Compact sensor based on CPW SSPP structure for highly sensitive dielectric constant detection

Abstract This paper presents a novel spoof surface plasmon polariton (SSPP) sensor designed to overcome the limitations of traditional microwave sensors. Compared with existing microwave sensors and recently developed SSPP-based structures, the proposed sensor demonstrates superior performance in both sensitivity and compactness. The sensor employs a coplanar waveguide (CPW) structure, with a spiral groove etched on one side of the CPW to construct the SSPP structure, which can effectively reduce the circuit area of the sensor. In addition, the sensor can utilize the localized field enhancement characteristics of the SSPP structure. The resonant frequency reflects the dielectric constant of the loaded sample, and the change in resonant frequency is used to achieve precise sensing of the dielectric constant. Experimental results demonstrate that the measured average sensitivity of the sensor can reach 4.61%, and a physical size of only <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>0.0078</mml:mn> <mml:msubsup> <mml:mi>λ</mml:mi> <mml:mi>g</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> , achieving a combination of high sensitivity and compact footprint and making it suitable for integrated design. Through full-wave electromagnetic simulation and experimental verification, it has been proven that this type of sensor has great potential in the field of measuring the relative dielectric constant of solid materials.