Higher Technological Institute 10th of Ramadan City Electrical Engineering Department Communications 2 EEC 223 Report 1 Name: Mahmoud Emad Abdel Hamid Abdel zaher Id: 20170837 Group: 6 Supervisor: Dr/ Zakaria Abdel Wahab Eng./ Islam – Amira Introduction PAM Multiplexing: The message information is contained in the amplitude of a series of signal pulses in pulse-amplitude modulation (PAM), a type of signal modulation. The amplitudes of a train of carrier pulses are adjusted according to the sample value of the message signal in this analogue pulse modulation system. Demodulation is accomplished by monitoring the carrier's amplitude level at each period. Pulse amplitude modulation can be divided into two categories: • A proper fixed DC bias is supplied to the signal in single polarity PAM to ensure that all of the pulses are positive. • The pulses in double polarity PAM are both positive and negative. Pulse-amplitude modulation is widely employed in digital data signal transmission, with pulse-code modulation and, more recently, pulse-position modulation mainly replacing non-baseband applications. In analogue PAM, the number of possible pulse amplitudes is potentially limitless. The number of pulse amplitudes is reduced to a power of two with digital PAM. For example, discrete pulse amplitudes are conceivable in 4level PAM; discrete pulse amplitudes are conceivable in 8-level PAM; and discrete pulse amplitudes are conceivable in 16-level PAM. (waveform representation of PAM signal) PAM Multiplexing experiment At our experiment We have four channels with four frequencies remains to input: F1 = 350 Hz F2 = 700Hz F3 = 1400Hz F4 = 2500Hz We can change in amplitude with dip switch. Peak To Peak: is the difference between the maximum positive and the maximum negative amplitudes of a waveform. In channel 1 dip switch ( 1 , 0 , 0 , 0 ) so the amplitude equal 1 v In channel 1 dip switch ( 0 , 1 , 0 , 0 ) so the amplitude equal 2 v In channel 1 dip switch ( 0 , 0 , 1 , 0 ) so the amplitude equal 3 v In channel 1 dip switch ( 0 , 0 , 0 , 1 ) so the amplitude equal 4 v 0 1 2 3 4 5 4 ON ON ON ON ON 3 ON ON ON ON 2 ON 1 ON ON ON ON V 6 7 8 9 10 - The variable of oscillator frequency is between 300Hz: 3KHz. 10 V is the maximum amplitude. The signal's amplitude is increased by the amplifier. The signal bandwidth is controlled by the B.P.F Band Pass Filter. Fm >= Fs/2 Fm: is the input of the signal. Fs: sampling frequency for the signal. We can connect it with short circuit. Before connection: V Peak to Peak = 10 V, Frequency = 352 Hz After connection: V Peak to Peak = 4.56V, Frequency is constant This situation when dipswitch is ( 1 , 0 , 0 , 0 ) (PAM Multiplexer connection) V Peak To Peak after measure = 0.5 V Peak To Peak before measure 0.5 V Peak To Peak before measure Equals V Peak To Peak after measure Limiter: It sets an Amplitude limit. The frame alignment signal extracts a sample from the signal and uses it to determine the first half of each frame. synchronization Signal generation: to recover signals at the same speed as they were transmitted. CH 0: Determine the start of each of the frames. Take a sample from each signal and channel ( 4 CH+ Cho) with the ring counter. The speed at which a clock generator generates a sampling signal is known as the clock generator sampling signal. Fast = 40 KHz & slow = 20KHz , we use fast 40 KHz is the best because every channel have 8KHz sampling ( 4*8 ) + 8 Cho = 40KHz Time interval = 1 / 40000 = 0000.25 sec