Design of stub based ultra wideband filter with low insertion loss

摘要

This paper proposes a microstrip ultra-wideband (UWB) filter using quarter wavelength long short circuited stubs. The designed filter is based on 5th order Chebyshev lowpass prototype with 0.1dB Passband ripple. The structure is designed on low cost Arlon substrate with relative dielectric constant of 2.6 and a thickness of 1.27 mm. The filter provides a fractional bandwidth (FBW) of 106% (3.13 GHz–10.4 GHz) and excellent scattering parameters with insertion loss below 0.1dB and return loss better than 16.5dB. As the phase response is ripple free over the entire passband, which gives a flat group delay of 0.3nsec, thus, filter is well suited for UWB applications.