Reconfigurable LNA Input Matching for Wideband RF Receivers
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Solution Overview
Problem
Low noise amplifiers (LNAs) face challenges in tuning and matching over wide bandwidths required for auxiliary inputs in RF receiver front-ends, affecting noise-figure, gain, and size performance.
Innovation Solution
The implementation of programmable switches and additional transistors in a cascode configuration allows for selective connection and disconnection to extend the operational frequency bands, using a combination of inductors and variable capacitors for tuning, and a programmable bias circuit to maintain performance across bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the AUX input to the LNA is implemented as a non-filtered input to cover wide frequency range, then the adaptability is improved, but the manufacturing precision and performance matching become more difficult
Solution Approach 1:
The input matching network is segmented into multiple parallel branches, each tuned for a specific frequency band. Switches selectively connect different branches to the LNA input based on the operating frequency, allowing precise matching across wide bandwidth by dividing the continuous tuning problem into discrete band-specific solutions
Solution Approach 2:
The input matching network transitions from a static design to a dynamic reconfigurable system. Switches controlled by band selection signals dynamically reconfigure which matching branch is active, enabling the system to adapt its input impedance to match different frequency bands while maintaining optimal performance
2Adaptability or versatility
If variable capacitors are used for fine tuning the LNA input frequency, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The tuning mechanism is segmented into coarse tuning (via switched capacitor banks with different capacitance values) and fine tuning (via variable capacitor). This segmentation allows the system to achieve wide frequency coverage through discrete capacitor selections while using the variable capacitor only for fine adjustments, reducing overall complexity compared to using variable capacitors across the entire frequency range
Solution Approach 2:
Instead of using a single variable capacitor to cover the entire frequency range, the design uses multiple discrete capacitor values that cover most of the required range, with the variable capacitor providing only partial fine-tuning action. This approach reduces complexity by minimizing the tuning range that requires continuous adjustment
Data Source
AI summary
Methods and devices to support multiple frequency bands in radio frequency (RF) circuits are shown. The described methods and devices are based on adjusting the effective width of a transistor in such circuits by selectively disposing matching transistors in parallel with the transistor. The presented devices and methods can be used in RF circuits including low noise amplifiers (LNAs), RF receiver front-ends or any other RF circuits where input matching to wideband inputs is required.