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phased.LinearFMWaveform System object

Package: phased

Linear FM pulse waveform

Description

The LinearFMWaveform object creates a linear FM pulse waveform.

To obtain waveform samples:

  1. Define and set up your linear FM waveform. See Construction.

  2. Call step to generate the linear FM waveform samples according to the properties of phased.LinearFMWaveform. The behavior of step is specific to each object in the toolbox.

Construction

H = phased.LinearFMWaveform creates a linear FM pulse waveform System object™, H. The object generates samples of a linear FM pulse waveform.

H = phased.LinearFMWaveform(Name,Value) creates a linear FM pulse waveform object, H, with each specified property Name set to the specified Value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

Properties

SampleRate

Sample rate

Specify the sample rate, in hertz, as a positive scalar. The quantity (SampleRate ./ PRF) is a scalar or vector that must contain only integers. The default value of this property corresponds to 1 MHz.

Default: 1e6

PulseWidth

Pulse width

Specify the length of each pulse (in seconds) as a positive scalar. The value must satisfy PulseWidth <= 1./PRF.

Default: 50e-6

PRF

Pulse repetition frequency

Specify the pulse repetition frequency (in hertz) as a scalar or a row vector. The default value of this property corresponds to 10 kHz.

To implement a constant PRF, specify PRF as a positive scalar. To implement a staggered PRF, specify PRF as a row vector with positive elements. When PRF is a vector, the output pulses use successive elements of the vector as the PRF. If the last element of the vector is reached, the process continues cyclically with the first element of the vector.

The value of this property must satisfy these constraints:

  • PRF is less than or equal to (1/PulseWidth).

  • (SampleRate ./ PRF) is a scalar or vector that contains only integers.

Default: 1e4

SweepBandwidth

FM sweep bandwidth

Specify the bandwidth of the linear FM sweeping (in hertz) as a positive scalar. The default value corresponds to 100 kHz.

Default: 1e5

SweepDirection

FM sweep direction

Specify the direction of the linear FM sweep as one of 'Up' or 'Down'.

Default: 'Up'

SweepInterval

Location of FM sweep interval

If you set this property value to 'Positive', the waveform sweeps in the interval between 0 and B, where B is the SweepBandwidth property value. If you set this property value to 'Symmetric', the waveform sweeps in the interval between –B/2 and B/2.

Default: 'Positive'

Envelope

Envelope function

Specify the envelope function as one of 'Rectangular' or 'Gaussian'.

Default: 'Rectangular'

OutputFormat

Output signal format

Specify the format of the output signal as one of 'Pulses' or 'Samples'. When you set the OutputFormat property to 'Pulses', the output of the step method is in the form of multiple pulses. In this case, the number of pulses is the value of the NumPulses property.

When you set the OutputFormat property to 'Samples', the output of the step method is in the form of multiple samples. In this case, the number of samples is the value of the NumSamples property.

Default: 'Pulses'

NumSamples

Number of samples in output

Specify the number of samples in the output of the step method as a positive integer. This property applies only when you set the OutputFormat property to 'Samples'.

Default: 100

NumPulses

Number of pulses in output

Specify the number of pulses in the output of the step method as a positive integer. This property applies only when you set the OutputFormat property to 'Pulses'.

Default: 1

Methods

bandwidthBandwidth of linear FM waveform
cloneCreate linear FM waveform object with same property values
getMatchedFilterMatched filter coefficients for waveform
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
getStretchProcessorCreate stretch processor for waveform
isLockedLocked status for input attributes and nontunable properties
plotPlot linear FM pulse waveform
releaseAllow property value and input characteristics changes
resetReset states of the linear FM waveform object
stepSamples of linear FM pulse waveform

Examples

Create and plot an upsweep linear FM pulse waveform.

hw = phased.LinearFMWaveform('SweepBandwidth',1e5,...
    'PulseWidth',1e-4);
plot(hw);

References

[1] Levanon, N. and E. Mozeson. Radar Signals. Hoboken, NJ: John Wiley & Sons, 2004.

[2] Richards, M. A. Fundamentals of Radar Signal Processing. New York: McGraw-Hill, 2005.

See Also

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