Electromagnetic Field Measurement Using Local Phase Reference
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Solution Overview
Problem
Measuring electromagnetic fields in three dimensions is challenging when characterizing fields radiated by self-contained wireless devices, as existing methods require modifications that alter the device's operation, making it difficult to accurately assess fields under typical use conditions, especially for specific absorption rate (SAR) measurements.
Innovation Solution
A system using an antenna arrangement to provide signals representative of the electromagnetic field at various locations, with a measurement arrangement that measures phase differences using a local phase reference signal from a fixed location on the measurement surface, allowing precise measurement without modifying the device under test.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a radiofrequency power signal applied to an antenna is used as a phase reference, then phase information can be obtained for electromagnetic field characterization, but modifications are necessary to the self-contained wireless device casing that alter the device's operation and electromagnetic field radiation
Solution Approach 1:
The patent introduces a local phase reference signal derived from signals already present at the antenna arrangement, rather than directly accessing the radiofrequency power signal inside the device. This intermediary approach allows phase measurement without physical modification to the device casing, thereby maintaining the device's original electromagnetic field radiation characteristics while still enabling precise phase information acquisition through the antenna arrangement's received signals
2Ease of operation
If the device casing is opened and a measurement cable is provided to access the radiofrequency power signal, then phase reference can be obtained, but the electromagnetic field radiation of the device is altered from typical use conditions
Solution Approach 1:
The patent enables the antenna arrangement to derive the local phase reference signal from signals it already receives from the electromagnetic field, without requiring external cables or modifications to access internal device signals. The system serves itself by utilizing the electromagnetic field signals naturally present during normal device operation, eliminating the need for invasive access methods while maintaining measurement accuracy
3Adaptability or versatility
If modifications are made to the self-contained wireless device to enable phase reference access, then measurement capability is improved, but the device cannot radiate electromagnetic field as it does under typical use conditions
Solution Approach 1:
The patent separates the measurement function from the device under test by using an independent antenna arrangement that derives the local phase reference from signals it receives in the electromagnetic field. This segmentation allows the device to operate in its typical enclosed form without modifications, while the measurement system independently acquires both amplitude and phase information through the field signals, maintaining device operational normality while enabling comprehensive measurement capability
Data Source
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AI summary
In a system (SYS) for measuring an electromagnetic field (EM), an antenna arrangement (AN) provides respective signals (AS) representative of the electromagnetic field (EM) at various respective locations on a measurement surface (MSF). A measurement arrangement (MS) measures respective phase differences (MP) between, on the one hand, respective signals representative of the electromagnetic field (EM) at various respective locations on the measurement surface (MSF) and, on the other hand, a phase reference signal representative of the electromagnetic field (EM) at a particular location on the measurement surface (MSF). The particular location for which the phase reference signal is representative of the electromagnetic field (EM) remains substantially fixed for the respective phase differences (MP) that are measured.