Cross coupled wiggly line hairpin filters with high selectivity and spurious suppression

A low cost and compact microstrip bandpass filter with high selectivity and suppressed harmonic is introduced in this paper. A simple hairpin resonators filter is manipulated to obtain the desired filter performance. Line widths of the resonators are perturbated to adjust odd mode phase velocities in order to lower the higher order modes. Furthermore, by implementing a proper cross coupling from input or output to nonadjacent coupled sections, virtually a quintuplet coupling scheme is realized to improve the filter selectivity. Then the final improved hairpin filter has a sharp cut-off, a low spurious level, and still has the same compact size. The proposed combined technique is very attractive for variety of miniature filter applications. A sample filter is designed for this purpose and it can be adopted in variety of wireless subassemblies including low power radio carriers, mobile communications, and WIMAX applications.