Varainductor with Ground and Floating Planes for High Frequency PLLs
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Solution Overview
Problem
Phase locked loops (PLLs) face challenges in high-frequency applications due to the decrease in Q factor of metal-oxide-semiconductor (MOS) varactors, which can prevent oscillation initiation and synchronization, especially as frequency increases.
Innovation Solution
A varainductor design that includes a substrate with a signal line, floating planes, and ground planes, where switches adjust the electrical connectivity between the ground and floating planes to enhance the Q factor and tuning range, using a dielectric material for insulation and optimizing dimensions and switch control signals to maintain low resistance and increase inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If MOS varactor is used in VCO for high frequency applications, then frequency range is extended, but Q factor decreases preventing oscillation initiation
Solution Approach 1:
The inductor is segmented into multiple sections with alternating ground planes and floating planes. This segmentation creates multiple resonant paths and reduces energy loss, thereby maintaining high Q factor at millimeter-wave frequencies while enabling extended frequency range operation.
Solution Approach 2:
Floating planes are introduced as intermediary elements between the signal line and ground planes. These floating planes act as resonant structures that enhance the inductor's Q factor by reducing parasitic losses, enabling reliable oscillation initiation at high frequencies where conventional inductors fail.
2Device complexity
If conventional inductor design is used, then structure is simple, but Q factor is insufficient for high frequency operation
Solution Approach 1:
The inductor design transitions from a planar two-dimensional structure to a three-dimensional multi-layer configuration with alternating ground and floating planes at different heights. This dimensional enhancement creates additional resonant modes and reduces parasitic effects, achieving high Q factor necessary for millimeter-wave applications.
Solution Approach 2:
The inductor employs a composite structure combining conductive signal lines, ground planes, and floating planes separated by dielectric layers. This composite architecture integrates multiple functional elements that work together to maintain low loss and high Q factor at high frequencies while managing parasitic capacitance and inductance.
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 varainductor design improves the Q factor and tuning range, enabling successful oscillation initiation and frequency synchronization in high-frequency applications, enhancing the performance of PLLs in millimeter-wave regions.
Implementation Method 1
A varainductor design that includes a substrate with a signal line, floating planes, and ground planes, where switches adjust the electrical connectivity between the ground and floating planes
Implementation Method 2
A varactor is a diode having a variable capacitance. In some instances, a metal-oxide-semiconductor (MOS) varactor is used in the VCO.
Implementation Method 3
A transmission-line-based inductor is also included in the VCO for high frequency applications, e.g., millimeter-wave region
Data Source
AI summary
A method using a phase locked loop (PLL) includes receiving a reference frequency. The method further includes generating a control signal based on the reference frequency. The method further includes adjusting an output signal based on the control signal. Adjusting the output signal includes operating a plurality of switches in response to the control signal, wherein operating the plurality of switches comprises selectively electrically connecting a first ground plane to a first floating plane, wherein the first floating plane is between the first ground plane and the signal line, and the first floating plane is a same distance from a substrate as the first ground plane.