This paper proposes two new multi-section dumbbell-shaped defected ground plane structures (DGS). The defects are created in the ground plane of the conventional single-layer microstrip transmission line. The proposed DGSpsilas application in microwave filtering is investigated. It turns out that these new DGSpsilas can be used to realize notch filters (i.e. narrow-band band-stop filters) with steep rejection characteristics in the stopband, and that the center frequency of the design can be systematically controlled through controlling one physical dimension of the DGS pattern.