IQ streams vs. plain streams
SeanS
Posts: 1
Hello,
Long time lurker here, I love reading all the technical discussions (especially P2 dev). I've noticed lots of smart folks here from all kinds of different industries. I have a long time question sitting in the back of my head that I could never figure out over the years. I thought I'd throw it out to you guys and see what happens.
I have the understanding that when representing a data stream to "do some dsp'ing on" you could use the plain stream itself straight from the adc, or convert it into an IQ stream. Both kinds represent the same information. You could pipe those streams untouched to the dac (convert IQ back down to plain if needed) and recreate what you originally captured.
That said,
Why not make an audio stream into an IQ stream? why do people not do this? You will not find audio dsp examples working on IQ streams. Likewise, all RF dsp examples I've ever tried to understand represent their streams in IQ only. What is so different between those domains that each industry represents their data streams in the way that they do when the alternative representation works just as well too? Some RF streams are well within the grasp of current converter/fpga technologies (like HF comms) as a plain stream.
I'm trying to figure out the technical reason why someone would use one representation over the other.
Do you know if it is simply historical reasons and nothing to do with technicalities? I end up empty handed trying to answer such a nuanced question w/google. What areas should I be looking into for further research? Feel free to lay the technicalities on me - longtime EE here (hence my love of P2 tech dev discussions over the years).
Long time lurker here, I love reading all the technical discussions (especially P2 dev). I've noticed lots of smart folks here from all kinds of different industries. I have a long time question sitting in the back of my head that I could never figure out over the years. I thought I'd throw it out to you guys and see what happens.
I have the understanding that when representing a data stream to "do some dsp'ing on" you could use the plain stream itself straight from the adc, or convert it into an IQ stream. Both kinds represent the same information. You could pipe those streams untouched to the dac (convert IQ back down to plain if needed) and recreate what you originally captured.
That said,
Why not make an audio stream into an IQ stream? why do people not do this? You will not find audio dsp examples working on IQ streams. Likewise, all RF dsp examples I've ever tried to understand represent their streams in IQ only. What is so different between those domains that each industry represents their data streams in the way that they do when the alternative representation works just as well too? Some RF streams are well within the grasp of current converter/fpga technologies (like HF comms) as a plain stream.
I'm trying to figure out the technical reason why someone would use one representation over the other.
Do you know if it is simply historical reasons and nothing to do with technicalities? I end up empty handed trying to answer such a nuanced question w/google. What areas should I be looking into for further research? Feel free to lay the technicalities on me - longtime EE here (hence my love of P2 tech dev discussions over the years).
Comments
In contrast a optical encoder most offen implements a quadrature signal that loads both lines equally so the bandwith can be one forth.
What brings many to the solution to use A as a direction and B as a step signal what brings resolution to 1/4th ;-)
But at least we here have realized, that having a symmetrical multicore system gives you an advantage.
And I also keep it for mandantory, to invest more in education the uneducated and not focus on the so called "elites". Because there is no blossom without substrate ;-)