RF Frontend Feedback Path Reuse for Low-Distortion Gain Modes

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Solution Overview

Problem

Existing RF processing circuits face challenges in achieving high linearity performance during attenuation mode while minimizing parasitic capacitive loading and noise figure degradation, especially when using bulk CMOS fabrication technologies.

Innovation Solution

A multi-input multi-gain RF processing circuit design that incorporates switchable active and passive paths, with a switchable feedback path allowing for attenuation prior to amplification, reducing the number of switches and parasitic capacitive loading, and utilizing a common node architecture for improved linearity and noise performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If attenuation is performed after amplification through the active path, then the RF signal can be processed with gain control, but linearity performance degrades and distortion increases

Engineering Contradiction:

Improvelinearity performanceVSAvoiddistortion

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent inverts the conventional signal processing order by performing attenuation before amplification instead of after. The switchable passive path provides attenuation at the input stage, and the amplifier subsequently amplifies the already-attenuated signal, thereby improving linearity and reducing distortion caused by post-amplification attenuation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent segments the RF signal processing function into two separate switchable paths: a passive attenuation path and an active amplification path. This segmentation allows independent optimization of each path's function, enabling the attenuation path to handle signal level control without introducing the distortion that would occur if attenuation were performed after amplification in a single path.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If multiple separate paths with dedicated switches are used for active and passive processing, then gain control flexibility is improved, but device complexity and parasitic capacitive loading increase

Engineering Contradiction:

Improvegain control flexibilityVSAvoidnumber of switches

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the functions of multiple separate paths into a unified architecture where a single switchable passive path and a single switchable active path share common input and output nodes. This consolidation reduces the number of required switches while maintaining the flexibility to selectively enable/disable attenuation and amplification functions independently, thereby reducing parasitic capacitive loading and device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The switchable passive path and switchable active path are designed as universal building blocks that can be selectively activated based on the desired gain mode. Each path can serve multiple functions: the passive path provides both attenuation and isolation, while the active path provides both amplification and gain control, reducing the need for dedicated components for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If multiple separate paths with dedicated switches are used for active and passive processing, then gain control flexibility is improved, but noise figure degradation increases

Engineering Contradiction:

Improvegain control flexibilityVSAvoidnoise figure

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary attenuation through the switchable passive path before the signal enters the amplifier. By establishing the desired signal level beforehand, the amplifier operates from a lower input level, which reduces the overall noise figure of the system compared to amplifying first and then attenuating, where the amplifier's noise would be fully amplified.

Inventive Principle:

Principle #10Preliminary action

4Object-affected harmful factors

If attenuation is performed through passive devices only, then parasitic capacitive loading is reduced, but the ability to provide gain greater than zero dB is limited

Engineering Contradiction:

Improveparasitic capacitive loadingVSAvoidgain range

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent implements a dynamic switchable architecture where the system can adaptively select between passive-only mode (for low gain applications with minimal parasitic loading) and active mode (for high gain applications requiring amplification). The switchable active path can be enabled or disabled based on the required gain level, allowing the system to dynamically optimize between parasitic loading and gain capability.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11405064B1Bypass path reuse as feedback path in frontend module

Publication Date: 2022.08.02 PSEMI CORP

AI summary

Methods and devices for processing of RF signals according to different gain modes are presented. According to one aspect, an active amplification mode is provided by switchable active paths coupled to respective input RF signals and a passive attenuation mode is provided by switchable passive paths coupled to the respective RF signals. According to another aspect, a common switchable feedback path coupled to the switchable active paths is used to provide an active attenuation mode. Coupling of the common switchable feedback path to the switchable active path is provided by switches of the switchable passive paths, including for coupling both ends of the common switchable feedback path or just one end.