What is phase modulation?

• A. A modulation technique that varies the amplitude of the carrier wave
• B. A technique that encodes data by varying the phase of the carrier wave
• C. A method of filtering unwanted signals
• D. A process for enhancing bandwidth

Answer: (B)

Phase modulation is a technique that encodes information by varying the phase of a carrier wave. In this method, the phase of the carrier signal is changed in accordance with the incoming data signal, allowing the transmission of information. This alteration in the phase of the carrier wave can represent different data values, and these changes can be detected by receivers tuned to the same carrier frequency.

Understanding phase modulation is essential because it effectively uses the properties of waves to convey information, differentiating it from other types of modulation such as amplitude modulation, which involves varying the signal's amplitude rather than its phase. The ability to encode information through phase changes makes phase modulation useful in many communication systems, particularly in digital broadcasting and telecommunications.

Additionally, techniques that manipulate amplitude or filter signals are not representative of phase modulation—these serve different purposes in signal processing. The enhancement of bandwidth is a separate consideration and is not a defining characteristic of phase modulation itself.