Why we use Low Pass FIlter in PCM

If a low pass filter is not implemented prior to the sampling modulator, we have to face more problems, when the voice is passing through a copper cable.

 In sampling modulator we use a low pass filter to pass only low frequency of the voice signal. It compressed human voice bandwidth (20 kHz-20000 kHz) into small bandwidth of 0.3 kHz-3.4 kHz.

                      We know if want to transmit more distance, need a low bandwidth. Human voice bandwidth is a wider one, using that bandwidth can’t transmit that much of distance through the copper cable. It needs small bandwidth. That’s why we use low pass filter.

                      If it is not implemented prior to sampling modulator can’t transmit signal much distance through the copper cable.

                      And ccItt experimented on the range which most suitable for voice transmission and found out that 0-4kHz would be sufficient enough to transmit any message clearly.