An investigation of SAR inside human heart for antenna directivity, surface current variations and effect on antenna frequency in presence of heart

Abstract

In this work, the impact of human heart on an 800 MHz inset fed rectangular microstrip patch antenna characteristics were investigated using CST Microwave Studio. The antenna was simulated over a mimic human heart muscle and the distance between them was varied to analyze the changes in Specific Absorption Rate (SAR) upon antenna performance parameters (specifically, directivity & surface current) for discreet and waveguide port feeding. The results exhibited that the center frequency of the antenna was shifted to lower value and an increase in SAR values when the antenna was closer to heart for both the feeding techniques. However, the discrete port had more values of SAR than the waveguide port but for both cases SAR decreased with the increment of antenna distance from heart. SAR values for up to 4 mm distance in between the antenna and human heart did not satisfy IEEE and ICNIRP standards. For increasing surface current, the SAR values decreases due to less penetration of flux inside the tissue for both feeding techniques. Increasing directivity resulted decrement of SAR values due to the fact that more reflection of the wave from the tissue happened for more directivity. This work demonstrates how mobile phone antennas of GSM band affect human heart and how human heart affects antenna resonance frequency when mobile phones are kept in chest pocket.