Switchable LNA Input Matching for Wideband RF Receivers

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Solution Overview

Problem

Existing RF receiver front-ends face challenges in supporting wideband inputs on auxiliary (AUX) inputs due to the difficulty in tuning/matching low noise amplifiers (LNAs) over the required wide bandwidth without compromising performance.

Innovation Solution

The implementation of a radio frequency (RF) circuit with a cascode configuration of transistors, including programmable switches that allow additional transistors to be selectively switched in or out, enabling the LNA to cover a wider frequency range with minimal impact on noise figure, gain, and size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the AUX input to the LNA is implemented as a non-filtered input to support wideband operation, then the frequency range coverage is improved, but the LNA performance (noise figure, gain) deteriorates due to difficulty in tuning/matching over wide bandwidth

Engineering Contradiction:

Improvefrequency range coverageVSAvoidLNA performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The LNA is divided into multiple parallel LNAs, each optimized for specific frequency sub-bands. Switches selectively connect different LNA paths based on the input frequency, allowing wideband operation while maintaining optimal performance in each sub-band through dedicated matching networks.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The LNA configuration is made dynamic through switchable paths that adapt to the input frequency. The system transitions between different LNA configurations based on frequency requirements, enabling optimal matching and performance across the entire wide frequency range rather than using a fixed configuration.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If additional transistors and switching components are added to extend frequency band support, then the adaptability is improved, but the device complexity increases

Engineering Contradiction:

Improvefrequency band supportVSAvoidcircuit structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple LNAs share common input and output nodes through switchable connections. The same physical infrastructure (input terminal, output terminal, matching networks) serves multiple frequency bands by dynamically reconfiguring which LNA path is active, reducing overall complexity compared to completely separate circuits for each band.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Multiple LNA circuits are merged at common input and output nodes with switchable interconnections. This consolidation allows different LNA paths to share infrastructure while maintaining independent optimization for different frequency bands, balancing complexity with functionality.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12341543B2Supporting wideband inputs on RF receivers

Publication Date: 2025.06.24 PSEMI CORP

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.