Lesson 32 Flashcards#
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1. What two conditions must be met for successful communication?
Line-of-sight (LOS)
Sufficient received power (or SNR above threshold)
2. What does the Friis equation calculate?
The received power at the antenna.
3. Write the Friis equation.
\[
P_R = P_T G_T G_R \frac{\lambda^2}{(4\pi R)^2}
\]
4. What happens to received power if distance doubles?
It decreases by a factor of 4.
5. What happens to received power if transmitted power doubles?
It doubles.
6. How do antenna gains affect received power?
They increase received power linearly.
7. What is the relationship between frequency and wavelength?
\[
\lambda = \frac{c}{f}
\]
8. Why do lower frequencies travel farther?
They have longer wavelengths, which increases received power.
9. What units must distance be in when using the Friis equation?
Meters.
10. What is SNR?
The ratio of signal power to noise power.
11. Write the SNR equation.
\[
SNR = \frac{P_{signal}}{P_{noise}}
\]
12. Write the thermal noise equation.
\[
P_{noise} = k T_{sys} BW
\]
13. What increases noise power?
Higher temperature
Larger bandwidth
14. What is a decibel (dB)?
A logarithmic representation of a power ratio.
15. Write the decibel equation.
\[
G_{dB} = 10 \log_{10}(G)
\]