Comparison Measurement for Specific Absorption Rate With Physically Different Procedure

Prospects for Millimeter-Wave Compliance Measurement Technologies [Measurements Corner]

“…Noninvasive systems assess the compliance of devices using measurements from outside of the sample without disturbing the structure of the sample. E-field probe-based systems [7], electro-optical (EO) probe-based systems [8], and optical fiber thermal sensor-based systems [9] are classified as invasive measurement systems. Infrared (IR) measurement systems [10], thermal scanner systems [11], power density (PD) measurements [12], and optical SAR systems [13], [14] can be classified as noninvasive measurement systems with minimal to no interactions between the device under test (DUT) and the measurement system.…”

“…E-field probes require calibration to preserve isotropy of the probe measurements. Additionally, measurement of E-field components within a few millimeters of the surface, where most of the energy is deposited at mm-wave frequencies, is challenging because of the loss of isotropy of the probes at the phantom edge due to the air/phantom boundary interactions with the dielectric fluid [9]. Measurements are conducted in relatively coarse resolution (a few millimeters), therefore, for accurate computation of SAR and estimation of the maximum energy deposition on the surface, several interpolation techniques are used.…”

“…Temperature-based dosimetry systems were developed using a 3-D array of optical fiber thermal sensors positioned inside a tissue-mimicking semisolid phantom [9], [21]. Average SAR is evaluated within a 1- or 10-g mass, covered by multiple optical fiber thermal sensors, by measuring the temperature rise Δ T due to field exposure in each sensor location and using $$\text{SAR}=C_{ph}\mathrm{\Delta }T/\mathrm{\Delta }t,$$ where C ph is the specific heat of the semisolid phantom material and Δ t is the exposure duration.…”

“…Thermal SAR evaluation systems show a good agreement with E-field probe measurements for frequencies <6 GHz [22]. Additionally, they are used for validating the standard based on E-field probes and for evaluating the uncertainty of the measurement system [9], [22]. Figure 8 illustrates an optical fiber thermal sensor and its features.…”

Heat equation inversion framework for average SAR calculation from magnetic resonance thermal imaging

“…SAR is conventionally measured in the wireless industry using electric ( E ) field probes [Schmid et al, 1996] that are mechanically moved in a point-by-point, grid-like fashion in three dimensional (3D) space inside a phantom filled with a liquid mimicking electrical properties of human tissues. Okano and Shimoji have shown that RF energy exposure quantification can be conducted by measuring temperature increase due to RF exposure using highly sensitive temperature probes [Okano and Shimoji, 2012]. Gultekin and Moeller [2013] have shown that magnetic resonance (MR) methods can be used to measure temperature increase due to RF energy absorption, where the magnitude of temperature increase was a function of RF power and exposure time in brain equivalent gels and brain tissue [Gultekin and Moeller, 2013].…”