Tunable RF Notch Filter With Coupled Inductors for Harmonic Rejection
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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 the number of mutual couplings, reducing the number of switches required and lowering costs while enhancing harmonic tunability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filters with strong harmonic rejection are implemented in RF communication systems, then harmonic rejection capability is improved, but device complexity and cost increase due to the need for numerous switches to achieve increased tunability
Solution Approach 1:
The patent combines multiple filter functions into a single tunable filter structure that can simultaneously or sequentially provide harmonic rejection for multiple frequency bands. The merged filter uses a shared switching network controlled by band select signals to achieve what would traditionally require separate filters and switches for each band, thereby reducing the total number of switches while maintaining strong harmonic rejection capability across multiple bands.
Solution Approach 2:
The tunable filter is designed to perform multiple functions: it can selectively reject harmonics for different frequency bands (first band, second band, etc.) using the same physical filter structure. By making the filter universal across multiple bands through tunable elements controlled by band select signals, the system eliminates the need for dedicated switches for each band's harmonic rejection, reducing overall device complexity.
2Reliability
If filters with strong harmonic rejection are implemented in RF communication systems, then harmonic rejection capability is improved, but cost increases due to the need for numerous switches
Solution Approach 1:
The patent merges multiple band-specific filter functions into a single tunable filter structure that can be controlled by band select signals. This consolidation reduces the total number of switches required in the system, and since switches are typically among the most expensive components in RF filter designs, the manufacturing cost is reduced while maintaining strong harmonic rejection capability across multiple frequency bands.
Solution Approach 2:
The filter design achieves multi-functionality by enabling a single filter structure to provide harmonic rejection for multiple frequency bands through tunable elements. This universality eliminates the need for separate dedicated filters and switches for each band, thereby reducing component count and manufacturing cost while preserving the required harmonic rejection performance.
3Adaptability or versatility
If increased tunability is provided to manage concurrent signals in multiple bands, then signal management capability is improved, but the number of switches required increases leading to higher complexity
Solution Approach 1:
The filter employs dynamic tuning capabilities where band select signals control tunable elements (such as variable capacitors or inductors) to adjust the filter's resonant frequency and rejection characteristics in real-time. This dynamic adaptability allows the same filter structure to be tuned for different frequency bands and harmonic rejection requirements, eliminating the need for static, band-specific filter paths and reducing the overall number of switches required.
Solution Approach 2:
The tunable filter structure is designed to be universal across multiple frequency bands, using band select signals to configure the same physical components for different operating conditions. This multi-functional design allows a single filter to replace what would traditionally require multiple dedicated filters and their associated switch networks, thereby maintaining high adaptability while reducing device 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, thus addressing the complexity and cost issues in RF communication systems.
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 second inductor mutually coupled to the first inductor
Implementation Method 3
a second inductor mutually 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 includes mutually coupled inductors and a tunable impedance circuit electrically connected to at least one of the mutually coupled inductors. The second tunable filter is coupled between an antenna switch and an antenna node. Related methods and wireless communication devices are also disclosed.