Reference : http://gnuradio.4.n7.nabble.com/8MHz-Tx-Bandwidth-Nightmare-and-Fear-tt14559.html#a14561
No system is capable of using 100% of the nyquist bandwidth, and the USRP is no exception.
On receive, our passband is flat out to about 75 or 80% of nyquist.
For 8 MS/s complex sampling, that gives more than 6 MHz of flat bandwidth.
On transmit, there are no halfband filters in there, so you will see more rolloff from the CIC filters.
If this is a problem, you have 3 options:
- If your generated signal is at less than 8 MS/s complex, then you
should just upsample in software.
- If your generated signal is at the full 8 MS/s then you can
pre-distort your signal to compensate for the CIC rolloff.
- Otherwise, I would suggest making a new FPGA image with halfband
filters in the TX side. You can make room in there by removing one
receive chain (leaving only one).
No system is capable of using 100% of the nyquist bandwidth, and the USRP is no exception.
On receive, our passband is flat out to about 75 or 80% of nyquist.
For 8 MS/s complex sampling, that gives more than 6 MHz of flat bandwidth.
On transmit, there are no halfband filters in there, so you will see more rolloff from the CIC filters.
If this is a problem, you have 3 options:
- If your generated signal is at less than 8 MS/s complex, then you
should just upsample in software.
- If your generated signal is at the full 8 MS/s then you can
pre-distort your signal to compensate for the CIC rolloff.
- Otherwise, I would suggest making a new FPGA image with halfband
filters in the TX side. You can make room in there by removing one
receive chain (leaving only one).
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