Design of broad‐stop band low pass filter using a novel quasi‐Yagi‐DGS‐resonators and metal box‐technique

A novel 1.8 GHz compact microstrip low pass Filter (LPF) based on quasi‐Yagi defected ground structure (DGS) and compensated capacitors is proposed in this article. The filter has a very sharp cut‐off frequency response with low insertion loss and achieves a wide reject band with overall 20 dB attenuation from 2.8 GHz up to 10 GHz. The equivalent circuit model of Yagi‐DGS unit is derived using AWR software and the circuit parameters are extracted by using a simple circuit analysis method. The advantage of this structure is that the reject band can be controlled by tuning the dimension of yagi‐arms at higher frequency rang. To improve the filter characteristics in reject band, a new metal box has been used to minimize the loss in pass band and to extend the reject band. The proposed LPFs are designed and fabricated. The compact filter occupies an area of (0.45 λg × 0.35 λg) with λg = 44 mm. A comparison between simulation and measurement results confirms the validity of the LPF configuration and design procedure.