A Wide Stop Band 6-Pole Stepped Impedance Low Pass Filter Using Double Equilateral U- Shaped Defected Ground Structure

Filters play an important role in microwave applications. Micro strip filters play various role in wireless communication or mobile communication systems. There is an increasing demand for newer microwave and millimeter wave system to meet the emerging telecommunication challenge with respect to size, cost and performance. This paper presents a compact microstrip stepped impedance lowpass filter with ultra-wide stop band. A compact double equilateral U-shaped defected ground structure (DGS) unit is proposed. In contrast to a single finite attenuation pole characteristic offered by the conventional dumbbell DGS the proposed DGS unit provide dual finite attenuation poles that can be independently controlled by the DGS lengths. A 1.5-GHz microstrip low pass filter using five cascaded double U-shaped DGS unit is designed and compared with conventional DGS low pass filter.