Failure of sending square wave over USRPs (back-to-back)

On 03/15/2014 02:57 AM, Activecat wrote:

frequency, that its output is a real signal of

I was using the term “analog” to distinguish from “digital”. The FPGA
also has up/downconverters for doing offsetting and “mop up”
operations on the signal stream, and those operations are,
necessarily, performed on a digital sample stream, rather than on an
electron stream.

A quadrature up (or down) converter is structurally very similar to a
real-valued converter, and most folks in the industry refer to
both as “upconversion” and “downconversion”. While the mathematical
expressions that describe them are, as you note, different,
they’re performing a very similar function, and use nearly-identical
hardware, except that in the complex (quadrature) case, you have
two mixers, and a phase-split local oscillator.

You can see the schematics of SBX (and other cards) here:

Sorry, Tom. I posted another in the thread before looking at you “drop
this thread” message. My bad.

On Sat, Mar 15, 2014 at 10:46 AM, Activecat [email protected] wrote:

In this case I shall rephrase my question to:
“How to compensate the error due to clock drift which is not handled
by a simple quadrature upconverter ?”

Could anyone of gnuradio forum gives me some idea ?
I hope this is no longer categorized as expecting Ettus to teach me
the fundamentals of RF.


It was mentioned earlier in this thread, you can use a PLL to lock to
a carrier. Basically, you need an algorithm that performs carrier

This thread is starting to get a little too confrontational, so we all
need to take a bit of a break. Please take a look at the PLL blocks in
GNU Radio; you can find them under the Synchronizers category in the
block tree of GRC. Spend some time understanding these blocks and how
to use them. If you still have questions, please open another email


I have found the answers.

On the Nutaq platforms (ZeptoSDR, PicoSDR) you can control VCXO voltage
DAC from GNU Radio (and from FPGA user logic) to implement carrier
frequency offset correction.

Thanks everyone for your help.