1. Review of Satellite Systems and Fundamentals

Question 1

why is the downlink typically on the lower band?

Answer 1

• Tougher to construct hgiher frequency recievers
• uplink are able to output more power and thus uplink receivers can be made more sensitive and are therefore more suited as an uplink

Question 2

What four kinds of interference need to be considered for satellite coms?

Answer 2

1. Satellite w/ terrestrial station
2. terrestrial station with satellite
3. earth station with terrestrial station
4. terrestrial with earth

Question 3

Which bodies regulate the use of satellite bands and which bands are the most utilised?

Answer 3

1. ITU (ITU-R), (ITU-T), (ITU-D)
2. Ku (10 - 20 GHz) - Ka (20 - 40 GHz)

Question 4

The ITU defines three regions. What must be considered for communications between two different regions?

Answer 4

The bands are often not overlapping and so consideration must be made to accomodate the change in band.

Question 5

How is the Van Allen belt defined?

Answer 5

• A zone of energetic charged particles, most of which originate from the solar wind
• They are captured by and held around a planet by that planet’s magnetic field.
• Solar cells, integrated circuits, and
  sensors can be damaged by radiation

Question 6

What are three advantages and disadvantages of using GEO?

Answer 6

A:
1. High coverage
2. Low(er) doppler correction
3. Consistant coverage of the same spot on earth’s surface

D:
1. Lots of loss (35000km path to earth)
2. Poor coverage of the poles
3. Large delay ~0.12s

Question 7

How is a satellite constellation defined?

Answer 7

A group of satellites working in concert, with coordinated ground coverage, operating together under shared control.

Question 8

Name two types of LEO constellation configurations?

Answer 8

1.Star Polar
2. Delta

Question 9

Why is a linear polarization more suited to a static transceiver system?

Answer 9

They have a constant relationship with each other and so the linear polarisations can be aligned with maximum gain. i.e. minimise losses from XPD.

Question 10

Explain the concept of Faraday rotation

Answer 10

• In the ionosphere, charged particles exposed to UV from the sun interact with ku band linear channels.
• The interaction causes rotation and thus depolarisation resulting in losses in the link.