Digital filter
AssigneeIcom Incorporated
InventorHirofumi Yamauchi
Life of this patent
Estimating the term…
Abstract
The object of the invention is to provide a technique of preventing the limit cycle, with a simplified structure, for the IIR digital filter adopting arithmetic operation part of finite word length. A digital filter shown in FIG. 1 includes an extracting means 2 to extract only 2 bits at a low end of an input signal S1 and to output the extracted signal; an amplifying means 3 to amplify the extracted signal at an amplitude level to a level larger than a critical input level of an IIR digital filter 1 and output the extracted signal as amplified; and an adding means 4 to add the input signal S1 and the extracted signal S3 as amplified and input them into the IIR digital filter 1.
Claims16
A digital filter comprising:
- an IIR digital filter;
- an extracting means to extract a signal comprising only a specified number of bits at a low end of an input signal, and to output the extracted signal;
- an amplifying means to amplify the extracted signal at an amplitude level to a level larger than a critical input level in which a limit cycle occurs in the IIR digital filter and to output the extracted signal as amplified;
- and
- an adding means to add the input signal and the extracted signal as amplified and to input the added signal into the IIR digital filter.
A digital filter comprising:
- an IIR digital filter;
- an extracting means to extract a signal comprising only a specified number of bits at a low end of an input signal, and to output the extracted signal;
- an amplifying means to amplify the extracted signal at an amplitude level to a level larger than a critical input level in which a limit cycle occurs in the IIR digital filter and to output the extracted signal as amplified;
- a level comparing means to detect an amplitude level of the input signal and to compare it with the critical input level;
- and
- an addingmeans to add the input signal and the extracted signal as amplified and to input the added signal into the IIR digital filter, when the amplitude level of the input signal is smaller than the critical input level.
Dependencies are inferred from the claim text.