Forums

Need of Eqaulization ?

Started by mite_learner September 27, 2013
On 9/27/2013 2:04 PM, Randy Yates wrote:
> Vladimir Vassilevsky <nospam@nowhere.com> writes: > >> On 9/27/2013 1:24 PM, Randy Yates wrote: >>> "mite_learner" <94814@dsprelated> writes: >>> >>>> Dear Members, >>>> >>>> I am experimenting on digital 4-FSK (orthogonal) communication system. On >>>> the demodulation side, I am using AGC and then 4 filters to detect tones >>>> and then using symbol timing. My question is how can I know that I need >>>> equalization looking at the signal if I transmit and receive the signal >>>> over the air? How can I verify that my signal is being affected by >>>> multipaths ? >>> >>> Did you mean AGC in front of your ADC? >>> >>> By the way, ignore Vlad. He's made a career out of calling people idiots >>> - doesn't mean they are. >> >> No matter how to call it, idiots are idiots. Let them make careers. >> I design DSP systems which work. And I do it very well. > > And you went from birth to designing DSP systems in, what, 15 minutes? >
In about a month. Out of of harsh necessity and despite lacking information and technical base. Vladimir Vassilevsky DSP and Mixed Signal Designs www.abvolt.com
On 9/27/13 12:21 PM, Vladimir Vassilevsky wrote:
> > In about a month. Out of of harsh necessity and despite lacking > information and technical base. >
well, *I* had to walk to school 4 miles through the North Dakota snow barefoot. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
On 9/27/2013 2:40 PM, robert bristow-johnson wrote:
> On 9/27/13 12:21 PM, Vladimir Vassilevsky wrote: >> >> In about a month. Out of of harsh necessity and despite lacking >> information and technical base. >> > > well, *I* had to walk to school 4 miles through the North Dakota snow > barefoot.
Really? Or may be that was Abraham Lincoln?
Vladimir Vassilevsky <nospam@nowhere.com> writes:

> On 9/27/2013 2:04 PM, Randy Yates wrote: >> Vladimir Vassilevsky <nospam@nowhere.com> writes: >> >>> On 9/27/2013 1:24 PM, Randy Yates wrote: >>>> "mite_learner" <94814@dsprelated> writes: >>>> >>>>> Dear Members, >>>>> >>>>> I am experimenting on digital 4-FSK (orthogonal) communication system. On >>>>> the demodulation side, I am using AGC and then 4 filters to detect tones >>>>> and then using symbol timing. My question is how can I know that I need >>>>> equalization looking at the signal if I transmit and receive the signal >>>>> over the air? How can I verify that my signal is being affected by >>>>> multipaths ? >>>> >>>> Did you mean AGC in front of your ADC? >>>> >>>> By the way, ignore Vlad. He's made a career out of calling people idiots >>>> - doesn't mean they are. >>> >>> No matter how to call it, idiots are idiots. Let them make careers. >>> I design DSP systems which work. And I do it very well. >> >> And you went from birth to designing DSP systems in, what, 15 minutes? >> > > In about a month. Out of of harsh necessity and despite lacking > information and technical base.
LOL :) Tell us a bedtime story, Vlad, about what people did before "the Internet"... -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
On Fri, 27 Sep 2013 07:39:48 -0500, "mite_learner" <94814@dsprelated>
wrote:

>Dear Members, > >I am experimenting on digital 4-FSK (orthogonal) communication system. On >the demodulation side, I am using AGC and then 4 filters to detect tones >and then using symbol timing. My question is how can I know that I need >equalization looking at the signal if I transmit and receive the signal >over the air? How can I verify that my signal is being affected by >multipaths ?
Do you have any means of sounding the channel, e.g., via a preamble or known signal transmission? Other than the easy steps of looking at the demodulator outputs and general performance, you kind of need some way to measure the channel to know whether there is multipath present and how much. A preamble or test signal that transmits all four tones in a usable fashion (e.g., stepped, random, etc.) and then analyzes the output can be used to do that. Look at the output in the frequency domain to look for channel frequency selectivity and correlate the received signal against the transmitted signal to estimate the channel impulse response. Estimating the channel impulse response with a data sequence is best done with a PN or similar sequence that allows easy correlation analysis.
> >-- >Mite > >_____________________________ >Posted through www.DSPRelated.com
Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
On 9/27/13 12:47 PM, Vladimir Vassilevsky wrote:
> On 9/27/2013 2:40 PM, robert bristow-johnson wrote: >> On 9/27/13 12:21 PM, Vladimir Vassilevsky wrote: >>> >>> In about a month. Out of of harsh necessity and despite lacking >>> information and technical base. >>> >> >> well, *I* had to walk to school 4 miles through the North Dakota snow >> barefoot. > > Really? Or may be that was Abraham Lincoln? >
that young whipper-snapper? i'm older than that dude ever was. and Illinois is a sauna bath compared to North Dakota, most times of the year. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
On Saturday, September 28, 2013 7:01:56 AM UTC+12, Vladimir Vassilevsky wrote:
> On 9/27/2013 1:24 PM, Randy Yates wrote: > > > "mite_learner" <94814@dsprelated> writes: > > > > > >> Dear Members, > > >> > > >> I am experimenting on digital 4-FSK (orthogonal) communication system. On > > >> the demodulation side, I am using AGC and then 4 filters to detect tones > > >> and then using symbol timing. My question is how can I know that I need > > >> equalization looking at the signal if I transmit and receive the signal > > >> over the air? How can I verify that my signal is being affected by > > >> multipaths ? > > > > > > Did you mean AGC in front of your ADC? > > > > > > By the way, ignore Vlad. He's made a career out of calling people idiots > > > - doesn't mean they are. > > > > No matter how to call it, idiots are idiots. Let them make careers. > > I design DSP systems which work. And I do it very well. > > > > >
Maybe you do, maybe you don't, I have never purchased your products so I don't know. However. I cannot see the point in you being in this - a tutorial style ng if you are not prepared to help others. So either help people or fuck off!
>"mite_learner" <94814@dsprelated> writes: > >> Dear Members, >> >> I am experimenting on digital 4-FSK (orthogonal) communication system.
On
>> the demodulation side, I am using AGC and then 4 filters to detect
tones
>> and then using symbol timing. My question is how can I know that I
need
>> equalization looking at the signal if I transmit and receive the signal >> over the air? How can I verify that my signal is being affected by >> multipaths ? > >Did you mean AGC in front of your ADC? > >By the way, ignore Vlad. He's made a career out of calling people idiots >- doesn't mean they are. >--
Currently I don't have AGC in front of ADC, but I am keeping my signal low so that ADC doesn't start clipping. I applied AGC on my baseband signal, after digitization, before doing matched filtering for individual tones. I am using this AGC to keep signal level in a range for symbol timing synchronization. But Vlad says AGC is harmful in this setup, why? I would have asked him but searching on the group, I found that he never gave an answer that could be *useful* for anybody in the world . -- Mite
>Randy Yates >Digital Signal Labs >http://www.digitalsignallabs.com >
_____________________________ Posted through www.DSPRelated.com
>On Fri, 27 Sep 2013 07:39:48 -0500, "mite_learner" <94814@dsprelated> >wrote: > >>Dear Members, >> >>I am experimenting on digital 4-FSK (orthogonal) communication system.
On
>>the demodulation side, I am using AGC and then 4 filters to detect tones >>and then using symbol timing. My question is how can I know that I need >>equalization looking at the signal if I transmit and receive the signal >>over the air? How can I verify that my signal is being affected by >>multipaths ? > >Do you have any means of sounding the channel, e.g., via a preamble or >known signal transmission? >
Yes Eric.
>Other than the easy steps of looking at the demodulator outputs and >general performance, you kind of need some way to measure the channel >to know whether there is multipath present and how much. A preamble >or test signal that transmits all four tones in a usable fashion >(e.g., stepped, random, etc.) and then analyzes the output can be used >to do that. Look at the output in the frequency domain to look for >channel frequency selectivity and correlate the received signal >against the transmitted signal to estimate the channel impulse >response. > >Estimating the channel impulse response with a data sequence is best >done with a PN or similar sequence that allows easy correlation >analysis. >
Yes, I can send the tones in controlled fashion (i.e I can send whatever data I want to). So, I need to send data sequence, lets say DATA1 and then I receive this and demodulate. If the data after demodulation is DATA2, then I have to correlate DATA1 and DATA2. What kind of correlation output indicates the affect and severity of multipaths? Mite
>> >>-- >>Mite >> >>_____________________________ >>Posted through www.DSPRelated.com > >Eric Jacobsen >Anchor Hill Communications >http://www.anchorhill.com >
_____________________________ Posted through www.DSPRelated.com
On 9/28/2013 1:47 AM, gyansorova@gmail.com wrote:
> On Saturday, September 28, 2013 7:01:56 AM UTC+12, Vladimir Vassilevsky wrote: >> On 9/27/2013 1:24 PM, Randy Yates wrote: >> >>> "mite_learner" <94814@dsprelated> writes: >> >>> >> >>>> Dear Members, >> >>>> >> >>>> I am experimenting on digital 4-FSK (orthogonal) communication system. On >> >>>> the demodulation side, I am using AGC and then 4 filters to detect tones >> >>>> and then using symbol timing. My question is how can I know that I need >> >>>> equalization looking at the signal if I transmit and receive the signal >> >>>> over the air? How can I verify that my signal is being affected by >> >>>> multipaths ? >> >>> >> >>> Did you mean AGC in front of your ADC? >> >>> >> >>> By the way, ignore Vlad. He's made a career out of calling people idiots >> >>> - doesn't mean they are. >> >> >> >> No matter how to call it, idiots are idiots. Let them make careers. >> >> I design DSP systems which work. And I do it very well. >> >> >> >> >> > Maybe you do, maybe you don't, I have never purchased your products so I don't know. However. I cannot see the point in you being in this - a tutorial style ng if you are not prepared to help others. So either help people or fuck off! >