Configurable Feedback LNA Filtering for Low-Loss Multi-Band RF Front Ends
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Solution Overview
Problem
Existing RF frontend architectures face a trade-off between cost and performance, with traditional designs either reducing cost by using a combined amplification path that degrades noise figure due to insertion loss or increasing cost and size by using dedicated amplification paths for each frequency band, and both require specific band filters that become costly and complex with emerging communication standards.
Innovation Solution
The integration of a filter circuit with an L-C tank configured for resonant frequency response within a low noise amplifier (LNA) circuit, which provides a narrowband frequency response and relaxes performance requirements of band filters, allowing for configurable feedback filtering to support multiple frequency bands without the need for multiple dedicated amplification paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a combined amplification path is used to reduce cost, then the number of components is reduced, but insertion loss increases and noise figure degrades
Solution Approach 1:
The patent combines the band filter and LNA into a single integrated circuit, merging previously separate components. This integration eliminates the need for external band filters while maintaining selective amplification capabilities across multiple frequency bands, thereby reducing component count and cost without sacrificing performance
Solution Approach 2:
The integrated LNA circuit is designed to handle multiple frequency bands (e.g., LTE bands 3, 7, 20 and 5G bands n78, n79) within a single device. The circuit provides universal functionality across different communication standards and frequency ranges, eliminating the need for separate dedicated amplification paths for each band
2Reliability
If dedicated amplification paths are used for each frequency band to improve performance, then noise figure improves, but cost and die area increase
Solution Approach 1:
Instead of using separate dedicated amplification paths for each frequency band, the patent merges multiple band handling capabilities into a single LNA circuit. The integrated design achieves comparable noise figure performance through internal filtering and selective amplification mechanisms, thereby reducing cost and die area while maintaining reliability
3Reliability
If dedicated amplification paths are used for each frequency band to improve performance, then noise figure improves, but die area increases
Solution Approach 1:
The patent integrates the band filter and LNA into a single compact circuit, significantly reducing the die area compared to having separate dedicated amplification paths for each frequency band. The merged design achieves efficient space utilization while maintaining noise figure performance through careful circuit architecture design
Solution Approach 2:
The integrated LNA circuit provides universal support for multiple frequency bands (LTE bands 3, 7, 20 and 5G bands n78, n79) within a single compact footprint. This multi-functional design eliminates the need for multiple separate amplification paths, thereby reducing overall die area while maintaining noise figure performance across all supported bands
4Measurement precision
If specific band filters are used for each frequency band, then frequency selectivity is improved, but filter complexity and cost increase with emerging communication standards
Solution Approach 1:
The patent merges the band filter functionality directly into the LNA circuit, creating an integrated filter-LNA device. This integration eliminates the need for separate external band filters and reduces filter complexity by implementing filtering functions within the amplifier circuit itself, while maintaining frequency selectivity for multiple LTE and 5G bands
Solution Approach 2:
The integrated LNA circuit provides universal frequency selectivity across multiple communication standards (LTE bands 3, 7, 20 and 5G bands n78, n79) through internal filtering mechanisms. This multi-functional design eliminates the need for separate dedicated filters for each band, thereby reducing overall filter complexity and cost while maintaining precise frequency selection capabilities
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 insertion loss and noise figure while maintaining performance across different frequency bands, offering improved linearity and reduced physical size and cost by integrating filtering functionality into the LNA, thus supporting emerging communication standards with increased flexibility.
Implementation Method 1
the L-C tank is configured to resonate at a resonant frequency to provide a narrowband frequency response of the LNA circuit
Data Source
AI summary
A low noise amplifier (LNA) with configurable feedback that includes a filter circuit for improved stability is presented. The filter circuit includes an L-C tank. The filter circuit further includes a resistor in parallel with the L-C tank. The filter circuit is tunable/adjustable/programmable. The filter circuit further includes a capacitor selectively arranged in parallel with the L-C tank. The filter circuit is coupled to an input of the LNA via a series resistor. The filter circuit is coupled between the input and an output of the LNA via one or more switches. The LNA includes a first stage with a common-source transistor and a common-gate transistor. The LNA further includes a wideband feedback circuit coupled between the input and output of the first stage. The LNA includes a source-follower circuit. The source follower circuit is configurable as a second stage, or a feedback circuit, coupled to the filter circuit.