Filtennas for wireless application: A review

In recent year, various filtenna circuits have been developed satisfying the objectives and prerequisites of wireless communication. Some of these developed designs are new or some are the improved version of previous works whereas the others are the combination of conventional methods. This article presents the review of filtenna circuits starting from the beginning to the improvements until date. This article starts with brief overview of various filters with their design strategies and ends in its implementation in filtenna designs followed by discussion on several filtenna designs in term of size and overall performances. Among various designs, bandpass, and bandstop filters are extensively used in filtenna realization as it provides a better selectivity in desired band. Various planar filtenna circuits, based on either defected ground structure (DGS) or resonator or SIW filters are reviewed and presented. Besides, planar filtennas, these filters are also integrated to the aperture of horn antennas for the realization of horn filtennas, applicable for high frequency operations. It is observed that SIW based filtennas exhibited narrow impedance bandwidth. This feature can be improved by doubling substrate layer as well as the number of metallic ways. Whereas, resonator based filtennas use resonator based filters along with DGSs to enhance impedance bandwidth as well as minimize mutual coupling and cross-polar radiation. Apart from single element filtenna, filtenna arrays, and reconfigurable filtennas (including planar and horn reconfigurable filtennas) are presented. This review article may be helpful for beginners working on filtenna circuits and also such a review process is not available in the open literature to the best of author's knowledge.