Re: [Discuss-gnuradio] speed difference between ADCs and DAC's

[Ebtisam Ahmed]

Hi all,

Well going into the basics, ADCs have a sample and hold circuits. It
holds the value and sometimes takes the average of some nearby values
and then convert that into digital for precision. While there is no
such thing in DACs; resulting in faster DACs.

Hope this helps..

Regards,
Ebtisam

On Sun, May 27, 2012 at 7:23 AM, wayne roberts wroberts92...@gmail.com wrote:
 I dont know if that tutorial covers the topic, try this
 http://www.analog.com/library/analogDialogue/archives/39-06/Chapter%202%20Sampled%20Data%20Systems%20F.pdf

 I think its simple to say why DAC and ADC operate a different speeds.
 Its not just speed, also dynamic range (ENOB) is also more difficult to
 achieve in ADC.
 Ultimately an ADC must guess at what the analog input is due to internal
 noises (sample and hold hi-z, etc), which is why the ENOB is always worse
 than the number of bits output digitally.

 By contrast, the DAC since it operates in reverse, it already knows exactly
 what the signal should be, and just needs to switch in the correct resistor
 to produce the correct analog value.

 A high speed ADC/DAC expert would say this is an over-simplification, but I
 only try to convey the basic idea.

 On Wed, May 23, 2012 at 2:41 AM, Sravya Reddy amuduru.sra...@gmail.com
 wrote:

 hi everyone,

 USRP board has ADC's and DAC's operating with different speeds. why DAC's
 are faster than ADC's? please excuse me if it is a basic question.

 thanks in advance,
 sravya.

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Re: [Discuss-gnuradio] gr_vector_map.cc has uninitialized loop index vars (patch attached)

[Tom Rondeau]

On Sat, May 26, 2012 at 4:23 PM, Porges, Donald
donald.por...@analog.com wrote:
 Hello list:

 The recently added file gr_vector_map.cc has two loops with index variables 
 that are never initialized.  (Surprisingly, g++ -Wall does not catch this 
 form.)  They look like


  for (unsigned int i; i  in_vlens.size(); i++) {
    in_sizeofs.push_back(in_vlens[i]*item_size);
  }

 g++ 4.6.3 (Ubuntu) managed to generate an init of 0 anyway; g++ 4.2.1 (Mac) 
 did not.

 I've attached a small patch.

Donald,

Thanks for the patch. I'll be pushing it soon.

Tom

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[Discuss-gnuradio] Any grc flowgraph example on bpsk (or any other digital modulation) transmission/reception?

[Nazmul Islam]

Hello,

Is there any bpsk transmission + reception flow graph in grc repository? I
know about the benchmark python codes but I am looking for a similar
gnuradio companion flowgraph. An email from last year (
http://lists.gnu.org/archive/html/discuss-gnuradio/2011-01/msg00255.html)
suggests that there is a bpsk flowgraph in the GRC examples folder but I
did not find any. In fact, if anyone has a grc flowgraph example on bit
generation - transmission - reception, I will appreciate if it is shared
here.

Thanks,

Nazmul


-- 
Muhammad Nazmul Islam

Graduate Student
Electrical  Computer Engineering
Wireless Information  Networking Laboratory
Rutgers, USA.
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