RF Transmit Power Back-Off for Time-Averaged SAR Control
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Solution Overview
Problem
Existing wireless communication technologies face challenges in efficiently complying with specific absorption rate (SAR) regulations without requiring extensive memory and processing resources, particularly when using higher radio frequencies and beamforming techniques that increase RF radiation.
Innovation Solution
Implementing a power back-off mechanism with a single accumulator to manage transmission power, setting a first limit below the regulatory limit and accumulating energy credits to allow temporary exceedance, thereby avoiding the need for complex integrals and sliding windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex integral and sliding window mechanisms are used to implement time-averaging SAR compliance, then measurement precision and regulatory compliance are improved, but device complexity and processing requirements increase
Solution Approach 1:
The patent transforms the continuous integral calculation into a discrete summation of power samples over a time window. By changing the mathematical approach from integral to discrete sum, and by using a fixed time window with predetermined parameters, the system achieves the same regulatory compliance goal with significantly reduced computational complexity suitable for mobile devices.
Solution Approach 2:
The patent divides the continuous time-averaging process into discrete time segments or samples. Instead of computing a continuous integral, the system segments the power measurement into discrete samples taken at regular intervals, sums these samples, and compares the result to a pre-calculated threshold. This segmentation converts a complex continuous problem into a series of simple discrete operations.
2Productivity
If transmit power is increased to maximize data throughput and connectivity range, then productivity is improved, but SAR radiation levels increase causing harmful effects
Solution Approach 1:
The patent implements periodic measurement of transmit power over a defined time window to calculate the time-averaged SAR value. By periodically monitoring and averaging the power output, the system can identify when the average SAR exceeds regulatory limits and temporarily reduce power accordingly, then restore full power when the average returns to acceptable levels, thus maximizing throughput while ensuring compliance.
Solution Approach 2:
The system continuously monitors transmit power levels, calculates the time-averaged SAR, and uses this information to provide feedback control on the transmit power. When the calculated average SAR approaches or exceeds regulatory limits, the system reduces power; when limits are not approached, the system maintains maximum power, creating a dynamic feedback loop that optimizes throughput subject to SAR constraints.
3Object-affected harmful factors
If transmit power is reduced to comply with SAR limits, then harmful radiation effects are reduced, but data throughput and connectivity range decrease
Solution Approach 1:
The patent implements dynamic power adjustment rather than static power reduction. The transmit power is continuously adapted based on real-time measurements of the time-averaged SAR. This allows the system to maintain maximum power when SAR limits are not approached and only reduce power temporarily when necessary to maintain compliance, thereby minimizing the impact on data throughput and connectivity range.
Solution Approach 2:
The system performs preliminary calculations to determine the relationship between transmit power levels and time-averaged SAR values. By pre-calculating power thresholds and averaging window parameters, the system can quickly determine the appropriate power level without complex real-time computations, enabling rapid power adjustment that minimizes disruption to data throughput while ensuring SAR compliance.
Data Source
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AI summary
Methods and devices configured to apply a power back-off (PBO) to limit a radio frequency (RF) transmitter power up to a first limit, wherein the first limit is below a pre-defined RF power limit; accumulate a difference between RF transmission power spent transmitting data and the pre-defined RF power limit over a duration to produce an accumulated energy budget; and once the accumulated energy budget reaches a pre-defined energy credit value, remove the PBO and allow RF transmitter power exceeding the pre-defined RF power limit until the accumulated energy budget meets a threshold.