Compact One-piece Coaxial In-line Comb Filters and Duplexers with Transmission Zeros

This paper introduces a specific class of in-line coaxial pass-band filters that do not require explicit cross couplings for the realization of transmission zeros. Both lower stopband and upper stopband TZs can be accommodated in the frequency response. The resulting structure is a compact one-piece metal filter or diplexer that can find application in low-loss, low PIM applications.