Wideband RF Receiver LNA Input Matching via Switchable Transistor Width

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Solution Overview

Problem

Existing RF receiver front-ends with tunable AUX inputs face challenges in matching wide bandwidth requirements without compromising noise-figure (NF), gain, and size, particularly in low noise amplifiers (LNAs).

Innovation Solution

Implementing programmable switches to selectively connect additional transistors in parallel with existing transistors in a cascode configuration, allowing the LNA to switch between higher and lower frequency bands by adjusting transistor width, and using a programmable bias circuit to maintain consistent DC bias current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the LNA is designed to cover wide frequency bands using traditional tuning methods (variable capacitors and inductors), then the frequency range is extended, but the noise-figure and gain performance deteriorate

Engineering Contradiction:

Improvefrequency band coverageVSAvoidnoise-figure and gain performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The LNA is divided into multiple parallel transistor branches, each optimized for specific frequency bands. Switches selectively connect different branches to the input terminal based on the target frequency band, allowing the system to maintain optimal noise-figure and gain performance for each band while achieving wide overall coverage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The LNA configuration is made dynamically reconfigurable through programmable switches that can selectively connect or disconnect transistor branches. This dynamic switching allows the LNA to adapt its internal structure to match the operating frequency band, thereby maintaining optimal performance across wide frequency ranges without compromising noise-figure or gain.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If additional transistors are added in parallel to extend frequency coverage, then the frequency band support is improved, but the device complexity and size increase

Engineering Contradiction:

Improvefrequency band coverageVSAvoidtransistor configuration complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple transistor branches are designed with similar structural characteristics but different sizing parameters, allowing them to serve different frequency bands. The switching mechanism provides universal control over which branch is active, reducing the need for completely different circuit topologies for each band and thereby managing complexity while extending coverage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If transistor width is adjusted to tune frequency bands, then the frequency selection capability is improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvefrequency tuning capabilityVSAvoidtransistor width fabrication accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

Instead of relying on precise transistor width fabrication for frequency tuning, the invention uses programmable switches to selectively connect pre-fabricated transistor branches with different width ratios. This shifts the tuning mechanism from fabrication-dependent parameter adjustment to post-fabrication electrical configuration, significantly reducing manufacturing precision requirements while maintaining frequency tuning capability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250309926A1Supporting wideband inputs on RF receivers

Publication Date: 2025.10.02 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.