How to model a stream up conversion with BW of 0.5 MHz?

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Ahmed Alaa

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Dear all,

Assume we have a bit stream [1 0 1 1 0 1 0 1 1 0 0 0 1 1] represents bits with a duration of 1 microseconds, thus its baseband BW = 0.5 MHz, if we want to model this stream's upconversion, we'll multiply by an 0.5 MHz carrier (minimum possible carrier freq). Does this mean that we'll multiply the above stream by [1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 ...] ? I am arguing my boss in that :smile:

Thanks,
Ahmed
 

Re: Up conversion

He says you must have some carrier cycles within one bit duration, otherwise you don't have a carrier. This confuses me because the problem is very basic and I'm sure I'm right.. I think his view is that when using the stream [1 -1 1 -1 1 -1 ...] we'll have half a cycle per bit duration, which means the spectrum starts sharply from zero till 2B where B is the baseband BW.

btw, why 2*0.5 MHz, this should be the sampling freq I think, but to avoid spectral overlapping, the minimum carrier = Baseband BW, right ?
 

Re: Up conversion

for baseband, Fs = BW but for passband Fs = 2*BW with rectangular pulse shaping, if you used ideal sinc function pulse shaping, I think you'd need Fs = BW for passband.

---------- Post added at 04:20 PM ---------- Previous post was at 04:18 PM ----------
Ahmed Alaa said:
He says you must have some carrier cycles within one bit duration, otherwise you don't have a carrier. This confuses me \
Click to expand...

1 cycle is enough for sinc pulse shaping but 2 for rectangular, which is what you seem to be using.

Maybe you should ask him for more info/explanation.
 
Re: Up conversion

I am using an array with each element represent a sample, this corresponds to a sinc not rect. Thank you, I didn't think about that before !
 

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