Phase Detection for Electric Field Body Scanner

Abstract

The authors are studying a technique to measure moisture distribution inside the human body by applying weak electric field at radio frequency (RF), 1 to 60MHz. RF signal is fed to an antenna that is as small as a few centimeters square, and the same type of antenna measures electric field intensity where two antennas are located 15 to 50 cm apart from each other. A portion of the living human body located between the antennas affects the signal intensity at the measurement side. Because of the principle, the method does not provide fine resolution. However, it has such advantages as simple, safe and cost-effective so that it can be used for health care, screening of medical care, and device for handicapped and elderly.

The recent experiments gave different patterns of signal changes caused by the human body and a phantom. Unlike the phantom that consisted of a small acrylic tank filled with water, the human body connected to the earth by electrostatic induction that was caused by relatively larger dimensions of the human body compared to the water tank. Measurement of the signal phases is thought to help discriminating the losses caused by the electrostatic induction from signal increments cause by water permittivity.

The experimental system has been upgraded to measure signal phases that used to measure signal strength only.

This paper introduces the new system and reports experiments where portions of the human body are measured by the system as well as water tank phantom for the comparison. Validity of the phase measurement is discussed with the results.