A Wideband Bandpass Power Divider With Out-of-Band Multi-Transmission Zeros and Controllable Equal-Ripple Levels

Abstract

In this article, a novel wideband bandpass power divider (PD) with out-of-band multi-transmission zeros (TZs) is presented. It consists of <inline-formula> <tex-math notation="LaTeX">$2M$ </tex-math></inline-formula> shunted short-circuited stubs (SCSs), (<inline-formula> <tex-math notation="LaTeX">$M + N$ </tex-math></inline-formula>) cascaded coupled line sections, and (<inline-formula> <tex-math notation="LaTeX">$M + N - K_{N}$ </tex-math></inline-formula>) isolation resistors. There are two types of topologies, and the number of TZs is solely determined by <inline-formula> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula>. Through even- and odd-mode analyses, general simultaneous equations for characteristic impedances, coupling strengths, and isolation resistors are derived with the proposed algorithm. By suitably selecting all the design parameters, all the <inline-formula> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula>-parameters (<inline-formula> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$S_{21} = S_{31}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$S_{22} = S_{33}$ </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">$S_{32}$ </tex-math></inline-formula>) of the proposed topology could provide an equal-ripple response with controllable ripple level in the passband. For a given fractional bandwidth (FBW), TZs and out-of-band rejection level can be designed independently. For further optimization, several isolation resistors can be omitted with the unchanged performances. For verification, two experimental circuits are fabricated and measured. Good agreement between the measured and simulated results is attained so as to successfully validate the correctness of the proposed design approach.