Multi-Channel Capacitive Sensor Arrays

Abstract

In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved.

A Microwave Microfluidic Sensor Based on a Dual-Mode Resonator for Dual-Sensing Applications

“…Also, microwave structures can be readily implemented in the integrated circuits, which have become a favourable platform due to their constantly decreasing cost. As such, microwave sensors have found numerous applications including permittivity sensing [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], strain and displacement sensing [ 16 , 17 , 18 , 19 , 20 ], detection of biomolecules [ 21 ], glucose monitoring [ 22 , 23 ], dielectric spectroscopy for food quality control [ 24 , 25 ], gas sensing [ 26 , 27 , 28 ], and concentration measurements of liquid solutions [ 29 ].…”

“…The operating principles of the proposed microwave sensors predominantly rely on the resonance concept [ 4 , 5 , 6 , 7 , 9 , 10 , 12 , 14 , 15 , 16 , 19 , 20 , 21 , 23 , 29 ], however there are also structures based on transmission line [ 1 , 2 , 18 , 26 , 27 , 28 ] and capacitive methods [ 13 , 17 , 22 ], as well as on more peculiar phenomena such as energy tunneling [ 3 , 11 ] and metasurfaces [ 8 ]. Besides split ring resonators (SRR) [ 4 , 9 , 14 , 15 , 16 , 19 , 20 , 21 ], which have been widely exploited in resonant-type sensors, there have also been proposed sensors with cavity [ 6 , 29 ] and stepped impedance resonators (SIR) [ 5 , 7 ].…”

“…Besides split ring resonators (SRR) [ 4 , 9 , 14 , 15 , 16 , 19 , 20 , 21 ], which have been widely exploited in resonant-type sensors, there have also been proposed sensors with cavity [ 6 , 29 ] and stepped impedance resonators (SIR) [ 5 , 7 ]. As for the transmission line-based sensors, the majority of them have been realized using the substrate integrated waveguide (SIW) [ 27 ], coplanar waveguide (CPW) [ 18 , 26 , 28 ], microstrip with electromagnetic bandgap (EBG) structures [ 2 ] and microstrip differential lines [ 1 ], whilst capacitive sensors have been realized as a gap [ 13 ], plate [ 17 ] or interdigital [ 22 ] capacitor in microstrip configurations.…”

“…Most multiple-sensing devices are based on sensor arrays [ 30 , 31 , 35 , 37 ], which demand multiple outlets and separate read-outs, thus making the structure more complex. Although the microwave sensors in [ 5 , 16 , 17 , 18 , 19 ] are aimed at multiple sensing and employ one read-out system, such operation is achieved using multiple, physically well-separated sensing elements, leading to cumbersome structures.…”

A Touch Sensing Technique Using the Effects of Extremely Low Frequency Fields on the Human Body

“…Many touch sensing technologies have therefore been developed for commercial purposes. Examples include technologies based on infra-red sensing elements [1,2,3,4], resistive [5,6] and capacitive touch panels [7,8,9], cameras [10], the acoustic and deflection characteristics of touch panels [11,12,13], and others [14,15,16]. One of the widely used techniques is the mutual capacitive method, which is used in almost all smartphones and tablets [17].…”