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ROLL NO:11090460 DATE:16-08-2012

EXPERIMENT NO: 1

AIM: To simulate AM Modulation.

SOFTWARE USED: VisSim Comm 6.0

BLOCK DIAGRAM:

Fig:- 1 Amplitude Modulation

THEORY:

Amplitude modulation is a process in which the amplitude of a carrier signal is varied in accordance with modulating signal. Amplitude modulation (AM) is a method of impressing data onto an alternating-current carrier waveform. The highest frequency of the modulating data is normally less than 10 percent of the carrier frequency. The instantaneous amplitude(overall signal power) varies depending on the instantaneous amplitude of the modulating data.

= initial phase of Carrier , A= Amplitude of Wave

ECE 419 1 MMEC,Mullana

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WAVEFORM:

RESULT: The Amplitude Modulation has been studied & Designed.


ROLL NO: 11090460 DATE :

EXPERIMENT NO: 2

AIM: To simulate FM Modulation.


BLOCK DIAGRAM:

Plot

Time (sec)0 2.5 5 7.5 10

-1

1

-1

1

sig

ph

FM ModFc= 2 Hz

Fig :- 2(a) FM Modulation

THEORY:

Frequency Modulation is type of continuous wave modulation. FM may be defined as the process in which a frequency of a signal called carrier is varied in accordance to instantaneous value of another signal called modulating signal. The signal resulting from the process of frequency modulation is called frequency modulated signal.

Modulation index:As with other modulation indices,this quantity indicates by how much the modulated variable varies around its unmodulated level. It relate to the variations in the frequency of the carrier signal.

Frequency modulation is a technique of modulating the frequency of the carrier signal in accordance with the frequency of the modulating or the information signal. As the information signal has a very low frequency, therefore it cannot be


transmitted over long distances. To increase the efficiency of the modulating signal it is fed upon a carrier signal which has a very high frequency. Now, this frequency of carrier signal is changed in accordance with the information signal.

ωi = instantaneous frequencyωc = carrier frequencyΔω = carrier deviationωm = modulation frequency

WAVEFORMS:

RESULT : The Frequency Modulation has been simulated and verified.



EXPERIMENT NO: 3

AIM: To simulate Phase Modulation.


BLOCK DIAGRAM:

Fig:- 3 Phase Modulation

THEORY:

Phase modulation (PM) is a method of impressing data onto an alternating-current (AC) waveform by varying the instantaneous phase of the wave. This scheme can be used with analog or digital data. the AC signal wave, also called the carrier, varies in a continuous manner. Thus, there are infinitely many possible carrier phase states. When the instantaneous data input waveform has positive polarity, the carrier phase shifts in one direction; when the instantaneous data input waveform has negative polarity, the carrier phase shifts in the opposite direction. At every instant in time, the extent of carrier-phase shift(the phase angle) is directly proportional to the extent to which the signal amplitude is positive or negative.


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WAVEFORMS:

RESULT: The Phase Modulation has been studied & Designed.



EXPERIMENT NO: 4

AIM: To simulate ASK Modulation and demodulation.


BLOCK DIAGRAM:

ASK MODULATION

ASK DEMODULATION


THEORY:

Basically digital modulation techniques may be classified into coherent and non -coherent techniques ,depending upon whether the receiver is equipped with phase recovery circuit or not.They are:

1. Coherent digital modulation techniques.2. Non- coherent digital modulation techniques.

Coherent Digital Modulation Techniques:These are those techniques which employ coherent detection .In coherent detection ,the local carrier generated at receiver is phase locked with carrier at transmitter.

Non – Coherent Digital Modulation Techniques:These are those techniques in which the detection process does not need the receiver carrier to be phase locked with transmitter.

Amplitude Shift Keying:It is a coherent digital modulation technique. In this method there is only one energy carrier and it is switched on or off depending upon the input binary sequence. It is also known as on –off keying.


WAVEFORMS:

RESULT: The Amplitude shift keying (ASK) has been simulated and studied.



EXPERIMENT NO: 5

AIM: To simulate FSK Modulation and demodulation.


BLOCK DIAGRAM:

Fig:- 5 (Frequency Shift Keying modulation and Demodulation)THEORY:

Frequency – Shift Keying (FSK) is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. The simplest FSK is binary FSK (BFSK). BFSK literally implies using a pair of discrete frequencies to transmit binary (0s and 1s) information . With this scheme , the “1” is called the mark frequency and the “0” is called the space frequency.


WAVEFORMS:

RESULT: The Frequency Shift Keying (FSK) Modulation and Demodulation has been studied & Simulated.



EXPERIMENT NO: 2

AIM: To simulate Phase Shift Keying.


BLOCK DIAGRAM:

Fig. 5(a) Phase Shift Keying Modulation and Demodulation


THEORY:

In Phase Shift Keying (PSK) modulation technique, the modulated output switches between in-phase and out-of phase component of the carrier for every “one” to “zero” transitions of modulating signal. The carrier frequency chosen for PSK modulation are 1MHZ (0 Degree) and 1 MHZ (180 Degree).The phase detector works ion the principle of squaring loops. First step in PSK detection is the square wave conversion using a Schmitt trigger. This enables the PSK detector to be built around digital IC’s. BPSK (also sometimes called PRK, Phase Reversal Keying, or 2PSK) is the simplest form of phase shift keying (PSK). It uses two phases which are separated by 180° and so can also be termed 2-PSK. A binary phase shift keying signal can be given as:

s(t) = A m(t) cos 2πfct

WAVEFORMS:

Fig. 5(b) Carrier Signal


Fig. 5(c) Modulating Signal

Fig. 5(d) Modulated Signal

Fig. 5(e) Demodulated Signal

RESULT : The Phase Shift Keying(PSK) modulation and demodulation has been studied and simulated .



EXPERIMENT NO: 7

AIM: To simulate Pulse Amplitude Modulation.


BLOCK DIAGRAM:

Fig:- 8 (Pulse Amplitude Modulation)

THEORY:


Pulse-amplitude modulation, acronym PAM, is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.. In this the signal is sampled at regular intervals and each sample is made proportional to the magnitude of the signal at the instant of sampling. These sampled pulses may then be sent either directly by a channel to the receiving end or may be made to modulated using a carrier wave before transmission.

WAVEFORMS:


http://en.wikipedia.org/wiki/Amplitude

http://en.wikipedia.org/wiki/Modulation

RESULT: The Pulse amplitude Modulation has been studied and simulated.


EXPERIMENT NO: 8

AIM: To simulate Pulse Position Modulation.


BLOCK DIAGRAM:

Fig:- 8 Pulse Position Modulation

THEORY:


Pulse-position modulation (PPM) is a form of signal modulation in which M message bits are encoded by transmitting a single pulse in one of 2M possible time-shifts. This is repeated every T seconds, such that the transmitted bit rate is M/T bits per second. It is primarily useful for optical communications systems.

Waveforms:

RESULT: The Pulse Position Modulation has been studied and simulated.


http://en.wikipedia.org/wiki/Optical_communication

http://en.wikipedia.org/wiki/Modulation


EXPERIMENT NO: 9

AIM: To simulate DPSK Modulation.


BLOCK DIAGRAM:

Fig 9-1 DPSK modulation

THEORY:

Differential phase shift keying (DPSK), a common form of phase modulation conveys data by changing the phase of carrier wave. In Phase shift keying, High state contains only one cycle but DPSK contains one and half cycle. High state is represented by a M in modulated signal and low state is represented by a wave


which appears like W in modulated signal DPSK encodes two distinct signals of same frequency with 180 degree phase difference between the two. This experiment requires two 180 degree out of phase carrier and modulating signals. Sine wave from oscillator is selected as carrier signal. DSG converts DC input voltage into pulse trains. These pulse trains are taken as modulating signals. In actual practice modulating signal is digital form of voice or data. Sine wave is selected as carrier and 180 degree phase shift is obtained using Op-amp as shown in figure below.

WAVEFORM:

RESULT: The DPSK modulation has been studied and stimulated.



EXPERIMENT NO: 10

AIM: To simulate DPSK Demodulation.


BLOCK DIAGRAM:

Fig 9-1 DPSK Demodulation

THEORY:

Differential phase shift keying (DPSK), a common form of phase modulation conveys data by changing the phase of carrier wave. In Phase shift keying, High state contains only one cycle but DPSK contains one and half cycle. High state is


represented by a M in modulated signal and low state is represented by a wave which appears like W in modulated signal DPSK encodes two distinct signals of same frequency with 180 degree phase difference between the two. This experiment requires two 180 degree out of phase carrier and modulating signals. Sine wave from oscillator is selected as carrier signal. DSG converts DC input voltage into pulse trains. These pulse trains are taken as modulating signals. In actual practice modulating signal is digital form of voice or data. Sine wave is selected as carrier and 180 degree phase shift is obtained using Op-amp as shown in figure below.

WAVEFORMS:


RESULT: The DPSK Demodulation has been studied and stimulated.


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