A Simple Frequency Reconfigurable Filtering Antenna for Highly Integrated IoT Applications

In this paper, a simple frequency reconfigurable filtering patch antenna is proposed for highly integrated Internet of Things (IoT) applications. This design successfully enables a single antenna to operate across multiple frequency bands while consistently delivering excellent anti-interference performance. The proposed design exhibits a two-layer structure, including a U-shaped feedline, two feeding strips, a radiating patch, and five tuning elements. Five varactors are employed to achieve frequency reconfiguration, enabling the synchronous adjustment of three in-band resonances and two out-of-band radiation nulls. The entire reconfiguration process can be accomplished by applying only one set of control voltages, effectively simplifying the operation procedure and significantly reducing the complexity. The proposed antenna has a size of 0.69λ0×0.69λ0×0.079λ0(λ0 denotes the wavelength corresponding to the center frequency at the lowest state), a frequency tuning range of 35.1% (2.42-3.45 GHz), and each state has an operating fractional bandwidth of more than 13.8%, maintaining good filtering performance.