Mr. Marcus Mueller, Thank you very much for suggestions. I have some more questions.
1) I searched for the GNU Radio mailing-list archive and found a discussion Subject: [Discuss-gnuradio] USRP1 4 Channel Subdev Issue Date: Tue, 19 Feb 2013 11:07:55 -0800 (PST) Then it would be possible to organize a 4-ch RX with USRP-1. (Some limitation is reported here, too.) But as you suggest, we can use only real (one) input for each frequency. Also I need to prepare the downward frequency conversion by our selves. Careful additional hardware design is necessary. I know this is not easy. 2) Your suggestion of "2 x B210" is very interesting. A good thing is that the frequency conversion is included in the board. But I want to know how to run 2 USRP boards from one application program. Is there an example? If possible I want to use GNU Radio Python code, but is this possible? If not, do we need to control from C++? In my application "phase coherency" across all inputs are necessary. "timing synchronization" is not necessary. 3) One more question. If 2) is possible, is it possible to run "2 x USRP-1" from a single application on a single PC? Regards, -- Mamoru Yamamoto / RISH, Kyoto University [email protected] Phone +81-774-38-3814, Cell +81-90-5653-7555 On 2014/08/08 1:00, [email protected] wrote:> Message: 8 Date: Thu, 07 Aug 2014 09:41:38 +0200 From: Marcus M?ller > <[email protected]> To: [email protected] Subject: Re: > [USRP-users] USRP-1 and 4ch receiver? Message-ID: > <[email protected]> Content-Type: text/plain; > charset=ISO-8859-1 Hi Mamoru Yamamoto, What daughterboards are you using > now? BasicRX? >> >I know that before it was possible to organize 4-ch receiver by setting > 2 Basic-RX on USRP-1, and use (in-total) 4 SMA connectors for inputs. > > The dual-BasicRX setup does give you four channels, but these 4 channels > are*real*, not complex. All other daughterboards mix the target > frequency down to complex baseband, which implies that you need 2 ADCs > per input (I+Q). > Now, the BasicRX just brings the raw inputs of your dual-ADC to SMA > connectors. That means you can still only receive one complex baseband > signal with a BasicRX, OR you can receive two independent real channels. > The problem at hand is that mixing down your RF signals to baseband will > usually result in complex signals, and thus the BasicRX really doesn't > give you two input channels for baseband signals. > >> >Sure coherency between signals are important. > Stock USRP1s cannot be made coherent across multiple USRP1s. There were > some tricks floating around, detailing how to use a shared clock between > USRP1s, but I haven't heard from someone doing this in a long time, > primarily because most people have switched to devices that support > external clocks from stock. > > (1) As explained before, if you really need 4 RF channels, you will have > to synchronize 4 complex baseband receivers, which needs at least two > USRP1s. The BasicRX approach only works for*real* baseband signals, and > it doesn't sound like this applies to you:( > > (2) There is no example code for synchronized USRP1s, because that > requires warranty-voiding hardware modification by the user. To get the > four real input signals of two BasicRX, just receive at 0Hz center > frequency, and set subdevice specs accordingly. > > (3) Various options exist: > a) 2 x B210 with an external 10MHz clock is the cheapest solution to > your problem, I guess. B210 have two coherent receiver chains each and > come with the RF hardware integrated, so you don't need daughterboards. > Instead of an external clock distributor, you can also use GPSDOs to get > coherent clocks; Ettus sells both. > b) If you need higher ADC resolution, using 4 x N2x0 + 4 Daughterboards > might be a good choice, too. You can re-use your existing > daughterboards. You will need an external clock distributor or a GPSDO > for each of your devices. > c) 2 x X3x0 + 4 daughterboards. This would be the most versatile > solution, but most likely also not the cheapest. Use an external clock > source, GPSDOs, or try the (still experimental) clock daisy-chaining. > X3x0 offer higher bandwidths than the other options, and a lot of FPGA > if you want to develop your own hardware signal processing. > > Greetings, > Marcus _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
