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SPACELINK DIGITAL LINK BUDGET SOFTWARE FOR COMSAT SYSTEMS

By Vanessa Martinez,2014-12-13 11:23

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RCW Communications and Electronics Inc. January 1999

SpaceLink - Digital Link Budget Software for Communications Satellite Systems

Most link budgets are prepared using spreadsheet software. The budgets tend to be quite detailed and, therefore, have the strong possibility of human errors that are difficult to detect since the code is hidden behind the spreadsheet shells. Moreover, the formulae are often modified to view special cases – changes which can be easily forgotten by the time a

new case is analyzed. The only way to verify the result is to check each cell of the spreadsheet containing code – a very tedious task. SpaceLink offers a means to prepare a link budget for common types of digital transmission and to quickly verify spreadsheet link budgets by providing a second computation.

The SpaceLink software system guides the user in the preparation of common types of digital link budgets within a short time. Important features of this software are as follows:

; Guides the user in the preparation of a communications satellite link budget for digital

transmission

; Software is written in robust Microsoft Visual Basic language providing standard,

familiar Windows performance. Operates under Windows 95 and 98.

; Program is ideal for Laptops as the Windows are sized to fit a Laptop screen (Window

displays look even better on large screens which provide more space for displaying

multiple windows)

; Easy to use – for anyone familiar with Windows 95 and the preparation of link budgets ; A training tool for students – the manual contains most of the formulae except the ITU

formulae which can be obtained by purchasing the relevant ITU documents which are

available at the ITU Web site for a nominal cost. Remaining formulae are based on

industry standard practice. References are provided including specific ITU references. ; Software is modularized into each major component of the link

; Software displays and prints uplink, downlink and end-to-end link budgets ; Also prints link budgets to files for later insertion into reports

; ITU propagation model including water vapor, oxygen, clouds and rain attenuation ; Link polarization (LP and CP) accounted for with respect to rain attenuation, antenna

polarization coupling loss and polarization discrimination

; Modules include:

; Carrier frequency assignment

; Uplink modulation and encoding

; Separate downlink modulation and encoding for regenerative repeaters

; Uplink earth terminal. Includes ITU EIRP limit.

; Downlink earth terminal

; Propagation

; Satellite repeater (including OBO controlled, fixed gain and regenerative repeater

configurations)

; Interference (uplink and downlink). Includes optional downlink C/I adjacent

satellites computation from ITU limit on adjacent satellite PFD emissions and earth