AIM: To study the Time division multiplexing and demultiplexing for two different frequency signals
APPARATUS :1. 2 channel TDM multiplexer kit - 1
2. Audio frequency signal generator - 1
3. Clock generator - 1
4. 2 channel TDM demultiplexer - 1
5. Passive low pass filter - 2
6. Audio amplifier
7. Dual trace C.R.O - 2
8. C.R.O probes
9. Connecting wires
PROCEDURE:
MULTIPLEXER1. Trace the circuit as per circuit diagram.
2. Observe the o/p of AF generator, it should be a sine wave of 100Hz with 3Vp-p amplitude.
3. Observe the o/p of AF generator2; it should be a sine of 200Hz with 3Vp-p amplitude.
4. Verify the operation of logic source with multimeter, o/p should be +5v in logic 1 and 0v in logic 0.
5. Verify the clock generator o/p, it should be a square of 500Hz to 15KHz freq with 5Vp-p amp.
6. Connect the CH-1& CH-2 inputs of the TDM multiplexer to the o/p of AF generator 1& 2 respectively.
7. Connect control i/p of the TDM multiplexer to the o/p of the logic source.
8. Keep control signal at logic 1 and observe the o/p of the TDM multiplexer and notice that the o/p of the TDM multiplexer is a signal which has been connected to CH-1 i/p. In this condition the signal at CH-2 i/p has no effect on mux o/p.
9. Repeat the above step-8 for logic source at 0 positions.
10. Disconnect logic source and connect clock o/p to the control I/p.
11. Observe TDM waveform using C.R.O at different values of clock freq I/p signal voltage level.
DEMULTIPLEXER
1. Verify the circuit as per circuit diagram.
2. Verify the operation of logic source with multimeter/ scope,o/p should be ±5v in logic-1 and ov in logic-0 position.
3. Observe the clock generator; it should be a square wave of 500Hz to 15 KHz freq with 5Vp-p.
4. Connect TDM signal to I/p of TDM de-multiplexer with the help of coaxial cable.
5. Connect control I/p to logic source o/p.
6. Put logic source to 1 position and observed that entire TDM is transferred to CH-1 o/p and has no signal at CH-2 o/p.
7. Repeat the above step-6 for logic -0.
8. Now disconnect logic source and connect clock from the transmitter.
9. Connect CH-1,CH-2 o/p to low pass filter and observe the o/p of the filter and compare with original A.F signals. Both are same in freq and shape.
THEORY:
A) Multiplexer
Time division multiplexer is the technique for simultaneous transmission of more than one intelligence signals on one channel and the signal carrier by utilizing the time scale without loss of identity of an individual signal.
In TDM multiplexer CD4052IC is used to generate TDM wave. It is a 4 channel analog multiplexer and is used as an active components in this circuit. One of the four channels (pin9) of 052 is grounded. So that 4052 acts as a two channel multiplexer and the other channel being terminated with control (pin10) signal of TDM multiplexer. The message signalsthat are to be transmitted has to be connected to CH-1 and CH-2 i/p’s of the CD4052.
When control signal i/p 1 i;e logic high (+5v)o/p of the 4052 is connect to CH-1 and whatever signal at CH-1 is there will be passed onto o/p. Similarly when control signal is 0(0v) o/p of the multiplexer connected to CH-2 and the signal at this i/p will be passed on to o/p. When drive the control signal with a clock signal of desired freq .the o/p of the multiplexer will be connected to CH-1 and CH-2 automatically in sequence depend on clock signal condition. i;e ON/OFF time. So multiplexer samples each the I/p signals in sequence and transmits over a single channel.
DEMULTIPLEXER:
IC CD4052 is a 4 channel analog demultiplexer one of the four channels (pin9) grounded and other one (pin10) is being terminated of control signal of a two channel TDM demultiplexer. So that CD4052 will act as a two channel TDM demultiplexer. When control signal is 1 I;e logic high (+5v) I/p of the 4052 is connect to CH-1 o/p and the signal which is at I/p will be passed on to o/p. When drive the control signal with a clock signal of desired freq. The i/p of the demultiplexer will be connect to CH -1 o/p and CH-2 o/p automatically is sequence depend on clock signal condition i;e. ON/OFF time. Demultiplexer at the receiver should be operate in synchronize with the multiplexer which is at transmitter in order to recover the original signals without any loss.
PRECAUTIONS:
1. Check the connections before switch on the power supply.
2. Avoid loose connections.
3. Observe the output on C.R.O and take the readings without parallax error.
RESULT:
VIVA VOICE:1. What is meant by multiplexing?
2. What is the difference between F.D.M and T.D.M?
3. What is the Aim of your expt?
4. What are the advantages by using T.D.M?
In which type of communication we are using T.D.M(either A.C or D.C)?
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