Health and Security :-

           A general public perception that microwaves are harmful has been a major obstacle to the acceptance of WPT. A major concern is that long-term exposure to low levels of microwaves might be unsafe and could even cause cancer. Scientific research indicates that the heating of humans exposed to the radiation is the only known effect, although there are also claims of low-level non-thermal effects.

          The WPT could pose challenges in clinical uses when working at high frequencies. To obtain high power transfer and a smaller reception coil size, the working frequency of the RF WPT must be increased to the GHz band. Within this band, precise impedance matching is required in both the receiving and transmitting circuits to perform the preferred transfer power delivery efficiency

          In addition, the impedance matching condition of both the receiving and transmitting coils are invisible in several medical applications because they are critical to the air gap and alignment between the receiving and transmitting coils, as well as the electrical characteristics of the bio-tissues among the coils. Careful configuration between the coils and precise understanding of the electrical properties of the propagation channel might be a challenge in medical applications. Moreover, conductive bio-tissues could considerably decrease the delivered transfer power in the RF band because of absorption. Following the IEEE Standard C95.1-2005, for safety levels with regard to human body exposure to RF electromagnetic waves, the allowable exposure level in the range of 2 to 100 GHz in public surroundings is 10W/m2.

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