Tunable Inductor With Coupling Structures For LC-Tank Oscillators
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Solution Overview
Problem
The limited tuning range and quality factor degradation of LC-tank oscillators in wireline communication systems, particularly at higher frequencies, due to parasitic effects and frequency divider limitations, necessitate the development of a tunable inductor with improved granularity and area efficiency.
Innovation Solution
A tunable inductor design incorporating primary and secondary coils with active and passive coupling structures, including parallel and cross-coupling configurations, to vary inductance in intermediate steps, reducing the step size of switchable inductance and enhancing the tuning range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If more varactor banks are used to increase tuning range, then capacitance variation increases, but capacitive and resistive parasitics increase which degrades quality factor
Solution Approach 1:
The inductor is divided into multiple discrete coils (first coil, second coil, third coil) that can be independently switched. This segmentation allows the tuning range to be extended by combining different coil configurations while maintaining quality factor by avoiding the parasitic issues associated with multiple varactor banks.
Solution Approach 2:
Coupling structures are introduced as intermediary elements between the coils to enable magnetic coupling. These coupling structures allow for continuous inductance tuning through intermediate steps without requiring direct switching between discrete varactor banks, thereby reducing parasitic effects and maintaining higher quality factor.
2Adaptability or versatility
If switchable inductor coils are used to extend frequency range, then tuning range increases, but resistive losses of closed switches degrade quality factor
Solution Approach 1:
The patent replaces direct switch-based inductor tuning with a magnetic coupling mechanism. Instead of using switches to directly connect/disconnect inductor paths (which introduces resistive losses), the invention uses magnetically coupled coils where the coupling coefficient can be varied continuously, eliminating the need for low-side switches and their associated resistive losses.
3Reliability
If varactor impedance is considered at lower frequencies, then quality factor is dominated by inductor, but at higher frequencies varactor quality factor decreases
Solution Approach 1:
The invention implements a dynamic tuning mechanism where the inductance can be continuously adjusted through varying the magnetic coupling coefficient between coils. This dynamic capability allows the system to maintain optimal quality factor across a wide frequency range by adapting the inductance setting to match the operating frequency, preventing the quality factor degradation that occurs with fixed inductor configurations at higher frequencies.
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 design achieves a wide inductance tuning range with finer granularity and improved quality factor performance, overcoming the limitations of existing technologies by reducing resistive losses and parasitic effects, thus enabling effective operation across a broader frequency range.
Implementation Method 1
passively coupling the primary coil and at least one secondary coil and/or at least two secondary coils by magnetically coupling the primary coil and at least one secondary coil and/or at least two secondary coils
Data Source
AI summary
An inductor and method of operating the inductor by combining primary and secondary coils with passive coupling, active parallel, or active cross-coupling structures. The first includes at least one passive coupling structure having at least one coupling coil arranged between a primary coil and at least one of the secondary coils and/or between two of the secondary coils. The second includes an active coupling structure arranged between a primary coil and at least one secondary coil and/or between at least two of the secondary coils, to selectively parallel couple the primary coil and one of the secondary coils and/or at least two of the secondary coils. The third includes an active coupling structure to selectively cross couple a primary coil and at least one of the secondary coils and/or to selectively cross couple at least two of the secondary coils.