Linear Frequency Modulated Waveform

why LFM waveform has varying amplitude when i take step of phased.LinearFMWaveform

[Wayne King]

Can you please show how you set the properties for your System object.

[Jagadeeshvelan kumar]

clc;
clear all;
pd=0.9;
pfa=1e-6;
max_range=1000;   
range_res=0.5 ;
fc=35e9;
prop_speed = physconst('LightSpeed');
pulse_bw = prop_speed/(2*range_res);
pulse_width=1/pulse_bw;              
fs = 2*pulse_bw;
noise_bw =2*pulse_bw;
c=3e8;
lambda=c/fc;
time_bandwidth_product=100;
prf= prop_speed/(2*max_range);     
hw=phased.LinearFMWaveform('SampleRate',fs,'PulseWidth',time_bandwidth_product/pulse_bw,'PRF',prf,'SweepBandwidth',pulse_bw,'NumPulses',1);
x=step(hw);
plot(hw);

[Honglei Chen]

added code format to the comment above.

Answer 1

[Honglei Chen]

The plot() function on LinearFMWaveform, plots only the real part of the waveform, so the amplitude is indeed varying.

If you are asking why in each period, the maximum amplitude seems to be varying, that is because in discrete time, you may not always be able to sample right at the peak in each period. However, if you plot

plot(abs(x))

You can see that the magnitude is constant.

HTH