Improvement of compactness of low pass filter using new quasi-yagi-DGS-resonator and multilayer-technique

Abstract

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 paper. 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. The proposed 1.8 low-pass filter is designed using microwave office electromagnetic software and fabricated on the RO4003 ceramic structure with dielectric constant of 3.38. The compact filter occupies an area of (0.45λg × 0.35λg) with λg = 44 mm. A comparison between simulation and measurement results confirms the validity of the LPF configuration and design procedure. In order to improve the compactness of the proposed LPF, a new multi-layer method has been employed. Finally, a new minimized LPF-topology 50% more compact than the conventional is realized.