*Question E7C06:
What are the characteristics of an elliptical filter?*  

*Correct Answer is  C: Extremely sharp cutoff with one or more notches in the stop band*  

### AI Response: (may contain errors)  

An elliptical filter is a type of analog filter that is characterized by its sharp cutoff and specific behavior in the stop band. Let's break down the correct answer and the other choices.

### Correct Answer: 
**Extremely sharp cutoff with one or more notches in the stop band.**

- **Explanation**: 
  - Elliptical filters are designed to have a very sharp transition between the passband and the stopband. This means they can effectively filter out unwanted frequencies while allowing desired frequencies to pass through with minimal loss.
  - The notches in the stop band are a result of the filter's design, which allows for specific frequencies to be attenuated more than others, creating a more complex frequency response.

### Why the Other Choices are Incorrect:

- **A: Gradual passband rolloff with minimal stop-band ripple**  
  - **Incorrect**: This describes a filter with a gentle transition and minimal variations in the stop band, which is more characteristic of Butterworth filters, not elliptical filters.

- **B: Extremely flat response over its pass band with gradually rounded stop-band corners**  
  - **Incorrect**: This describes a filter that maintains a flat response in the passband, which is typical of Chebyshev filters. Elliptical filters do not have a flat passband response; they have ripples in the passband.

- **D: Gradual passband rolloff with extreme stop-band ripple**  
  - **Incorrect**: This suggests a filter that has a slow transition and significant variations in the stop band, which is not a feature of elliptical filters. Elliptical filters have a sharp cutoff and controlled ripple, not extreme variations.

### Summary:
- Elliptical filters are known for their sharp cutoff and the presence of notches in the stop band, making them effective for applications requiring precise frequency selection.
- Understanding the characteristics of different filter types is crucial for selecting the right filter for specific applications in radio communications.