MATLAB中的频移键控不起作用

我的FSK调制工作不正常。而不是FSK频移，我只是得到一个更高频率的ASK信号。我需要改变什么？我在代码顶部有原始信号和数字量化。 解调后的位信号和解调后的信号都很好，但FSK图看起来不正确

   clear all
clc
syms t n

T = 10;
f = 1/T;
w = 2*pi*f;
N = 25;
fs = 2001;

syms t n

a = -t - 5; 
b = 4*t;
c = t;
d = -4*t + 20;

A_0 = (1/T)*(int(a,t,-5,-1)+int(b,t,-1,0)+ ...
      int(c,t,0,4)+int(d,t,4,5));
A_n = (2/T)*(int(a*cos(n*w*t),t,-5,-1)+int(b*cos(n*w*t),t,-1,0)+ ...
      int(c*cos(n*w*t),t,0,4)+int(d*cos(n*w*t),t,4,5));
B_n = (2/T)*(int(a*sin(n*w*t),t,-5,-1)+int(b*sin(n*w*t),t,-1,0)+ ...
      int(c*sin(n*w*t),t,0,4)+int(d*sin(n*w*t),t,4,5));
 

% summation loop to get An, Bn, Vt
for n = 1:N
    An(n) = (2/T)*(int(a*cos(n*w*t),t,-5,-1)+int(b*cos(n*w*t),t,-1,0)+ ...
      int(c*cos(n*w*t),t,0,4)+int(d*cos(n*w*t),t,4,5));
    
    Bn(n) = (2/T)*(int(a*sin(n*w*t),t,-5,-1)+int(b*sin(n*w*t),t,-1,0)+ ...
      int(c*sin(n*w*t),t,0,4)+int(d*sin(n*w*t),t,4,5));
    
    v_t(n) = An(n)*cos(w*n*t) + Bn(n)*sin(w*n*t);
    
end

 Cn = sqrt((An.^2)+(Bn.^2));
 
%Function of original signal 
 Vt = A_0 + sum(v_t);
 t = 0:0.01:20;
 Voft = eval(Vt);

 %quantization 
 deltaXu = 2^(-(8)); 
 deltaXuM = 1- deltaXu ;
 s = [];
 ts = [];
 for i=1:100:2001
    ts = [ts, t(i)];
    s = [s, ((Voft(i)+4)/8)*deltaXuM];
 end
 
 bitstr = [];
 for i = 1:21 
     s(i) = round(s(i)/deltaXu); 
     bitstr = [bitstr, dec2bin(s(i),8)];
 end
 
 tbs(1:1000) = 1; 
 voltbitstr = [];
 Vzeroes = 0*tbs;
 Vones = 1*tbs;
 for i = 1:168
     if bitstr(i)=='1'
         voltbitstr = [voltbitstr, Vones];
     else 
         voltbitstr = [voltbitstr, Vzeroes];
     end
 end
 
%% FSK mod
 Fc = 16000 ;
 delta = 2.5e-7;
 Tbit = 0:delta:(2.5e-4)-delta;
 biteqn = sin(2*pi*Fc*Tbit);
 biteqn1 = sin(2*pi*Fc*4*Tbit);
 TSK = 0:delta:0.042-delta;
 v = [];
 Vzero = 0*biteqn ;
 Vone = 1*biteqn1 ;
 
 for i = 1:168
     if bitstr(i) == '1'
         v = [v, Vone];
     else 
         v = [v, Vzero];
     end
 end

 %% FSK DEmod
 vdemod = diff(v);
 vdemod = [vdemod, vdemod(1,end)];
 envl = abs(hilbert(vdemod));
 dc = 0.04;
 envl = envl - dc ;
 demodulation_scale = 11 ;
 envl = envl.*demodulation_scale;
 [b,a] = butter(10,0.15,'low');
 demod = (filtfilt(b,a,envl));
 
 bitstr2 = [];
 for i=500:1000:167500
     bitstr2 = [bitstr2, round(demod(i))];
 end
 vout = [];
 r = [];
 for i = 1:21
     for n = 1:8
         r = [r, num2str(bitstr2(8*(i-1)+n))];
     end
     m(i) = bin2dec(r);
     r = [];
     vout(i) = (m(i)/128)-1;
 end
 vout = vout.*4;
 
%% Plots
%Plot of original signal
 figure(1)
 subplot(2,1,1); 
 plot(t,eval(Vt));
 xlim([0,20]);
 ylabel('Amplitude');
 xlabel('time[s]');
 title('Created Signal');
 grid on;
 
%Plot of frequency domain
 subplot(2,1,2); 
 stem(1:N,Cn);
 ylabel('Amplitude');
 xlabel('Number of components');
 title('Frequency Plot');
 grid on;
 
%Sampled Plot
 figure(2)
 subplot (2,1,1);
 scatter(ts, s, 'b*');
 xlim([0,10]);
 xlabel("time[s]");
 ylabel("Amplitude");
 title("Quantized signal");
 grid on;
 
 subplot(2,1,2);
 plot(TSK, voltbitstr);
 axis([0 2.5e-3 -0.25 2.5]);
 ylabel("Amplitude");
 xlabel("time(s)");
 title("Sampled Bit String");
 grid on;
 
 %FSK Plots
 
 figure(3)
 subplot(3,1,1);
 plot(TSK, v);
 axis([0 2.5e-3 -1.2 1.2]);
 ylabel("Amplitude");
 xlabel("Time [s]");
 title("Mod Bit String");
 grid on;
 
 subplot(3,1,2);
 plot(TSK, demod);
 axis([0 2.5e-3 -0.25 2.5])
 ylabel("Amplitude");
 xlabel("Time[s]");
 title("Demod Bit String");
 grid on;
 
 subplot(3,1,3);
 plot(ts, vout);
 ylabel("Amplitude");
 xlabel("Time[s]");
 title("Demod Signal");
 grid on;