I'm experiencing a weird effect on my captures. It may just be due to my bad dsp understanding.
I'm using an E310 SDR platform to capture a multitone (4 carriers) signal:
- Fc = 150 MHz
- Bw = 286 KHz
- fs = 3 Msps (I tried several values ranging from 300 ksps to 3 Msps)
- format = short (IQ components, 16 bit each)
- Time of capture: 10 s
And then using Matlab to plot it:
% Read signal from file fid = open(filename, 'r'); IQ = fread(fid, 'int16'); rx_signal = complex(IQ(1:2:end), IQ(2:2:end)); % Plot PSD pwelch(rx_signal, , , , 3e6, 'centered')
And the result is shown in the figure below:
That ~10dB noise floor slope does not look good. Shouldn't the noise floor be flatter? What may I be doing wrong?
ps- I'm new to this community but I hope I'll be around for a good while :)