Как убрать помеху и восстановить сигнал

L=1800
Fs=1000
NFFT = 2^nextpow2(L)
f = Fs/2*linspace(0,1,NFFT/2+1)
a=textread('1.txt')
A = fft(a,NFFT)/L
plot(f,2*abs(A(1:NFFT/2+1)))

clc; close all; clear;
load data111
y_AM = MSr;
fs = 96e3;
L = length(y_AM);
t = (0:L-1)/fs;
y_demod = abs(hilbert(y_AM));
%%
Rp = -3; % dB
Rs = -60; % dB
Wp = 2*[0.7 1.4]*1e3/fs;
Ws = 2*[0.4 1.8]*1e3/fs;
[n, Wn]=buttord(Wp,Ws,Rp,Rs);
[z, p, k] = butter(n,Wn,'bandpass');
[sos,g]=zp2sos(z,p,k);
Hd = dfilt.df2sos(sos,g);
[K, w] = freqz(Hd, 4096);
y_out = filter(Hd, y_demod);
%%
nfft = 2^nextpow2(L);
freq = fs/2*linspace(-1, 1, nfft);
S = fft([y_AM abs(hilbert(y_AM)) y_out], nfft);
Mag = abs(S);
%%
figure('Units', 'Normalized', 'Position', [.01 .05 .98 .8])
hA(1) = subplot(221);
plot(freq/1e3, fftshift(10*log10(Mag(:, 1:2)), 1)); grid on
xlabel('f, kHz')
ylabel('|S|, dB')
xlim([0 fs/2]/1e3)
legend({'Исходный сигнал', 'Детектированный сигнал'}, 'location', 'southeast')
 
hA(2) = subplot(223);
plot(freq/1e3, fftshift(10*log10(Mag(:, 3)))); grid on
xlabel('f, kHz')
ylabel('|S|, dB')
xlim([0 fs/2]/1e3)
 
hA(3) = subplot(222);
plot(fs/2*w/pi, 20*log10(abs(K))); grid on
xlabel('f, kHz')
ylabel('|K|, dB')
title('АЧХ фильтра')
xlim([0.3 2]*1e3)
 
linkaxes(hA(1:2), 'x')
 
%%
temp = 100*y_out*ones(1,3);
temp = temp(:);
sound(temp, fs)