Tunable RF Front End Filters for Harmonic Rejection With Fewer Switches
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Solution Overview
Problem
Current radio frequency (RF) communication systems face challenges in meeting harmonic rejection specifications, particularly with the integration of multiple bands in 5G New Radio (NR) technology, where filters require increased tunability to manage concurrent signals effectively, leading to high costs and complexity due to the need for numerous switches.
Innovation Solution
The implementation of tunable filters with mutually coupled inductors and a tunable impedance circuit, which uses switches to selectively couple capacitors, allowing for M×2N harmonic states, where M is greater than 2, reducing the number of switches required and lowering costs while enhancing harmonic tunability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple switches are used to provide tunability for managing concurrent signals in multiple bands, then harmonic rejection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple filter functions into a single tunable filter structure that can dynamically adjust its characteristics. Instead of using separate fixed filters for different bands (which would require multiple switches), the invention uses one tunable filter with adjustable resonant frequencies to serve multiple band requirements, thereby reducing the number of switches while maintaining harmonic rejection capability.
Solution Approach 2:
The patent employs dynamic tuning mechanisms that allow the filter characteristics to change adaptively based on the operating band. By making the filter tunable through dynamic adjustment of its resonant frequencies, the system can effectively manage concurrent signals across multiple bands without requiring static multiple-filter architectures that would increase switch count and complexity.
2Adaptability or versatility
If numerous switches are implemented to achieve increased tunability for multiple bands, then adaptability is improved, but die area and cost increase
Solution Approach 1:
The patent designs a universal tunable filter structure that can perform multiple filtering functions across different frequency bands. This single multi-functional filter replaces what would traditionally require multiple separate fixed filters and associated switches, thereby reducing the overall die area while maintaining adaptability to various bands through dynamic tuning rather than through multiple physical components.
3Reliability
If fixed filters are used for each band, then filtering performance is improved, but device complexity and cost increase due to need for numerous switches
Solution Approach 1:
The patent transitions from static fixed filters to a dynamic tunable filter architecture. The tunable filter can adjust its resonant frequencies and filtering characteristics dynamically to match different band requirements, eliminating the need for a complex switching network that would be required to select between multiple fixed filters. This dynamic approach maintains high filtering performance while significantly reducing switching complexity.
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 reduces the number of switches needed, decreases die area and cost, and effectively filters harmonics such as second, third, fourth, and fifth harmonics, while providing strong harmonic rejection and notch filtering capabilities, improving RF system performance without increasing complexity.
Implementation Method 1
The second tunable filter can include a first inductor, a second inductor mutually coupled to the first inductor, and a tunable capacitance circuit coupled to the first inductor
Implementation Method 2
a tunable capacitance circuit coupled to the first inductor
Data Source
AI summary
Aspects of this disclosure relate to a radio frequency system with tunable notch filtering. The radio frequency system includes a first tunable filter and a second tunable filter. The first tunable filter is coupled between an output of a power amplifier and a radio frequency switch. The second tunable filter is coupled between an antenna switch and an antenna node. The second tunable filter has a notch at a lower frequency than a notch of the first tunable filter. Related methods and wireless communication devices are also disclosed.