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Baseband signal g(t) Modulation Concept and Different Modulation Scheme with equations

Modulation is used to modulate baseband signal. Basically it is a technique used to generate a strong signal from a weak signal with help of a transporter signal known as carrier signal.

A baseband signal is main source of any signal. It can be a sinusoidal wave or discrete pulse. In communication a baseband signal need to traverse long distance, but it become weak with respect to distance so that we need to add a carrier which carry the base band signal and send baseband signal to destination.

A baseband signal pass through a modulator with carrier frequency then transmission starts, on other side demodulator demodulate signal and receive the original signal.
 
Practical example: If we through a paper it will traverse some distance but if we through it along with a stone it will traverse more distance. Here paper is baseband signal and stone is carrier.

Modulation concept
Basic signal modulation concept with carrier frequency

There are three basic type of Modulation schemes which are describe below:

1. Analogue Modulation
2. Digital Modulation
3. Pulse Modulation

Analogue Modulation:

This modulation scheme works with analogue signal (continuous signal varies in time) to traverse forward.

AM:Amplitude Modulation
FM:Frequency Modulation
PM:Phase Modulation


Digital Modulation:

This modulation scheme works with digital signal (discrete signal)

ASK:Amplitude Shift Keying
FSK:Frequency Shift Keying
PSK:Phase Shift Keying

Pulse Modulation:

This modulation scheme works with pulse wave.

PAM:Pulse Amplitude Modulation
PFM:Pulse Frequency Modulation
PPM:Pulse Position Modulation
PWM:Pulse Width Modulation
Modulation Schemes
Different Modulation Schemes

Amplitude Modulation Equation for Baseband Signal in frequency domain is:-

S(t)=[1+ mg(t)]c(t)
     =A[1+ mg(t)] cos(wct)
            A = Amplitude
            m = Modulation Index
            g(t) = Baseband Signal
            wc =  Angular Frequency (rad/sec)

Frequency Modulation Equation:
s(t) = A cos Ø(i)t

Where Ø(i)t is instantaneous phase

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