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 Sponsor --------------------~--> Get to your groups with one click. Know instantly when new email arrives http://us.click.yahoo.com/.7bhrC/MGxNAA/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/
