findClutterSampleIndices

Clutter sample indices

Since R2023b

Syntax

[I1,I2,…,IN] = findClutterSampleIndices(genclutter,dim1,dim2,…,dimN=value1,value2,…,valueN)

[I1,I2,…,IN] = findClutterSampleIndices(genclutter,dim1,dim2,…,dimN=value1,value2,…,valueN,Name=Value)

Description

[I1,I2,…,IN] = findClutterSampleIndices(genclutter,dim1,dim2,…,dimN=value1,value2,…,valueN) finds the set of subscripts (I1, I2, …, IN) into the multidimensional signal data that correspond to surface clutter patches genclutter that were generated in the latest call to the scenario or platform detect or receive object functions. The subscripts can be used to extract samples of the surface clutter from a datacube.

[I1,I2,…,IN] = findClutterSampleIndices(genclutter,dim1,dim2,…,dimN=value1,value2,…,valueN,Name=Value) specifies additional Name-Value pair arguments.

Examples

Generate Clutter Indices for Land Clutter

Create a radar scenario containing a land surface. Use the radarTransceiver and the clutterGenerator to create clutter.

scenario = radarScenario;
landSurface(scenario);
rdr = radarTransceiver;
platform(scenario,'Sensors',rdr,'Position',[0 0 1e3]);
clutgen = clutterGenerator(scenario,rdr);

Create IQ data samples using the receive function.

iqsig = receive(scenario);

Use the phased.RangeAngleResponse System object™ to create the range-angle response at azimuth angles from $-{20}^{\circ }$ to ${20}^{\circ }$ degrees along a constant elevation cut at $-{10}^{\circ }$ degrees. Obtain the response, the range grid and the azimuth grid.

elcut = -10;
resp = phased.RangeAngleResponse(AngleSpan=[-20 20],ElevationAngle=elcut);
[dataRngAz,rnggrid,azgrid] = resp(iqsig{1}, ...
    rdr.Waveform.getMatchedFilter);

Using the findClutterSampleIndices function, find the indices corresponding to the clutter samples. Use the time2range function to get the size of the range ambiguity. Set the bin width of the elevation cut to $2^{\circ }$.

rngAmbg = time2range(1/rdr.Waveform.PRF);
[subsRng,subsAz] = findClutterSampleIndices(clutgen, ...
    Range=rnggrid,Azimuth=azgrid,Elevation=elcut, ...
    ElevationBinWidth=2,UnambiguousRange=rngAmbg);

Convert the clutter indices to linear form for extracting samples from the data matrix.

idxlin = sub2ind([numel(rnggrid),numel(azgrid)],subsRng,subsAz);

Plot a histogram of the power levels.

clutPwrSamps = abs(dataRngAz(idxlin)).^2;
nexttile
histogram(pow2db(clutPwrSamps))
xlabel('Clutter Power (dBW)')
ylabel('Counts')

Create a scatter plot of the clutter power levels showing the distribution of clutter power over range and azimuth.

nexttile
scatter(azgrid(subsAz),rnggrid(subsRng),20,clutPwrSamps,'Filled')
xlabel('Azimuth (deg)')
ylabel('Range (m)')
title('Clutter Power (W)')
colorbar

Input Arguments

genclutter — Clutter generator

ClutterGenerator object

Clutter generator, specified as a clutter generator object ClutterGenerator.

dim1 — Dimension name

char | string

Dimension names, specified as a char or string. Each dimension can have an assigned name according to the order they are indexed in the data. The dimensions of the data are ordered: Range, Azimuth, Elevation, and, Doppler although all of them may not be used in a specific data set. Dimension names, specified as one or more of the following:

Dimension Name	Units
Range	meters
Azimuth	degrees
Elevation	degrees
Doppler	Hz

You can use the permute and ipermute functions to swap the order of dimensions of the datacube.

Azimuth and elevation are defined with respect to the sensor mounting frame.

Data Types: char | string

dim2 — Dimension name

char | string

Second dimension name, specified as a char or string.

Data Types: char | string

dimN — Dimension name

char | string

N^th dimension name, specified as a char or string.

Data Types: char | string

value1 — Data values

scalar | real-valued vector

Data values, specified as a scalar or vector. Values specify the domain of the corresponding dimension. The data values are ordered: Range, Azimuth, Elevation and Doppler when used.

Data Types: char | string

value2 — Data values

scalar | real-valued vector

Second set of data values, specified as a scalar or vector. Values specify the domain of the corresponding dimension. The data values are ordered: Range, Azimuth, Elevation and Doppler when used.

Data Types: char | string

valueN — Data values

scalar | real-valued vector

N^th set of data values, specified as a scalar or vector. Values specify the domain of the corresponding dimension. The data values are ordered: Range, Azimuth, Elevation and Doppler when used.

Data Types: char | string

Name-Value Arguments

Example: RangeBinWidth = 50

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

RangeBinWidth — Range bin width

positive scalar

Range bin width, specified as a positive scalar. Specify this Name-Value pair only if the range domain is specified as a scalar. Otherwise, it is ignored. Units are in meters.

Data Types: single | double

DopplerBinWidth — Doppler bin width

positive scalar

Doppler bin width, specified as a positive scalar. Specify this Name-Value pair only if the Doppler domain is specified as a scalar. Otherwise, it is ignored. Units are in Hz.

Data Types: single | double

AzimuthBinWidth — Azimuth angle bin width

positive scalar

Azimuth angle bin width, specified as a positive scalar. Specify this Name-Value pair only if the Azimuth domain is specified as a scalar. Otherwise, it is ignored. Units are in degrees.

Example: 35

Data Types: single | double

ElevationBinWidth — Elevation angle bin width

positive scalar

Elevation angle bin width, specified as a positive scalar. Specify this Name-Value pair only if the Elevation domain is specified as a scalar. Otherwise, it is ignored. Units are in degrees.

Data Types: single | double

UnambiguousRange — c

inf (default) | positive scalar

Maximum unambiguous range, specified as positive scalar. Units are in meters.

Data Types: single | double

UnambiguousDoppler — Maximum unambiguous Doppler

inf (default) | positive scalar

Maximum unambiguous Doppler, specified as a positive scalar. Units are in Hz.

Example: 3.0

Data Types: single | double

Output Arguments

I1 — Indices of vector subscripts

positive integer-valued vector

First set of indices of vector subscripts, returned as a positive integer-valued vector. I1 is a vector of subscripts into the first dimension of the datacube. The indices of the data are ordered: Range, Azimuth, Elevation and Doppler when used. For example, if the data is only over Azimuth and Doppler, I1 corresponds to Azimuth and I2 corresponds to Doppler. You can use permute and ipermute functions to swap dimensions of an array as needed.

I2 — Indices of vector subscripts

positive integer-valued vector

Second set of Indices of vector subscripts, returned as a positive integer-valued vector. I2 is a vector of subscripts into the second dimension of the datacube. The indices of the data are ordered: Range, Azimuth, Elevation and Doppler when they are used. For example, if the data is only over Azimuth and Doppler, I2 corresponds to Doppler dimension. You can use permute and ipermute functions to swap dimensions of an array as needed.

IN — Indices of vector subscripts

positive integer-valued vector

N^th set of indices of vector subscripts, returned as a positive integer-valued vector. IN is a vector of subscripts into the N^th dimension of the datacube. The indices of the data are ordered: Range, Azimuth, Elevation and Doppler when they are used. You can use permute and ipermute functions to swap dimensions of an array as needed.

Version History

Introduced in R2023b