Band Pass Sampling

However when the given signal is a Band Pass signal then a different criterion must be used to sample the signal , the Band Pass signal x(t) whose maximum BW is ‘2f_{m}/W‘ Hz can be completely represented and recovered from it’s samples if it is  sampled at the minimum rate of greater than or  equals to twice that of the BW.

then sampling rate f_{s}\geq 2 X BW

i.e, f_{s}\geq 4f_{m} or f_{s}\geq 2W

Any band pass signal in time-domain can be represented in it’s in-phase x_{I}(t) and quadrature phase x_{Q}(t) components as 

x(t) = x_{I}(t)cos 2\pi f_{c}t \pm x_{Q}(t)sin 2\pi f_{c}t

after sampling the band pass signal, the signal after reconstruction is 

x(t) = \sum_{n=-\infty }^{\infty }sinc(2f_{m}t-\frac{n}{2})cos(2\pi f_{c}(t-\frac{n}{4f_{m}}))

 T_{s} = \frac{1}{4f_{m}}, where BW of band pass signal is 2f_{m}  Hz

 

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Author: Lakshmi Prasanna Ponnala

Completed M.Tech in Digital Electronics and Communication Systems and currently working as a faculty.