The distortion due to aperture effect can be corrected by:

SOLUTION

Aperture effect is a phenomenon usually observed when Flat-top sampling is used.

Flat-Top sampling:

In this, the pulses will have flat-tops.

The top of the sample remains constant and is equal to the instantaneous value of baseband signal g(t) at the start of the sampling:

\(s\left( t \right) = \mathop \sum \limits_{n = \infty }^\infty g\left( {n{T_s}} \right) \cdot h\left( {t - n{T_s}} \right)\)

\(s\left( f \right) = {f_s} \cdot \mathop \sum \limits_{n = - \infty }^\infty G\left( {f - n{f_s}} \right) \cdot H\left( f \right)\)

The above equation represents the spectrum of the flat top sampled signal.

Aperture effect:

• In flat-top sampling, due to lengthening of the sample, amplitude distortion and delay is introduced. This distortion is referred to as the aperture effect and occurs during the reconstruction of g(t) form s(t).
• The high-frequency roll-off filter with transfer function H(f) acts as a Low Pass filter that alternates the upper portion of the message spectrum, resulting in the distortion of the original signal.
• Aperture effect can be eliminated by using “Equalizer” in cascade with a reconstruction filter at the receiver to cancel the effect produced by the filter H(f) discussed.