Design and simulation of small-sized antenna in microwave transmission method for water content measurement instrument

Herein, the microwave transmission method is proposed that demonstrates such advantages as non-invasiveness, excellent penetration performance, and fast detection. As a key component of the microwave method water content measurement instrument, the antenna is required to have a smaller radiation size than the inner diameter of the oil pipe. To address this technical challenge, a small-sized microwave projection method based on water content measurement antenna is designed in this study for the water content measurement of oil-water mixtures in downhole pipelines. Also, the half-cut antenna with a size of 17 x 45 mm(2) is proposed to operate in the frequency band of 2-6 GHz (The measured gain of the antenna varies from 2.48 dBi to 4.98 dBi). Then, the designed half-cut antenna is applied to the established water-content test environment for analysis as to the relationship between water content and the variation in transmission coefficient of the half-cut antenna. According to the test results, the relative water content error is about 0.31% between the simulation and measured results for the transmission coefficient S-21 in the range of 0%-30%, while that is about 0.16% for the transmission coefficient S-21 in the range of 40%-100%. The experimental results can be extended to the measurement of the part with high water content of the oil-water mixture in the pipeline, which provides a practical reference for field tests and basic research.