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Polarization diversity is an antenna feature that has been widely researched to increase the capacity of a wireless communication system. The conceptual theory of polarization states that all polarization vectors can be decomposed into two orthogonal electric field vector modes. This study proposes a novel framework to bridge the gap between circular polarization (CP) technique and filtering antenna design using two orthogonal resonators with the ability to represent any polarization. The proposed method combines the techniques of antenna–filter and CP design into a single integrated step. To achieve the second-order antenna–filter integration and generate CP, the two orthogonal resonators modeled as a rectangular radiator and a $\lambda $ /4 resonator combined. The CP filtering antenna operates at a frequency of 4.65 GHz, with an impedance bandwidth of 4.7%, an axial ratio (AR) bandwidth of 3.2%, and a gain of 6.2-dBi. To validate the CP filtering antenna, simulations and measurements were performed, and the results were found to be in good agreement.

Integration of high-sensitivity sensors with multiple sensing performance for the environmental detection of permittivity (εr), conductivity (σ), and the refractive index (n) is required to support Societies 5.0. However, there are still many sensors with low sensitivity that stand alone. A shear-horizontal surface acoustic wave (SH-SAW) sensor is usually used because of its high-sensitivity performance in detecting electrical properties. Moreover, localized surface plasmon resonance (LSPR) sensors show remarkable optical side capability. Here, we have successfully combined these advantages with an additional benefit of sensitivity enhancement. We propose a hybrid acoustoplasmonic sensor generated by integrating SH-SAW and LSPR devices to simultaneously detect εr, σ, and n. The SH-SAW sensor was fabricated on a 36XY-LiTaO3substrate using a developed interdigital transducer. Then, the LSPR sensor was implemented by the deposition of gold nanoparticles (AuNPs) on the propagation surfaces of the SH-SAW sensor. Fascinatingly, the AuNPs not only generate the LSPR effect but also enhance the SH-SAW sensor sensitivity. Comprehensive investigations were performed with atomic force microscopy imaging, CST software used for plasmonic E-field simulation, and hybrid sensing evaluation. Moreover, the SH-SAW sensitivity enhancement achieved using AuNPs was verified by frequency-domain and time-domain measurements. Thus, the SH-SAW sensor with AuNPs has a wide εrdetection range (25–85), sensing capabilities for ultrasmall σ (0.00528–0.02504 S/m), and high sensitivity for ndetection (45.5–201.9 nm/RIU). The cross-sectional effects were also evaluated. The effect of the LSPR device on the SH-SAW device was examined by turning the light OFF or ON (hereafter OFF/ON). The impact of the SH-SAW device on the LSPR device was investigated by turning the sine signal OFF/ON. We found that the SH-SAW sensor was not impacted by light. Interestingly, the presence of the SH-SAW sensor affects the positions of the AuNPs, which consistently generates a small blueshift in the LSPR effect. However, insignificant variation was noted in independent performances. In general, the SH-SAW sensor with AuNPs shows multifunctional independent characteristics and high-sensitivity performance, making it suitable for a chemical environment, with the possibility of integration with a wireless network.