A Group-Delay-Based Sensor Using Active EIT-Like Effect With Double Sensing Applications

A high-sensitive microwave sensor based on the variation of group delay is presented in this paper. The sensor is designed by mimicking the concept of electromagnetically induced transparency (EIT). The EIT-like effect that applied in the microwave circuit can provide a narrow transmission window in the stop band, which also brings ultraslow group velocity. Combined with the utilization of active resonator, the quality factor and group delay of the sensor are significantly enhanced. The active resonator is actualized by appending an active feedback loop that couples with the split-ring resonator of the EIT-like structure. The group delay of the active EIT-like sensor is particularly sensitive to the tiny phase variation of the active feedback loop, which is adopted to the high-performance sensing functions. The active EIT-like sensor with double sensing applications in this paper was fabricated and tested. The sensitivity of the proposed sensor is 0.012 pF/ns and 0.03 mV/ns, respectively.