Compact Millimeter-Wave High-Selectivity Filtennas and Arrays Incorporating Multiparasitic Structures for Miniaturized Wireless Devices

In this article, compact millimeter-wave (mmWave) filtennas are proposed based on the multiparasitic structure incorporation technique to achieve high selectivity, and their working principle is systematically analyzed using equivalent lumped circuits. Initially, a single-polarized filtenna is designed in the form of a proximity-coupled stacked patch antenna. Cross and ring patches are employed to achieve compact size, while high selectivity is realized by incorporating multiparasitic structures, i.e., shorted stubs, ring patches, and C-shaped strips. Subsequently, the single-polarized filtenna is extended to a dual-polarized version by utilizing two sets of identical feeding structures, while maintaining high polarization isolation. Prototypes of both the single- and dual-polarized filtennas are fabricated and measured. The results indicate that the −10-dB impedance bandwidths of the filtennas cover a broad mmWave band ranging from 24.25 to 29.5 GHz, with out-of-band suppression exceeding 20 dB. Furthermore, two $1\times 4$ arrays are constructed using the proposed single- and dual-polarized filtennas, respectively, incorporating essential decoupling structures to improve the port and polarization isolation. Experimental results confirm the exceptional scanning and filtering performances of the two arrays. The merits of all the proposed filtennas and arrays make them promising candidates for B5G/6G miniaturized wireless devices.