Design of periodically elevated groundplane SSS band-pass filter with suppressed second harmonic

Using periodically elevated groundplane along the coupled line sections in the lower cavity of suspended substrate stripline (SSS), a parallel-coupled line band-pass filter having suppressed harmonic at 2f₀ has been designed. Even and odd mode phase velocities in each coupled line section at 2f₀ have been equalised by using the right number of periodic grounding cells with proper dimensions. Based on this equalisation technique, a filter at 2.4 GHz has been designed and fabricated to prove the concept.