RF Inductor Network Segmentation for High-Frequency Harmonic Rejection
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Solution Overview
Problem
Radio frequency devices face challenges in impedance matching and filtering due to the degradation of inductors' quality factor and inductance at higher frequencies, leading to insufficient attenuation of high-order harmonics and spurious effects, as the quality factor (Q-factor) of coils decreases with increasing signal frequency.
Innovation Solution
The use of a series connection of at least two inductors instead of a single inductor to adjust the resonance frequency and reduce parasitic capacitance, allowing for improved performance at high frequencies by maintaining effective inductance while increasing the resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single inductor is used in RF filters and impedance matching networks, then the device complexity is low, but the quality factor (Q-factor) decreases and inductance value decreases abruptly above a certain critical frequency, leading to insufficient attenuation of high-order harmonics
Solution Approach 1:
The patent divides a single inductor into multiple inductors connected in series. Each inductor in the series connection has its own parasitic capacitance, but the total parasitic capacitance of the series combination is reduced compared to a single inductor with the same total inductance. This segmentation allows the filter to maintain effective Q-factor and inductance values at higher frequencies, thereby improving filter effectiveness without significantly increasing device complexity.
2Speed
If the frequency of signals applied to inductors is increased to meet modern RF requirements, then the RF circuit performance improves, but the quality factor (Q-factor) of the coil decreases and inductance value decreases abruptly above a certain critical frequency
Solution Approach 1:
By segmenting a single inductor into multiple series-connected inductors, the patent reduces the total parasitic capacitance of the inductor network. This reduction in parasitic capacitance raises the self-resonant frequency of the inductor combination, allowing the inductor to maintain stable inductance values and Q-factor at higher signal frequencies, thus enabling modern RF circuits to operate at higher frequencies without suffering from inductor performance degradation.
Solution Approach 2:
The patent changes the electrical parameters of the inductor network by connecting multiple inductors in series. This configuration changes the equivalent parasitic capacitance and self-resonant frequency of the inductor, allowing it to maintain reliable performance at higher operating frequencies. The series connection transforms the inductor's frequency response characteristics, extending its useful frequency range.
3Reliability
If discrete inductors with higher nominal inductance values are used, then the filter can effectively attenuate lower-order harmonics, but the equivalent series resonant frequency (SRF) decreases, limiting the inductor effectiveness for rejection of high-order harmonics
Solution Approach 1:
The patent segments a single high-inductance inductor into multiple lower-inductance inductors connected in series. This segmentation maintains the same total inductance value (for effective low-order harmonic attenuation) while reducing the parasitic capacitance of each individual inductor. Since SRF is inversely related to parasitic capacitance, the series connection raises the overall SRF of the inductor network, enabling effective rejection of high-order harmonics without sacrificing low-order harmonic attenuation performance.
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
This approach effectively shifts the resonance frequency to higher values, enhancing the ability to reject high-order harmonics and spurious effects, and allows for the use of cheaper inductor implementations without significant cost increases, thereby improving the performance of RF filters and impedance matching networks.
Implementation Method 1
The use of a series connection of at least two inductors instead of a single inductor to adjust the resonance frequency and reduce parasitic capacitance
Implementation Method 2
adjust the resonance frequency. The method may further be implemented by a computer program
Data Source
AI summary
Radio frequency devices and methods are provided where a network like a filter network or impedance matching network comprises a series connection of at least two inductors.