Copyright © 2005 The Institute of Electronics, Information and Communication Engineers
Special Section of 2004 International Symposium on Electromagnetic Compatibility -- Papers -- Biological Effects |
Method for Estimating Complex Permittivity Based on Measuring Effective Permittivity of Dielectric Mixtures in Radio Frequency Band
1 The authors are with NTT DoCoMo, Inc., Yokosuka-shi, 239-8536 Japan., 2 The authors are with Aoyama Gakuin University, Sagamihara-shi, 229-8558 Japan. E-mail: ebara{at}nttdocomo.co.jp
This paper proposes a method for estimating the complex permittivity of a small quantity of a sample such as a biological membrane. The feature of this method is that a material with an unknown complex permittivity is mixed with a material with a known complex permittivity in a number of volume ratios. The unknown complex permittivity is estimated by measuring the effective permittivity of the mixtures and by using the mixing formula, which is applied to the composite material. The validity of this estimation method is evaluated using a phospholipid, which is the primary constituent of a biological membrane, in the frequency range from 0.8 GHz to 6 GHz. We confirm that the measured effective permittivity of the phospholipid mixtures, which comprise the phospholipid and Ringer's solution in a number of volume ratios, corresponds to that of the Lichtenecker formula. Additionally, by preparing a number of samples with varying volume ratios the estimation error can be decreased. This estimation method is considered to be effective in the measurement of the complex permittivity for a biological membrane.
Key Words: dielectric measurement, coaxial line, phospholipid, effective permittivity, mixing formula
Manuscript received November 18, 2004. Manuscript revised March 14, 2005.