Number of filter taps in Gaussian filter design

25 次查看（过去 30 天）
Jay
Jay 2023-9-24
评论： Jay 2023-9-24
Hello,
I'm desinging a pulse shaping filter where the filter covers a span of 5 inputs symbols and 12 times of input symbol rate (e.g., 3.25 MHz). So I tried to use "gaussdesign" with parameter BT = 0.3, span = 5, and sps = 12.
I was expecting 60 coefficients which can be implemented with a polyphase FIR filter with a total 12 phases. However, the design with "gaussdesign" generated 61 taps. So what's happening here...? Am I missing something?
Thanks,
Jay

请先登录，再回答此问题。

采纳的回答

Paul
Paul 2023-9-24
Hi Jay,
The doc page for gaussdesign states
"The number of symbols between the start and end of the impulse (span) and the number of samples per symbol (sps) determine the length of the impulse response: span×sps+1."
The impulse response for the given parameters is of length 61 and the number of delays needed to realize such a filter is 60, i.e.,
H(z) = h[0] + h[1]*z^-1 + .... h[60]*z^-60.
So there are 60 "taps," if by tap we mean "delay element."
  3 个评论
显示 1更早的评论
Paul
Paul 2023-9-24
I don't why span x sps must be even.
My guess is that it's important to have the impulse response be symmetric around the peak, which can only occur if the duration of the impulse response, span*sps + 1, is odd.
Jay
Jay 2023-9-24
One realization might be simpler than the other but both filters are implementable for sure whatever even or odd number of taps. Putting this restriction in MATLAB sounds strange to me.
Thanks Paul for the discussion. It helps.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Filter Design 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by