Hi Zorro, I have two questions. First that lowpass gaussian filter there is the one in gmsk gsm or not?. Second, the lowpass you said there is RC? I have already added several RC-RC-RC but the negative side still exit. I may use active lowpass instead.
So that active RC solution is the one used in GSM GMSK or not?. I am not sure of that. Is there anyone know about GSM gaussian filter?. I could not find it.
If I want to create gaussian pulse, I use several RC-RC filter (150ohm-10ns) to shape that pulse to gaussian pulse. But the shape is not 100% look like (see picture).
@LvW, please explain more about " rising fillter degree " I do not quite understand this term. Is that the simple series RC?. In that case designing the perfect gaussian pulse will not be possible. It is just approximately. The pulse signal through the RC always have the rising exponential and then the falling exponential.
Curiously your attachments are two out of >10000 edaboard attachments that display correctly. They neither display in firefox.@FvM. I think some things wrong with your browser. I used firefox instead and I can see the picture. Please use another browser.
@ LvM. Yes, I have increased number of RC in series. The gaussian does not look exactly as perfect gaussian pulse. The time is also longer than the rec_pulse. So from what you said we cannot have a perfect gaussian pulse isnt it?.
As verbosely explained, a real gaussian filter won't be "perfect". I only took a brief look at GSM 05.04 and 05.05. As far as I understand, the filter performance is specified as maximum modulation phase error (and the modulation spectrum mask on the other hand). Something you most likely need to calculate if you don't have other literature deriving the filter specification explicitely.If gaussian filter is not perfect the data may not be corrected I think. Dont know how gaussian is used in real gsm
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