A low profile band pass DGS filter for harmonic suppression

This paper introduces a novel low profile microstrip band pass DGS filter for blocking undesired resonant frequencies when higher modes are excited. The proposed filter is combined with a microstrip inset-fed rectangular patch antenna. The higher modes are excited for implementation of DGS band pass filter harmonic rejection. This filtenna structure performs as the combination of a low profile BPF and an antenna. The bandwidth of proposed filter varies from 150 MHz to 4.5 GHz according to whether a single mode or several modes are selected which could be adjusted by changing the series capacitance in the ground plate. This DGS filter uses FR4 epoxy as substrate (with dielectric constant=4.3, tangent loss=0.025, thickness of 63 mil). The BPF reaches to 90% efficiency in insertion loss and 20dB/GHz attenuation rate for the transition band region. In addition, the proposed BPF has a compact size of 10mm*14mm for notch filter and 10mm*10mm for ultra-wide-band (UWB) antenna with input impedance of 50 Ω.