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