RFFE LNA Topology for Carrier Aggregation Isolation and Low Loss
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Solution Overview
Problem
Current receiver front end circuits face challenges in achieving high output-to-output isolation and low losses while handling broad frequency ranges, particularly in carrier aggregation scenarios, leading to interference, distortion, and degradation in receiver sensitivity and noise figure.
Innovation Solution
A flexible receiver front end circuit design incorporating three LNAs, including two single-mode LNAs and a split LNA, with a controller to select appropriate operational modes for different signal types, allowing efficient amplification of single-band and multi-band RF signals with low noise and high linearity, and sharing hardware to minimize die size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a passive splitter is used to handle carrier aggregation signals, then signal distribution to multiple downconverters is enabled, but output-to-output isolation is insufficient leading to interference and distortion
Solution Approach 1:
The invention divides the single LNA output into multiple separate amplification paths using individual LNAs for each downconverter. Instead of one splitter serving multiple converters, each downconverter has its own dedicated LNA, effectively segmenting the signal path to eliminate cross-interference while maintaining signal distribution capability.
Solution Approach 2:
The invention introduces mode selector switches as intermediary components between the antenna input and the LNA/downconverter chain. These switches act as mediators that can route signals through different paths (single-mode or split-mode) and provide isolation between parallel signal paths, preventing harmful interactions between carrier aggregation channels.
2Adaptability or versatility
If the LNA operates over a broad frequency band to handle multiple bands, then carrier aggregation capability is improved, but isolation between bands deteriorates causing signal degradation
Solution Approach 1:
The invention segments the broad frequency coverage into multiple narrower bands, each handled by a dedicated LNA tuned to that specific band. This allows each LNA to operate optimally within its designated frequency range while maintaining high isolation from other bands, thus achieving broad coverage without signal degradation.
Solution Approach 2:
The invention applies local quality by tuning each LNA to specific frequency characteristics appropriate for its designated band. Each LNA has optimized parameters (resonant frequency, impedance matching, gain) tailored to its specific frequency range, ensuring high performance and isolation for that local frequency region while contributing to overall broad coverage.
3Object-affected harmful factors
If multiple LNAs are used to improve isolation and reduce losses, then signal quality is improved, but device complexity and die size increase
Solution Approach 1:
The invention introduces dynamic control through mode selector switches that can reconfigure the signal path based on operational mode (single-mode or split-mode). This dynamic switching capability allows the system to use multiple LNAs when needed for carrier aggregation while maintaining a simpler single-LNA configuration for standard operation, thus managing complexity adaptively rather than statically.
Solution Approach 2:
The invention designs the LNA circuitry and switching network to serve multiple functions: single-LNA operation for standard signals, multi-LNA operation for carrier aggregation, and configurable routing for different frequency bands. This multi-functionality reduces the need for completely separate circuitry for different operating modes, thereby managing overall device complexity.
Data Source
AI summary
A receiver topology for supporting various combinations of interband carrier aggregation (CA) signals, intraband non-contiguous CA and non-CA signals having different combinations of signals aggregated therein.