Still hoping to get example or instructions on how to operate & send tuning commands for the case of external LO with N310....
On Mon, Apr 9, 2018 at 12:35 PM, Rob Kossler <rkoss...@nd.edu> wrote: > Hi Robin, > I have duplicated the issue using the "rx_samples_to_file" stock example. > Attached you will find 2 screen shots as well as a console log containing > two executions of the rx_samples_to_file program. In the first run, the > rx_lo_source is set to internal while in the second run, it is external. > Note that the two command lines are identical with the exception of the > rx_lo_source and the capture filename. > > In the first screenshot (ending in 33.png), you will see a spectral plot > of 100 equally spaced CW tones centered at 2444 MHz (slightly offset from > Rx center frequency of 2442 MHz). This plot shows the expected capture > spectrum. In the second plot, you will see a distorted spectrum with > mirroring of tones across the Rx center frequency. > > It seems to me that the problem is either a bug or else improper usage of > the external LO option. If the latter, perhaps you could comment on why > the rx_samples_to_file example program will not work correctly in an > external LO configuration. > > I am using an X310/UBX-160 to supply both the multitone signal (Tx 0) and > the LO reference (Tx 1). The multitone signal is split 4 ways and applied > to the four Rx2 inputs on the N310 (with appropriate atten). The LO CW > tone is split 2 ways and applied to the two rx_LO inputs on the N310 (4884 > MHz, 3 dBm at each LO input). Both of these signals were transmitting > constantly during both of the experiments. > > Note that although I applied the multitone signal to all four channels, > only the first channel (channel 0) is evaluated here because the > rx_samples_to_file program can not capture multiple channels. > > By the way, during the course of debugging this external LO issue, I came > across two unrelated UHD problems: > 1) rx_samples_to_file now includes a "channel" argument to specify which > channel you want. However, it is not a useful feature because none of the > other channel setting options (such as setting gain, freq, etc) respect the > channel argument. So, it really only works for channel 0 as it did all > along. > 2) kitchen_sink does not compile. I tried to run this utility because of > problems / limitations with rx_samples_to_file. However, it presently does > not compile because of recent UHD changes (messaging). > > Rob > > On Sat, Apr 7, 2018 at 10:31 PM, Robin Coxe <robin.c...@ettus.com> wrote: > >> Hi Rob. You are specifying use of the RX external LO correctly via >> device arguments. Each of the daughtercards on the N310 contains a single >> Analog Device AD9371 2 TX x 2 Rx RF integrated transceiver. The two Tx >> channels share an LO and the 2 Rx channels share an LO. Consequently, the >> TX or RX frequency of RF channel 0 and RF channel 1 are constrained by the >> RFIC to be the same and the TX or RF frequency of RF channel 2 and RF >> channel 3 must be the same. The AD9371 is capable of FDD operation, so >> the TX frequency does not need to be equal to the RX frequency. >> >> The LO tuning code for the N310 daughterboard in UHD is (not obviously) >> located here and, as you correctly point out, is handled differently from >> previous USRPs: >> https://github.com/EttusResearch/uhd/tree/maint/host/lib/ >> usrp/dboard/magnesium >> >> Magnesium is the internal code Ettus Research name for the N310 >> daughterboard. We will make this obscure fact more obvious in the >> documentation. >> >> -Robin >> >> >> On Sun, Apr 8, 2018 at 2:31 AM, Marcus D. Leech via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> >>> On 04/07/2018 10:39 AM, Rob Kossler wrote: >>> >>> Hi Marcus, >>> No, I haven't fooled with LO level adjustments. I set the LO at about 3 >>> dBm and did not change it. The LO freq is indeed 2x (LO at 4884MHz with >>> center freq at 2442MHz). I suspect that my custom software, which was >>> developed for first B210 and then X310 with several daughterboard variants, >>> may be sending tune commands in a way that is not ideal for an external LO >>> configuration. There was a similar issue when I first started using TwinRx >>> with "companion" or "external" LO and UHD would issue warnings about tuning >>> one channel first and then the other when both channels had to be at the >>> same freq because they shared an LO. So, my request for examples was to >>> help me see if I am issuing the tuning requests correctly for this external >>> LO config. >>> >>> Rob >>> >>> Understood. >>> >>> Hopefully, one of the R&D folks will chime in here. I don't currently >>> have one in my inventory, so running a bit blind. >>> >>> >>> >>> On Fri, Apr 6, 2018 at 7:32 PM, Marcus D. Leech via USRP-users < >>> usrp-users@lists.ettus.com> wrote: >>> >>>> On 04/06/2018 05:14 PM, Rob Kossler via USRP-users wrote: >>>> >>>>> Hi, >>>>> Are there any examples for using the N310 with external LO? I have >>>>> gotten some strange results (strange spectral mirror-ing) when using as >>>>> just a 4 channel receiver. I am using the "args" argument to set >>>>> rx_lo_source, but my code is setting the individual channel frequencies as >>>>> I do for other USRPs and I noticed various warnings in the terminal window >>>>> for each channel that I tune. >>>>> >>>>> On a separate note, I get some strange results if I set the >>>>> clock_source to external in the args (using with OctoClock). If I leave it >>>>> internal, no problem. For now, I am leaving it internal until I can solve >>>>> the problem above with LO source. >>>>> >>>>> Rob >>>>> >>>>> >>>>> Rob, just shooting from the hip here, since I haven't "lived" with an >>>> N310 yet... >>>> >>>> Have you tried adjusting the LO levels let's say 2dB in either >>>> direction to see if that changes the imaging behavior? Also, remember that >>>> the external LO input >>>> on the N310 must be a 2XLO -- at twice the desired Fc, and only up to >>>> 8GHz (giving a 4GHz antenna frequency). >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> USRP-users mailing list >>>> USRP-users@lists.ettus.com >>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>> >>> >>> >>> >>> _______________________________________________ >>> USRP-users mailing list >>> USRP-users@lists.ettus.com >>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>> >>> >> >
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