(英) |
A variable digital filter (variable-filter) has tunable frequency response, and when a new frequency response is required, one just needs to change its coefficients. However, a recursive variable-filter may become unstable when its coefficients are changed. So far, the author has proposed an effective method for ensuring the stability of a recursive variable-filter. The method transforms the denominator coefficients of the transfer function into a set of new parameters, and then the optimal values of those new parameters are sought without imposing any design constraints. This parameter-transformation-based method is able to guarantee the stability of a recursive variable-filter, but needs a special function for the parameter transformations. In this paper, a lot of such functions are developed and presented. |