3-D Printed Vertically Integrated Composite Right/Left-Handed Transmission Line and Its Applications to Microwave Circuits

This article demonstrates a new design concept of 3-D printed multilayer vertically integrated composite right/left-handed (VI-CRLH) transmission lines (TLs) with compact size, broadband, and a balanced CRLH dispersion performance. For proof-of-concept, the proposed 3-D VI-CRLH TLs are applied for designing a new bandpass filter (BPF) and a new coupler, respectively. The VI-CRLH BPF consists of one VI-CRLH unit, two open-loaded stubs, and two short-loaded stubs with compact size, wide operational band, great in-band flatness, and good out-of-band rejection. The VI-CRLH coupler consists of two VI-CRLH TLs located at the top and bottom sides of the substrate with excellent magnitude and phase balances. The additively manufactured electronics (AME) solution, which can 3-D print conductive and dielectric layers simultaneously, is discussed to implement the proposed multilayer VI-CRLH BPF and coupler. The complex permittivity of the dielectric materials is measured using a quasi-optical cavity test system. Finally, the proposed BPF and coupler are manufactured and measured. Good agreement between the simulated and measured results indicates that the VI-CRLH TLs can be fully 3-D printed to achieve miniaturized microwave circuits with excellent performance.