Differential-Mode Low-Pass Filter Using Hybrid CPS and G-CPS With Intrinsic Common-Mode Rejection

In this paper, a novel class of differential-mode (DM) low-pass filter (LPF) with intrinsic common-mode (CM) rejection is proposed for the first time using the hybrid coplanar stripline (CPS) and the grounded CPS (G-CPS). The CPS section of the proposed DM LPF only supports DM signals and rejects its counterpart CM intrinsically. Then, the DM performances are left to be focused on in the design process of the proposed DM LPF. By utilizing the feature of high-characteristic impedance CPS and low-characteristic impedance G-CPS transmission lines, two DM LPF prototypes are designed, fabricated, and measured: one for validating the conception of DM LPF with intrinsic CM rejection and another one with the same design specifications for achieving enhanced stopband and miniaturized size simultaneously against the above-designed one. All simulated and measured frequency responses of these two DM LPFs are found to match well with each other, which further demonstrates the claimed superior performances of the proposed LPFs in terms of intrinsic CM rejection, enhanced stopband, and miniaturized size.