Tuning of end-coupled line bandpass filter for 2.4 GHz using defected ground structure (DGS) parameters

Defected ground structures (DGS) have known to be serving for the improvement in characteristics of many microwave circuits. Not only DGS has various advantages in the area of microwave power amplifier, Wilkinson power divider, microwave antennas, couplers etc, it is also used in the design of microwave filter to achieve stopband effects, slow-wave effects, frequency adjustment etc. A bandpass filter based on Dumbbell-shaped DGS unit is presented here. This unit provides two transmission zeros near the passband edges. The center frequency has been tuned to 2.4 GHz using different dimensions of DGS. This filter gives an insertion loss of -0.42 dB, a return loss of -12.31 dB and -3 dB bandwidth of 0.92 GHz. The tuning of end-coupled line bandpass filter, using dumbbell DGS structure parameters is discussed here. The measurements show a close agreement with simulation results.