`Please help me, I have been struck here for a long time.`

Here is my problem

I have a real signal in the time domain.I need to remove a band of

frequency from it to get a new real signal. So first I FFT this

input real signal and multiply the FFT ouput by a filter function I

chose from matlab. I hope I can get a new power spectrum with that

designated band of frequency zero. But I tried many ways, I can not

get it successfully.Below is my matlab file:

% the original pulse input

t=0.3721124:0.3721124:0.3721124*160;

wQ*1034.631154/1000000;

x=0.0082*cos(-t*w);

plot(x(1:160))

title('singnal quarter of cosine')

xlabel('timestep')

% I want to remove the low frequency band from 0.05-0.07, my

sampling interval is about 0.372114

ff = [0 0.04*0.37 0.05*0.37 0.07*0.37 0.08*0.37 1];

aa = [1 1 0 0 1 1];

nn = 160;

bb = firls(nn,ff,aa);

[h,w] = freqz(bb);

plot(ff,aa,w/pi,abs(h))

legend('Ideal','firls Design')

Xt(x);

Xh = filter(bb,1,X);

% fft to get the whole frequency content

f=1/0.3721124/160*(0:20);

Pxx=Xh.* conj(Xh)/160

We=exp(-10*log(10));

Ub=log10((Pxx)+We);

plot(f,Ub(1:21))

title('frequency content')

xlabel('frequency')

Here is my problem

I have a real signal in the time domain.I need to remove a band of

frequency from it to get a new real signal. So first I FFT this

input real signal and multiply the FFT ouput by a filter function I

chose from matlab. I hope I can get a new power spectrum with that

designated band of frequency zero. But I tried many ways, I can not

get it successfully.Below is my matlab file:

% the original pulse input

t=0.3721124:0.3721124:0.3721124*160;

wQ*1034.631154/1000000;

x=0.0082*cos(-t*w);

plot(x(1:160))

title('singnal quarter of cosine')

xlabel('timestep')

% I want to remove the low frequency band from 0.05-0.07, my

sampling interval is about 0.372114

ff = [0 0.04*0.37 0.05*0.37 0.07*0.37 0.08*0.37 1];

aa = [1 1 0 0 1 1];

nn = 160;

bb = firls(nn,ff,aa);

[h,w] = freqz(bb);

plot(ff,aa,w/pi,abs(h))

legend('Ideal','firls Design')

Xt(x);

Xh = filter(bb,1,X);

% fft to get the whole frequency content

f=1/0.3721124/160*(0:20);

Pxx=Xh.* conj(Xh)/160

We=exp(-10*log(10));

Ub=log10((Pxx)+We);

plot(f,Ub(1:21))

title('frequency content')

xlabel('frequency')