The midband frequencies of the two passbands are 1.8GHz and 2.4GHz, respectively. The equal-ripple (0.01dB) fractional-bandwidths of both passbands are 4%.

A microstrip two-degree dual-band bandstop filter. The midband frequencies of the two stopbands are 1.7GHz and 2.3GHz, respectively. The equal-ripple (0.1dB) fractional bandwidths of both stopbands are 40%.

A UWB filter using a dual-mode ring resonator loaded with a short-circuited stub and a piece of aperture-enhanced parallel- coupled lines. The filter has a 50% fractional bandwidth. The passband insertion loss is less than 1.2dB, and the group delay is less than 0.8ns.

A three-degree UWB filter using parallel-coupled line resonators. The filter has an insertion loss better than 1dB and return loss greater than 15dB at most frequencies within the passband.

A millimeter-wave UWB filter using dual-mode ring resonator and multiple-mode parallel-coupled line structure. Within the passband, the insertion loss of the filter is less than 2dB, and the return loss is larger than 15dB at most frequencies.

Compact Waveguide Filter Using Planar Resonator with Transmission Zeros