# Multi-Gigabit Microwave and Millimeter-Wave Wireless CommunicationsAnswers to RF Cafe Quiz #34

All RF Cafe quizzes would make perfect fodder in employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job.

Note: Some material based on books have quoted passages.

This quiz is based on the information presented in Multi-Gigabit Microwave and Millimeter-Wave Wireless Communications, by Jonathan Wells. Artech House is the publisher. Note: Some of these books are available as prizes in the monthly RF Cafe Giveaway.

1.  Which entity is the primary regulatory agency in the world with responsibility for coordinating
shared global use of the radio spectrum?

d)  ITU (International Telecommunication Union)
The ITU is the primary regulatory agency in the world with the responsibility for coordinating
the shared global use of the radio spectrum. (see page 5)

2.  What is a primary obstacle to FSO (Free Space Optics) terrestrial usage?

a)  Very high attenuation.
Communications at optical  frequencies are especially sensitive to atmospheric and
environmental conditions, particularly fog, which can drastically limit distance. (see page 13)

3.  Which condition causes the least amount of attenuation on electromagnetic signals?

b)  Dry air.

See the chart of atmospheric attenuation versus frequency on page 25.

4.  What is the equation for determining attenuation factor (specific attenuation) due to snow and ice?
(R=snowfall rate in mm/hr, λ=wavelength in mm)

d)  Attenuation Factor = [(0.00349*R1.6)/λ4] + [(0.00224*R)/λ]
The effects of snow and ice on atmospheric attenuation at high frequencies have not been
as well studied as those of rain and fog. (see page 37)
See author's reference document for attenuation factor

5.  What is the equation for determining attenuation due to foliage?
(f=frequency in MHz, R=depth of foliage in m)

d)  Loss = 0.2f0.3R0.6
Losses due to foliage can be significant at high frequencies. (see page 38)
(BTW, a, b, and c are all equivalent equations)

6.  What is a primary feature of a plesiochronous digital hierarchy (PDH) system?

a)  Running in a state where different parts of the network are nearly,
but not quite perfectly, synchronized. (see page 48)

7.  What does the image to the right depict?

b)  256 QAM with phase noise
Phase noise manifests itself as
jitter in an IQ constellation. An
ideal pattern is also shown for
reference. (see page 66)

8.  Which frequencies in the 60 GHz band are allocated by the FCC for unlicensed use?

a)  57 to 64 GHz
In 2001, the FCC allocated 7 GHz of spectrum from 57 GHz to 64 GHz for unlicensed use.
(see page 104)

9.  What is a link budget?

d)  An accounting of all gains and losses in a communications system
A link budget is a method of accounting for all the gains and losses in a communications system,
from the power out of the transmitter, through the free space medium, to the received signal at