Parametric Analysis of the Edge Capacitance of Uniform Slots and Application to Frequency-Variation Permittivity Sensors

This paper presents a parametric analysis relative to the effects of the dielectric constant of the substrate, substrate thickness and slot width on the edge capacitance of a slot-based resonator. The interest is to find the conditions (ranges of the previously cited parameters) compatible with the presence of a quasi-magnetic wall in the plane of the slot (or plane of the metallization). If such magnetic wall is present (or roughly present), the electric field in the plane of the slot is tangential (or quasi-tangential) to it and the edge capacitance can be considered to be the parallel combination of the capacitances at both sides of the slot. Moreover, variations in one of such capacitances, e.g., caused by a change in the material on top of the slot, or by a modification of the dielectric constant of the substrate do not affect the opposite capacitance. Under the magnetic wall approximation, the capacitance of certain electrically small slot-based resonators can be easily linked to the dielectric constant of the material present on top of it. The consequence is that such resonators can be used as sensing elements in a permittivity sensor and the dielectric constant of the so-called material under test (MUT) can be determined from the measured resonance frequency and a simple analytical expression. In this paper, the results of this parametric analysis are validated by considering several sensing structures based on dumbbell defect ground structure (DB-DGS) resonators of different dimensions.

Dual-Band Quarter Mode SIW Cavity Back Slot Antenna

A miniaturized quadrant slot antenna backed by the cavity using QMSIW technique is developed for dual-frequency applications. The design process is begun with FMSIW circular cavity which has been cut along magnetic wall twice to get quadrant sector of a circular cavity that is said to be a QMSIW cavity. The QMSIW cavity excited in TM210 and TM020 modes is loaded by quadrant slot which helps to decrease the resonant frequencies. The CST microwave studio is used to study the operating mechanism of various modes in the cavity. The antenna has been fabricated and measured the S11 and principle pattern and also compared with simulated results. The experimental results prove that the antenna S11 in dB is low at dual-frequency. One of the resonant frequencies is at 8.05 GHz and other 9.95 GHz with peak gains are around 6.25 dBi and 6.45 dBi respectively.