Design of a 5.8 GHz Narrow Band-pass Filter with Second Harmonic Suppression Using the Open Stubs

In this paper, integration of bandstop filter with the flexible narrow bandwidth of bandpass filter with lambda_g/2 open stubs by microstrip line on duroid substrate is presented. This kind of filter shows flexible bandwidth with variation of the position of the open stubs using the external quality factor, Qe without changing the impedance value at microwave range. On the other hand, by replacing the series quarter-wavelength connecting lines with the equivalent T-shaped line, one could have compact stub bandpass filter with second harmonic suppression. This filter shows the insertion loss of 1.2 dB and the return loss of 21.9 dB at the center frequency of 5.8 GHz.