[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] calculated vs observed pulse length

From: seph 004
Subject: Re: [Discuss-gnuradio] calculated vs observed pulse length
Date: Wed, 30 May 2007 13:52:45 -0700 (PDT)

Matt Ettus <address@hidden> wrote:
seph 004 wrote:
> This would mean that to obtain a total rate of 32 Msamples/sec to the
> DAC, the data rate of the I and Q channels would have to be 16
> Msamples/sec each, and thus 128 000 samples/sec each into the txchain
> modules. This should mean that if I provide a samples set of 128 I
> samples, and 128 Q samples, I should get 1 msec worth of complex
> output signal.

The bus carrying IQ data to the 9862 TX runs at 64 MHz, so it is 32 MS/s
for each.

Thanks for the reply.

I see what you are saying about the bus. It means that the pulse is longer instead of shorter, which makes more sense. Going with this though, I have done tests with the new numbers and I still get a longer pulse than expected. I thought the problem might have been a delay from the cic shifter or the DAC, but even those should only have added a few microseconds, not over 100 microseconds.

From the logic analyser , it seems that the counter I use for advancing the read pointer for the RAM might be running slow, though the Quartus simulator shows it running at the right speed. Would such a problem stem from using an interp rate like 125 within the FPGA? Has anyone who has done USRP FPGA builds that use counters noticed a similar variance?



Choose the right car based on your needs. Check out Yahoo! Autos new Car Finder tool.
reply via email to

[Prev in Thread] Current Thread [Next in Thread]