Ultra-Compact Power Divider Using Dual-Function Input External Quality Factor for Good Filtering Response and Isolation

Abstract

An ultra-compact filtering power divider is proposed with a simple circuit topology by using dual-function input external quality factor Qe-in. First, $\mathcal{\pmb{Q}}_{\pmb{e}}$ -in represents the coupling effect between input port and input resonator, which is important to realize a good filtering response. Second, $\mathcal{\pmb{Q}}_{\pmb{e}}$ -in can be regarded as an admittance inverter of 90-degree phase delay, which can be used as an impedance transformer for good outputs isolation. Consequently, the $\pmb{\lambda/4}$ transmission lines, commonly used in previously published filtering power dividers, can be removed in this work, resulting in a very compact configuration. By further employing the compact dual composite right- and lefthanded (D-CRLH) resonators, over 45% size reduction can be realized when compared with the published filtering power dividers. For demonstration, a compact filtering power divider is designed and fabricated. The measured results are in good agreement with the simulations.