[EMAIL PROTECTED] wrote: > > > Adnan Yusuf wrote: > > What is the difference between a software defined radio and a digital > > radio? I am working on an SDR project and I keep getting asked this > > question. > > > > > > > It depends what you mean by 'Digital Radio'... > > Software Defined Radio uses a different method of implementing the > detection system, converting the incoming Radio Frequency signals into I > and Q channels for processing in the software. The nearest to SDR is > probably direct conversion radios where the incoming signal is mixed > with another frequency that is very close (like a crystal on 3.560.0MHz > mixed with an oncoming signal on 3.560.6MHz would give the sum and the > difference of +/-600Hz, then you filter one out and just receive the > other). But I guess you know how mixing and detection works if you are > developing an SDR anyway... > > Dave (G0DJA) >
That is a topic that is up in the air, too many personal definitions. That definition is too restrictive, You don't have to have I and Q signals in order for it to be a software defined radio. I and Q make image rejection possible otherwise it can be all done in the software without I and Q and it's still a SDR. A SDR is a radio whose main components such as mixers, demodulators, filters, AGC, noise reduction, etc, are implemented in software. Just how much is hardware is up front and how much is software is where the arguments gets going. For example you can have an amplifier and band pass filter followed by one very high speed A/D converter, the rest of the functions of the radio are implemented in software, this is a Software Defined Radio, but there is no I and Q signals going into the computer, you can even do it without having I and Q signals in the software, but you won't have image rejection but it will still work as a radio. -- Cecil K5NWA www.qrpradio.com www.softrockradio.org "Blessed are the cracked, for they shall let in the light."
