Thanks for the response. Reading that page about the tune_request_t it says "*The daughterboards that support this functionality are: WBX (all revisions), WBX-120, SBX (all revisions), SBX-120, CBX, CBX-120, UBX, UBX-160*" so will that work for the N320? I actually am trying to avoid the DC signal and have manually tuned 2MHz above the LO (fc=220MHz, BW=2MHz-4MHz) but still see this behavior.
I haven't exactly measured the dBm of my signals. I'm transmitting over the air from one N320 and receiving from a second N320, but by strong/weak I mean my "weak" signal is -30dB down from my "strong" signal. I don't see any clipping in my "strong" signal. I guess what should I expect from the digital samples out from the SDR and how does that work? Should I see +/- 1.0 for -15dBm, and then +/-0.001 for a -45dBm signal? (my understanding is that's NOT how it works). Is there some kind of adaptive behavior that autoscales the data, and are there any details available how that works or how to turn it off? It appears to me from my sporadic testing that in short time scales (e.g. microseconds) a XdB change in signal level does result in an XdB change in digital output, but from longer timescales (e.g. 100's of milliseconds or just receive command to receive command) they do not appear correlated. Thank you, Steve On Mon, Nov 13, 2023 at 8:04 AM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 13/11/2023 05:08, Steve Hamn wrote: > > Hello, > > > > Does the Ettus N320 employ any type of AGC? If so is there a detailed > > description of it anywhere? Or can it be disabled? > I don't believe the N320 implements any type of AGC. > > > > I notice that if I send in a strong signal the digital output from the > > SDR is approx +/-1. If I send in a weak signal it's also +/-1 just > > noisier. I've been experimenting with sending in amplitude modulated > > pulses. Seems like over 'long' timescales there is some sort of > > automatic adjustment going on that is corrupting my measurements. What > > am I missing here? > A narrowband signal right at the tuning center can get modified by the > built-in DC offset compensation in the DSP logic > in the radio. Look into "offset tuning": > > https://files.ettus.com/manual/page_general.html > > And the API bits here: > > https://files.ettus.com/manual/structuhd_1_1tune__request__t.html > > The idea is that you ask the radio to offset the LO away from the DC > anomaly, and then the DSP in the radio shifts the bandwidth > so that you get exactly the desired center frequency that you asked for. > > > > What do you mean by "weak" and "strong" signal. The maximum recommended > input to the radio is -15dBM, and its narrowband > MDS at max gain is probably somewhere south of -120dBm. So both > your "weak" and "strong" signals may just be clipping, or > you're mis-interpreting the data that you are collecting. The radio > really does have a quite high dynamic range, but it > does not implement AGC as far as I know. That would be something > you'd have to implement in your signal processing flow. > > > > > > Conversely it appears I am able to control the TX signal by just > > sending out smaller numbers, and I don't see this (or am I just > > missing it)? > > > > Thanks in advance for any help or insight you can provide! > > > > Thanks, > > > > Steve > > > > _______________________________________________ > > USRP-users mailing list -- usrp-users@lists.ettus.com > > To unsubscribe send an email to usrp-users-le...@lists.ettus.com > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-le...@lists.ettus.com >
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