Why am I getting this error "??? error using ==> times matrix dimensions must agree" in matlab?

design a FIR low pass filter using Kaiser window

a1phap=0.1

a1phas=44

ws=30

wp=20

wsf=100

B=ws-wp

wc=0.5*(ws+wp)

wcr=wc*2*pi/wsf

D=(a1phas-7.95)/14.36

N=ceil((wsf*D/B)+1)

a1pha=(N-1)/2

gamma=(.5842*(a1phas-21).^(0.4)+0.07886*(a1phas-21))

n=0:1:N-1

hd=sin(wcr*(n-a1pha))./(pi*(n-a1pha))

hd(a1pha+1)=0.5

wk=(kaiser(N,gamma))

hn=hd.*wk     % *(HERE I AM GETTING THIS ERROR)*

W=85:5:120

h=freqz(hn,1,W)

plot(W/pi,20*log10(abs(h)))

those two matrices have the same dimensions of 27..still why this error?

Answer 1

[Cedric]

You have to transpose either wk or hd, because one is a column vector and the other a row vector. E.g.

 hn = hd .* wk.'

Answer 2

[the cyclist]

I don't have the Signal Processing Toolbox, so I can't execute the kaiser() function. However, the documentation indicates that it will output a column vector. Your vector hd is a row vector, so it does not actually have the same dimension. You need to transpose one of them.

Answer 3

[Chandra Shekhar]

Don't use dot product,edit that line like this

hn=hd*wk;

but you will get single value after multiplying,but 'freqz' function requires vector as a input.

if you need vector then do like this, you will get waveform.

hn=hd. * wk ' ;