A Double-armed Planar Equiangular Spiral Patch Probe for Biomedical Measurements

Abstract

A double-armed equiangular spiral patch probe fed by coaxial line is presented in this paper, which is very useful for noninvasive measurement of layered tissues at a wide frequency range. The field distribution in tissues and the |S₁₁| responding to frequencies when the probe contacts with tissues directly are calculated using a commercial software HFSS based on finite-element method (FEM). Calculation results show that the proposed probe could radiate the fields into deeper tissues and the |S₁₁| varied with frequencies greatly. Moreover, experiments in 1% saline solution are performed to verify the computations. And the measurement results are in a good agreement with the numerical results. Meanwhile, the probing depth of the proposed probe is measured and compared to that of the open-ended coaxial probe. Results show that the probing depth of the proposed probe is almost twice as much as that of open-ended coaxial line. Both calculation results and experimental results demonstrate that the proposed patch probe is far prior to open-ended coaxial line, not only in probing depth, but in sensitivity of reflection coefficient to the variation of frequency.