Python Matlab滤波器与Scipy滤波器

嗨，我正在尝试用Python转换一个Matlab代码。我的代码在调制前工作正常，但当我添加噪声并进行过滤时，我得到了错误的结果。我认为基本问题在于过滤器

Python代码

from __future__ import division
import numpy as np
from numpy import *
import cmath
from pylab import *
from matplotlib import *
from scipy.signal import  firwin ,lfilter, freqz

a1=array([0,0,1])
a2=arange(0,2,1)
N_bits=1e2

bits1=ceil(len(a2)*rand(N_bits))

bits=a1[array(bits1,dtype=int)]
N_bits=len(bits)
delta1=zeros(((N_bits/4)+1,) , dtype=np.complex)
delta2=zeros(((N_bits/4)+1,) , dtype=np.complex)

k=1

C=zeros(((N_bits/4)+1,) , dtype=np.complex)
D=zeros(((N_bits/4)+1,) , dtype=np.complex)

C[0]=2+2j
D[0]=1+1j

for l in arange(0,N_bits,4):
    if (bits[l]==0 & bits[l+1]==0):
         delta1[k]=0
    elif(bits[l]==0 & bits[l+1]==1):
        delta1[k]=np.pi/2
    elif (bits[l]==1)&(bits[l+1]==1):
         delta1[k]=np.pi
    else:
        delta1[k]=3*(np.pi/2)
    if (bits[l+2]==0)&(bits[l+3]==0):
             delta2[k]=0
    elif(bits[l+2]==0)&(bits[l+3]==1):
        delta2[k]=np.pi/2
    elif (bits[l+2]==1)& (bits[l+3]==1):
         delta2[k]=np.pi;
    else:
     delta2[k]=3* np.pi/2

    C[k]=C[k-1]*(np.cos(delta1[k])+1j*np.sin(delta1[k]))
    D[k]=D[k-1]*(np.cos(delta2[k])+1j*np.sin(delta2[k]))    
    k=k+1
S=C+D
len_S=len(S)
a=int((N_bits/4)+1)
T=20e-3
B=0.99
Fc=8/T
dt=(1/8)/Fc
sa=T/dt

Convfac=5

alph_a=S.real
alph_b=S.imag

alph_aa1=array(zeros((a*sa)))
alph_bb1=array(zeros((a*sa)))

j=0

for k in range(0,len_S):
     alph_aa1[j:j+sa-1]=np.kron(ones(1,float,sa),alph_a[k])
     alph_bb1[j:j+sa-1]=np.kron(ones(1,float,sa),alph_b[k]) 
     j=j+sa


h_1=alph_aa1.shape

print(len(alph_aa1))   

clip_level=1
t1=linspace(-T/2,T/2,sa)
raised=(cos(pi*(t1/T)))**3
f_index=(raised>clip_level).nonzero()
raised[f_index]=clip_level
raised=raised/norm(raised)

alph_aa=(convolve(alph_aa1,raised))/Convfac
alph_aa=alph_aa[(sa/2)-1:-sa/2]
h_2=alph_aa.shape

alph_bb=(convolve(alph_bb1,raised))/Convfac
alph_bb=alph_bb[(sa/2)-1:-sa/2]
print(len(alph_bb))

t=arange(dt,(a*T)+dt,dt)
tt=t.shape
aaa=alph_aa.shape
###############
# Modulation WORKS FINE up to here
mod=alph_aa*cos(2*pi*Fc*t)-alph_bb*sin(2*pi*Fc*t)

phi=(0/180)*pi
Es=10
SNR=10
variance=Es*10**(-SNR/10)
std_dev=sqrt(variance/2)
noise=(np.random.randn(len(mod)))*std_dev
mod_noisy=mod+noise

###############
#Demodulation Problem start here
##############

demod_1_a=mod_noisy*2*cos(2*pi*Fc*t+phi)

N=10
Fc=40
Fs=1600

# Filter PART consider this part
d=firwin(numtaps=N,cutoff=40,nyq=Fs/2)
Hd=lfilter( d, 1.0, demod_1_a)


y2=(convolve(Hd,raised))/Convfac
y2=y2[(sa/2)-1:-sa/2]
demod_3_a=y2[(sa/2)-1:sa:,]

demod_1_b=-1*mod_noisy*2*sin(2*pi*Fc*t+phi)

Hd=lfilter(d,1.0,demod_1_b)
y2=(convolve(Hd,raised))/Convfac
y2=y2[(sa/2)-1:-sa/2]
demod_3_b=y2[(sa/2)-1:sa:,]

#########3333
#Demod

 demod=demod_3_a+(1j)*demod_3_b
 print(demod)

Matlab代码：

%%%%%%%%%%%%%%ENCODING%%%%%%%%%%%%%%%%
a1=[0,1];
N_bits=1e2;
bits=a1(ceil(length(a1)*rand(1,N_bits)));
delt1=zeros(1,N_bits/4);
delt2=zeros(1,N_bits/4);
k=2;
C=zeros(1,N_bits/4);
D=zeros(1,N_bits/4);
C(1)=2+2j;
D(1)=1+1j;

for i=1:4:N_bits
    if bits(i)==0&&bits(i+1)==0
        delt1(k)=0;
    elseif bits(i)==0&&bits(i+1)==1
        delt1(k)=pi/2;
    elseif bits(i)==1&&bits(i+1)==1
        delt1(k)=pi;
    else
        delt1(k)=3*pi/2;
    end 

    if bits(i+2)==0&&bits(i+3)==0
        delt2(k)=0;
    elseif bits(i+2)==0&&bits(i+3)==1
        delt2(k)=pi/2;
    elseif bits(i+2)==1&&bits(i+3)==1
        delt2(k)=pi; 
    else%if x(3)==1&&x(4)==0
        delt2(k)=3*pi/2;
    end

    C(k)=C(k-1)*(cos(delt1(k))+1j*sin(delt1(k)));
    D(k)=D(k-1)*(cos(delt2(k))+1j*sin(delt2(k)));
    k=k+1;
end

S=C+D;
% S=S(1,2:end);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

a=N_bits/4+1;

T=20e-3;

B=0.99;

Fc=8/T;

dt=1/8/Fc;

sa=T/dt;

ConvFac=5

alph_a=real(S);
alph_b=imag(S);
aplh_aa1=zeros(1,a*sa);
alph_bb1=zeros(1,a*sa);

j=1;

for k=1:a
    alph_aa1(1,j:j+sa-1)=repmat(alph_a(k),1,sa);
    alph_bb1(1,j:j+sa-1)=repmat(alph_b(k),1,sa);
    j=j+sa;
end

h_1=size(alph_aa1)

%%%%%%%%% raised cosine %%%%%%%%%

clip_level=1;

t1=linspace(-T/2,T/2,sa);

raised=cos(pi*t1/T).^3

f_index= find(raised>clip_level)

raised(f_index)=clip_level

raised=raised/norm(raised);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%convolving with raised cosine%%%%%

alph_aa=conv(alph_aa1,raised)/ConvFac;

alph_aa=alph_aa(sa/2:end-(sa/2));

h_2=size(alph_aa)

alph_bb=conv(alph_bb1,raised)/ConvFac;

alph_bb=alph_bb(sa/2:end-(sa/2));

%%%%%%%%%%%modulation%%%%%%%%%%%

t=dt:dt:a*T;

length(t)

tt=size(t)

aaa=size(alph_aa)

mod=alph_aa.*cos(2*pi*Fc.*t)-alph_bb.*sin(2*pi*Fc.*t);

%%%%%%%%%%%%%%%%%%%CHANNEL%%%%%%%%%%%%%

phi=0/180*pi;

%mod=awgn(mod,10);

Es=10;

SNR=10;
variance=Es*10^(-SNR/10);

std_dev=sqrt(variance/2);

noise=(randn(1,length(mod)))*std_dev;

mod_noisy=mod+noise;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%demodulation%%%%%%%%%%%%

demod_1_a=mod_noisy*2.*cos(2*pi*Fc*t+phi);

d=fdesign.lowpass('N,Fc',10,40,1600);

Hd = design(d); 

y = filter(Hd,demod_1_a);

y2=conv(y,raised)/ConvFac;

y2=y2(sa/2:end-(sa/2));

demod_3_a=y2(sa/2:sa:end);

%%%%%%%%%%%%%%%%%%%%%%%%%%

demod_1_b=-1*mod_noisy*2.*sin(2*pi*Fc*t+phi);

y = filter(Hd,demod_1_b);

y2=conv(y,raised)/ConvFac;

y2=y2(sa/2:end-(sa/2));

demod_3_b=y2(sa/2:sa:end);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%

demod=demod_3_a+1i*demod_3_b

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我认为这个过滤器设计得不好。从解调和滤波的角度考虑代码。 有几件事可能会提高响应的几率：在代码中添加更多注释，解释错误或不需要的输出。如果您可以在开始输入时发布相关摘录，则无需发布所有代码。此外，如果您认为罪魁祸首是您使用的say d=fdesign.lowpass'N，Fc'，10,401600；您可能希望限制自己询问如何正确使用该功能。