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When developing a wireless communication system, a designer should consider the associated radiated power density, electromagnetic compatibility (EMC), and speciflc absorption rate (SAR). In this paper, high-impedance surfaces (HISs) are designed as an EM protection screen to reduce the interaction between an antenna and the user behind the screen. The efiects of an HIS screen with a flnite number of cells placed near a monopole antenna for the application of the 2.4GHz WLAN band were thoroughly investigated. The screen is flrst-ever proposed not only to reduce the backward radiation from the antenna, but also to shift the impedance-matching band of the antenna and to adjust the corresponding bandwidth. As a result, the SAR behind the screen is noticeably lowered, and the out-of-band spurious emission from the antenna can be reduced. Two typical kinds of HIS structures, mushroom-shaped and Jerusalem

When developing a wireless communication system, a designer should consider their antenna performance, total radiated power (TRP), total isotropic sensitivity (TIS), and specific absorption rate (SAR). In this study, the electromagnetic (EM) protective sheets including metallic plates, R-cards, RF absorbers, and high impedance surfaces (HISs), were used to reduce radiation hazard to a user. The performance of EM protective sheets was evaluated in terms of their effects on the SAR, radiated power, and various other parameters of a WLAN antenna.

In this study, high impedance surface (HIS) structures were used to reduce interaction between a wireless antenna and its user. Mushroom and Jerusalem Cross HIS structures were designed for the PCS band (1.8 GHz). The performance of these HIS structures were investigated by surface-wave and reflection-phase methods. A new test method was also proposed to characterize the reflection phase of an HIS by using a GTEM cell. The effects of HIS sheets on antenna performance and the SAR were studied. Results revealed that these HIS structures can reduce SAR values.