A Novel Design of Two Loosely Coupled Bandpass Filter Based on Hilbert-zz Resonator with Higher Harmonic Suppression

New characteristics of fractal design scheme has been introduced to generate compact two poles capacitively coupled microstrip bandpass filter by using additional coupling stubs for different wireless applications. The presented fractal scheme is based on specific type of Hilbert space-filling curve which is called Hilbert-zz fractal geometry. The performance of generated bandpass filter structure has been analyzed using Sonnet software package with a relative dielectric constant of 9 and a substrate thickness of 1.27 mm. Results show that these filters possess good transmission and return loss characteristics, besides higher harmonics suppressions; meeting the specifications of most of wireless communication systems.