Concept Flashcards

Concept Flashcards#

1. Why is modulation necessary?

To enable communication over long distances and transmit multiple signals over a single channel.

2. What is a carrier signal?

A sinusoidal signal used to carry information.

3. What is a message signal?

The information signal (voice, data, etc.) that is embedded into the carrier.

4. What does it mean to modulate a signal?

To change a property of a carrier signal to encode information.

5. What is the mathematical form of a carrier signal?

\[ v_c(t) = A_c \cos(360^\circ f_c t + \phi_c) \]

6. What parameters of a carrier can be modulated?

Amplitude, frequency, and phase.

7. What are the three basic types of modulation?

8. Why is AM more susceptible to noise?

Because noise affects amplitude, which carries the information.

9. Why are FM and PM more noise resistant?

Because the information is not contained in the amplitude.

10. What device is used to implement AM?

A function multiplier (mixer).

11. What does a function multiplier do?

Produces an output equal to the product of two signals.

12. What is the AM signal equation?

\[ v_{out}(t) = A_c\cos(360^\circ f_c t)\left[B + A_m\cos(360^\circ f_m t)\right] \]

13. What frequencies are produced in AM?

14. What is the modulation index?

\[ \alpha = \frac{A_m}{V_{bias}} \]

15. How is modulation classified?