“…With microwave measurement techniques, there are several methods to indicate liquid ingredients from liquid-mixture solutions, e.g., resonance frequency [18], [30]- [32], transmission level [17], [32]- [33], phase and quality factor (Q-factor) [23]. Various liquid-mixture sensors based on microwave technologies have been extensively investigated, such as split-ring resonator [34]- [36], complementary split-ring resonator (CSRR) structures [17], [31]- [32], [37]- [38], interdigital structures [8], substrate integrated-waveguide (SIW) structures [18], waveguide structures [30] and mushroom-like structures [23]. These techniques offer a good measurement accuracy [17]- [18], [31], with, generally, nondestructive measurement and short assay time.…”