Quadrature Amplitude Modulation (QAM) and Pilot carrier

Quadrature Amplitude Modulation (QAM)

a.) Have same bandwidth used for two DSB-SC signals
b.) Is also known as Bandwidth Conservation scheme
c.) Is used in color television
d.) All of the above

Correct answer: All of the above

Explanation:

The modulation scheme Quadrature Amplitude Modulation (QAM) enables same bandwidth used for transmission of two DSB-SC signals. It is also known as Bandwidth Conservation scheme. However it needs synchronous detection so it needs an additional system for generation of carrier. Also known as Quadrature Carrier Multiplexing, the scheme is used in color television.

Pilot carrier is

a.) Used with DSB-SC signal
b.) A small carrier transmitted with modulated signal
c.) Used for synchronization with local carrier at the receiver
d.) All of the above

Correct answer: d) All of the above

Explanation:

Pilot carrier is a small carrier transmitted with modulated signal from the transmitter. It is separated at the receiver and used to phase lock the locally generated carrier signal generated at the receiver. It provides synchronization at the receiver.

As a weak carrier is transmitted with the DSB signal, it is also referred to as partially suppressed carrier system, as the carrier is not totally suppressed. So it is a case of over modulation.