how to find H(e j(ω π) ) if you know H(e j(ω), you found out H(e j(ω) by using freqz

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Anh Dao 2019-10-13

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https://ww2.mathworks.cn/matlabcentral/answers/485010-how-to-find-h-e-j-if-you-know-h-e-j-you-found-out-h-e-j-by-using-freqz

回答： Dimitris Kalogiros 2019-10-14

how to find H(e j(ω +π) ) if you know H(e j(ω), you found out H(e j(ω) by using freqz

For instance, you have H(e(jw)) by having an array of h, and then you find out h(e^(jw)) by using [h,w]=freqz(h).But now I want to know how to find H(e^(jw+pi)). Thank you!

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Dimitris Kalogiros 2019-10-13

You have to restate with more details.

What exactly do you want to find out ?

Anh Dao 2019-10-13

I restated it with more details! Thank you!

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Dimitris Kalogiros 2019-10-14

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https://ww2.mathworks.cn/matlabcentral/answers/485010-how-to-find-h-e-j-if-you-know-h-e-j-you-found-out-h-e-j-by-using-freqz#answer_396233

Keep in mind that,

is a periodic function of ω , with period

Have a look at the following figure. Focus on the "blue" and the "green" graphs, where the magnitude of the signals is depicted. I think that you have to use freqz() with the parameter 'whole', in order to calculate the right green graph into the interval [0 , 2pi] .