Compact Mixed‐Type Filtering Power Dividers Using Microstrip Asymmetric Coupled‐Lines and Lumped Components

In this letter, two compact mixed‐type filtering power dividers (FPDs) using microstrip asymmetric coupled‐lines (ACLs) and lumped components are proposed. The frequency mapping of ACLs and lumped components is realized by a modified Richard's transformation, and then the transformation formulas for two types of ACLs and lumped components are derived. Two types of second‐order coupled‐resonator filters with different port impedances are used as prototype for FPDs. Two configurations of the mixed‐type FPDs are demonstrated with different response characteristics. One of them is fabricated using a low‐cost process, demonstrating good performance and the smallest size among reported PDs and FPDs. The center frequency of the FPD is 1.1 GHz with the minimum additional insertion loss of 0.59 dB and a fractional 3‐dB bandwidth of 51%. The upper stopband with attenuation larger than 17.5 dB is from 2.1 to 6.8 GHz.