Monolithically Integrated Coaxial Resonator-Based Filtennas Using SLA Three-Dimensional Printing

Three Dimensional Printed Vertically-Stacked Single-/Multi-Band Coaxial Filters and RF Diplexers

“…The proposed RF filtering technologies exhibit the following unique features: 1) low form-factor due to the use of vertically stacked, low-profile capacitively-loaded coaxial cavity resonators and due to their monolithic integration; 2) multiple TZs that increase the selectivity of the filter thanks to the space arrangement of the resonators that enable the realization of cross-couplings; and 3) versatile single band and dual-band quasi-elliptic transfer functions that are realized with 3-D coaxial high-Q resonators. Compared to the authors' previous work in [45], [46], [47], [48], [49], the filtering architectures in this manuscript demonstrate a higher level of geometrical complexity where vertical-stacking, cross-couplings, electrical/magnetic couplings, and novel external coupling structures are combined within a monolithically-integrated RF component. Furthermore, advanced transfer-functions are uniquely demonstrated using compact monolithically-integrated coaxial resonators.…”

“…Furthermore, compared to the BPF in [29] where TZs are generated using cross couplings, this work proposed a new type of CRD to facilitate TZ generation by super-positioning two filtering paths as validated by the three-pole/two-TZ BPF. With regard to the dual-band BPF in [22], the filter in this work exhibits a TZ between the two passbands to improve the isolation due to the use of different coupling elements in the two filtering sections Compared to the authors' prior work in [45], [46], [47], [48], and [49], the filters presented in this work exhibit a significantly higher level of complexity including the combination of vertical-stacking, cross-coupling, positive, and negative coupling elements. Furthermore, novel external coupling structures, resulting in filtering components with higher order, and advanced transfer functions have been demonstrated.…”

“…On the other hand, coaxial resonator-based devices are mostly manufactured using split-block approaches [43], [44], which result in higher weight and volume due to the assembly screws and radiation loss which led to a high IL in the BPF e.g., 1.3 dB in [28]. Recently, a monolithic integration concept of coaxial cavity resonators using SLA 3-D printing has been proposed for the realization of BPFs with TZ, extended spurious-free range, multiband functionality, and co-design of the filtering antenna [45], [46], [47], [48], [49].…”

Seamless Integration Technology for Filtenna Toward 5G/6G Wireless Communications

“…To safeguard the primary filtering characteristics, the radiation quality factor of the filtenna (Q r ) needs to coincide with the external quality factor of the filter, and the coupling coefficients between resonators and radiating antenna are calculated by means of customary coupled resonator theory. With merits of low-loss and high-power capability, a large number of resonant-cavity-based filtennas such as SIW [60]- [66] and waveguide [67]- [71] have been thoroughly reported in the designs of the microwave/mmWave antenna with excellent frequency selectivity. To maintain high frequency selectivity, direct-coupled filtennas typically possess relatively large size, making them challenging to implement for multi-beam applications.…”

A Monolithically Printed Filtering Waveguide Aperture Antenna

“…However, the performance sensitivity of filtering antennas to the fabrication tolerance and fabrication cost remains as two significant challenges. In [17][18][19], the 3-D printing techniques have adapted for the design of narrow bandwidth filtering antennas. It should be mentioned that the 3-D printing technique has numerous advantages over conventional techniques such as making the whole filtering antenna device out of a single piece.…”