# What is Single pole filter?

Can anybody tell me why do we use single pole filter? And may be an example of Single pole filter in matlab. Good literature recommendations are also welcomed.Moreover, that would be good if anyone graphically explains, what happens to the signal when single pole filter is applied?

• Stating the obvious: A single pole filter is a filter with only one pole. You can make filters with any number of poles that suitable for your application including 1. It's actually the simplest. What else do you want to know ? – Hilmar Jul 28 '15 at 17:57
• one more thing (maybe less obvious): usually, when we say "one-pole filter", we mean also that there are no zeros. so $$H(z) = \frac{1}{z-p}$$ is a single pole filter and while this filter $$H(z) = \frac{z-q}{z-p}$$ has only one pole, we usually don't call that a "single pole filter" because it has one pole and one zero. we would call both a "first-order filter". – robert bristow-johnson Jul 28 '15 at 18:56
• Thanks Hilmar & robert. I need to design single pole filter in matlab. – Urban_Yogi Jul 28 '15 at 18:59
• $$y[n] = (1-p) \, x[n] + p \, y[n-1]$$ – robert bristow-johnson Jul 28 '15 at 19:01
• Does anyone let me know where does that fileters got used? – gmotree Jul 29 '15 at 7:09