply voltages and inductor sizes, which result in lower quality factors and increased thermal noise.
Innovation Solution
The proposed oscillator circuit incorporates a tapped inductor with multiple conductive segments forming an 8-shaped physical loop, coupled with transconductance amplifiers, allowing for reduced phase noise and improved performance by offsetting induced currents and adjusting terminal positions to optimize power consumption and output amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the inductor size is decreased to reduce the oscillator circuit size, then the area occupied by the inductor is reduced, but the quality factor of the inductor decreases and thermal noise increases
Solution Approach 1:
The inductor is divided into multiple segments (first inductor segment, second inductor segment, third inductor segment) connected in series. This segmentation allows the total inductance to be achieved with smaller individual segments, reducing the overall area while maintaining or improving the quality factor through optimized segment configuration and reduced parasitic effects.
Solution Approach 2:
The patent employs multi-layer interconnection structures where inductor segments are distributed across different metal layers (first metal layer, second metal layer, third metal layer). This three-dimensional arrangement reduces the planar area occupation while maintaining the electrical performance and quality factor of the inductor.
2Use of energy by stationary object
If the supply voltage is decreased to meet power requirements, then the power consumption is reduced, but the signal power and noise performance deteriorate
Solution Approach 1:
The patent optimizes the inductor segment configuration and capacitance values to achieve resonant frequency and impedance matching that maximizes signal power at lower supply voltages. By adjusting the electrical parameters of the segmented inductor and associated capacitors, the circuit maintains noise performance while operating at reduced power consumption.
3Speed
If the inductor size is decreased to increase the operating frequency, then the frequency response is improved, but the quality factor decreases and thermal noise increases
Solution Approach 1:
The segmented inductor structure enables higher operating frequencies by reducing the parasitic capacitance and inductance of individual segments. The series connection of multiple smaller inductor segments achieves the required total inductance with reduced parasitic effects, maintaining quality factor at higher frequencies.
Solution Approach 2:
The multi-layer configuration of inductor segments allows for optimized current paths and reduced parasitic effects in the vertical dimension, enabling higher frequency operation while maintaining quality factor through improved electrical characteristics.
Data Source
AI summary
An oscillator circuit includes an amplifier including a first transconductance amplifier and a second transconductance amplifier; and a resonator including a capacitor element and an inductor element. The capacitor element includes a first capacitor and a second capacitor, the inductor element includes a tapped inductor, the tapped inductor includes a first segment of inductor and a second segment of inductor, and the first segment of inductor and the second segment of inductor are coupled using the first capacitor. The first segment of inductor includes a first terminal and a second terminal coupled to an input terminal and an output terminal of the first transconductance amplifier respectively. The second segment of inductor includes a third terminal and a fourth terminal coupled to an input terminal and an output terminal of the second transconductance amplifier, respectively.