Subband RF Power Limits for Exposure-Compliant Wireless Transmission

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Solution Overview

Problem

Current RF exposure compliance certification processes determine a single transmit power limit for each frequency band, which can lead to sub-optimal performance due to variations in RF exposure within the band, resulting in reduced throughput, increased latency, and increased design complexity for wireless devices.

Innovation Solution

Determine and apply transmit power limits on a subband level for each transmit scenario, using a time-averaging operation to account for variations in RF exposure within frequency bands, thereby optimizing performance and reducing design complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single transmit power limit is determined for each frequency band, then RF exposure compliance is ensured, but wireless device performance deteriorates due to sub-optimal power control

Engineering Contradiction:

ImproveRF exposure complianceVSAvoidwireless device performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The frequency band is divided into multiple subbands, and separate transmit power limits are determined for each subband. This segmentation allows the system to optimize power control within each subband rather than applying a uniform limit across the entire band, thereby improving wireless device performance while maintaining RF exposure compliance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different transmit power limits are applied to different subbands within the frequency band. This local quality approach recognizes that RF exposure characteristics vary across different frequency regions, allowing each subband to have optimized power control parameters that balance compliance and performance.

Inventive Principle:

Principle #3Local quality

2Device complexity

If a single transmit power limit is applied for the entire frequency band, then compliance assessment is simplified, but throughput is reduced and latency increases

Engineering Contradiction:

Improvecompliance assessment complexityVSAvoidthroughput and latency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The frequency band is segmented into subbands, and power control is performed independently for each subband. This segmentation enables more precise power optimization that improves throughput and reduces latency while keeping the compliance assessment manageable through structured subband management.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transmit power limit is made dynamic by determining separate limits for each subband based on their specific RF exposure characteristics. This dynamic approach allows the system to adapt power levels to actual operating conditions within each subband, improving performance metrics like throughput and latency.

Inventive Principle:

Principle #15Dynamics

3Productivity

If subband-level transmit power limits are determined, then wireless device performance is optimized, but design complexity for antennas and RF circuitry increases

Engineering Contradiction:

Improvewireless device performanceVSAvoidantenna and RF circuitry design complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The frequency band is divided into subbands with separate power control, but this segmentation is implemented at the signal processing level rather than requiring separate physical antenna elements. The baseband or RF processor applies different power limits to different subbands through digital signal processing, avoiding the need for complex analog antenna structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces complex mechanical/analog antenna design solutions with digital signal processing approaches. Instead of designing separate physical antenna systems for each subband, the system uses a single antenna system with digital power control applied at the signal processing level, thereby reducing hardware complexity while maintaining performance benefits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20250344164A1Radio frequency exposure compliance using subband transmission power limits

Publication Date: 2025.11.06 QUALCOMM INC

AI summary

Techniques and apparatus for radio frequency (RF) exposure compliance based on subband transmit power limits are described. An example method that may be performed by a wireless device includes determining a transmit frequency band of at least one radio of the wireless device for transmission of a signal having an operating transmit frequency in the transmit frequency band. A transmit power limit associated with a subband in the transmit frequency band is determined based at least in part on the transmit frequency band. The operating transmit frequency of the signal is in the subband. The signal is transmitted using the at least one radio at a transmit power determined based at least in part on the transmit power limit in compliance with an RF exposure limit.