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Experiment- 1(i)
Aim:- To study and simulate Amplitude Modulation (AM).
Simulator Used:- Vis Sim Com 6.0
Circuit Plot:-
Fig. 1(a) Amplitude Modulation
Theory:- Amplitude modulation is a process of translating information signal from
low band frequency to high band frequency. Information signal is usually of low
frequency, so it cannot be transmitted for long distances. It thus needs a carrier
signal of higher frequency for long distance destination. Figure 1 shows a basic
block diagram of a modulator. The inputs are carrier and information (modulating)
signals while the output is called modulated signal.
In amplitude modulated (AM) signal, amplitude of the carrier signal varies with the
information signal. The equation representing Amplitude Modulation is:
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Fsignal(t) = A(t)sin(ωt)
Waveforms:-
Fig. 1(b) Modulating Signal
Fig. 1(c)
Modulated wave
Result:- Amplitude Modulation has been studied and simulated.
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Experiment-1(ii)
Aim:- To study and simulate Amplitude Modulation(AM).
Simulator Used:- Vis Sim Comm 6.0
Circuit Plot:-
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Fig. 1(d) Amplitude Modulation
Waveforms:-
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Fig. 1(e) Information Signal
Fig. 1(f) Carrier Signal
Fig. 1(g) Modulated Signal
Result:- Amplitude Modulation has been studied and simulated.
Experiment-2
Aim:- To study and simulate Frequency Modulation (FM).
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Aug 17, 2011
Simulator Used:- Vis Sim Comm 6.0
Circuit Plot:-
Fig. 2(a) Frequency Modulation
Theory:- 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. Frequency
Modulation can be mathematically represented as
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Waveforms:-
Fig. 2(c) Information Signal
Fig. 2(d) Output modulated signal
Result:- Frequency Modulation has been studied and simulated.
Experiment-3
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Aug 24, 2011
Aim:- To study and simulate Phase modulation(PM).
Simulator Used:- Vis Sim Comm 6.0
Circuit Plot:-
Fig. 3(a) Pulse Modulation Circuit Block Diagram
Theory:- Phase modulation (PM) is a method of impressing data onto a
waveform by varying the instantaneous phase of the wave. This scheme can
be used with analog or digital data. In analog PM, the phase of the 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,
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the carrier phase shifts in the opposite direction. Phase Modulation can be
mathematically represented as:
Waveforms:-
Fig. 3(b) Modulating Signal
Fig. 3(c) PM modulated wave
Result:- Phase Modulation(PM) has been studied and simulated.
Experiment-4
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Aim:- To study and simulate Amplitude Shift Keying(ASK).
Simulator Used:- Vis Sim Comm 6.0
Circuit Plot:-
Fig. 4(a) Amplitude Shift Keying
Theory:- Amplitude shift keying - ASK - in the context of digital
communications is a modulation process which imparts to a sinusoid two or
more discrete amplitude levels. These are related to the number of levels
adopted by the digital message. For a binary message sequence there are two
levels, one of which is typically zero. Thus the modulated waveform consists
of bursts of a sinusoid. There are sharp discontinuities shown at the
transition instants. These result in the signal having an unnecessarily wide
bandwidth. Amplitude Shift Keying can be mathematically represented as:
s(t) = 2P cos 2fct, 0 < t < T
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Waveforms:-
Fig. 4(b) Sine Wave I/p
Fig. 4(c) PN Sequence
Fig. 4(d) ASK modulated wave
ASK Demodulation
Circuit Plot:-
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Fig. 4(e) ASK demodulation
Waveforms:-
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Fig. 4(f) Sine wave
Fig. 4(g) ASK output
Fig. 4(h) ASK demodulator output
Result:- ASK demodulation has been studied and simulated.
EXPERIMENT -5
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Aim: To design FSK Modulator and Demodulator
Simulator Used: VisSim Comm 6.0
Circuit Plot:
Fig. 6(a) FSK Modulation block diagram
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 uses a pair of discrete frequencies to transmit binary (0s and 1s) information.
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With this scheme, the "1" is called the mark frequency and the "0" is called the space frequency.
Waveform:
Fig. 6(b) FSK modulation
Result:- Frequency Shift keying(FSK) has been studied and simulated.
Experiment-6
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Aim:- To study and simulate Phase Shift Keying(PSK).
Simulator Used:- Vis Sim Comm 6.0
Circuit Layout:-
Fig. 6(a) PSK Modulation
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
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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.
Waveforms:-
Fig. 6(b) Sine wave
Fig. 6(c) PN sequence
Fig. 6(d) PSK modulated wave from Mutiplier
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Fig. 6(f) PSK demodulated wave from Integrator and dump ckt.
Result:- Phase Shift Keying has been studied and simulated.
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EXPERIMENT NO. 7
Aim: To study and stimulate Pulse Position Modulation.
Software used: VisSim comm.
Circuit Plot:
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Input Waveform:
Output waveform :
Result: The Pulse Position Modulation has been simulated and verified.
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