Surface RCS as a function of range and Doppler
nrcs– normalized radar cross-section
rbins– range bin centers
freq– radar frequency
alt– radar altitude
dopres– Doppler resolution
speed– radar speed
dive– radar dive angle
are the input arguments.
Radar Clutter Cross-Section of Flat Land
Calculate clutter RCS in a set of range-Doppler cells. The range swath begins at 3000 m and extends to 5000 m with a 50 m range bin width. The radar center frequency is 30 GHz and with a Doppler resolution of 100 Hz. The radar travels at an altitude of 1000 m and with a speed of 100 m/s with a dive angle.
rngbins= 3000:50:5000; freq = 30e9; doplrres = 100; rdralt = 1000; rdrspeed = 100; dive = 10;
Use a constant-gamma flatland reflectivity model to get the normalized radar cross-section at each range bin. Then compute the grazing angle using the
grazingang function. Compute the normalized surface reflectivity.
gamma = surfacegamma('Flatland'); refl = surfaceReflectivityLand( ... 'Model','ConstantGamma','Gamma',gamma); graze = grazingang(rdralt,rngbins,'Model','Flat'); nrcs = refl(graze,freq);
Calculate and display the radar cross-section of the clutter.
[rcs,dop] = clutterSurfaceRangeDopplerRCS( ... nrcs,rngbins,freq,doplrres,rdralt, ... rdrspeed,dive); rcs(rcs < 10^-2) = 10^-2; imagesc(dop/1000.0,rngbins,10*log10(rcs)) title('Radar Cross Section (dBsm)') xlabel('Doppler (kHz)') ylabel('Range (m)') axis('xy') colorbar
nrcs — Normalized radar cross section
length-N nonnegative vector
Normalized radar cross section of the surface, specified as a
length-N nonnegative vector. Each entry in
nrcs corresponds to a range specified in
rbins. Units are dimensionless but often expressed as
rbins — Range bin center values
length-N nonnegative vector (default)
Range bin centers, specified as a real-valued length-N vector.
rbins must appear in increasing order and must have at
least two elements. The total range swath starts below the first element of
rbins and extends beyond the last element of
rbins by half the range bin width. The starting and ending ranges
are extrapolated from the first and last bins. Range bins need not be uniformly spaced.
No range wrapping due to ambiguous range is performed. Units are in meters.
[20 25 30 35]
freq — Radar frequency
Radar frequency, specified as a positive scalar. Units are in Hz.
dopres — Doppler resolution
Doppler resolution, specified as a positive scalar. By default, no wrapping is performed in Doppler space. Doppler bins will cover the full Doppler spectrum of clutter at the specified resolution. Units are in Hz.
alt — Radar altitude
Radar altitude, specified as a non-negative scalar. Units are in meters.
speed — Radar speed
Radar speed, specified as a non-negative scalar. Units are in meters/sec.
dive — Radar dive angle
Radar dive angle, specified as a scalar between –90° and 90°. The dive angle is the angle that the radar velocity vector makes with the horizontal plane. A positive dive angle indicates that the velocity vector is pointing down. Units are in degrees.
ndop — Number of Doppler bins
Number of dc-centered Doppler bins, specified as a positive integer. Specifying this
parameter enables Doppler wrapping. Use this argument with the
NumDopplerBins name-value pair.
c — Signal propagation speed
physconst('LightSpeed') (default) | positive scalar
Signal propagation speed, specified as a positive scalar. Use this argument with the
PropagationSpeed name-value pair. The default propagation speed
is the value obtained from
physconst('LightSpeed'). Units are in
nri — Number of integration points per range bin
40 (default) | positive integer
Number of integration points per range bin, specified as a positive integer. Use
this argument with the
rcs — Radar cross section
complex-valued N-by-M matrix
Radar cross section, returned as an complex-valued N-by-M matrix where RCS(i,j) gives the RCS of surface clutter in the range-Doppler cell at the ith range and jth Doppler bin. Units are in m².
dopbins — Doppler bins
Doppler bins, returned as length-M vector. By default, the
Doppler bins extend over the entire Doppler spectrum of clutter at the resolution
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