Is it possible to utilise USRP2 with a daughter board to receive a signal on
the Ku band? I checked Ettus website but all the available daughterboards
have carrier frequencies less than the required.
What do you think?
The usual way people do that is to use a Ku-band LNBF – the same type
that people use for satellite TV.
These downconvert into L-band, so a DBSRX or WBX card can be used to
receive the downconverted
signal. Get one that is “digital ready”–they have better local
oscillators that are more stable.
Typical units downconvert 11.7GHz to 12.7GHz down to 950Mhz to 1800MHz.
I don’t seem to be able to decimate the 100 MSps to these rates. is there
away to do this?
You can only sample at integer decimations of the 100Msps native sample
rate of the N210. So you can get 50Msps (only possible with 8 bit
recently added to UHD), 33.3333Msps, 25Msps, 20Msps, etc.
DVB-S2 uses QPSK or 8PSK, so your symbol rate will be divided down from
bit rate accordingly, and the required sample rate is a function of
rate (plus rolloff), not bit rate. As a result, you can sample at lower
sample rates than the native bit rate to receive your DVB-S2 signal. The
rolloff of DVB-S2 30.9Mbit is 0.20, so the maximum channel occupancy of
30.9Mbit QPSK (2 bits per symbol) stream would be
Sampling at 20Msps with the N210 would suffice in this instance to
completely capture the signal. For 8PSK 29.7Mbit (rolloff=0.25, 3 bits
symbol), you need 1.25*(29.7/3)=12.375Msps. The closest sample rate
then be 12.5Msps.
If your decoding scheme requires an integral number of samples per
you can resample the incoming stream using Gnuradio’s polyphase
block to achieve whatever sample rate you require.
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