question about grand clutter simulation

i would used the phased.ConstantGammaClutter to simulintor the clutter.but i change the parameter the speed of the plateform.the centrel frequency of the clutter is still zero.how could i change the centrel frequency of the clutter.

Answer 1

[Honglei Chen]

Could you explain in more details? The clutter itself simulates a GMTI scene so the there is a correlation between the velocity and direction. Thus you see a clutter ridge in the angle-Doppler plane. I believe when the velocity changes, what changes is the slope of the ridge.

HTH

[JIM GREEN]

i am grateful for you answer.follow is the test code and the file.i plot the figure of the grand clutter frequency.but even though i change the parameter speed.the spectrum do not change.what is wrong with my code.

Nele = 4;
c = physconst('Lightspeed');
fc = 24e9;
lambda = c/fc;
ula = phased.ULA('NumElements',Nele,'ElementSpacing',lambda/2);
fs = 1.0e6;
prf = 10.0e3;
height = 0.5;
direction = [90;0];
speed = 100;
depang = 30;

Create the clutter simulation object and configure it to accept an transmit signal as an input argument. The configuration assumes the earth is flat. The maximum clutter range of interest is 5 km, and the maximum azimuth coverage is ±60°.

Rmax = 300.0;
Azcov = 120.0;
trgamma = surfacegamma('flatland');
clutter = phased.ConstantGammaClutter('Sensor',ula,...
    'PropagationSpeed',c,'OperatingFrequency',fc,'PRF',prf,...
    'SampleRate',fs,'Gamma',tergamma,'EarthModel','Flat',...
    'TransmitSignalInputPort',true,'PlatformHeight',height,...
    'PlatformSpeed',speed,'PlatformDirection',direction,...
    'BroadsideDepressionAngle',depang,'MaximumRange',Rmax,...
    'AzimuthCoverage',Azcov,'SeedSource','Property',...
    'Seed',40547);

Simulate the clutter return for 10 pulses. At each step, pass the transmit signal as an input argument. The software computes the effective transmitted power of the signal. The transmit signal is a rectangular waveform with a pulse width of 2 μs.

tpower = 5.0e3;
pw = 2.0e-5;
X = tpower*ones(floor(pw*fs),1);
Nsamp = fs/prf;
sig = step(clutter,X);

Plot the angle-Doppler response of the clutter at the 20th range bin.

plot(abs(fft(sum(sig.'))));

[Xin Dong]

你仿真的是正侧视针，波束主瓣指向不随着目标变，永远是0度，所以出现了这个问题。你应该调整阵列的权值，将主瓣指向不要是0度。

[ahmed hussain]

with the platform look direction as [90,0], clutter central frequency will always be zero,..irrespective of platform velocity