*Question E7H10:
What information is contained in the lookup table of a direct digital synthesizer (DDS)?*  

*Correct Answer is  B: Amplitude values that represent the desired waveform*  

### AI Response: (may contain errors)  

In a Direct Digital Synthesizer (DDS), the lookup table is crucial for generating waveforms. Let's break down the correct answer and the other options.

### Correct Answer: 
**B: Amplitude values that represent the desired waveform**

- The lookup table in a DDS contains pre-calculated amplitude values for a specific waveform, such as a sine wave, triangle wave, or square wave. 
- These values are used to create the output signal by converting digital values into corresponding analog voltages through a Digital-to-Analog Converter (DAC). 

### Why the Other Choices are Incorrect:

- **A: The phase relationship between a reference oscillator and the output waveform**
  - While phase information is important in DDS, the lookup table itself does not store phase relationships. Instead, phase information is typically managed by the frequency control word and the reference oscillator.

- **C: The phase relationship between a voltage-controlled oscillator and the output waveform**
  - Similar to option A, this choice refers to phase relationships, which are not directly stored in the lookup table. The DDS generates output based on frequency and amplitude, not directly on phase relationships with a voltage-controlled oscillator.

- **D: Frequently used receiver and transmitter frequencies**
  - This option is unrelated to the function of the lookup table in a DDS. While DDS can be used to generate specific frequencies, the lookup table does not contain frequency information; it contains amplitude values for waveform generation.

### Summary:
- The lookup table in a DDS is essential for producing the desired waveform by providing amplitude values.
- Understanding the role of the lookup table helps clarify how DDS technology synthesizes signals effectively. 

This knowledge is vital for the Extra Class exam, as it demonstrates an understanding of digital signal generation and synthesis techniques.