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Re: [Discuss-gnuradio] sampling rate of tx_sampless.cc and rx_streaming_

From: Per Zetterberg
Subject: Re: [Discuss-gnuradio] sampling rate of tx_sampless.cc and rx_streaming_sampless.cc
Date: Thu, 08 Apr 2010 16:31:38 +0200
User-agent: Thunderbird (X11/20100317)


My understanding is that we can regard the sample rate of the DAC and ADC as 100MHz (although the DAC uses internally a larger rate, this is what I have read). Thus the rate at which samples are leaving or entering the RF sections at are 100MHz. The maximum rate at the host side is 25MHz, then that rate is interpolated/decimated in the FPGA to/from the 100MHz. The tx_sampless.cc and rx_streaming_sampless.cc reads and writes from file and therefore 25MHz host sample-rate may not be possible. Thus you should typically use the same interpolation/decimation factor in the transmitter and receiver.


Krishna S wrote:
So, if i am setting interpolation rate 16 at transmitter side(tx_samples.cc), according to the equation the program is sampling at

   Sampling rate = 400/16 = 25M samples/sec.

but, I am able to receive the data only at the same decimation rate 16(rx_streaming_samples.cc) , for which the program is sampling at

Sampling rate =100/16 =6.25M samples/sec But for me to transmit and receive data i have to send and receive at 25M samples /sec right ??

if i try to do that i.e., at receiver side samp rate = 100/4 = 25M samples /sec

I don't receive at all ...?

everything boils down to one question ?

the sampling rate what we are talking here is the sampling rate at which the samples have been sampled before sending to RF as discussed in COMMUNICATION THEORY (following the Nyquist Criteria)

or the sampling rate calculated to find the allowed no.of samples/sec the ETHERNET can take to connect the host to USRP2. but inside the sampling rate is different ?

As i am dealing with RF communication i need to know exactly what sampling rate the USRP2 is sampling the data and sending over the air ?


--- On *Wed, 7/4/10, Per Zetterberg /<address@hidden>/* wrote:

    From: Per Zetterberg <address@hidden>
    Subject: Re: [Discuss-gnuradio] sampling rate of tx_sampless.cc
    and rx_streaming_sampless.cc
    To: "Krishna S" <address@hidden>
    Cc: "gnu" <address@hidden>
    Date: Wednesday, 7 April, 2010, 7:52 AM

    Krishna S wrote:
    > Hi,
    >     i am trying to calculate at what sampling rate does the
    tx_sampless.cc and rx_streaming samples.cc  are sending the data
    (file). from 1 USRP2 to another USRP2.
    > i am setting interpolation as 16 at transmitter side
    (tx_samples.cc) and decimation rate of 16 at receiver side
    > according to formula what i have learnt from WEB is
    > Tx Side :  Sampling Rate =  DAC rate/ Interpolation rate;
    > Rx Side : Sampling Rate =  ADC rate/ Decimation rate;
    > are the above equation are correct for determining the sampling
    rate ????
    > Thank You
    > Regards
    > Your Mail works best with the New Yahoo Optimized IE8. Get it

    > _______________________________________________
    > Discuss-gnuradio mailing list
    > address@hidden </mc/address@hidden>
    > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
    Yes, it is the sample-rate on the host-side. DAC rate and ADC rate
    is 100MHz.


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