In this paper, a systematic experimental study is presented to explore the impact of reduced parasitic capacitance on the sensitivity of the proposed contact-based LC Coplanar Sensor (LCCS), by manipulating its ground conductors. The LCCS is configured with a meander-IDC (Interdigital Capacitor) structure on a coplanar waveguide transmission line (CPW TL). To study the effect of reduced parasitic capacitance on the sensitivity, prototypes of two sensor designs are proposed: (a) LC Coplanar Sensor (LCCS), where conventional CPW TL grounds are present on either side of the signal conductor, (b) LC Coplanar Sensor with Altered Ground Conductors (LCCS-AGC), where the ground conductors around the sensing area of IDC are patterned circularly to reduce the parasitic capacitance. The proposed sensors are fabricated on an FR4 substrate, and the sensing area is configured using polydimethylsiloxane (PDMS) polymer to hold a liquid sample. RF experiments have been conducted with glucose solution samples, with a concentration range 0.0–0.5g/ml, within the 1–10 GHz frequency range. The experimental results exhibited sensitivity of LCCS is 9.311dB/g/ml, 193.943MHz/g/ml, 2.043dB/g/ml, and 140.57MHz/g/ml for <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$S_{11}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>S</mi> <mn>11</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$S_{21}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>S</mi> <mn>21</mn> </msub> </math></EquationSource> </InlineEquation>, with coefficients of linearity 0.981, 0.963, 0.993 and 0.759, respectively. In LCCS-AGC, the improved sensitivity is 10.444dB/g/ml, 288.143MHz/g/ml, 2.1316dB/g/ml, and 312.143 MHz/g/ml for <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$S_{11}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>S</mi> <mn>11</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$S_{21}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>S</mi> <mn>21</mn> </msub> </math></EquationSource> </InlineEquation>, with coefficients of linearity 0.986, 0.964, 0.998 and 0.980, respectively. The experimental findings reveal that the LCCS-AGC exhibits a significant enhancement in sensitivity.

Sensitivity Enhancement by Introducing Altered Ground Conductors Around the Sensing Area of the Coplanar Meander-Interdigital Capacitor Structure Sensor

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发表日期：

2025年8月12日

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Swati Todi,
Poonam Agarwal

摘要

In this paper, a systematic experimental study is presented to explore the impact of reduced parasitic capacitance on the sensitivity of the proposed contact-based LC Coplanar Sensor (LCCS), by manipulating its ground conductors. The LCCS is configured with a meander-IDC (Interdigital Capacitor) structure on a coplanar waveguide transmission line (CPW TL). To study the effect of reduced parasitic capacitance on the sensitivity, prototypes of two sensor designs are proposed: (a) LC Coplanar Sensor (LCCS), where conventional CPW TL grounds are present on either side of the signal conductor, (b) LC Coplanar Sensor with Altered Ground Conductors (LCCS-AGC), where the ground conductors around the sensing area of IDC are patterned circularly to reduce the parasitic capacitance. The proposed sensors are fabricated on an FR4 substrate, and the sensing area is configured using polydimethylsiloxane (PDMS) polymer to hold a liquid sample. RF experiments have been conducted with glucose solution samples, with a concentration range 0.0–0.5g/ml, within the 1–10 GHz frequency range. The experimental results exhibited sensitivity of LCCS is 9.311dB/g/ml, 193.943MHz/g/ml, 2.043dB/g/ml, and 140.57MHz/g/ml for $S_{11}$ $S_{11}$ and $S_{21}$ $S_{21}$ , with coefficients of linearity 0.981, 0.963, 0.993 and 0.759, respectively. In LCCS-AGC, the improved sensitivity is 10.444dB/g/ml, 288.143MHz/g/ml, 2.1316dB/g/ml, and 312.143 MHz/g/ml for $S_{11}$ $S_{11}$ and $S_{21}$ $S_{21}$ , with coefficients of linearity 0.986, 0.964, 0.998 and 0.980, respectively. The experimental findings reveal that the LCCS-AGC exhibits a significant enhancement in sensitivity.