Tapped Inductor VCO Layout for High-Q Low-Noise Oscillation
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Solution Overview
Problem
As RF frequencies increase and supply voltages decrease, traditional voltage controlled oscillators (VCOs) face challenges in meeting system noise and power requirements while maintaining smaller size, lower cost, and higher frequency performance, due to the decrease in inductor size leading to reduced quality factor and increased thermal noise.
Innovation Solution
A voltage controlled oscillator design employing a tapped inductor with a novel topology and layout, where the inductor is divided into parts with electrical connections forming loops within an interior space, allowing for higher energy storage and reduced noise performance, enabling higher Q at higher frequencies and lower power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the inductor size is decreased to meet smaller size requirements and avoid hot carrier injection at lower supply voltages, then the quality factor decreases and thermal noise increases
Solution Approach 1:
The patent employs nested inductor structures where smaller inductor loops are placed within the interior space of larger inductor loops. This nesting arrangement allows multiple inductors to share the same physical space, effectively increasing the total inductance value without proportionally increasing the chip area. The nested configuration maintains higher quality factors by preserving larger effective inductor sizes while meeting the compact size requirements for modern RF circuits operating at lower supply voltages.
2Volume of moving object
If the inductor size is decreased to meet smaller size requirements, then the energy storage capability decreases leading to increased noise performance
Solution Approach 1:
The nested inductor configuration increases the total energy storage capability by combining multiple inductors in series within the same footprint. The energy stored in an LC tank is proportional to the inductance value, and the nested structure achieves higher effective inductance without increasing the physical area. This maintains sufficient energy storage to suppress thermal noise while meeting compact size requirements for modern RF integrated circuits.
3Reliability
If the supply voltage is decreased to avoid hot carrier injection, then the signal power decreases requiring larger inductors which increases device size
Solution Approach 1:
The nested inductor structure provides higher effective inductance values within the same chip area, compensating for the reduced signal power resulting from lower supply voltages. By achieving larger effective L values through nesting rather than physical size increases, the design maintains adequate signal power levels while keeping device dimensions small and avoiding hot carrier injection effects in the amplifier transistors.
Data Source
AI summary
A voltage controlled oscillator includes a resonator and an amplifier. The resonator includes a capacitive element and an inductive element. The inductive element has a plurality of conductive segments forming a physical loop. The inductive element has electrical connections on the physical loop to the plurality of conductive segments forming at least one electrical loop disposed within an interior space formed by the physical loop. The amplifier has an input and an output, the input coupled to a first conductive segment forming a first impedance and the output coupled to a second conductive segment forming a second impedance.