Lesson 29 Flashcards

Lesson 29 Flashcards#

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1. What happens when a message signal contains multiple frequencies?

Each message frequency produces two output frequencies:

  • \(f_c + f_m\)

  • \(f_c - f_m\)

2. How many output frequencies are produced for $N$ message frequencies?
\[ 2N \text{ frequencies} \]
3. Where are AM frequencies located in the spectrum?

They are symmetric about the carrier frequency \(f_c\).

4. How are upper sideband frequencies calculated?
\[ f_{USB} = f_c + f_m \]
5. How are lower sideband frequencies calculated?
\[ f_{LSB} = f_c - f_m \]
6. How is the amplitude of each sideband determined?
\[ A = \frac{A_m A_c}{2} \]
7. What is the step-by-step method to build an AM spectrum?

  1. Add \(f_c\) to each \(f_m\)

  2. Compute amplitudes using \(\frac{A_m A_c}{2}\)

  3. Reflect around \(f_c\)

8. What is bandwidth?

The range of frequencies occupied by a signal.

9. How is bandwidth calculated?
\[ BW = f_{high} - f_{low} \]
10. What is the bandwidth of an AM signal?
\[ BW = 2f_{m,\ max} \]
11. What is Amplitude Shift Keying (ASK)?

A digital modulation scheme where amplitude represents binary values.

  • 0 → low amplitude

  • 1 → high amplitude

12. What is Frequency Shift Keying (FSK)?

A digital modulation scheme where frequency represents binary values.

  • 0 → one frequency

  • 1 → another frequency

13. What is Frequency Division Multiplexing (FDM)?

A method where multiple signals are transmitted simultaneously using different frequency bands.

14. How does FDM prevent signal interference?

By assigning each signal a unique frequency band and using filters to limit bandwidth.

15. What role do low-pass filters play in FDM systems?

They limit each signal’s bandwidth to prevent overlap with other channels.