I have been reading a paper that specifies the spectral mask for certain communication devices attempting transmit over a channel

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Can someone explain

1) importance if this spectral mask, is it a filter ?

2) what do we mean by roll off at the pass band from -28 dBr to -20 dBr.

3) Also why is the unit of measurement dBr and not db

Thank you very much

  • $\begingroup$ Spectral mask is used for a definition of the standardised bandwidth in order to minimize the interference. It is not a filter per se, it's simply a requirement for the particular standard. I.e. here is some example of the mask for a wi-fi. Spectral roll-off is what it is, as it defines how steep is the curve. dBr is a definition used for any unit with respect to a reference level. I.e. for sound pressure dBr is with reference to 20uPa. $\endgroup$ – jojek May 24 '15 at 17:01
  • $\begingroup$ Thank you very much for clear explanation, if it is not a filter, then how can devices such as wifi devices make sure they meet this requirement? i.e what do they use to meet this spectral mask? @jojek $\endgroup$ – Tyrone May 24 '15 at 17:03
  • $\begingroup$ Like I said, it is not a filter - it's a requirement and every device must comply to that. Whether you use filters, design you device in a specific way - it's up to you. You must be sure that it is met. One analogy is a filter mask used when designing any type of an A-weighted auditory filter. No one cares how you do it - it must be within the boundaries. $\endgroup$ – jojek May 24 '15 at 17:10
  • $\begingroup$ Thank you very much. Would you like to write this an asnwer so I can accept it.? $\endgroup$ – Tyrone May 24 '15 at 17:12

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