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phased.SteppedFMWaveform System object

Package: phased

Stepped FM pulse waveform

Description

The SteppedFMWaveform object creates a stepped FM pulse waveform.

To obtain waveform samples:

  1. Define and set up your stepped FM pulse waveform. See Construction.

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

Construction

H = phased.SteppedFMWaveform creates a stepped FM pulse waveform System object™, H. The object generates samples of a linearly stepped FM pulse waveform.

H = phased.SteppedFMWaveform(Name,Value) creates a stepped 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

FrequencyStep

Linear frequency step size

Specify the linear frequency step size (in hertz) as a positive scalar. The default value of this property corresponds to 20 kHz.

Default: 2e4

NumSteps

Specify the number of frequency steps as a positive integer. When NumSteps is 1, the stepped FM waveform reduces to a rectangular waveform.

Default: 5

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

Definitions

Stepped FM Waveform

In a stepped FM waveform, a group of pulses together sweep a certain bandwidth. Each pulse in this group occupies a given center frequency and these center frequencies are uniformly located within the total bandwidth.

Examples

Create a stepped frequency pulse waveform object, and plot the third pulse.

hw = phased.SteppedFMWaveform('NumSteps',3,'FrequencyStep',2e4);
plot(hw,'PulseIdx',3);

References

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

See Also

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