Browsing by Author "Chen-Yi, Lee"

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Algorithm for a memory-based Viterbi decoder
(2004-12-23)
Chen-Yi, Lee
;
Chien-Ching, Lin
;
Chia-Cho, Wu
An algorithm for a memory-based Viterbi decoder is disclosed in the invention, which employs the property of a trace-back path; that is, the similarity between two consecutive trace-back paths becomes higher as the data error rate goes down. Therefore, the algorithm of the invention is to save the previous trace-back path into a register, and as soon as the current trace-back path is found to be the same as the previous one, the demanded path is obtained. After that, the memory read operations will stop, and thus the power consumption made by the memory read operations would be largely reduced. Besides, before the path trace-back, the path prediction can be executed by utilizing the property that the minimum path metric and the path are consecutive. In conclusion, the invention is capable of reducing the number of memory access operations and the power consumption by employing the mechanisms of path matching and path prediction.
Phase frequency detector with a narrow control pulse
(2004-07-29)
Chen-Yi, Lee
;
Pao-Lung, Chen
A phase frequency detector with a narrow control pulse comprises mainly two substantially equivalent phase latches with a narrow control pulse, and a reset signal generating unit. Each phase latch of a narrow control pulse has a clock pulse input end and a signal output end. Both latches also be connected to the reset signal generating unit. The logic value of each signal output end is decided by which clock pulse input appears first. The reset signal generating unit decides whether or not to generate a reset signal according to the logic values of both signal output ends. The reset signal is then sent to both phase latches of a narrow control pulse, if generated. The present invention can be implemented by a simple circuit. Comparing with the RS NAND PFD or master-slave D PFD, the PFD of the invention has the advantages of faster speed, saving more power and smaller IC chip area. Comparing with dynamic PFD, because the PFD of the invention has a feedback circuit, the storage charges of internal nodes will not be lost due to the leakage current and therefore the working frequency range is wider.