One 、 Mixer introduction

The frequency of the output signal of the mixer is equal to the sum of the two input signal frequencies 、 Difference or other combination of the two circuits .

Two 、Matlab Code

Realization function ： Input two 500kHz Signal mixing output 1000kHz And filter out the sinusoidal signal output of the DC component

% Set system parameters 
fi=500000;              % Input signal frequency 
fc=500000;              % Frequency of LO signal 
Fs=5000000;             % sampling frequency 
L=1024;                 % Data length 
N=10;                   % Quantization Bits 
% Generate input signal 
t=0:1/Fs:(1/Fs)*(L-1);  % Generate a time series of sampling frequencies 
theta=rand()*2*pi;      % Generate a random phase angle 
si=sin(2*pi*fi*t+theta);% Generate sine wave input signal with random starting phase 
si=round(si*(2^(N-1)-1));%10bit quantitative 
% Generate LO signal 
sc=sin(2*pi*fc*t);      % Generate LO signal 
sc=round(sc*(2^(N-1)-1));%10bit quantitative 
% Simulate the mixing output and draw pictures 
so=si.*sc;               % Mixer output 
sof=so-mean(so);        % The mixer filters out the DC component and outputs 
fso=abs(fft(so,L));     % seek FFT Transformed amplitude value 
% normalization 
sc=sc/max(abs(sc));
si=si/max(abs(si));
so=so/max(abs(so));
sof=sof/max(abs(sof));
fso=fso/max(fso);
% Convert it into a signal symmetrical relative to the origin 
fso=[fso(L/2+1:L),fso(1:L/2)];      % drawing 
m=[-L/2:1:(L/2-1)]*Fs/L*(10^(-6));  % Generate frequency axis , Unit is MHz
t=t*(10^6);                         % Generate time axis , Unit is us
subplot(221);plot(t(1:32),si(1:32));
xlabel(' Time /us');ylabel(' Range ');
title('10bit Quantized input signal (a)','fontsize',8);
subplot(222);plot(t(1:32),so(1:32));
xlabel(' Time /us');ylabel(' Range ');
title('20bit Quantized mixing output signal (b)','fontsize',8);
subplot(223);plot(t(1:32),sof(1:32));
xlabel(' Time /us');ylabel(' Range ');
title(' The mixing output signal after filtering the DC component (c)','fontsize',8);
subplot(224);plot(m,fso);
xlabel(' frequency /MHz');ylabel(' Range ');
title(' Amplitude frequency response of mixing output signal (d)','fontsize',8);

3、 ... and 、 Waveform simulation