Sampling frequency and bandwidth

Hi,

I would like to know the relation between sampling frequency and bandwidth of a filter. For a given filter order as sampling frequency increases bandwidth increases.Why is that so? Could anyone please help me in finding a valid justification for this.

With Regards

Krishnakumar

Answer 1

[Wayne King]

Imagine you design a lowpass filter where the cutoff frequency is pi/4 radians/sample. That filter will pass [-pi/4 pi/4] radians/sample. Now what is that bandwidth in radians/second?

[-pi/4 pi/4] multiplied by the sampling frequency.

(radians/sample)(samples/second)

The larger the sampling frequency, the larger the bandwidth.

As a simple example, just take a 20-point (order 20) FIR moving average filter.

Assume a sampling rate of 1000 Hz.

    b = 1/20*ones(20,1);
    fvtool(b,1,'Fs',1000)

Now increase the sampling rate by a factor of 10 and you'll see the bandwidth increases by the same factor

   fvtool(b,1,'Fs',1e4)