A Rat-Head Exposure System for Exposure to RF Fields from Handheld Wireless Telephones

Abstract

A rat-head exposure system has been developed for Wireless Technology Research, LLC (WR) through a contract with Dr. C.K. Chou who was at the City of Hope National Medical Center during the development of the system. In the first phase of the development of the system the finite-difference time-domain (FDTD) method was used to calculate the specific absorption rates (SARs) in ellipsoidal rat models with simulated fields from different loop antennas located at various distances from the models. From this analytical work a 3 cm x 1 cm rectangular loop was designed with optimized energy coupling and impedance matching.Sprague Dowley rats were then exposed using the 3 cm x 1 cm loop antennas, tuned either to 837 MHz or 1957 MHz for the determination of SAR distribution utilizing the thermographic technique. In addition, point SARs in the brains of restrained rats were measured using fiber optic probes. The calculated and measured SAR patterns were in general agreement. The average brain-to-whole body SAR ratio was 20 to 1 for both frequencies. At 837 MHz, the maximum measured SAR in the restrained rat brain was 51 W/kg/W in the cerebellum and 40 W/kg/W at the top of the cerebellum. For a maximum SAR of 10 W/kg, only 0.2 W input power to the loop is required. The average brain SAR in a 300-g medium size rat for 0.2 W input power is estimated to be 4.8 W/kg.The exposure system has been used to expose Sprague Dawley rats to 837 MHz using analog, TDMA, and CDMA cellular phones as generators of the signals to the loop antennas. At this time, the longest duration of exposure has been 3 hours.KeywordsInput PowerExposure SystemTime Division Multiple AccessSpecific Absorption RateFiber Optic ProbeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.