High-accuracy variable-phase filter design utilising iterative linear-programming strategy

ABSTRACT

This paper proposes an iterative strategy employing the linear programming (LP) method for the design of an all-pass variable-phase (AP-VP) digital filter in the minimax error sense. Mathematically, designing an AP-VP digital filter belongs to a non-linear optimisation problem. The novel LP design method first reduces this non-linear minimisation problem to a linear minimisation problem and then solves the linearised optimisation problem iteratively via using the LP method. The iterative LP-solving scheme is able to reduce the largest design errors significantly and thus can get a considerable accuracy improvement as compared to the noniterative one. We will utilise three design examples to show that this iterative scheme can get much better design results (much smaller maximum errors) than the noniterative method in the literature. Therefore, this iterative LP design strategy can significantly enhance the performance of the AP-VP digital filter.

KEYWORDS:

• Variable-phase (VP) filter
• all-pass VP (AP-VP) digital filter
• phase error
• maximum phase error
• linear programming (LP) problem

Acknowledgement

JSPS KAKENHI (Grant Number 16K06368) supported this work.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

JSPS KAKENHI (Grant Number 16K06368) supported this work.