Where did you get what the definition of a SDR is? What is the difference between the software in a PC a DSP or a FPGA, don't they all use a defined program to make a machine behave in a described way?
On Fri, 2006-06-09 at 23:42 +0200, Andreas Troschka wrote: > It is just an evolution. > > Using an ADC as close as possible to the antenna is just marring a philosophy > where SDR is as much as possible Software Defined (duh!). > After signals are converted to numbers they can be processed as such. So > software can be really the main part of the SDR in this case. > > Therefore some guys misunderstand much about the subsequent stages of the SDR. > > The purist's solution is to use DSP after the ADC and this is the real > software approach in the mentality of a real SDR architecture. > But actual DSprocessors aren't good enough to crunch the enormous amount of > data coming from the ADC used in a oversampling concept, so somebody propose > a decimation of data before processing it with a DSP (or a software on the > PC). > This is actually realisable with FPGAs. > Yes, this is an interesting (and performant) solution, but to be honest this > is a wide step approaching to a RHDR, Reconfigurable Hybrid Defined Radio, > not to the SDR. > > What is done with FPGAs is to introduce in the radio a reconfigurable HW > chip, not a software data processor, and whose homework is mainly to absolve > to the decimation task. > It is possible to use ASICs also, specialised chips, and again this is > hardware substituting software tasks. > > So what we are experimenting in this days is not really SDR but much more a > HDR, the Hybrid Defined Radio. > > Experimentation of direct sampling techniques with ADCs as the LTC2208/9 puts > important steps towards the SDR. > Therefore, limitations imposed by the actual technologies make this solution > already less performant as more classical architectures as IF sampling do. > > The use of the PC's soundcard and 0Hz-IF has its own history placement on the > oldest solution after the "1st IF sampling" architectures, with the related > consequences, eg. of being more far away from SDR. > Please, take in mind that it has been a first-try solution, and that > experimentation has gone over. > > Another point is discussing actual realisable architectures. In other words, > what the state-of-the-art chips permit to obtain in therms of highest > performances (to be compared to that offered by more traditional solutions in > commercial equipment). > > This is an interesting subject offering a plethora of experimentation > opportunities. > > Yes, it is always important to keep an eye out. Therefore setting milestones > will help to see things in the right chronology and in having a better view > of the "state-of-the-art". > > vy 73s de Andreas - ik2wqi > > > > [EMAIL PROTECTED] wrote: > > Alberto: > > > > Everyone seems to find A/D interesting. I believe though that the > > simplicity of the sound card will remain most useful with the majority of > > people. The A/D idea may be mostly taken up by manufacturers of radios > > with special software for that particular radio. > > > > But I will keep an eye out for the developments. > > > > ka9rza > > > > > Yahoo! Groups Links > > > > > > -- Cecil KD5NWA www.qrpradio.com ------------------------ Yahoo! Groups Sponsor --------------------~--> Home is just a click away. Make Yahoo! your home page now. http://us.click.yahoo.com/DHchtC/3FxNAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
