Sensitivity Enhancement of CSRR Sensor Using Interdigital Structure in Detecting Ammoniacal Nitrogen for Water Quality Applications

This paper presents the design of a Complementary Split Ring Resonator (CSRR) with sensitivity enhancement to detect ammoniacal nitrogen for water quality applications. Based on the literature review, the lowest concentration of AMN that has been sensed by using the CSRR is 100mg/L, which is beyond the safety level, specified by the National Water Quality Standard for Malaysia (NWQS). According to the standard, extensive water treatment is required for an AMN’s concentration of 0.9mg/L and above. To improve the sensitivity of the CSRR, an interdigital capacitor was introduced at the ring gap of the CSRR. Simulation results show that the maximum shift of the resonance frequency (0.84 GHz) was achieved with 4 fingers interdigital capacitor structure when the thickness of the ammonia layer is 0.5mm, while the initial CSRR resulted in a frequency shift of 0.61 GHz for the same thickness. Therefore, the sensitivity of the CSRR has improved with the addition of the IDS.