Which modulation technique is primarily associated with changing the phase of the carrier signal?

The modulation technique that focuses on changing the phase of the carrier signal is Phase Shift Keying (PSK). In PSK, information is conveyed by varying the phase of the carrier wave. This approach allows for the efficient transmission of digital data over communication channels. Each distinct phase shift represents a specific symbol or bit pattern, enabling reliable data transmission.

In contrast, Amplitude Modulation (AM) alters the amplitude of the carrier signal to convey information, while Frequency Modulation (FM) varies the frequency of the carrier wave. Quadrature Amplitude Modulation (QAM) combines both amplitude and phase changes to encode information, but it is primarily recognized for its use in higher-level data transmission rather than focusing solely on phase modifications. Thus, PSK is exclusively dedicated to phase changes, making it the correct answer for this question.