17. Wireless Signals and Modulation

Question 1

What is a frequency?

Answer 1

The number of times a signal makes a complete cycle in 1 second

Question 2

In what is frequency measured?

Answer 2

Herts –> x1000 Khz –> x1000 Mhz –> x1000 Ghz

Question 3

What is the 2,4 Ghz band?

Answer 3

2.4 - 2.4835

Question 4

What is the 5Ghz band?

Answer 4

5. 150 - 5.250
6. 250 - 5.350
7. 480 - 5.725
8. 725 - 5.825

Question 5

How is the actual frequency range called?

Answer 5

Bandwidth

Question 6

What is important about the phase of a signal?

Answer 6

Signals in phase tend to add

Signals out of phase ten to cancel each other out

Question 7

What is the EIRP?

Answer 7

Transmitting power level + length of cable + antenna gain

Question 8

What is dBd (dB-dipole)?

Answer 8

When a diabolic antenna has been used you need to add 2,14 dBi

Question 9

What is the link budget?

Answer 9

Transmitting power level - length of cable + antenna gain - free space loss + antenna gain - length of cable

Question 10

What is a fact about free space path loss?

Answer 10

• The signal weakens faster near the transmitter but more slowly farther away.

Question 11

What is the RSSI?

Answer 11

Signals power 0-255

Question 12

What is the sensitivity level?

Answer 12

Signal below is not heard by the receiver

Question 13

What is the SNR?

Answer 13

Difference between the signal and the noise

Question 14

What are the 3 goals for a RF modulation scheme?

Answer 14

• Carry data at predefined rate
• Be reasonably immune to noise
• Be practical to transmit and receive

Question 15

What are the 3 things a modulation scheme can alter?

Answer 15

• Frequency
• Phase
• Amplitude

Question 16

What is MIMO?

Answer 16

Multiple-input multiple-output

Question 17

What is SISO?

Answer 17

Single-input Single-output

Question 18

What is maximal ratio combining?

Answer 18

When signal is transmitted through MIMO the receiver MRC can combine them to make the best signal.