Split LNA Receiver Architecture for Lower Noise Figure

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Solution Overview

Problem

Modern integrated CMOS transceivers in the WiFi range face limitations in noise figure due to integration into Si substrates and inherent CMOS technology limitations, leading to suboptimal receiver sensitivity and bandwidth utilization.

Innovation Solution

A split LNA configuration with a shared input matching network is used, where two or more LNAs are connected to the same antenna, each with a separate quadrature down-convert mixer and baseband filters, and their outputs are digitally summed to improve signal-to-noise ratio and reduce noise figure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single LNA is integrated into CMOS transceiver, then device integration is achieved, but noise figure deteriorates to 4-5dB

Engineering Contradiction:

ImproveintegrationVSAvoidnoise figure

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The LNA function is segmented into multiple parallel LNAs (first LNA, second LNA, etc.) that operate simultaneously. Each LNA processes a portion of the signal, and their outputs are combined through a summer to achieve improved noise figure while maintaining CMOS integration. This segmentation allows the system to overcome the noise limitations of a single integrated LNA.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If multiple LNAs are used with separate processing paths, then noise figure improves, but device complexity increases

Engineering Contradiction:

Improvenoise figureVSAvoidcircuit structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Multiple LNA paths are merged at the summer stage where their outputs are combined. The patent uses a common summer component to aggregate signals from multiple LNAs, reducing the overall circuit complexity compared to having completely separate processing chains. This merging approach maintains the noise performance benefits of multiple LNAs while simplifying the overall architecture.

Inventive Principle:

Principle #5Merging (Combining)

3Object-affected harmful factors

If external SOI/GaAs RF front-end is used, then noise figure performance improves, but cost and circuit area increase

Engineering Contradiction:

Improvenoise figureVSAvoidcircuit area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

Instead of using expensive external SOI/GaAs RF front-end components, the patent creates a copied implementation using multiple CMOS LNAs that replicate the functionality. The summer component copies the signal combining function that would otherwise require external hardware, allowing the system to achieve similar noise performance using only integrated CMOS components, thereby reducing both cost and external component requirements.

Inventive Principle:

Principle #26Copying

Data Source

PatentEP4012931A1Receiver with reduced noise figure using split LNA and digital combining

Publication Date: 2022.06.15 INTEL CORP

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AI summary

Systems and methods of reducing SNR and increasing bandwidth of received signals are disclosed. LNAs receive signals from an antenna via a common input matching network. The amplified signals are downconverted, filtered and digitized before being coherently combined at a DSP. Depending on the LO frequencies used by mixers in the different receiver paths, the combined signals reduce the SNR when the LO frequencies are the same by reducing the non-correlated noise introduced by the LNAs or increase the bandwidth processed when the LO frequencies are different. The bandwidths are contiguous or non-contiguous.