BPSK transmitter - time domain waveform

GNU Radio
1

Hi all,

I have some doubt on the time domain view of bpsk signal generated in
Gnuradio and usrp. I used psk mod block in GRC (sps =2) and created bpsk
(baseband )waveform with vector source producing 0,1,1 continuously.

When I plotted the output of psk mod block using scope sink, I seen
waveform of constant 1 for some samples (for 0) , inverted root-raised
cosine waveform (for 1) and another inverted root-raised cosine waveform
(for 1). This is repeated continuously and i understand that it because
of
transmit pulse shaping.

Now, the question is when I give this signal to USRP for transmission,
how
the time-domain view of that waveform look like? Will it look like
sinusoid signal with 180deg phase shift as we all seen in stand.
communication text books? I guess it will not the case. I tried
multiplying the baseband waveform with signal source (complex) –
mathematical equivalent of what happening in usrp – and seen waveform.
No
smooth shift of 180deg.

If anyone having usrp and digital oscilloscope, could you please send me
the pic of time domain view of output of usrp?

Thanks
Senthil

2

I am sorry that i was not able to attach my flowgraph and output
waveforms
with this mail though i had .If any one need, pls ping me. I will mail
those for your view.

3

On Thu, Apr 5, 2012 at 9:33 AM, senthil murugan
[email protected] wrote:

pulse shaping.

Thanks
Senthil

If you want to see this in simulation, make sure that you are
upsampling your signal before doing the frequency conversion so your
sample rate can support the new frequency range you are interested in
seeing.

The answer is yes, the resulting waveform will be a sinusoid at the
carrier frequency with a lower frequency BPSK envelope. If you are
doing this over the air, remember that if the oscillators in your
transmitter and receiver are not locked together, there will be a
frequency offset between them.

Tom