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Re: re[Discuss-gnuradio] garding the format and type of data in GRC

From: lokesh reddy
Subject: Re: re[Discuss-gnuradio] garding the format and type of data in GRC
Date: Wed, 16 Jun 2010 02:32:41 -0700 (PDT)

Thanks for your reply..

Then what will be the data rate across USB2.0?.

Normally in USRP documentation they have given that the samples were
transfered in IQIQIQIQ fashion and each complex sample is a combination of
two 16-bit integers,so 4 bytes per each complex sample ,hence the maximum
data rate across the USB (for complex sampling)comes to(32/4=8) 8Mega
complex samples per second

In this case for wireless microphone I have used the USRP output type as
complex in GRC and as told by you,each complex sample  has 64bits (4byte
float+j*4byte float).and i set the decimation for 128,so the sampling rate
is(64M/128=500K)500K samples/second

Does the maximum data rate across the USB becomes(32M/8 bytes=4M)4M complex
samples per second?

Does the actual data rate across USB in this case is 500K*8=4M

If i go below this decimation(128)then the (demodulated signal is not
audiable in my experiment) then the data rate exceeds 4M saples/second,does
this mean that i may lose some data across the USB?

Does the complex sampling for FM,WiFi is really necessary?,in which cases we
need to employee complex samping?

please help me out 


lokesh reddy wrote:
> hi all
> I have captured the Wireless Microphone signals using GRC and USRP,
> flowgraph i have used was USRP Source-->File_sink.
> In USRP source i have selected format option as complex and for file_sink
> i have selected  input format as complex.
> Does the format of data written into file a complex data with each sample
> has a size of 64bits? and what will be the data type and size of real and
> imaginary values in each complex sample.
> one more thing how to get the python code generated by GRC?
> Regards 
> Lokesh Reddy

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