*Question G8A02:
What is the name of the process that changes the phase angle of an RF signal to convey information?*  

*Correct Answer is  B: Phase modulation*  

### AI Response: (may contain errors)  

The correct answer is **Phase modulation**.

1. **Why the correct answer is correct:**
   - **Phase Modulation (PM)** is a technique used to encode information onto a carrier wave by varying the phase angle of the wave. In PM, the phase of the carrier signal is changed in accordance with the instantaneous amplitude of the modulating signal. This is a common method used in radio communications to convey information.

2. **Why the other choices are incorrect:**
   - **Phase convolution**: This is not a standard term in the context of RF signal modulation. Convolution is a mathematical operation used in signal processing, but it does not refer to changing the phase angle to convey information.
   - **Phase transformation**: This term generally refers to changing the phase of a signal, but it is not specifically used to describe a modulation technique for conveying information.
   - **Phase inversion**: This refers to flipping the phase of a signal by 180 degrees, which is not a method for encoding information onto a carrier wave.

3. **Useful formulas or rules of thumb:**
   - In phase modulation, the phase of the carrier signal $\phi(t)$ is varied according to the modulating signal $m(t)$:
     $$ \phi(t) = \phi_0 + k_p \cdot m(t) $$
     where:
     - $\phi_0$ is the initial phase of the carrier.
     - $k_p$ is the phase sensitivity (a constant that determines how much the phase changes with the modulating signal).
     - $m(t)$ is the modulating signal.

Understanding phase modulation is crucial for recognizing how information can be encoded in the phase of a signal, which is a key concept in advanced radio communications.