Re: [Discuss-gnuradio] Smart Antenna

[Martin Dvh]

Roberto Mastrodonato wrote:
> Hi all
> 
> is there anybody that experienced USRP projects with SMART Antenna
> technology? If yes, where can I find codes or something else related to
> USRP-SMART Antenna?
> Thanks a lot
I have been experimenting with direction finding and passive radar using 
gnuradio and multiple antenna's.
These experiments are on hold for now, due to lack of time, but I hope to 
continue with them sometime in the future.

What exactly would you like to do and with how much array-elements.
The simplest smart antenna using usrp/gnuradio I can think of is a smart 
transmitter using two antenna's.
The phase-difference you introduce between the two signals, combined with the 
positioning of your two antenna's determines the maximum and
minimum gain direction(s) of the whole system.

Introducing a fixed phase difference is just multiplying with a const complex 
number.
Phi=wanted phase difference in radians
signal=original signal to transmit
sink1=sink where the first output should go
sink2=sink where the second output should go

phasediff=gr.multiply_const_cc(gr_complex(cos(Phi),sin(Phi))
fg.connect(signal,sink1)
fg.connect(signal,phasediff,sink2)

The same goes for reception:
Phi=expected phase difference in radians

input1=signal from first antenna
input2=signal from second antenna
receiver=reception chain

phasediff=gr.multiply_const_cc(gr_complex(cos(Phi),sin(Phi))
adder=gr.add_cc()
fg.connect(signal1,(adder,0))
fg.connect(signal2,phasediff,(adder,1))
fg.connect(adder,receiver)

If you want to automatically determine the phase-differences and amplitudes 
things get much more complicated but can still be done.

I even tested with a very slow correlator and agc which automatically 
determined the phase difference of the strongest signal received and tuned
the two antenna array for maximum sensitivity for this signal.


Greetings,
Martin
> 
> Roberto
> 
> 
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