The filter and antenna are two key components of the radio frequency (RF) front⁃end. When the antenna is directly connected with the filter, additional mismatch losses will be caused. Therefore, the antenna and filter are integrated into a single device to provide both filtering and radiating functions. In this way, many advantages, like low cost, light weight, small size and lower insertion loss can be obtained. In this paper, the co⁃design approaches of RF filter⁃antenna are reviewed. Based on the open literatures, the integrated approaches of filtering antenna can be classified into five main categories:1) Co⁃design by optimizing the interfacing impedance, 2) co⁃design according to the synthesis approach of filter, 3) co⁃design by embedding novel resonators within the feeding structures, 4) co⁃design by employing auxiliary physical structures, and 5) other methods. The RF filter⁃antenna system can improve the integration degree of RF front⁃end, reduce its size and cost, and optimize its performance.
filtering antenna; Co⁃design; RF front⁃end