A stepped frequency pulse waveform consists of a series of N narrowband pulses. The frequency is increased from step to step by a fixed amount, Δf, in Hz.
Similar to linear FM pulse waveforms, stepped frequency waveforms are a popular pulse compression technique. Using this approach enables you to increase the range resolution of the radar without sacrificing target detection capability.
To create a stepped FM pulse waveform, use
The stepped frequency pulse waveform has the following modifiable properties:
SampleRate — Sampling
rate in Hz
PulseWidth — Pulse duration
PRF — Pulse repetition
frequency in Hz
FrequencyStep — Frequency
step in Hz
NumSteps — Number of frequency
OutputFormat — Output
format in pulses or samples
NumSamples — Number of
samples in the output when the
NumPulses — Number of
pulses in the output when the
Enter the following to construct a stepped FM pulse waveform
with a pulse duration (width) of 50 μs, a PRF of 10 kHz, and
five steps of 20 kHz. The sampling rate is 1 MHz. By default the
is equal to
'Pulses' and the number of pulses in
the output is equal to one. The example uses the
to demonstrate that the bandwidth of the stepped FM pulse waveform
is the product of the frequency step and the number of steps
hs = phased.SteppedFMWaveform('SampleRate',1e6,... 'PulseWidth',5e-5,'PRF',1e4,... 'FrequencyStep',2e4,'NumSteps',5); bandwidth(hs) % equal to hs.NumSteps*hs.FrequencyStep
OutputFormat property is set
'Pulses' and the
is set to 1, calling the
step method returns one
pulse repetition interval (PRI). The pulse duration within that interval
is equal to the
PulseWidth property. The remainder
of the PRI consists of zeros.
The initial pulse has a frequency of zero, and is a DC pulse.
NumPulses property set to 1, each time
step, the frequency of the narrowband pulse
increments by the value of the
If you call
step more times than the value of the
the process repeats, starting over with the DC pulse.
step to return successively higher frequency
pulses. Plot the pulses one by one in the same figure window. Pause
the loop to visualize the increment in frequency with each successive
step. Make an additional call to
demonstrate that the process starts over with the DC (rectangular)
t = unigrid(0,1/hs.SampleRate,1/hs.PRF,'[)'); for i = 1:hs.NumSteps plot(t,real(step(hs))); pause(0.5); axis tight; end % calling step again starts over with a DC pulse y = step(hs);
The next figure shows the plot in the final iteration of the loop.