A single grooved coupled line bandpass filter with improved
pass band response and first harmonic suppression is described.
The suppression of the first spurious harmonic was done by using rightangle
triangle grooves in the middle of each of the coupled-microstrip
lines that construct the bandpass filter. As the number of grooves increase
as the shift in the operating frequencies increase also, so it is
suitable to use less numbers of grooves as possible. A three stage bandpass
filter using coupled-microstrip lines was designed, simulated, and realized
to illustrate this idea. The simulated results illustrate a good performance
for right-angle triangle groove over the corresponding rectangular
groove. The measured S-parameters measurement of the realized bandpass
filter shows the suppression of the second resonance frequency and less
shift in the center frequency