Definition of BT in an FSK system

BT denotes the product of the 3 dB bandwidth of the shaping
pulse in an FSK system and the symbol time.

My question has to do with the conventional definition of B.

My first thought was to use the 3 dB bandwidth of a bandpass
function obtained by translating the baseband pulse up
to the FSK center frequency; or equivalently, twice the
bandwidth (from 0 Hz to the 3 dB point) of the pulse viewed as 
a lowpass function at baseband.

However, doing it this way results in a curve that disagrees
with some published shaping curves; it appears people (in
at least some cases) leave the factor of two out, and just
look at the bandwidth of the lowpass function, from 0 Hz
to the positive 3 dB point.

What is the convention here?

Thanks,

Steve

Steve Pope wrote:

> BT denotes the product of the 3 dB bandwidth of the shaping
> pulse in an FSK system and the symbol time.
> 
> My question has to do with the conventional definition of B.

BT has to do with the real pulse and real bandwidth. That is lowpass 
function.

VLV

On 7/15/2010 11:30 AM, Steve Pope wrote:
> BT denotes the product of the 3 dB bandwidth of the shaping
> pulse in an FSK system and the symbol time.
>
> My question has to do with the conventional definition of B.
>

I do not know about FSK. But I checked my class notes now, and it says 
that BT (band width) is the transmission bandwidth, while B is the 
baseband bandwidth.

For example, for normal AM, BT=2*B, for AM, Single sided, BT=B.

--Nasser

Vladimir Vassilevsky  <nospam@nowhere.com> wrote:

>Steve Pope wrote:

>> BT denotes the product of the 3 dB bandwidth of the shaping
>> pulse in an FSK system and the symbol time.

>> My question has to do with the conventional definition of B.

>BT has to do with the real pulse and real bandwidth. That is lowpass 
>function.

Thanks.  

Steve