Modal analysis on insulated loop antenna immersed in liquid

An insulated circular loop antenna (ICLA) immersed in tissue-equivalent liquid is one of candidates for reference antenna to calibrate probes which are used to evaluate SAR (specific absorption rate) for mobile communication devices operated in the MHz band. To clarify operation principle of ICLA immersed in the liquid, ICLA fed at a point along the loop is analyzed by the method of moments with characteristic modes. It is found that the pattern is composed by fundamental and second-harmonic cosine current distributions. Also, it is found that the fundamental cosine current distribution is dominant in the direction of the central axis to measure the near-field gain of ICLA.