Dan, Any chance you can attach those pictures in a different way and resend, I couldn't find a way to view them and I'm curious to see them. -Ian
On Jun 11, 2013, at 10:12 PM, Dan CaJacob <dan.caja...@gmail.com> wrote: > There are two parameters that will affect your TX power: digital amplitude > and RF gain. The digital amplitude sets the amplitude of your signal going > into the DAC. UHD expects a signal between 0 and 1.0, but to keep your > output nice and linear, keep your signal amplitude belw 0.2. Conversely, > 0.02 seems pretty low. RF gain is applied in the aughtercard once your > signal has been up converted. My practice is to keep the signal amplitude at > 0.2 max amplitude, then adjust RF gain to control power. You'll end up > getting less than the max rated power output (e.g. 20 dBm for WBX, but you'll > have a clean RF signal. > > I very recently characterized a WBX across the full range of amplitude and > gain settings. Here's the result. Note that the non linearity belw a gain > of about -10 dB is due to the signal power being belw the bottom range of the > power sensor. > > > And here's a plot for just the 0.2 amplitude curve. > > > > > On Tuesday, June 11, 2013, yeran wrote: > Dear all, > > I am doing channel estimation in gnu radio narrow-band. I'm collecting data > at the receiver side after the time_recov block. It has been through the > gr.firdes.root_raised_cosine in the time_recov. But the plot I get is as the > figures in the attachment. It looks like the fluctuation of the channel > amplitude has some pattern, it looks like signal pulse shaping in there. But > doesn't the gr.firdes.root_raised_cosine works as the rrc matched filter, and > already take off the pulse shaping? > > Also, when I do experiment, I found out something strange. According to my > understanding, the --tx-amplitude on the transmitter benchmark sets the > transmission power. So the bigger the amplitude is, the better performance it > should be, since the SNR will be bigger. But in actual experiment, it is > totally the opposite way! The amplitude of 0.02, or even 0.002 works better > than the default 0.25. Has anyone come across the same problems? > > Highly appreciate if anyone can give me some suggestions on this! Thanks in > advance!! > > Ada > <rrc.png> > > > -- > Very Respectfully, > > Dan CaJacob > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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