A design scheme for electromagnetic shielding clothes via numerical computation and time domain measurements

SUMMARY Electromagnetic shielding clothes for reducing human ex-posure to radio waves have been commercialized. However, their effect has so far been confirmed only in the form of the raw material. In this paper, we develop a new compact scheme for measuring electromagnetic radiations using a short dipole antenna and Gaussian pulses in order to evaluate the effect of the shielding clothes over a wide frequency range with the aid of time-domain measurements and FDTD computation. The proposed method is based on a time-domain analysis technique and pulse compression technique, which enables the user to separate the direct trans-mission wave from the reflection from the floor as well as from the refracted wave around the neck of the clothes. The direct advantage is that measure-ments can be made in an ordinary laboratory without the function of an electromagnetic anechoic chamber. Also, we can separate direct transmis-sion wave and diffraction wave from the measurement result by using pulse compression technique, then each frequency characteristic of the shielding shirt can be evaluated. The performance of the separation is confirmed by comparing the measurements with those of a shirt with no opening. We further demonstrate the possibility of predicting the effective conductivity of the material as a function of frequency by comparing the measured re-sults with realistic FDTD computations, which will enable us to design a shielding shirt via numerical means. key words: electromagnetic shielding clothes, time domain measurement, FDTD method, effective conductivity, numerical evaluation scheme 1