4 A/D receiver for 4 antennas

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s52d
Posts: 2
Joined: Tue Sep 12, 2017 7:58 am

4 A/D receiver for 4 antennas

Post by s52d » Tue Sep 12, 2017 8:09 am

Hi!
Is there a ossibility to link two (or more) RPs in a way so clocks and FPGAs are synchronized?
Main goal is 4 times RX diversity: thus, phase synchronization has to be kept
over filtering/decimation process beside common A/D clock.

Best reagrds, 73
Iztok, S52D

pavel
Posts: 516
Joined: Sat May 23, 2015 5:22 pm

Re: 4 A/D receiver for 4 antennas

Post by pavel » Tue Sep 12, 2017 8:49 am

Hi Iztok,

In my opinion, Red Pitaya isn't the most suitable board for the 4 times RX diversity. A solution with one FPGA and four synchronized ADCs would be more suitable for this kind of project.

At the following link, you can find a solution based on the Digilent Zedboard and Analog Devices
AD9253 ADC evaluation board:

http://g4guo.blogspot.be/2016/04/back-d ... oject.html

Best regards,

Pavel

s52d
Posts: 2
Joined: Tue Sep 12, 2017 7:58 am

Re: 4 A/D receiver for 4 antennas

Post by s52d » Tue Sep 12, 2017 11:10 am

hi Paul!

Thanks a lot for the answer.

I've been looking at AFEDRI http://www.afedri-sdr.com/.
12 bit A/D, two ch. standard, 4 ch available. Works with linrad (2ch).
It is in red pitaya price range ...

RP is 14 bit/ but lacks low pass filter and preamplifier.
Also, FPGA is more capable: your code to have 6 separate receivers is perfect.
If they can be split to two A/Ds, thus having two RX diversity on 3 separate frequency bands.

How about an idea:
Take two RP boards. use common 125 MHz clock. connect two RX antennas to each of RPs.
generate sync signal with master RP D/A and feed it into all receivers.
Would it be possible to obtain phase sync over all inputs?

BR
Iztok, s52d

pavel
Posts: 516
Joined: Sat May 23, 2015 5:22 pm

Re: 4 A/D receiver for 4 antennas

Post by pavel » Tue Sep 12, 2017 12:40 pm

If they can be split to two A/Ds, thus having two RX diversity on 3 separate frequency bands.
Yes, they can be split. The inputs corresponding to each receiver are the command line arguments for sdr-receiver-hpsdr.
How about an idea:
Take two RP boards. use common 125 MHz clock. connect two RX antennas to each of RPs.
generate sync signal with master RP D/A and feed it into all receivers.
Would it be possible to obtain phase sync over all inputs?
You'll also need a reset signal simultaneously resetting both ADCs and FPGAs.
Last edited by pavel on Tue Sep 12, 2017 1:04 pm, edited 1 time in total.

pavel
Posts: 516
Joined: Sat May 23, 2015 5:22 pm

Re: 4 A/D receiver for 4 antennas

Post by pavel » Tue Sep 12, 2017 12:53 pm

BTW, the combination of ZedBoard and AD9253 evaluation board costs less than four AFEDRI boards:
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JB
Posts: 14
Joined: Tue Jul 12, 2016 10:34 am

Re: 4 A/D receiver for 4 antennas

Post by JB » Mon Oct 30, 2017 3:11 pm

Hi Iztok,

this might be a bit too late, but there is a project which synchronizes multiple RPs: https://www.koheron.com/blog/2016/11/29 ... ya-cluster

This can be exended to the ADCs with a bit of soldering.

Greetings
Jonas

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