On 02/06/2019 12:05 PM, freed.pointer--- via USRP-users wrote:
[Note: I have already sent this message to the list, but before
subscribing to it, and it seems that for this reason, the message has
not been delivered. I am making a second attempt after having
subscribed. Please accept my apologies in case you received it twice.]
Hi,
I am using an Ettus USRP N210 with a LF RX daughterboard [1] to
*receive* signals.
After having tuned to a frequency of 1 MHz with this call (which I
understand corresponds to a full 'automatic policy' for the tuning):
uhd::tune_request_t frequency{1.0};
uhd::tune_result_t t_res;
t_res = usrp->set_rx_freq(freq, chan);
I display results of the tuning request using 't_res.to_pp_string()'
and get:
Tune Result:
Target RF Freq: 1.000000 (MHz)
Actual RF Freq: 0.000000 (MHz)
Target DSP Freq: -1.000000 (MHz)
Actual DSP Freq: -1.000000 (MHz)
Now, this section of the documentation [2] stipulates:
<<
Note that the meaning of the DSP frequency's sign differs between TX
and RX operations. The target frequency is the result of target_freq =
rf_freq + sign * dsp_freq. For TX, sign is negative, and for RX, sign
is positive.
The LF RX has no local frequency-conversion hardware. So, frequency
conversion down to complex-baseband is done entirely in the DSP
in the FPGA.
If you want to look at a 1MHz signal, the DSP has to bring it *down* by
1MHz to baseband, so that is indicated by the negative DSP frequency value.
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
