Mutually Coupled Inductor Filter for Tunable Harmonic Rejection
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Solution Overview
Problem
Existing RF communication systems face challenges in achieving strong harmonic rejection, particularly with the increasing complexity of 5G New Radio (NR) technology, which requires more tunability in filters to meet harmonic specifications across various bands.
Innovation Solution
The implementation of tunable filters with mutually coupled inductors and a tunable impedance circuit, which includes switches to adjust the effective capacitance, allowing for the tuning of harmonic rejection for multiple harmonics by changing the state of the switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional filters are used to achieve harmonic rejection, then the filter structure becomes complex with many switches, but this increases device complexity and die area
Solution Approach 1:
The patent combines multiple filter functions into a single unified structure using mutually coupled inductors. The coupled inductors create multiple notches in the frequency response simultaneously, allowing one filter structure to reject multiple harmonics that would traditionally require separate filter sections and multiple switches.
Solution Approach 2:
The mutually coupled inductor structure serves multiple functions: it provides harmonic rejection for multiple frequency bands, enables tunable notches through a single switch, and maintains signal transmission in the passband. This multi-functionality reduces the need for separate components that would otherwise be required.
2Adaptability or versatility
If more switches are added to tune multiple harmonics, then harmonic rejection improves, but cost and die area increase
Solution Approach 1:
The patent merges the tuning function for multiple harmonics into a single switch that controls the mutual coupling between inductors. This single switch can adjust the coupling coefficient to tune notches for multiple harmonics simultaneously, eliminating the need for separate switches for each harmonic that would consume additional die area.
Solution Approach 2:
The patent changes the coupling coefficient parameter between mutually coupled inductors to tune the filter characteristics. By adjusting this single parameter through a single switch, the filter can achieve different notch configurations for multiple harmonics without adding physical components, thereby reducing die area.
3Device complexity
If the filter structure is simplified to reduce complexity, then device complexity decreases, but the ability to reject multiple harmonics is compromised
Solution Approach 1:
The patent merges multiple filter functions into a compact structure using mutually coupled inductors. This structure naturally produces multiple notches in the frequency response due to the coupling between inductors, providing multi-harmonic rejection without requiring complex cascaded filter sections.
Solution Approach 2:
The patent introduces dynamic tuning capability to the simplified structure by using a switch to control the mutual coupling between inductors. This allows the filter to adaptively tune its notch positions to reject different harmonics as needed, maintaining multi-harmonic rejection capability while keeping the base structure simple.
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 solution enables the tunable filters to achieve up to 2×2N harmonic states using N switches, reducing the need for a large number of switches and thereby reducing cost and die area, while effectively rejecting harmonics across a wide range of frequencies.
Implementation Method 1
a second inductor mutually coupled with the first inductor
Data Source
AI summary
Aspects of this disclosure relate to a tunable filter with tunable rejection. The tunable filter includes mutually coupled inductors and a tunable impedance circuit electrically connected to at least one of the mutually coupled inductors. The tunable impedance circuit is configured to adjust at least two notches in a frequency response of the tunable filter by changing a state of a switch. The tunable filter can filter a radio frequency signal. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.