Adaptive SAR Measurement for Multi-Antenna Devices
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Solution Overview
Problem
Current methods for electromagnetic safety compliance in portable wireless devices with multiple antennas are inadequate, as they require excessive time to measure specific absorption rate (SAR) for all possible transmitted signals, leading to inefficiencies in compliance verification due to exponential growth in the number of phase combinations.
Innovation Solution
A method that uses adaptive signal measurement to rapidly determine electromagnetic exposure metrics, such as SAR, by broadcasting predetermined signals, adapting to find maximum exposure patterns, and approximating total exposure using a two-stage analysis to reduce measurement time, allowing for compliance verification regardless of the number of antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SAR measurement methods are used for multi-antenna devices, then measurement completeness is improved, but measurement time increases exponentially
Solution Approach 1:
The patent segments the SAR measurement process into two distinct stages: (1) measuring SAR for each individual antenna separately, and (2) estimating the total SAR for all antenna combinations using the individual measurements and channel state information. This segmentation avoids the exponential growth of measuring all possible antenna combinations directly, reducing measurement time from exponential to linear complexity.
Solution Approach 2:
The patent performs preliminary measurements of individual antenna SAR values before conducting the actual compliance verification. By pre-measuring and storing the SAR contribution of each antenna, the system eliminates the need to re-measure these values for every possible antenna combination, significantly reducing the time required for complete compliance verification.
2Reliability
If all possible transmitted signals are tested, then compliance accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces channel state information (CSI) as an intermediary element that bridges the gap between individual antenna measurements and total SAR estimation. The CSI captures the coupling effects and interference between antennas, allowing the system to accurately estimate total SAR for all antenna combinations without directly measuring each combination, thus maintaining compliance accuracy while reducing system complexity.
3Measurement precision
If beamforming codebook testing is performed, then exposure compliance accuracy is improved, but measurement time increases
Solution Approach 1:
The patent changes the measurement approach from testing each beamforming codebook entry individually to using the measured individual antenna SAR values and CSI to estimate the SAR for all beamforming combinations. This parameter change in the measurement methodology maintains accuracy for beamforming operations while dramatically reducing the time required, as the estimation leverages the pre-measured individual antenna characteristics rather than requiring separate measurements for each beam.
Data Source
AI summary
A method of determining electromagnetic exposure values for radiative compliance tests a transmitting device with multiple transmitters or antenna. The device transmits a first set of excitation signals that are chosen in advance. These signals are measured for their electromagnetic exposure values. A second set of excitation signals are then transmitted that are adaptively chosen based on result of a previous measurements of the first excitation signals. The second set of signals are also measured. From the measurements of the predetermined and adaptive signals, the electromagnetic exposure values of all possible transmitted signals are inferred.