Multi-Input LNA Bypass Paths for Wide-Band Impedance Matching
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Solution Overview
Problem
Conventional LNA architectures face challenges in achieving simultaneous optimization of gain, noise figure, linearity, and impedance matching, particularly in wide-band RF systems, especially for newer frequency bands like 5G mobile network bands and millimeter wave ranges, due to limitations in bandwidth and impedance matching performance.
Innovation Solution
The development of new multi-input LNA architectures that reconfigure bypass path routes to achieve wide-band bypass matching, allowing for dedicated paths to RF output and optional bypassing of impedance matching networks and input inductors, enabling improved passive mode negative gain performance across a range of frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a traditional LNA architecture with series input matching inductor is used, then input impedance matching is improved, but bandwidth is limited
Solution Approach 1:
The LNA is divided into multiple independent LNA circuits operating in parallel, each optimized for specific frequency bands. This segmentation allows each circuit to maintain narrowband impedance matching while the collective system achieves wideband operation across multiple bands including 5G NR bands.
Solution Approach 2:
The multi-input LNA architecture provides universal coverage across multiple frequency bands and channels by enabling selective activation of different LNA circuits based on the operating band. The system can handle both wideband signals and narrowband signals through appropriate circuit selection and combination.
2Power
If high gain is achieved in LNA, then signal amplification is improved, but noise figure deteriorates
Solution Approach 1:
Different LNA circuits are optimized with different quality characteristics suited for their specific operating bands. Each circuit can be independently tuned to achieve optimal noise figure and gain tradeoffs for its target frequency range, allowing local optimization rather than global compromise.
3Reliability
If linearity is improved in LNA, then signal fidelity is enhanced, but gain in low-gain modes deteriorates
Solution Approach 1:
The system dynamically selects and switches between different LNA circuits based on operating conditions, signal strength, and required gain mode. This dynamic reconfiguration allows optimization of linearity for strong signals while maintaining adequate gain for weak signals by selecting appropriate circuits.
4Manufacturing precision
If impedance matching is optimized for specific bands, then performance in those bands is improved, but performance in other frequency bands deteriorates
Solution Approach 1:
The overall LNA system is segmented into multiple specialized LNA circuits, each with impedance matching optimized for specific frequency bands. This allows precise matching in each band while the aggregate system covers a wide frequency range including current and future 5G NR bands.
Data Source
AI summary
New multi-input LNA architectures with improved passive mode negative gain performance that reconfigure the bypass path routes to achieve wide-band bypass matching and make bypass matching for lower frequency bands possible to achieve desired gain specifications. In a first embodiment, improved wide-band performance is provided by a bypass path that optionally does not pass through an impedance matching network and thus has a dedicated path to RFOUT. In a second embodiment, improved wide-band performance is provided by a bypass path that does not pass through an input inductor. In a third embodiment, improved wide-band performance is provided by a bypass path that has a first portion that optionally does not pass through an impedance matching network, and a second portion that does not pass through an input inductor. In a fourth embodiment, improved wide-band performance is provided by selectively disabling a load inductor in some modes of operation.