Concept Flashcards#
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?
Add \(f_c\) to each \(f_m\)
Compute amplitudes using \(\frac{A_m A_c}{2}\)
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.