A low-cost photonic band gap (PBG) microstrip line resonator for dielectric characterization of liquids

Abstract

Abstract In this paper, hybrid integration of planar microstrip line and Photonic Band Gap (PBG) structure is proposed for the dielectric characterization of liquids. To implement the PBG structure of the microstrip line, a microfluidic channel with periodic form is introduced into the substrate and filled with different liquids. Based on this configuration, the operation principle of the sensor is based on a frequency shift due to the variation in the center of the bandgap, which in turn changes with the variation of the permittivity of LUT filled in the microfluidic channel. The proposed sensor exploits the behavior of the bandgap as a reflector to construct a resonant structure sensitive to the variation in LUT permittivity. The dimensions of the planar structure are optimized to achieve high precision and discrimination capability. The different empirical expressions describing the complex permittivity with the measured parameters were carried out. To validate the proposed concept, the sensor prototype is designed, fabricated, and tested. The frequency shift related to a change of 3.2 in LUT permittivity corresponds to 180 MHz around 6 GHz. The resonant-mode sensor spans a permittivity range from 1 to 80 with a precision better than 7.2%. The proposed sensor is simple in design and low cost, which may be applied in different applications at the industrial.