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getStretchProcessor

System object: phased.LinearFMWaveform
Package: phased

Create stretch processor for waveform

Syntax

HS = getStretchProcessor(H)
HS = getStretchProcessor(H,refrng)
HS = getStretchProcessor(H,refrng,rngspan)
HS = getStretchProcessor(H,refrng,rngspan,v)

Description

HS = getStretchProcessor(H) returns the stretch processor for the waveform, H. HS is set up so the reference range corresponds to 1/4 of the maximum unambiguous range of a pulse. The range span corresponds to 1/10 of the distance traveled by the wave within the pulse width. The propagation speed is the speed of light.

HS = getStretchProcessor(H,refrng) specifies the reference range.

HS = getStretchProcessor(H,refrng,rngspan) specifies the range span. The reference interval is centered at refrng.

HS = getStretchProcessor(H,refrng,rngspan,v) specifies the propagation speed.

Input Arguments

H

Linear FM pulse waveform object.

refrng

Reference range, in meters, as a positive scalar.

Default: 1/4 of the maximum unambiguous range of a pulse

rngspan

Length of the interval of ranges of interest, in meters, as a positive scalar. The center of the interval is the range value specified in the refrng argument.

Default: 1/10 of the distance traveled by the wave within the pulse width

v

Propagation speed, in meters per second, as a positive scalar.

Default: Speed of light

Output Arguments

HS

Stretch processor as a phased.StretchProcessor System object™.

Examples

expand all

Use stretch processing to locate a target at a range of 4950 m.

Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent step syntax. For example, replace myObject(x) with step(myObject,x).

Simulate the signal.

waveform = phased.LinearFMWaveform;
x = waveform();
c = physconst('LightSpeed');
rng = 4950.0;
num_samples = round(rng/(c/(2*waveform.SampleRate)));
x = circshift(x,num_samples);

Perform stretch processing.

stretchproc = getStretchProcessor(waveform,5000,200,c);
y = stretchproc(x);

Plot the spectrum of the resulting signal.

[Pxx,F] = periodogram(y,[],2048,stretchproc.SampleRate,'centered');
plot(F/1000,10*log10(Pxx))
grid
xlabel('Frequency (kHz)')
ylabel('Power/Frequency (dB/Hz)')
title('Periodogram Power Spectrum Density Estimate')

Detect the range.

[~,rngidx] = findpeaks(pow2db(Pxx/max(Pxx)),'MinPeakHeight',-5);
rngfreq = F(rngidx);
rng = stretchfreq2rng(rngfreq,stretchproc.SweepSlope,stretchproc.ReferenceRange,c)
rng = 4.9634e+03
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