ECE 5233 Satellite Communications. Prepared by: Dr . Ivica Kostanic Lecture 6: Satellite sub-systems (Section 3.1-3.4). Spring 2014. Outline . Satellite subsystems Communication subsystem Satellite transponders Examples.
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Dr. Ivica Kostanic
Lecture 6: Satellite sub-systems
Important note: Slides present summary of the results. Detailed derivations are given in notes.
Major components of a Lockheed Martin remote sensing satellite
BBC Documentary - How to build a satellite: https://www.youtube.com/watch?v=_Rp53U4mzZA
Example of spin stabilized satellite
Different methods for satellite stabilization
Boeing 376 – one of the most popular GEO Comm. Satellites
Operates in C, Ku bands
Usually 24 transponders
50 satellites over five continents, used by more than 20 companies
Block diagram of TTC&M system
Block diagram of solar power generation system
Example 1. Consider a case where a spin-stabilized satellite has to generate 2000 watts of electrical power from the solar panels. Assuming that the solar flux falling normal to the solar cells in the worst case is 1250W/m2, the area of each solar cell is 4 cm2 and the conversion efficiency of the solar cells including the losses due to cabling, etc., is 15 %, determine the number of solar cells needed to generate the desired power. What would be the number of cells required if the sun rays fell obliquely, making an angle of 10◦ with the normal?
Required number of cells: 83777
For 10% angle, required number of cells is 85070
Example 2. It is desired that the battery system on board the satellite is capable of meeting the full power requirement of 3600 watts for the worst case eclipse period of 72 minutes. If the satellite uses nickel–hydrogen cells of 1.3 volts, 90 A h capacity each with an allowable depth of discharge of 80 %, and discharge efficiency of 95 %, find
Outline of satellite communication system
Basics of “bent pipe” architecture
Satellite with onboard processing
Example of transponder arrangement for RCA’s SATCOM
1. Input signal
3. Output signal- translated by frequency of LO
2. After mixing stage