Design of a Multifrequency One-Quarter-Rings Microstrip Antenna

A novel multifrequency one-quarter-rings microstrip antenna is presented in this letter. The proposed antenna consists of two one-quarter rings in different sizes, with an inverted T-shaped slot loaded. The T-shaped slot is used to suppress the higher-order mode. The relationship of the resonant frequency $f$ with different physical size parameters for the single one-quarter-ring microstrip antenna is also reported, and it contributes to the antenna design. The resonant frequencies of the multifrequency antenna are determined by the size of the one-quarter rings. The experimental results show that the proposed antenna operates at 0.9, 1.4, 1.8, and 2.4 GHz, respectively. The radiation patterns at different resonant frequencies are similar.