SAR effect reduction using Reject Band Filter arrays for Wi-Fi portable devices

摘要

This paper suggests a novel 1D Reject Band Filter (RBF) array to prevent the radiation leakage from portable devices around 2.45 GHz. The proposed RBF array is constructed from eight-unit cell elements mounted on the same side of an FR-4 substrate of 1.5-mm thickness. Each two adjacent unit cells are separated with 2 mm. The individual unit cell design is based on fractal-based open-loop resonators of a modified first iteration Minkowski configuration. Such configuration is coupled with an open-stub transmission line to increase the selectivity of the filter stopband response at the frequency of interest. The unit cell performance is evaluated numerically and analytically, and then compared against measurements. Next, the optimal RBF array is fabricated and simulated to evaluate the Specific Absorption Rate (SAR) at 2.45 GHz. The SAR effect on the human thigh tissue is studied numerically to show an excellent reduction from 0.912 to 0.352 W/kg. Finally, the field strength before and after introducing the proposed array underneath a laptop computer, just below the Wi-Fi antenna, is measured and found to be reduced from 497.1 to 171.8 mV/m.