Problem:
If we put a signal of 20 MBits/s (about 19 MHz of bandwidth) and therefore a sample rate of 20M in GNURadio, the signal is missing at the RX1 output of the USRP. The degradation is from a sample rate of 12M, the output signal is strongly degraded (we only see bursts). The Bandwidth in USRP block seems to have no effect and the number of overflow (in buffer ?) increase with the sample rates. In addition, I have warning message : “The bandwidth of ADCXXX is only 100 MHz”
It is concluded that we cannot use the USRP for broadband use ie with an input signal having 20 or 40 MHz of band ?
The input signal (5 Mbps) sent on TX1 does not undergo "deformation". It is correctly rendered with a sample rate of 8M but the signal bandwidth is limited to about 7.8M.
Configuration:
Tested solutions :
Questions: I thought the ADC rate on each analog RX channel is 200 MS/s quadrature, which provides a theoretical analog bandwidth of approximately 80% of the Nyquist bandwidth. Do I need to use resampling block in GNURadio to increase the bandwidth ? Or use the 10 Gbits/s interface to increase the sample rate to 80M so the bandwidth around 80 MHz ?
We want to directly receive and transmit a signal with USRP and with a band of 80 MHz @1200 MHz on GNURadio. What solution can you propose ? Thank you
If increasing your rate damages your signal, it's almost certainly not a problem of the USRP - but of your PC not keeping up with the rate it needs to consume.
You might be seeing "O" or "D" ("U" or "S" if you're transmitting) printed to your console - this is UHD telling you that the USRP's buffers ran over, because your PC did not consume data fast enough (that the USRP ran out of samples to convert to analog before your PC supplied sufficiently enough new ones if you're transmitting).
So, the only solution here is make sure your signal processing is sufficiently optimized, and your computer is sufficiently fast, to work at the sample rate you need.
To answer your questions directly:
… from a sample rate of 12M
12 MS/s is not a supported sampling rate on the USRP N300, see the official documentation. UHD warns you about having to use a different sample rate – and since you didn't spot that I guess you're not reading the console output!
I thought the ADC rate on each analog RX channel is 200 MS/s quadrature,
Nope, 122.88 MHz, 125.0 MHz or 153.6 MHz.
which provides a theoretical analog bandwidth of approximately 80% of the Nyquist bandwidth.
yep, a fair bit more than 80%, but that depends on how "flat" you need to be.
Do I need to use resampling block in GNURadio to increase the bandwidth ?
You couldn't increase the bandwidth that way; the bandwidth is defined by the hardware, not your digital signal.
Or use the 10 Gbits/s interface to increase the sample rate to 80M so the bandwidth around 80 MHz ?
For 80 MS/s you definitely can't use Gigabit ethernet: your samples amount to more than a billion bits per second. But for 20 MS/s, Gigabit ethernet does suffice.
We want to directly receive and transmit a signal with USRP and with a band of 80 MHz @1200 MHz on GNURadio.
So, you'll need 10 GbE, no matter what. You will also need a pretty fast PC, and chances are, you'll need to highly optimize the computation you're doing on the signal at these rates – but that fully depends on what you're doing.