A Compact Filtering Antenna for WLAN Applications

This paper considers a type of antenna widely referred to as a filtenna. Here, the filtering element is incorporated into a regular patch antenna, with the primary function not suffering from radiation performance. Described in this article is a microstrip filtering antenna designed for WLAN communicating systems operating at a 5.5 GHz band. Such an innovative antenna design achieves essential radiation characteristics and out-of-band rejection features to synthesize two functions of antenna function and filter in one device. The antenna structure consists of four U-shaped resonators, one L-shaped resonator, and many parallel coupling lines. The parallel coupling lines act as an admittance transformer to the integration of a filter with the antenna, while the highest-order resonator filter is the L shaped resonator, enhancing the filtering effect. Simulation results of designed filtering antennas at an operation frequency of 5.5 GHz display the return loss values of less than 15 dB. It is followed by a detailed analysis of gain response, impedance characteristics, and radiation performance. Compared to other conventional designs, this antenna is compact and very tiny in overall size.