clutterSurfaceRangeDopplerRCS

Surface RCS as a function of range and Doppler

Since R2022b

Syntax

rcs = clutterSurfaceRangeDopplerRCS(nrcs,rbins,freq,dopres,alt,speed,dive)

rcs = clutterSurfaceRangeDopplerRCS(___,PropagationSpeed=c)

rcs = clutterSurfaceRangeDopplerRCS(___,NumDopplerBins=ndop)

rcs = clutterSurfaceRangeDopplerRCS(___,NumIntegrationPoints=nri)

[rcs,dopbins] = clutterSurfaceRangeDopplerRCS(___)

Description

rcs = clutterSurfaceRangeDopplerRCS(nrcs,rbins,freq,dopres,alt,speed,dive) returns the radar cross-section rcs of a surface illuminated by monostatic radar, where

• 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.

rcs = clutterSurfaceRangeDopplerRCS(___,PropagationSpeed=c) also specifies the signal propagation speed c.

rcs = clutterSurfaceRangeDopplerRCS(___,NumDopplerBins=ndop) also specifies the number of Doppler bins, ndop. Using this parameter enables Doppler wrapping and makes the clutter output DC-centered.

rcs = clutterSurfaceRangeDopplerRCS(___,NumIntegrationPoints=nri) also specifies the number of points per range bin nri used for numerical integration of the reflectivity.

[rcs,dopbins] = clutterSurfaceRangeDopplerRCS(___) also returns the Doppler-shift bin values dopbins. Units are in Hz.

Examples

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${10}^{\circ }$ 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

Input Arguments

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 m²/m².

Data Types: double

rbins — Range bin center values

length-N nonnegative vector (default)

Range bin centers, specified as a real-valued length-N vector. Elements of 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.

Example: [20 25 30 35]

Data Types: double

freq — Radar frequency

positive scalar

Radar frequency, specified as a positive scalar. Units are in Hz.

Data Types: double

dopres — Doppler resolution

positive scalar

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.

Example: 50

Data Types: double

alt — Radar altitude

scalar

Radar altitude, specified as a non-negative scalar. Units are in meters.

Data Types: double

speed — Radar speed

positive scalar

Radar speed, specified as a non-negative scalar. Units are in meters/sec.

Example: 50

Data Types: double

dive — Radar dive angle

scalar

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.

Data Types: double

ndop — Number of Doppler bins

nonnegative integer

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.

Example: NumDopplerBins=128

Data Types: double

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 meters/second.

Example: PropagationSpeed=3e8

Data Types: double

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 NumIntegrationPoints name-value pair.

Example: NumIntegrationPoints=100

Data Types: double

Output Arguments

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 i^th range and j^th Doppler bin. Units are in m².

dopbins — Doppler bins

length-M vector

Doppler bins, returned as length-M vector. By default, the Doppler bins extend over the entire Doppler spectrum of clutter at the resolution specified by dopres.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2022b