First, introduction

1. Radar working principle
Radar is the drum of radar (radio detection and ranging), meaning "radio detection and ranging", using radio waves to detect targets and measure the location of the target, which is also the function of the radar device in the initial stage. A typical radar system is composed of a transmitter, antenna, receiver, data processing, timing control, and display, and other devices. Using radar can know the target, the target slate, the target angular position, the target relative speed, and the like. Modern high-resolution radar extends the original radar concept, which has the ability to imaging and identifying moving targets (aircraft, missiles, etc.) and regional objectives (ground, etc.). The application of radar is getting wider.



2. Linear FM (LFM) signal
Pulse compression radar can simultaneously increase the role of radar and distance resolution. This system uses wide pulse emissions to increase the average power of the emission, ensuring a sufficiently large action distance; and the corresponding pulse compression algorithm is received when accepted the narrow pulse to improve the distance resolution, better solve the radar action distance and distance distinguish The contradiction between the rate.
The most common modulation signal of pulse compression radar is a linear frequency mode signal, and a matching filter compression pulse is received when receiving.
The mathematical expression of the LFM signal (also known as the Chirp signal) is:

3. Matching filtering of the LFM pulse
The time domain pulse response of the signal matched filter is:

Second, source code

%%demo of LFM pulse radar
%==================================================================
function LFM_radar(T,B,Rmin,Rmax,R,RCS)
if nargin==0
    T=10e-6;                                          %pulse duration 10us
    B=30e6;                                           %chirp frequency modulation bandwidth 30MHz
    Rmin=10000;Rmax=15000;              %range bin
    R=[10500,11000,12000,12008,13000,13002];  %position of ideal point targets
    RCS=[1 1 1 1 1 1];                           %radar cross section
end
%==================================================================
%%Parameter
C=3e8;                                            %propagation speed
K=B/T;                                             %chirp slope
Rwid=Rmax-Rmin;                           %receive window in meter
Twid=2*Rwid/C;                               %receive window in second
Fs=5*B;Ts=1/Fs;                             %sampling frequency and sampling spacing
Nwid=ceil(Twid/Ts);                         %receive window in number
%==================================================================
%%Gnerate the echo      
t=linspace(2*Rmin/C,2*Rmax/C,Nwid); %receive window
                                                            %open window when t=2*Rmin/C
                                                            %close window when t=2*Rmax/C                            
M=length(R);                                        %number of targets                                        
td=ones(M,1)*t-2*R'/C*ones(1,Nwid);
Srt=RCS*(exp(j*pi*K*td.^2).*(abs(td)<T/2));%radar echo from point targets  
%%demo of chirp signal
T=10e-6;                                  %pulse duration10us
B=30e6;                                   %chirp frequency modulation bandwidth 30MHz
K=B/T;                                      %chirp slope
Fs=2*B;Ts=1/Fs;                      %sampling frequency and sampling spacing
N=T/Ts;
t=linspace(-T/2,T/2,N);
St=exp(j*pi*K*t.^2);                    %generate chirp signal

Third, the result

Fourth, note

Complete code or writing added QQ1564658423
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