The Study Of The Complex Permittivity Measurement For Biology With Coaxial Line

The uses of electromagnetic wave are more and more widespread in medicine, food,environment,communication,military,agriculture and so on,and the frequency develops gradually to the microwave high frequency band.While widespread utilization microwave,people also pay attention to the microwave security problem, but the Complex Permittivity which is an important parameter affect the results of the microwave acting the medium,its accurate survey has the vital significance.When study the biology and tissue's electromagnetism characteristic in the Electromagnetic field,it is necessary to get the Complex Permittivity accurately,so to seek or to establish one method for measuring the biological tissue Complex Permittivity is extremely important.After analyses the present the methods and the experiment results and along with the electromagnetism characteristic of biology,this article discovers that the bridge method and the coaxial probe method are suitable for the measurement of biology to a certain extent,but all has certain limitation.This article which carries on the thorough analysis to the Electric-bridge method and the coaxial probe method,re-modify the original model of the coaxial probe method,and establishes the new survey model which has introduced allowance R and the measuring technique-double probes method and the single probe method.The measurement results,which are separately carried on the original model and the revision model to the identical sample,show that the re-modified model has much better result for the imaginary part of methanol than the original model.The experiments indicated that the re-modified model expanded the applicable scope of original model.Later,the researches to several biology samples indicate that the introduction allowance R may be ignored at low frequency if the error permits,so measurement can be carried on the original method,but at much higher frequency,the loss part is small which should be more accurate if measured by the new model.In view of the measurement frequency which is less than 3.5GHZ usually,for biology tissue,and the actual condition which some biology should be processed before measuring——such as turning massive body into paste or powder,which maybe causes the change of biology electromagnetism character.In view of these questions,this article measures some samples made from the different biology and some different samples made from the same biology with the new method at 10MHZ-4.8GHZ.The experimental results indicated that the new method has a good result at 10MHZ-4.8GHZ,and the change of sample structure can cause the change of electricity attribute.At low frequency,the difference is big,and the measurement value can not be direct identified directly with the result of the samples which keep original condition;Along with the frequency ascension,the difference reduces gradually,in the erroneous scope,the observed value may reflect the original sample electricity attribute.