what is practical meaning of impulse response?

问题:

Impulse response is usually used in filter and for convolution but i always find it difficult to explain my self what is this and how does it help.

My question what is practical meaning of impulse response, either it an equation or characteristic of a system in response to input.

回答1:

Definition:

In signal processing, the impulse response, or impulse response function, of a dynamic system is its output when presented with a brief input signal, called an impulse.

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Explanation: Think of it from a system perspective. Lets look at an airplane. Sitting at the controls, a test pilot will get to a smooth level flight. Then they will push the flight stick all the way forward, then bring it all the way back to center position, as fast as possible. They then see what the planes response is. Some will just drop in altitude, then level off. Some will start to dive and keep diving at a constant rate, and some (OH NO!) will start to dive faster and faster!

So knowing what the impulse response is, goes a long way in telling the characteristics of a system.

A designer should know what the impulse response should be, then design the system to it.

Resource:

http://en.wikipedia.org

http://www.edaboard.com/thread129957.html

回答2:

The definition of impulse is given by the function

δ(t)= { 1 , t=0 | 0 , otherwise }

When you want to analyze a system from its frequency, you transform the time domain to the frequency.

First we find the transfer function of the system, so we spent this function to the frequency domain (Fourier transform). The system input and output are related by Y(jW)=H(jW)*X(jW) Where Y(jW) is the output, X(jW) is the input and H(jW) is our transfer function. To analyze how our system behaves in frequency, we take as input X(jW) a unit impulse.

Applying the Fourier transform for δ(t) we have δ(jW)=1

Y(jW)=H(jW)*1 ---> Y(jW)=H(jW)

Thus our output does not change with the entry of a unit impulse, and we can analize our system in two different domains. This is usually used for filter projects. However, there are several other applications for this tool.