New SPUDT cell structures

The present paper describes SPUDT cells, all fingers of which are wider than /spl lambda//8 while maintaining the unidirectional effect. The first solution is related to a SPUDT consisting of /spl lambda//4 and /spl lambda//2 wide fingers arranged in two tracks. Each track has no significant unidirectional effect. Both tracks form a waveguide and the waveguide coupling generates the interaction of the tracks. As a result of that interaction a unidirectional effect arises. It has been verified by experiment. A second solution is suggested that includes, in contrast to DART, EWC and Hunsinger cells, SPUDT cell fingers with one and the same width only. Cell types with /spl lambda//6, /spl lambda//5 and /spl lambda//3 wide fingers are considered. One of these cell types including /spl lambda//5 wide fingers only is experimentally investigated and a unidirectional effect is found. For this cell type, no waveguide coupling is required.