Hello to the list
I am trying to build a simple SSB transmitter using GRC - GR-3.2.2.
I use the 32Khz sampled audio source and bandpass it to reduce bandwidth
In order to match USRP usable interpolation, I have to set an
interpolation by 10 to the bandpass, so that 32K * 10 *
400 = 128MSPS.
I’ve actually managed to get the RF signal out of the USRP, but it isn’t
The 10-interpolated spectrum contains my baseband signal’s spectral
replicas spaced by 32kHz, as it always is the
case when interpolate.
My problem is that if I put a lowpass filter between the bandpass and
USRP sink, working at 320kHz, the CPU cannot
keep up and I get uUuUaOaO like raining.
I use an AMD-3X Phenom with 3x2.3GHz cores and Ubuntu 9.04.
Actually I see that 1 of the cores jumps to full 2.3G speed and gets
stuck at 100% usage.
From the theory I understand that we should lowpass after interpolating.
Is there any more efficient way to get rid of the spectral replicas,
working at 320kSPS?
Thanks in advance for any suggestion.
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