PCM spectral efficiency

Discussion in 'Wireless & RF Design' started by pregnant_joe, Aug 11, 2009.

  1. pregnant_joe

    Thread Starter New Member

    Aug 11, 2009
    Hello all..

    Im a newbie..I have question to ask for your favour..im studying abroad, i left my notes there and im in my home country..Please help me..

    Below are the questions:

    1. A baseband transmission channel with a raised cosine frequency response with a roll-off factor of 0.4. The channel has an absolute bandwidth of 1200 kHz. An analogue signal is converted into binary PCM with 64 level quantization before being transmitted over the channel. State the maximum limit on the bandwidth of the analogue signal?


    2. 25 input signals, each band-limited to 3.3kHz are each sampled at an 8kHz rate and then time division multiplexed. Calculate the minimum bandwidth required to transmit this multiplexed signal in the presence of noise if the modulation used is:
    ii)Quantised PPM with a required level resolution of 5%
    iii)Binary PCM with a required level resolution of >0.5%

    *Please orrect me if i'm wrong..what i understand from the question is

    Bandwidth = 3.3kHz
    fs = 8kHz
    Signal channel = 25
    Rs = 8 * 25 = 200kHz
    i know that H = log2 M but i can't see how to find the answers.

    im sure that i have to use n=(R*H)/B but i'm stuck.


    3. A DSB-AM transmitter delivers a mean output power of 33W when a modulating signal comprising a signle tone is applied to it. If the power contained in one sideband is 4W, calculate
    i)the carrier power
    ii)The modulation index
    iii)the peak voltage of the AM signal driving the transmitter antenna if the resistance of the lates is 50ohm

    note: Pc=Pt-2Ps


    thank you for you concern!!..