Active Microwave Resonance Sensing Based on Spoof Localized Surface Plasmon Oscillators

Spoof localized surface plasmons (SLSP) present compatibility with planar printed circuit technologies, which allow it to be combined with active circuits to enhance its sensing ability and simplify the detection process. In this work, we propose an active microwave resonance sensing scheme, which can measure the permittivity change of the sample placed on the SLSP surface. The SLSP oscillator consists of an SLSP resonator, a microstrip line coupler, and a low noise amplifier (LNA) with its peripheral circuits. This oscillator is designed around 2.5 GHz using an SLSP resonator consisting of spiral lines. The SLSP resonator is used as the filtering network of the oscillator, forming a positive feedback loop with LNA. The permittivity around the SLSP surface could change the oscillation frequency of the SLSP oscillator. The proposed SLSP oscillator provides a convenient way to output the resonance shift signal of a passive resonance sensor and drives the evolution of SLSP sensors toward more compact sensing systems.