On Tuesday, September 15, 2015 at 1:09:26 PM UTC-4, Tim Wescott wrote:> On Tue, 15 Sep 2015 07:21:05 -0700, makolber wrote: > > > On Tuesday, September 15, 2015 at 9:35:36 AM UTC-4, Tauno Voipio wrote: > >> On 15.9.15 16:06, b2508 wrote: > >> > Well, probably sounds stupid but I get quite confused on this. In my > >> > specification I get Intermediate Frequency data as real from third > >> > party RF Front end. > >> > > >> > Isn't RF Data suppose to be real? Then I assume it was mixed with > >> > some LO to downconvert it from RF to IF. How this this result in a > >> > real signal? > >>Then there are no negative numbers too? Imaginary numbers is how God draws circles.> >> > >> You may have either, depending on the mixer. If nothing is said, it is > >> pretty safe to assume that IF is a real, band-limited signal. > >> > >> If the mixer has two channels with local oscillators at 90 degree phase > >> difference, you can have complex IF signal pair at the output. > >> > >> -- > >> > >> -TV > > > > as a simple minded hardware guy... my rule is > > > > if the signal takes one cable to transport, it is real.. > > if the signal takes two cables to transport i.e I and Q. , it is > > complex, > > > > not sure if this is technically correct. > > It's not an IIF proposition. You can turn it around: > > If the signal is real it only takes one cable to transport. > If the signal is quadrature it must have two cables to transport. > > But there are other ways you can put a group of related signals onto > multiple cables that aren't I and Q. > > Being a stickler about this, I wouldn't even say "I and Q is complex" -- > I would say "I and Q is _pretending_ to be complex". Because -- there > ain't no imaginary numbers in this real world of ours. > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com
Is IF Data real or complex
Started by ●September 15, 2015
Reply by ●September 16, 20152015-09-16
Reply by ●September 16, 20152015-09-16
> > > > If the signal is real it only takes one cable to transport. > > If the signal is quadrature it must have two cables to transport. > >it is also more clear if you use an alternate terminology.. real = single dimensional complex = two dimensional imaginary = the second dimension of the two dimensional values. Mark
Reply by ●September 17, 20152015-09-17
On 9/16/15 9:02 AM, makolber@yahoo.com wrote:> >>> >>> If the signal is real it only takes one cable to transport. >>> If the signal is quadrature it must have two cables to transport. >>> > > it is also more clear if you use an alternate terminology.. > > real = single dimensional > > complex = two dimensional > > imaginary = the second dimension of the two dimensional values. >problem is that this terminology is not always correct. C != R^2 two-vectors are not the same as complex numbers. they have different operations (and rules) regarding each. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●September 23, 20152015-09-23
>On Tue, 15 Sep 2015 08:06:22 -0500, b2508 wrote:>Or, to get even more distressingly physical, because in a REAL radio you>can't have IMAGINARY numbers running around? So the circuit designers >are constrained -- yes, constrained!, tied down!, chained, even! -- to >either having a single LO signal or trying to simulate a complex signal >by making a pair of them that are very accurately 90 degrees apart (which>isn't at all trivial, even in an IC)?>Tim Wescott >Wescott Design Services >http://www.wescottdesign.comWhy would they try to simulate complex signal out of real one? What is the benefit of this? Is there anywhere a very good article explaining the reasons to use IQ data at all? I don't get it anymore, are they complex, are they used for easier modulation process, are they fake, what are they? --------------------------------------- Posted through http://www.DSPRelated.com
Reply by ●September 23, 20152015-09-23
On 23.9.15 17:34, b2508 wrote:>> On Tue, 15 Sep 2015 08:06:22 -0500, b2508 wrote: > >> Or, to get even more distressingly physical, because in a REAL radio you > >> can't have IMAGINARY numbers running around? So the circuit designers >> are constrained -- yes, constrained!, tied down!, chained, even! -- to >> either having a single LO signal or trying to simulate a complex signal >> by making a pair of them that are very accurately 90 degrees apart (which > >> isn't at all trivial, even in an IC)? > >> Tim Wescott >> Wescott Design Services >> http://www.wescottdesign.com > > Why would they try to simulate complex signal out of real one? What is the > benefit of this? Is there anywhere a very good article explaining the > reasons to use IQ data at all? I don't get it anymore, are they complex, > are they used for easier modulation process, are they fake, what are they? > > --------------------------------------- > Posted through http://www.DSPRelated.comGoogle for 'image rejection mixer'. -- -TV
