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3.8 Ground Hardware

The ground hardware will be accessible during the experiments, so we will have some flexibility to make decisions and adjustments much easier if the need arises, but the initial design for the duration of our collections will be as encompassing as possible. In the previous sections we discussed the different modulation techniques, antenna designs, and the like that will shape the hardware decisions we make in step two. In these hardware sections we talk about how those decisions will be factored in to the overall design of the experiments.


The atmospheric parameters (such as rain attenuation, gaseous absorption, sky noise, etc) [1] will be used to set the initial models. As discussed in that section, these variables can impair the communication along the high frequency band. This is alright, because we would like to measure just how each parameter effects the transitions. Antennas, amplifiers, and filters will need to be chosen based on the concluded model that will best analyze not only the values but the variation in these variables. Specifically, deep-fade antennas will be considered. Even though they are not normally considered for communication, their properties may become especially useful since the goal is to gather information over various circumstances. Below is an example of a block diagram layout for a ground transmitter in the W-band that is used on the DAVID project [2]. It is not exactly what ours would look like, but it demonstrates a good example of one that is currently designed.

Figure 1. A block diagram of a simulator model uplink satellite transmission segment in W-band.
 



The decision of where to put the terrestrial locations will shape the data we collect and analyze. For this reason research was done on finding various locations across the United States that could encompass a variable range of both atmospheric and trajectory-based parameters. Due to the large nature of the devices and the goal of the experiments, Army bases would be ideal for storing and maintaining the ground units. Security would not need to be worried about, and Army bases are located in many places throughout the country. Below is a list of 6 possible locations for the semi-permanent collection stations.



Location Elevation Angle Azimuth Comments

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AK - Fort Greely 9.46 131.38 High latitude for comparison purposes.
WA - Fort Lewis 31.56 150.43 High precipitation and cloud cover.
AZ - Yuma Proving Ground 48.41 154.80 Located in Sonoran desert.
GA - Fort Gillem 47.43 206.87 Potential base outside of Atlanta.
FL - Camp Blanding 49.88 213.08 Close to equator, so low latitude. East coast location
HI - Fort Shafter 21.64 102.86 Close to equator, so low latitude. Located far away from longitude of satellite. Potential high precipitation region.

​The geo-location information above was gathered from [3].  A possible map has been provided below for visual purposes.

​Figure 2. A map of possible ground locations at military bases laid out.



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As mentioned, the locations were chosen to provide a wide range of variation among the collection parameters. Places such as Alaska, Florida, and Hawaii were chosen to vary how close to the coordinates of the satellite the base units would be, and thus vary the elevation angle / azimuth of the dishes. Other locations such as in Washington or Arizona were chosen to vary weather conditions in hopes of collecting different information for comparison purposes. Atlanta can act as the hub, where the information can be sent and analyzed. All elevation angles and Azimuths were calculated using Eq. 1, Eq. 2, and Eq. 3 below [4] .

​References

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[1] Pratt, Timothy, Charles Bostian, and Jeremy Allnutt. Satellite Communications. Hoboken, NJ: John Wiley & Sons, 2003.

[2] Claudio Sacchi, Anelia Grigorova. Use of Trellis-Coded Modulation for Gigabit/sec Transmissions over W-Band Satellite Links. Trento (Italy)

[3] US Military Bases - Air Force Bases, Army Bases, Navy Bases. http://militarybases.com/. December 1, 2012
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[4] Pratt, Timothy, Charles Bostian, and Jeremy Allnutt. Satellite Communications. Hoboken, NJ: John Wiley & Sons, 2003.

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