Compact planar ultra-wide pass-band filters with source-load coupling and impedance stubs

New configurations of folded and compact planar ultra-wideband filters with source- load cross coupling and impedance stubs are presented. Stepped impedance resonators and coupled-line sections as inverter circuits form the basic filter structures. High-low impedance lines connect individual resonators. Effective techniques such as open-stub lines and source-load cross coupling are utilized in order to add return-loss poles in the pass-band and create transmission zeros in the lower/upper stop-band region. Several filters are designed with 3dB fractional bandwidths of 80 percent, computed insertion losses better than 1 dB and return losses larger than 10 dB. Rejection levels in the upper/lower stop-bands are better than 35 dB. The designs are verified by results obtained with commercial electromagnetic software packages.