LPF a random signal

I have a random signal and its psd:

x=randn(1000,1);
Fs=4000;
pd = psd(spectrum.periodogram,u,'Fs',Fs);
plot(pd)

I want to remove the high frequency components(LPF or smooth), so that 'x' is close to practical/measured noise. Does this help?

 y=filter(b,a,x);

What should be the coefficients 'b' and 'a' for my applciation? Please help

Answer 1

[Honglei Chen]

You need to first determine what are the frequencies you want to keep and what are the frequencies you want to filter out. You can then use tools to help you design the filter.

Any DSP book will talk about the theory. For tools, take a look at the following documentation

doc fdatool
doc fdesign

Here is an example

x = rand(1024,1);
hd = design(fdesign.lowpass);
y = filter(hd,x);

[zozo]

thank you Sir.