| 摘要 |
PROBLEM TO BE SOLVED: To realize a digital filter with a simple configuration and with software processing by using a memory table system, where all filter coefficients are stored in the memory. SOLUTION: An input symbol 1 is fetched into a shift register 8 at symbol timing 18. A counter 9 counts sample timing 19, and a counted value is inputted to an address of a memory 11. In the memory 11, all filter coefficients are divided into a filter coefficient group equivalent to one symbol period and each is stored in the form in which a difference is taken. An integrating part 12 outputs a filter coefficient before difference by successively integrating differential filter coefficients in the memory 11. A sign converting part 13 performs sign conversion of a corresponding filter coefficient, according to the value of each stage of the register 8. It is possible to perform digital filter processing on a series that is subjected to oversampling due to zero insertion, by calculating the total sum of each filter coefficient after sign conversion.
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