Granted Patent B2

US 6,968,000 · App. 09/767,831 · Granted Nov 22, 2005

Abstract

Claims (15)

1. A filter arrangement with a linear phase characteristic comprising:

a first filter having an amplitude characteristic that meets a predefined amplitude specification and having a phase characteristic that is a non-linear function of frequency; and

a second filter, cascade coupled to said first filter, said second filter having a phase characteristic that is substantially equal to the sum of a linear function of frequency and the opposite phase characteristic of said first filter,

wherein said second filter is an anti-causal version of a fictive digital all-pass filter having a phase characteristic that is substantially equal to the sum of a linear function of frequency and said phase characteristic of said first filter.

2. The filter arrangement according to claim 1 , wherein said first filter is an analog filter.

3. The filter arrangement according to claim 1 , wherein said first filter is a digital filter.

4. A method to develop a filter arrangement with a linear phase characteristic, wherein the method comprises:

designing a first filter so that its amplitude characteristic meets a predefined amplitude specification;

implementing said first filter;

determining a phase characteristic of said first filter, said phase characteristic being a non-linear function of frequency;

implementing a second filter so that its phase characteristic is substantially equal to the sum of a linear function of frequency and the opposite phase characteristic of said first filter; and

cascade coupling said first filter and said second filter, wherein

implementing said second filter comprises:

designing a fictive digital all-pass filter so that its phase characteristic is substantially equal to the sum of a linear function of frequency and equal said phase characteristic of said first filter; and

implementing said second filter as an anti-causal version of said fictive digital all-pass filter.

Assignments (8)