Question s in End-to-End Radar System

I'm replacing some parameters in End-to-End Radar System example with my needs.

https://www.mathworks.com/help/phased/gs/end-to-end-radar-system.html

Now I just replacing:

'waveform' to LinearFMWaveform

'PRF' to 1/160e-6

'sampling frequency' to 1e7

'Operating Frequency' to 77GHz

'Pulse Width' to 60e-6

with FMCW automotive radar.

But even in range estimation, I can't find the peak in the correct range index.

clear;close all;clc;

fc = 77e9;
fs = 1e7;
PRT = 160e-6;
T_sweep = 60e-6;

waveform = phased.LinearFMWaveform('PulseWidth',T_sweep,...
    'PRF',1/PRT,'OutputFormat','Pulses','NumPulses',1,'SampleRate',fs);

antenna = phased.IsotropicAntennaElement('FrequencyRange',[1e9 81e9]);

target = phased.RadarTarget('Model','Nonfluctuating','MeanRCS',0.5,...
    'PropagationSpeed',physconst('LightSpeed'),'OperatingFrequency',fc);

antennaplatform = phased.Platform('InitialPosition',[0;0;0],'Velocity',[0;0;0]);
targetplatform = phased.Platform('InitialPosition',[7000; 5000; 0],...
    'Velocity',[0;0;0]);

[tgtrng,tgtang] = rangeangle(targetplatform.InitialPosition,...
    antennaplatform.InitialPosition);

Pd = 0.9;
Pfa = 1e-6;
numpulses = 10;
SNR = albersheim(Pd,Pfa,10);

maxrange = 1.5e4;
lambda = physconst('LightSpeed')/fc;
tau = waveform.PulseWidth;
Pt = radareqpow(lambda,maxrange,SNR,tau,'RCS',0.5,'Gain',20);

transmitter = phased.Transmitter('PeakPower',50e3,'Gain',20,'LossFactor',0,...
    'InUseOutputPort',true,'CoherentOnTransmit',true);

radiator = phased.Radiator('Sensor',antenna,...
    'PropagationSpeed',physconst('LightSpeed'),'OperatingFrequency',fc);
collector = phased.Collector('Sensor',antenna,...
    'PropagationSpeed',physconst('LightSpeed'),'Wavefront','Plane',...
    'OperatingFrequency',fc);

receiver = phased.ReceiverPreamp('Gain',20,'NoiseFigure',2,...
    'ReferenceTemperature',290,'SampleRate',fs,...
    'EnableInputPort',true,'SeedSource','Property','Seed',1e3);

channel = phased.FreeSpace(...
    'PropagationSpeed',physconst('LightSpeed'),...
    'OperatingFrequency',fc,'TwoWayPropagation',false,...
    'SampleRate',fs);

T = 1/waveform.PRF;
% Get antenna position
txpos = antennaplatform.InitialPosition;
% Allocate array for received echoes

rxsig = zeros(int16(fs*T),numpulses);

for n = 1:numpulses
    % Update the target position
    [tgtpos,tgtvel] = targetplatform(T);
    % Get the range and angle to the target
    [tgtrng,tgtang] = rangeangle(tgtpos,txpos);
    % Generate the pulse
    sig = waveform();
    % Transmit the pulse. Output transmitter status
    [sig,txstatus] = transmitter(sig);
    % Radiate the pulse toward the target
    sig = radiator(sig,tgtang);
    % Propagate the pulse to the target in free space
    sig = channel(sig,txpos,tgtpos,[0;0;0],tgtvel);
    % Reflect the pulse off the target
    sig = target(sig);
    % Propagate the echo to the antenna in free space
    sig = channel(sig,tgtpos,txpos,tgtvel,[0;0;0]);
    % Collect the echo from the incident angle at the antenna
    sig = collector(sig,tgtang);
    % Receive the echo at the antenna when not transmitting
    rxsig(:,n) = receiver(sig,~txstatus);
end

rxsig = pulsint(rxsig,'noncoherent');
t = unigrid(0,1/receiver.SampleRate,T,'[)');
rangegates = (physconst('LightSpeed')*t)/2;
plot(rangegates/1e3,rxsig)
hold on
xlabel('range (km)')
ylabel('Power');
ylim = get(gca,'YLim');
plot([tgtrng/1e3,tgtrng/1e3],[0 ylim(2)],'r')
hold off

Since every step in toolbox object is like blackbox.

Can you tell me what's going on? I've dealt with this for days.

Thank you very much!

Answer 1

[Kaushik Vasanth]

Hey,

I am not completely aware of whats happening when you are trying to calculate the range here.

Maybe you could use another method to calculate the range.

Take radar cube data and plot the magnitude spectrum for the received samples.

From this plot you can find out the beat frequency and use this value to calculate the range by using the formula:

R = (c*fb*tchirp)/2*BW

Hope this can solve the problem!