Chapter 17: Wireless Signals and Modulation Flashcards
The frequency range from around 3 kHz to 300 GHz.
Radio frequency (RF)
What category of frequency ranges do the 2.4 and 5 GHz bands used for WLANs fall into?
Microwave
T/F
The 5 GHz WLAN band contains 4 contiguous bands 5.150 and 5.825.
False
There is a gap between 5.350 and 5.470
- 150 to 5.250 GHz
- 250 to 5.350 GHz
- 470 to 5.725 GHz
- 725 to 5.825 GHz
A contiguous range of frequencies.
Band
Specific frequencies that bands are divided into.
Channels
How wide is each channel in the 2.4 GHz band?
5 MHz (.005 GHz)
What do wireless devices use to ignore parts of a signal that falls outside the bandwidth boundaries?
Spectral Mask
The range of frequencies used by a single channel or
a single RF signal.
Bandwidth
T/F
Channel width should be less than signal bandwidth.
False.
Signal bandwidth should be less than the channel
width.
A measure of shift in time relative to the start of a cycle.
Phase
Phase is measured in:
A. MHz
B. Ohms
C. Degrees
D. kHz
C. Degrees
A measure of the physical distance that a wave travels over one cycle.
Wavelength
T/F
Radio waves travel at exactly the speed of light through air.
False
Radio waves travel at exactly the speed of light through a vacuum.
Radio waves travel at slightly less than the speed of light through air.
What happens to wavelength as frequency increases?
Wavelength decreases
The strength of a wireless signal.
Amplitude
Amplitude is measured in:
A. Amps
B. Watts
C. Joules
D. Voltage
B. Watts
A function that uses logarithms to compare one absolute measurement to another.
dB
A value of 0 dB means the two absolute power levels are equal.
Law of zero.
A value of 3 dB means that the power value of
interest is double the reference value; a value of −3 dB means the power value of interest is half the reference.
Law of 3s.
A value of 10 dB means that the power value of interest is 10 times the reference value; a value of −10 dB means the power value of interest is 1/10 of the reference. When P2 is 10 times P1, the ratio is always 10. Therefore,
Law of 10s.
An ideal, theoretical antenna that radiates RF equally in every direction.
Isotropic antenna.
Effective isotropic radiated power (EIRP)
The power level that is radiated from the antenna.
What is the formula needed to calculate EIRP?
(transmitter power level + antenna gain) - cable length
Cumulative sum of gains and losses measured in dB over the complete RF signal path
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