This work was supported in part by the National Science Council of Taiwan, R.O.C., under grants NSC-99-2220-E-009-028, NSC-99-2220-E-009-030, and NSC-99-2220-E-009-071. The authors would also like to express their sincere appreciation to the UMC University Shuttle Program and the National Chip Implementation Center for chip fabrication and testing service.