*Question E7F04:
Which method generates an SSB signal using digital signal processing?*  

*Correct Answer is  D: Signals are combined in quadrature phase relationship*  

### AI Response: (may contain errors)  

To generate a Single Sideband (SSB) signal using digital signal processing, the correct method is:

**Correct Answer: D: Signals are combined in quadrature phase relationship**

### Explanation of the Correct Answer:
- **Quadrature Phase Relationship**: In SSB modulation, the signal is created by combining two signals that are 90 degrees out of phase (quadrature). This allows for the suppression of one of the sidebands (either upper or lower) and the carrier, resulting in a more efficient transmission. The mathematical representation of combining signals in quadrature can be expressed as:

$$
S(t) = A \cos(2\pi f_c t) + A \sin(2\pi f_c t)
$$

where:
- $S(t)$ is the resulting SSB signal,
- $A$ is the amplitude,
- $f_c$ is the carrier frequency.

### Why the Other Choices are Incorrect:
- **A: Mixing products are converted to voltages and subtracted by adder circuits**: 
  - This describes a mixing process but does not specifically relate to the generation of SSB signals. Mixing can create sidebands, but it does not inherently produce SSB without further processing.

- **B: A frequency synthesizer removes unwanted sidebands**: 
  - While frequency synthesizers can generate specific frequencies, they do not inherently create SSB signals. Removing unwanted sidebands is a separate process that may occur after SSB generation.

- **C: Varying quartz crystal characteristics are emulated in digital form**: 
  - This option refers to frequency stability and control but does not directly relate to the SSB modulation process. Quartz crystals are used for frequency control, not for generating SSB signals.

### Summary:
- The generation of SSB signals relies on the combination of signals in quadrature phase, which effectively suppresses unwanted components. Understanding the role of quadrature in SSB modulation is crucial for the Extra Class exam.