NOVEL MICROSTRIP-LINE DIRECTIONAL FILTERS

This paper presents two new structures of four-port microwave directio nal filters incorporating microstrip-line resonators, uniplanar 180 de grees phase-reversal units, and two or four identical p-i-n diodes, Th ese filters provide substantially improved frequency characteristics c ompared to the conventional constructions. The unique feature of them is that they ensure high-level isolation independent of frequency betw een opposite ports, Due to this electrical property the proposed filte rs may be suitable for some pulse-radar applications.