A Frequency-Reconfigurable Antenna With Filtering Characteristics Using Characteristic Mode Analysis

In this letter, a planar filtering antenna with reconfigurable frequency selectivity is proposed. The basic structure is a linear array of three patches. Unlike the conventional gap-coupled patch antennas, the electric and magnetic coupling between adjacent patches is formed respectively by placing a row of shorting pins on the chosen edge of a patch. As a result, the mixed coupling effect makes the antenna array have filtering characteristics with no extra circuit. With the aid of characteristic mode analysis, intuitive but physical insights are shed upon its working mechanism. Besides, it shows that the resonant frequency and coupling strength are sensitive to the number and the locations of shorting pins. By using diodes to control the shorting state of each pin, the frequency band can be finely tuned from 2.19 to 2.81 GHz while maintaining stable filtering performance within nearly constant bandwidth.