Tunable Defected Ground Structure Band Pass Filter for Cognitive Radio Applications

This paper introduces tunable bandpass filter (BPF) based on two coupled resonators defected ground structure (DGS). The DGS slots are the essential components of our designed BPF. The two E-Shape slots are etched in ground plane with lumped capacitor to operate in cognitive radio applications. The lumped capacitor expands the effective capacitance of the resonator and reduces its resonant frequency, which prompts compact size. The proposed BPF has center frequency of 2.4 GHz, bandwidth from 2.2 to 2.6 GHz and rejection higher than 20 dB up to more than 6 GHz in the stop band region. The filter has insertion loss lower than 0.4 dB within the pass band region. The simulated and measured results are introduced to confirm the filter realizations.