Design of Compact Quadrature Power Splitters Using CM/CPW Transmission Lines

This paper presents two miniaturized designs of quadrature power splitter (QPS) using the state-of-the-art composite microstrip and coplanar-waveguide (CM/CPW) transmission line at 1 GHz. Two compact QPSs, Design A and Design B, are optimized with zigzag-CM/CPW lines in small sizes of 0.057×0.027 λ
²
and 0.050×0.037 λ
²
, respectively. They both have advantages of low cost and easy fabrication attributed to the use of only a single dielectric substrate-layer. While ensuring the miniaturization of circuit board, the power imbalance is minimized at 0.2 dB between two output ports, whereas the error of quadrature (90°) phase is suppressed as low as 0.2° at the center frequency. Besides, high levels of port isolation are achieved within the overlapped fractional bandwidth (15 dB) from 0.78 to 1.29 GHz (Design A) and 0.75 to 1.22 GHz (Design B), respectively. This kind of design has great research and reference value for the miniaturization design of linear vector modulator and micro broadcast circuit design in the future.