I think the range across which you have acceptable linearity may be somewhat related to the type of signal you are using. The general recommendation in the past has been to stick below 0.2 The graphs show that you only lose about 7 dBm of total possible power by backing off the digital amplitude to 0.2 max and you get a linear 1 dBm power output increase for every 1 dB gain increase across the entire gain range of the WBX.
By they, it is a bit unrelated, but I also measured -119 dBm for 12 dB SINAD on the RX side with an 8920A specan. Very Respectfully, Dan CaJacob On Wed, Jun 12, 2013 at 10:29 AM, Karan Talasila <karan....@gmail.com>wrote: > I think you mean from the curve that for tx-amplitude as 0.2 and then > increasing gain gives you the most linear output compared to all other > amplitudes . Am I right? > > > On Wed, Jun 12, 2013 at 7:45 PM, Dan CaJacob <dan.caja...@gmail.com>wrote: > >> Sure. Sorry. >> >> Very Respectfully, >> >> Dan CaJacob >> >> >> On Wed, Jun 12, 2013 at 1:52 AM, Ian Buckley <i...@ionconcepts.com>wrote: >> >>> 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 >>> >>> >>> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > > > -- > Regards > Karan Talasila >
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