Printed Circuit Coupled-Line Filters for Bandwidths Up to and Greater Than an Octave

The realization of edge-coupled-line filters as printed circuits has generally been assumed to be confined to filters with fractional bandwidths of 30 percent or less. However, the design technique described herein has eliminated the 30-percent restriction and such filters may now be constructed for fractional bandwidths up to approximately 100 percent. Instead of constraining the physical realization to be a cascade of coupled lines, the technique allows the realization to consist of coupled lines and simple lengths of line cascaded in such a way that resultant circuit dimensions are practicable for the bandwidth specified. Practical examples are specified.