Bandpass Random Processes :

        A random process is called a band-pass process if its power spectrum is zero outside a band . is called the band-width and is called the centre frequency of the band-pass process . If is very small compared to the centre frequency , then is called a narrow-band process.

        We can similarly define a low-pass random process as a random process if its power spectral density is zero outside the band

• In telecommunication, we often deal with random signals which have PSD concentrated in a small frequency band and negligible outside this band. The information bearing signals like speech, image and video are low-pass signals. These information-bearing signals modulate a sinusoidal carrier for transmitting over the communication channel that acts as a bandpass filter. For example, the amplitude- modulated waveform received by a communication receiver is modelled as an amplitude-modulated random-phase sinusoid