Glass-Based Bandpass Filters for New Radio (NR) K-/Ka-Band Communications

Abstract

Highly miniaturized substrate integrated coaxial (SIC) bandpass filters (BPFs) are presented for new radio (NR) communications. They are based on glass-integrated two-post SIC resonators and mixed electromagnetic (EM) couplings that contribute to two poles and one transmission zero (TZ) to the overall BPF transfer function. The concept can be extended to high-order quasi-elliptic configurations shaped by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2N$ </tex-math></inline-formula> poles and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> TZs by readily cascading <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> two-post SIC cavities through inter-stage transmission lines (TLs). A high-frequency glass-based integration platform is explored as a low-loss and high-frequency integration mechanism. To practically validate the concept, three glass-integrated BPF prototypes were designed, manufactured, and tested. They include a: 1) two-pole/one-TZ BPF with a passband centered at 26 GHz, fractional bandwidth (FBW) of 21%, and a TZ at 32 GHz; 2) two-pole/one-TZ BPF with a passband centered at 26.7 GHz, FBW of 11%, and a TZ at 23.6 GHz; and 3) a four-pole/two-TZ BPF with a passband centered at 26.7 GHz, FBW of 11%, and two TZs at 24 and 31.3 GHz.