Study of Correlation between Sugar Content of Solution and Transmission Coefficient with Microwave

Abstract

This paper presents a study of a microwave transmission coefficient transmitted to soluble solid contents in order to investigate a level of sugar contents of the soluble solid contents. The proposed microwave sensor uses microstrip antennas to be transmitting and receiving antennas. The antennas are designed at the operating frequency of 2.45 GHz. The testing process is accomplished by a microwave transmission to a sample solution of the syrup, which is diluted by water. The sugar content levels are measured by a brix refractometer classified by 7-sample levels of sugar contents with 0, 5, 10, 15, 20, 25 and 30 %brix. The transmitting and receiving antennas are located at the both sides of the container. The synthesizer uses to generate the frequency of 2.45 GHz in order to feed the transmitting antenna. The 2.45 GHz EM wave is transmitted from the transmitting antenna to the receiving antenna via the sample solution in order to a measured coupling signal. The measured coupling signal between transmitting and receiving antenna is converted to DC voltage. From the measured results of the sample solution, it is found the average voltage with 2.420-2.549 volt can be clearly classified the sugar constant into 0-30 %brix by 0.02 volt of voltage difference in each level. With the low standard deviation of the results accomplished by 10 times of sample measurements, it is enough to separate the levels of soluble solid contents. The proposed system is appropriated for detecting sugar content.