Power Spectral Density two approaches

Hi all,

Please, can you explain me why I get two different results of Gaussian pulse Power Spectral Density? This two approaches should lead to the equivalent results but do not. I really dont know where I make mistake. Thank you very much. I also attached the source file. The code:

 if true
% 
% GAUSSIAN PULSE PSD
fc = 2e9;                           % Center frequency
tc = gmonopuls('cutoff',fc);        % Width of each pulse
fs=50*fc;                           % Sampling frequency
SegmentDuration = 2*tc;
N = fs*SegmentDuration;
t  = -SegmentDuration:(1/fs):(SegmentDuration-1/fs);         % Signal evaluation time
y = gmonopuls(t,fc); 
figure();
plot(t,y)
figure();
periodogram(y, rectwin(length(y)), [], fs, 'oneside', 'power');
hgcf = gcf;
hgcf.Color = [1,1,1];
mean_power = mean(y.^2);
mean_power_dBm = 10*log10(1000*mean_power);
%---------------------------------------------------------------------------------------------------------
fc = 2e9;                           % Center frequency
Fs = 100e9;                        % Sampling frequency
tc = gmonopuls('cutoff',fc);        % Width of each pulse
t = 0:1/Fs:(4*tc-1/Fs);             % Signal evaluation time
x = pulstran(t,2*tc,@gmonopuls,fc);
figure();
plot(t,x)
N = length(x);
NFFT = 2^nextpow2(N);
xdft = fft(x,NFFT);
xdft = xdft(1:NFFT/2+1);
psdx = (1/(Fs*NFFT)) * abs(xdft).^2;
psdx(2:end-1) = 2*psdx(2:end-1);
freq = 0:Fs/NFFT:Fs/2;
figure();
plot(freq,10*log10(psdx))
grid on
title('Periodogram Using FFT')
xlabel('Frequency (Hz)')
ylabel('Power/Frequency (dB/Hz)')
end

Answer 1

[Rick Rosson]

Please replace the following line of code:

   periodogram(y, rectwin(length(y)), [], fs, 'oneside', 'power');

with:

   periodogram(y, rectwin(length(y)), [], fs, 'oneside', 'psd');

[Martin Kovac]

Thank you very much. This is exactly what i need to know. Thank you once again.