Browse Prior Art Database

MOBILE SATELLITE SYSTEM TEST APPARATUS

IP.com Disclosure Number: IPCOM000009721D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-12
Document File: 2 page(s) / 108K

Publishing Venue

Motorola

Related People

Mike Andresen: AUTHOR [+2]

Abstract

A communications satellite using multiple beams in low earth orbit has a relatively short beam in view time. This paper describes a test apparatus which assesses the performance of a satellite com- munications system while deployed in a low earth orbit. This apparatus can also be used to perform on-orbit calibration of the transponder.

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0 M M-LA Technical Developments

MOBILE SATELLITE SYSTEM TEST APPARATUS

by Mike Andresen and Hal Hamilton

ABSTRACT

  A communications satellite using multiple beams in low earth orbit has a relatively short beam in view time. This paper describes a test apparatus which assesses the performance of a satellite com- munications system while deployed in a low earth orbit. This apparatus can also be used to perform on-orbit calibration of the transponder.

PROBLEM

  Once a satellite is deployed to a low earth orbit, determining communications transponder perfor- mance from the ground may be difficult. Some low earth orbit systems, such as Iridium, use multiple beams for coverage. These beams are in view for a short period of time during which an assessment of the receiver, transmitter and antenna system must be made. Bit error rate assessment can be a lengthy process if low bit error rates are used as the operat- ing point of the test. Performance analysis is neces- sary so that the coverage and link margin of the sys- tem can be determined. Also with the pressure to launch early in the mobile satellite system market, performing calibration of the transponder on-orbit can reduce the time to providing market services.

SOLUTION

  This device provides a method for separately evaluating the performance of an on-orbit satellite transmitter and receiver in a time efficient manner. These measurements allow the system developer to evaluate the performance of the satellite beams over the lifetime of the satellite. The use of pmgramma- ble attenuators and bit-error-rate (BER) discrimina- tors arranged in a 2% BER forcing control loop pro- vide for a direct measurement of link margin. This is an improvement over conventional measurement methods which require prolonged measurement

periods to measure very low bit-error-rates. Novel features of this apparatus are:

  l Independent uplink and downlink measure- ments

l Unique control loop architecture

  l Allows for on-orbit calibration speeding time to launch

THEORY OF OPERATION

  The Mobile Satellite Test Apparatus will be deployed when a particular SV beam is suspected of being degraded. It is the mission of the Mobile Satellite Test Apparatus to measure the extent of the degradation, if any. The Mobile Satellite Test Apparatus will acquire on the target beam and SV and establish a loop back channel.

  The Mob...