Communication Lab Experimental Trainer kits Details
(1) To generate the DSB-SC Modulated wave and to observe the phase reversal at the
zero crossing of the modulating signal. (MOD-13)
Balanced modulator is used for generating DSB-SC signal. A balanced modulator consists of
two standard amplitude modulators arranged in a balanced configuration so as to suppress the carrier
wave. The two modulators are identical except the reversal of sign of the modulating signal applied to
(2) To generate the SSB-SC Modulation and Demodulation. (MOD-14)
An SSB signal is produced by passing the DSB signal through a highly selective band pass filter. This filter selects either the upper or the lower sideband. Hence transmission bandwidth can be cut by half if one sideband is entirely suppressed. This leads to single-sideband modulation (SSB).
(3) To study the functioning of Pre-Emphasis and De-Emphasis circuits. (MOD-15)
The noise has a effect on the higher modulating frequencies than on the lower ones. Thus, if the
higher frequencies were artificially boosted at the transmitter and correspondingly cut at the receiver, an improvement in noise immunity could be expected, there by increasing the SNR ratio. This boosting of the higher modulating frequencies at the transmitter is known as pre-emphasis and the compensation at the receiver is called de-emphasis.
(4) To generate Pulse amplitude modulated(PAM) signal and demodulate it. (MOD-16)
PAM is the simplest form of data modulation .The amplitude of uniformly spaced pulses is varied in
proportion to the corresponding sample values of a continuous message .
A PAM waveform consists of a sequence of flat-topped pulses. The amplitude of each pulse corresponds to the value of the message signal at the leading edge of the pulse.
The pulse amplitude modulation is the process in which the amplitudes of regularity spaced rectangular pulses vary with the instantaneous sample values of a continuous message signal in a one-one fashion.
(5) To generate Pulse Positon modulated(PPM) signal and demodulate it. (MOD-17)
In Pulse Position Modulation, both the pulse amplitude and pulse duration are held constant but the
position of the pulse is varied in proportional to the sampled values of the message signal. In PPM the analog sample value determines the position of a narrow pulse relative to the clocking time. In PPM rise time of pulse decides the channel bandwidth. It has low noise interference.
(6) To generate Pulse Width modulated (PWM/PTM/PLM/PDM) signal and
demodulate it. (MOD-18)
Pulse Time Modulation is also known as Pulse Width Modulation or Pulse Length Modulation. In PWM, the samples of the message signal are used to vary the duration of the individual pulses. Width may be varied by varying the time of occurrence of leading edge, the trailing edge or both edges of the pulse in accordance with modulating wave. It is also called Pulse Duration Modulation.