Validation of computed portable radio handset near fields by measurement

摘要

This paper compares the measured and computed fields of a portable radio at 850 MHz operated adjacent to a simple representation of the head, either a box or a sphere. The measurement uses an aluminum box for a handset, with a quarter-wave monopole antenna. The box or sphere representing the head is a thin plexiglas shell filled with liquid having the electrical properties of the human brain. The measurement setup uses a near field scanner to measure the vertical component of the electric field over planes 50 by 50 cm in size. The computation uses the finite-difference time-domain method, with a sinusoidal generator at the base of the monopole and time-stepping to steady-state. Comparing measured and computed contour maps of Ez shows good agreement for the handset alone, with “hot spots” at the base of the case, at the top of the case near the antenna feed point, and at the tip of the antenna. When the box or sphere “head” is present, reasonable agreement is obtained, and the “hot spots” remain.