Self-Packaged Inkjet-Printed Vertically Integrated RF Co-Designed Bandpass Filtering Baluns

A new class of self-packaged RF co-designed bandpass filtering baluns (BPF-Bs) is proposed with alongside a novel integration scheme utilizing vertically integrated inkjet-printed multicoupled transmission lines (TLs). Furthermore, the manuscript outlines a comprehensive design methodology for their realization, exploiting the design freedom afforded by a two-material inkjet printing process, which enables the creation of tightly coupled vertically integrated TLs. The concept has been verified experimentally through the manufacturing and testing of wideband (WB) and ultrawideband (UWB) BPF-B prototypes, having f₀ = 5 GHz, footprints of 0.019 λ_g² and 0.025 λ_g², and 3 dB fractional bandwidths (FBWs) of 24% and 111%, respectively. For the WB and UWB designs, power loss, phase imbalance (PI), and amplitude imbalance (AI) were measured between 4.4 and 7.4 dB and 1.8-4.8 dB, 4° ± 4° and 2° ± 2°, and 0.45 ± 0.45 dB and 0.4 ± 0.4 dB, respectively.