Noise Equivalent Bandwidth

An amplifier or a filter will have a non-ideal frequency response , in order to easily describe the noise power effect through the amplifier or a filter, we need a Noise Equivalent Bandwidth.









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SIFS/DIFS/PIFS (802.11 Mac Layer)

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1.What is Short Inter-frame Space (SIFS)? Ans : the small time interval between the data frame and its acknowledgment . Used for the highest priority transmissions enabling stations with this type of information to access the radio link first. 2. What is the content of SIFS ? Ans :This value is fixed per PHY and is calculated in such a way that transmitting station will be able to switch back to receive mode and be capable of decoding the incoming packets. A SIFS duration is a constant value and it depends on the amendments . 3.What is  DCF inter-frame space( DIFS) ? Ans : The DIFS is used by stations operating under the DCF method to transmit data frames and management.(Read more : DCF Method ) 4.How to use DIFS? Ans : A station using the DCF is allowed to transmit if it determines that the medium is idle for the duration of the DIFS, or if it determines that the medium is idle for the duration of the DIFS + the remaining back-off time following the recept...
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Spread Spectrum Clock Generation (SSCG)

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Spread-spectrum clock generation (SSCG) is used in some  synchronous digital system   to reduce the spectral density of the  electromagnetic interference (EMI).   Jitter will cause transmitted bit error Because the generated clock will have variation between 5 GHz ~ 4.97 GHz, thus in the time domain , the clock waveform will have time variation. If the variation is too much, then the received waveform will have certain error because of clock timing variation which can be founded in the following figure :
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Perl Learning Note - Column Swap Function

Suppose we want to have a function to deal with a global matrix (@matrix) to do column swap, then we can declare the  function  as following : sub ColSwap {     my ($Idx1,$Idx2) = @_;  # Idx1 and Idx2 are global variable     my ($idx, $Tmp0);       # idx and Tmp0 are local variable , only exist in this function     for ($idx = 0; $idx < $max_col; $idx++)     {            $Tmp0 = $matrix[$Idx1*$max_col + $idx];            $matrix[$Idx1*$max_col + $idx] = $matrix[$Idx2*$max_col + $idx];            $matrix[$Idx2*$max_col + $idx] = $Tmp0;     } } NOTE : matrix and max_col are global variable , we don't need to give any input argument to ColSwap. We can use this kind of function using  &ColSwap (Column#1 , Column#2); We can return value like we  program  in C , for example : s...
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