What is the carrier signal used for pulse modulation?

In pulse modulation, the carrier signal is typically a continuous analog waveform, such as a sine wave or square wave, that serves as the basis for transmitting information. The modulation process involves varying certain properties of this carrier wave—such as its amplitude, width, or position—according to the information signal. This modulation allows the information to be encoded and transmitted efficiently over various communication channels. Common types of pulse modulation include Pulse Amplitude Modulation (PAM), Pulse Width Modulation (PWM), and Pulse Position Modulation (PPM).