Analog low pass filter zero-phase

Hi, I'm trying to design in Matlab an analog low pass filter, to implement in Simulink for online filtering. The filter should have a passband frequency of 50rad/s and stopband frequency of 100rad/s. My problem is that I need zero-phase (therefore small delay in time) almost until 100rad/s then the filter should behave with a decreasing phase (in Bode diagram); I tried to use 'butter' function but I do not find how to implement the specification about zero-phase. Do you know some function or toolbox to do it? Thanks.

Answer 1

[Fei Deng]

Hi Macro, you can access zero-phase zero-phase analysis method via Filter Designer App. https://www.mathworks.com/help/signal/ug/getting-started-with-filter-designer.html 1. Type filterDesigner in Command window. 2. Right-click the y-axis of the plot and select Zero-phase from the context menu.

You can also try function filtfilt: https://www.mathworks.com/help/signal/ref/filtfilt.html