Consider a binary transmission system where symbols 0 and 1 are r
Consider a binary transmission system where symbols 0 and 1 are represented in the constellation diagram as shown:
The modulation scheme used is:
A. Frequency Shift Keying
B. Binary Phase Shift Keying
C. Amplitude Shift Keying
D. Quadrature amplitude modulation
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Right Answer is: B
SOLUTION
ASK, PSK and FSK are signaling schemes used to transmit binary sequences through free space. In these schemes, bit-by-bit transmission through free space occurs.
In ASK (Amplitude shift keying) binary ‘1’ is represented with the presence of a carrier and binary ‘0’ is represented with the absence of a carrier:
For binary ‘1’ → S1 (t) = Acos 2π fct
For binary ‘0’ → S2 (t) = 0
The Constellation Diagram Representation is as shown:
where ‘I’ is the in-phase Component and ‘Q’ is the Quadrature phase.
In PSK (phase shift keying) binary 1 is represented with a carrier signal and binary O is represented with 180° phase shift of a carrier
For binary ‘1’ → S1 (A) = Acos 2π fct
For binary ‘0’ → S2 (t) = A cos (2πfct + 180°) = - A cos 2π fct
The Constellation Diagram Representation is as shown:
In FSK (Frequency Shift Keying) binary 1 is represented with a high-frequency carrier signal and binary 0 is represented with a low-frequency carrier.
For binary ‘1’ → S1 (A) = Acos 2π fHt
For binary ‘0’ → S2 (t) = A cos 2π fLt . The constellation diagram is as shown:
