pulseCompressionLibrary
Description
The pulseCompressionLibrary
System object™ creates a pulse compression library.
The library contains sets of parameters that describe pulse compression operations performed
on received signals to generate their range response. You can use this library to perform
matched filtering or stretch processing. This object can process waveforms created by the
pulseWaveformLibrary
object.
To make a pulse compression library
Create the
pulseCompressionLibrary
object and set its properties.Call the object with arguments, as if it were a function.
To learn more about how System objects work, see What Are System Objects?
Creation
Description
System object creates a pulse compression library, complib
= pulseCompressionLibrary()complib
, with
default property values.
creates a pulse compression library with each property complib
= pulseCompressionLibrary(Name
,Value
)Name
set to a
specified Value
. You can specify additional name-value pair arguments
in any order as
(Name1
,Value1
,...,NameN
,ValueN
).
Enclose each property name in single quotes.
Example: complib =
pulseCompressionLibrary('SampleRate',1e9,'WaveformSpecification',{{'Rectangular','PRF',1e4,'PulseWidth',100e-6},{'SteppedFM','PRF',1e4}},'ProcessingSpecification',{{'MatchedFilter','SpectrumWindow','Hann'},{'MatchedFilter','SpectrumWindow','Taylor'}})
creates a library with two matched filters. One is matched to a rectangular waveform and
the other to a stepped FM waveform. The matched filters use a Hann window and a Taylor
window, respectively.
Properties
Unless otherwise indicated, properties are nontunable, which means you cannot change their
values after calling the object. Objects lock when you call them, and the
release
function unlocks them.
If a property is tunable, you can change its value at any time.
For more information on changing property values, see System Design in MATLAB Using System Objects.
SampleRate
— Waveform sample rate
1e6
(default) | positive scalar
Waveform sample rate, specified as a positive scalar. All waveforms have the same sample rate. Units are in hertz.
Example:
100e3
Data Types: double
PropagationSpeed
— Signal propagation speed
physconst('LightSpeed')
(default) | positive scalar
Signal propagation speed, specified as a positive scalar. Units are in meters per second. The
default propagation speed is the value returned by
physconst('LightSpeed')
. See physconst
for more information.
Example: 3e8
Data Types: double
WaveformSpecification
— Pulse waveforms
{{'Rectangular','PRF',10e3,'PulseWidth',100e-6},{'LinearFM','PRF',1e4,'PulseWidth',50e-6,'SweepBandwidth',1e5,'SweepDirection','Up','SweepInterval','Positive'}}
(default) | cell array
Pulse waveforms, specified as a cell array. Each cell of the array contains the specification of one waveform.
{{Waveform 1 Specification},{Waveform 2 Specification},{Waveform 3 Specification}, ...}
{PulseIdentifier,Name1,Value1,Name2,Value2, ...}
This System object supports four built-in waveforms and also lets you specify custom waveforms. For the built-in waveforms, the waveform specifier consists of a waveform identifier followed by several name-value pairs setting the properties of the waveform. For the custom waveforms, the waveform specifier consists of a handle to a user-define waveform function and the functions input arguments.
Waveform Types
Pulse Type | Pulse Identifier | Waveform Arguments |
Linear FM | 'LinearFM' | Linear FM Waveform Arguments |
Phase coded | 'PhaseCoded' | Phase-Coded Waveform Arguments |
Rectangular | 'Rectangular' | Rectangular Waveform Arguments |
Stepped FM | 'SteppedFM' | Stepped FM Waveform Arguments |
Custom | Function handle | Custom Waveform Arguments |
Example: {{'Rectangular','PRF',10e3,'PulseWidth',100e-6},{'Rectangular','PRF',100e3,'PulseWidth',20e-6}}
Data Types: cell
ProcessingSpecification
— Pulse compression descriptions
{{'MatchedFilter','SpectrumWindow','None'},{'StretchProcessor','RangeSpan',200,'ReferenceRange',5e3,'RangeWindow','None'}}
(default) | cell array
Pulse compression descriptions, specified as a cell array of processing specifications. Each cell defines a different processing specification. Each processing specification is itself a cell array containing the processing type and processing arguments.
{{Processing 1 Specification},{Processing 2 Specification},{Processing 3 Specification}, ...}
{ProcessType,Name,Value,...}
ProcessType
is either 'MatchedFilter'
or 'StretchProcessor'
.
'MatchedFilter'
– The name-value pair arguments are'Coefficients'
,coeff
– specifies the matched filter coefficients,coeff
, as a column vector. When not specified, the coefficients are calculated from theWaveformSpecification
property. For the Stepped FM waveform containing multiple pulses,coeff
corresponds to each pulse until the pulse index,idx
changes.'SpectrumWindow'
,sw
– specifies the spectrum weighting window,sw
, applied to the waveform. Window values are one of'None'
,'Hamming'
,'Chebyshev'
,'Hann'
,'Kaiser'
, and'Taylor'
. The default value is'None'
.'SidelobeAttenuation'
,slb
– specifies the sidelobe attenuation window,slb
, of the Chebyshev or Taylor window as a positive scalar. The default value is 30. This parameter applies when you set'SpectrumWindow'
to'Chebyshev'
or'Taylor'
.'Beta'
,beta
– specifies the parameter,beta
, that determines the Kaiser window sidelobe attenuation as a nonnegative scalar. The default value is 0.5. This parameter applies when you set'SpectrumWindow'
to'Kaiser'
.'Nbar'
,nbar
– specifies the number of nearly constant level sidelobes,nbar
, next to the main lobe in a Taylor window as a positive integer. The default value is 4. This parameter applies when you set'SpectrumWindow'
to'Taylor'
.'SpectrumRange'
,sr
– specifies the spectrum region,sr
, on which the spectrum window is applied as a 1-by-2 vector having the form[StartFrequency EndFrequency]
. The default value is [0 1.0e5]. This parameter applies when you set the'SpectrumWindow'
to any value other than 'None'. Units are in Hz.Both
StartFrequency
andEndFrequency
are measured in the baseband region [-Fs/2 Fs/2]. Fs is the sample rate specified by theSampleRate
property.StartFrequency
cannot be larger thanEndFrequency
.
'StretchProcessor'
– The name-value pair arguments are'ReferenceRange'
,refrng
– specifies the center of the ranges of interest,refrng
, as a positive scalar. Therefrng
must be within the unambiguous range of one pulse. The default value is 5000. Units are in meters.'RangeSpan'
,rngspan
– specifies the span of the ranges of interest.rngspan
, as a positive scalar. The range span is centered at the range value specified in the'ReferenceRange'
parameter. The default value is 500. Units are in meters.'RangeFFTLength'
,len
– specifies the FFT length in the range domain,len
, as a positive integer. If not specified, the default value is same as the input data length.'RangeWindow'
,rw
specifies the window used for range processing,rw
, as one of'None'
,'Hamming'
,'Chebyshev'
,'Hann'
,'Kaiser'
, and'Taylor'
. The default value is'None'
.
Example: 'StretchProcessor'
Data Types: string
| struct
Linear FM Waveform Arguments
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.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: {'LinearFM','PRF',1e4,'PulseWidth',50e-6,'SweepBandwidth',1e5,...
'SweepDirection','Up','SweepInterval','Positive'}
PRF
— Pulse repetition frequency
1e4
(default) | positive scalar
Pulse repetition frequency (PRF), specified as a positive scalar. Units are in hertz. See Pulse Repetition Frequency Restrictions for restrictions on the PRF.
Example: 20e3
Data Types: double
PulseWidth
— Pulse duration
5e-5
(default) | positive scalar
Pulse duration, specified as a positive scalar. Units are in seconds. You cannot
specify both PulseWidth
and DutyCycle
.
Example: 100e-6
Data Types: double
DutyCycle
— Pulse duty cycle
0.5
| positive scalar
Pulse duty cycle, specified as a positive scalar greater than zero and less than
or equal to one. You cannot specify both PulseWidth
and
DutyCycle
.
Example: 0.7
Data Types: double
SweepBandwidth
— Bandwidth of the FM sweep
1e5
(default) | positive scalar
Bandwidth of the FM sweep, specified as a positive scalar. Units are in hertz.
Example: 100e3
Data Types: double
SweepDirection
— Bandwidth of the FM sweep
'Up'
(default) | 'Down'
Direction of the FM sweep, specified as 'Up'
or
'Down'
. 'Up'
corresponds to increasing
frequency. 'Down'
corresponds to decreasing frequency.
Data Types: char
SweepInterval
— FM sweep interval
'Positive'
(default) | 'Symmetric'
FM sweep interval, specified as 'Positive'
or
'Symmetric'
. If you set this property value to
'Positive'
, the waveform sweeps the interval between 0 and
B, where B is the
SweepBandwidth
argument value. If you set this property value
to 'Symmetric'
, the waveform sweeps the interval between
–B/2 and B/2.
Example: 'Symmetric'
Data Types: char
Envelope
— Envelope function
'Rectangular'
(default) | 'Gaussian'
Envelope function, specified as 'Rectangular'
or
'Gaussian'
.
Example: 'Gaussian'
Data Types: char
FrequencyOffset
— Frequency offset of pulse
0
(default) | scalar
Frequency offset of pulse, specified as a scalar. The frequency offset shifts the frequency of the generated pulse waveform. Units are in hertz.
Example: 100e3
Data Types: double
Phase-Coded Waveform Arguments
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.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: {'PhaseCoded','PRF',1e4,'Code','Zadoff-Chu',
'SequenceIndex',3,'ChipWidth',5e-6,'NumChips',8}
PRF
— Pulse repetition frequency
1e4
(default) | positive scalar
Pulse repetition frequency (PRF), specified as a positive scalar. Units are in hertz. See Pulse Repetition Frequency Restrictions for restrictions on the PRF.
Example: 20e3
Data Types: double
Code
— Type of phase modulation code
'Frank'
(default) | 'P1'
| 'P2'
'Px'
| 'Zadoff-Chu'
| 'P3'
| 'P4'
| 'Barker'
Type of phase modulation code, specified as 'Frank'
,
'P1'
, 'P2'
, 'Px'
,
'Zadoff-Chu'
, 'P3'
, 'P4'
,
or 'Barker'
.
Example: 'P1'
Data Types: char
SequenceIndex
— Zadoff-Chu
sequence index
1
(default) | positive integer
Sequence index used for the Zadoff-Chu
code, specified as a
positive integer. The value of SequenceIndex
must be relatively
prime to the value of NumChips
.
Example: 3
Dependencies
To enable this name-value pair, set the Code
property to
'Zadoff-Chu'
.
Data Types: double
ChipWidth
— Chip duration
1e-5
(default) | positive scalar
Chip duration, specified as a positive scalar. Units are in seconds. See Chip Restrictions for restrictions on chip sizes.
Example: 30e-3
Data Types: double
NumChips
— Number of chips in waveform
4
(default) | positive integer
Number of chips in waveform, specified as a positive integer. See Chip Restrictions for restrictions on chip sizes.
Example: 3
Data Types: double
FrequencyOffset
— Frequency offset of pulse
0
(default) | scalar
Frequency offset of pulse, specified as a scalar. The frequency offset shifts the frequency of the generated pulse waveform. Units are in hertz.
Example: 100e3
Data Types: double
Rectangular Waveform Arguments
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.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: {'Rectangular','PRF',10e3,'PulseWidth',100e-6}
PRF
— Pulse repetition frequency
1e4
(default) | positive scalar
Pulse repetition frequency (PRF), specified as a positive scalar. Units are in hertz. See Pulse Repetition Frequency Restrictions for restrictions on the PRF.
Example: 20e3
Data Types: double
PulseWidth
— Pulse duration
5e-5
(default) | positive scalar
Pulse duration, specified as a positive scalar. Units are in seconds. You cannot
specify both PulseWidth
and DutyCycle
.
Example: 100e-6
Data Types: double
DutyCycle
— Pulse duty cycle
0.5
| positive scalar
Pulse duty cycle, specified as a positive scalar greater than zero and less than
or equal to one. You cannot specify both PulseWidth
and
DutyCycle
.
Example: 0.7
Data Types: double
FrequencyOffset
— Frequency offset of pulse
0
(default) | scalar
Frequency offset of pulse, specified as a scalar. The frequency offset shifts the frequency of the generated pulse waveform. Units are in hertz.
Example: 100e3
Data Types: double
Stepped FM Waveform Arguments
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.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: {'SteppedFM','PRF',10e-4}
PRF
— Pulse repetition frequency
1e4
(default) | positive scalar
Pulse repetition frequency (PRF), specified as a positive scalar. Units are in hertz. See Pulse Repetition Frequency Restrictions for restrictions on the PRF.
Example: 20e3
Data Types: double
PulseWidth
— Pulse duration
5e-5
(default) | positive scalar
Pulse duration, specified as a positive scalar. Units are in seconds. You cannot
specify both PulseWidth
and DutyCycle
.
Example: 100e-6
Data Types: double
DutyCycle
— Pulse duty cycle
0.5
| positive scalar
Pulse duty cycle, specified as a positive scalar greater than zero and less than
or equal to one. You cannot specify both PulseWidth
and
DutyCycle
.
Example: 0.7
Data Types: double
NumSteps
— Number of frequency steps in waveform
5
(default) | positive integer
Number of frequency steps in waveform, specified as a positive integer.
Example: 3
Data Types: double
FrequencyStep
— Linear frequency step size
20e3
(default) | positive scalar
Linear frequency step size, specified as a positive scalar.
Example: 100.0
Data Types: double
FrequencyOffset
— Frequency offset of pulse
0
(default) | scalar
Frequency offset of pulse, specified as a scalar. The frequency offset shifts the frequency of the generated pulse waveform. Units are in hertz.
Example: 100e3
Data Types: double
Custom Waveform Arguments
You can create a custom waveform from a user-defined function. The first input argument of the function must be the sample rate. For example, specify a hyperbolic waveform function,
function wav = HyperbolicFM(fs,prf,pw,freq,bw,fcent),
fs
is the sample rate and prf
,
pw
, freq
, bw
, and
fcent
are other waveform arguments. The function must have at least one
output argument, wav
, to return the samples of each pulse. This output
must be a column vector. There can be other outputs returned following the waveform
samples.Then, create a waveform specification using a function handle instead of the waveform identifier. The first cell in the waveform specification must be a function handle. The remaining cells contain all function input arguments except the sample rate. Specify all input arguments in the order they are passed into the function.
waveformspec = {@HyperbolicFM,prf,pw,freq,bw,fcent}
Usage
Description
Input Arguments
X
— Input signal
complex-valued K-by-L matrix | complex-valued K-by-N matrix | complex-valued
K-by-N-by-L array
Input signal, specified as a complex-valued K-by-L matrix, complex-valued K-by-N matrix, or a complex-valued K-by-N-by-L array. K denotes the number of fast time samples, L the number of pulses, and N is the number of channels. Channels can be array elements or beams.
Data Types: double
Complex Number Support: Yes
idx
— Index of processing specification in pulse compression library
positive integer
Index of the processing specification in the pulse compression library, specified as a positive integer.
Data Types: double
Output Arguments
Y
— Output signal
complex-valued K-by-L matrix | complex-valued K-by-N matrix | complex-valued
K-by-N-by-L array
Output signal, returned as a complex-valued
M-by-L matrix, complex-valued
M-by-N matrix, or a complex-valued
M-by-N-by-L array.
M denotes the number of fast time samples, L
the number of pulses, and N is the number of channels. Channels can
be array elements or beams. The number of dimensions of Y
matches
the number of dimensions of X
.
When matched filtering is performed, M is equal to the number
of rows in X
. When stretch processing is performed and you
specify a value for the RangeFFTLength
name-value pair,
M is set to the value of RangeFFTLength
. When
you do not specify RangeFFTLength
, M is equal to
the number of rows in X
.
Data Types: double
Complex Number Support: Yes
rng
— Sample range
real-valued length-M vector
Sample ranges, returned as a real-valued length-M vector where
M is the number of rows of Y
. Elements of
this vector denote the ranges corresponding to the rows of Y
.
Data Types: double
Object Functions
To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named obj
, use
this syntax:
release(obj)
Specific to pulseCompressionLibrary
plotResponse | Plot range response from pulse compression library |
Examples
Range Processing of Two Waveforms
Create a rectangular waveform and a linear FM waveform. Use the processing methods in the pulse compression library to range-process the waveforms. Use matched filtering for the rectangular waveform and stretch processing for the linear FM waveform.
Create two waveforms using the pulseWaveformLibrary
System object™. The sampling frequency is 1 MHz and the pulse repetition frequency for both waveforms is 1 kHz. The pulse width is also the same at 50 microsec.
fs = 1.0e6; prf = 1e3; pw = 50e-6; waveform1 = {'Rectangular','PRF',prf,'PulseWidth',pw}; waveform2 = {'LinearFM','PRF',prf,'PulseWidth',pw,... 'SweepBandwidth',1e5,'SweepDirection','Up',... 'SweepInterval', 'Positive'}; pulselib = pulseWaveformLibrary('WaveformSpecification',... {waveform1,waveform2},'SampleRate',fs);
Retrieve the waveforms for processing by the pulse compression library.
rectwav = pulselib(1); lfmwav = pulselib(2);
Create the compression processing library using the pulseCompressionLibrary
System object™ with two processing specifications. The first processing specification is matched filtering and the second is stretch processing.
mf = getMatchedFilter(pulselib,1); procspec1 = {'MatchedFilter','Coefficients',mf}; procspec2 = {'StretchProcessor','ReferenceRange',5000,... 'RangeSpan',200,'RangeWindow','Hamming'}; comprlib = pulseCompressionLibrary( ..., 'WaveformSpecification',{waveform1,waveform2}, ... 'ProcessingSpecification',{procspec1,procspec2}, ... 'SampleRate',fs,'PropagationSpeed',physconst('Lightspeed'));
Process both waveforms.
rect_out = comprlib(rectwav,1); lfm_out = comprlib(lfmwav,2); nsamp = fs/prf; t = [0:(nsamp-1)]/fs; plot(t*1000,real(rect_out)) hold on plot(t*1000,real(lfm_out)) hold off title('Pulse Compression Output') xlabel('Time (millsec)') ylabel('Amplitude')
Range Response for Three Targets
Plot the range response of an LFM signal hitting three targets at ranges of 2000, 4000, and 5500 meters. Assuming the maximum range of the radar is 10 km, determine the pulse repetition interval from the maximum range.
% Create the pulse waveform. rmax = 10.0e3; c = physconst('Lightspeed'); pri = 2*rmax/c; fs = 1e6; pri = ceil(pri*fs)/fs; prf = 1/pri; nsamp = pri*fs; rxdata = zeros(nsamp,1); t1 = 2*2000/c; t2 = 2*4000/c; t3 = 2*5500/c; idx1 = floor(t1*fs); idx2 = floor(t2*fs); idx3 = floor(t3*fs); lfm = phased.LinearFMWaveform('PulseWidth',10/fs,'PRF',prf, ... 'SweepBandwidth',(30*fs)/40); w = lfm(); %% % Imbed the waveform part of the pulse into the received signal. x = w(1:11); rxdata(idx1:idx1+10) = x; rxdata(idx2:idx2+10) = x; rxdata(idx3:idx3+10) = x; %% % Create the pulse waveform library. w1 = {'LinearFM','PulseWidth',10/fs,'PRF',prf,... 'SweepBandwidth',(30*fs)/40}; wavlib = pulseWaveformLibrary('SampleRate',fs,'WaveformSpecification',{w1}); wav = wavlib(1); %% % Generate the range response signal. p1 = {'MatchedFilter','Coefficients',getMatchedFilter(wavlib,1),'SpectrumWindow','None'}; idx = 1; complib = pulseCompressionLibrary( ... 'WaveformSpecification',{w1}, ... 'ProcessingSpecification',{p1}, ... 'SampleRate',fs, ... 'PropagationSpeed',c); y = complib(rxdata,1); %% % Plot range response of processed data plotResponse(complib,rxdata,idx,'Unit','mag');
More About
Pulse Repetition Frequency Restrictions
The PRF
property must satisfy these restrictions:
The product of
PRF
andPulseWidth
must be less than or equal to one. This condition expresses the requirement that the pulse width is less than one pulse repetition interval.The ratio of
SampleRate
toPRF
must be an integer. This condition expresses the requirement that the number of samples in one pulse repetition interval is an integer.
Chip Restrictions
The values of the ChipWidth
and NumChips
properties must satisfy these constraints:
The product of
PRF
,ChipWidth
, andNumChips
must be less than or equal to one. This condition expresses the requirement that the sum of the durations of all chips is less than one pulse repetition interval.The product of
SampleRate
andChipWidth
must be an integer. This condition expresses the requirement that the number of samples in a chip must be an integer.
The table shows additional constraints on the number of chips for different code types.
If the Code Property Is ... | Then the NumChips Property Must Be... |
---|---|
'Frank' , 'P1' , or
'Px' | A perfect square. |
'P2' | An even number that is a perfect square. |
'Barker' | 2 , 3 , 4 ,
5 , 7 , 11 , or
13 |
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
The plotResponse
object function is not supported for code
generation.
See System Objects in MATLAB Code Generation (MATLAB Coder).
Version History
Introduced in R2021a
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