Browse Prior Art Database

METHOD AND APPARATUS TO REDUCE RADIO INTERFERENCE OF A SATELLITE COMMUNICATION SYSTEM ON RADIO ASTRONOMY

IP.com Disclosure Number: IPCOM000004667D
Original Publication Date: 2001-Mar-27
Included in the Prior Art Database: 2001-Mar-27
Document File: 2 page(s) / 8K

Publishing Venue

Motorola

Related People

Min Sou Kim: AUTHOR [+2]

Abstract

METHOD AND APPARATUS TO REDUCE RADIO INTERFERENCE OF A SATELLITE COMMUNICATION SYSTEM ON RADIO ASTRONOMY

This text was extracted from a Rich Text Format document.
This is the abbreviated version, containing approximately 54% of the total text.

METHOD AND APPARATUS TO REDUCE RADIO INTERFERENCE OF A SATELLITE COMMUNICATION SYSTEM ON RADIO ASTRONOMY

by Min Sou Kim and Yih Guang Jan

BACKGROUND

When a new satellite communication is introduced it is a requirement posed by the world communication regulatory body that the effect of the signal radiating from this new system on existing communication systems should be below certain allowable level. When Iridium satellite communication system was introduced many radio astronomy operators worried about the interference level they would have on their sites when the Iridium system was operated. The following methods and processes have been proposed and implemented by the Iridium system engineers to reduce its possible interference on Radio Astronomy sites:

1) Implement a specification stringent transmitting filter in the transmitter

From the signal radiation patterns a spectral mask was carefully created and generated so that when the resulting signal radiation pattern follows the spectral mask its transmitting level would be within the allowable level on all sites concerned. After this spectral mask is available, a series of transmitting filers are designed, implemented and tested before an appropriate one is selected.

2) Stop radiating signal when the system reaches Radio Astronomy sites

When the system is reaching a radio astronomy site it is forced to stop its signal radiation in order to have no radio interference on the Radio Astronomy site. In other words the system is unavailable for subscribers at this time when it is near the Radio Astronomy site.

3) Move the system operating frequency away from radio astronomy frequency band

It intends to move the system operating frequency away from the Radio Astronomy frequency band. In considering radio frequency band, it is not only difficult to reallocate new communication frequency band from the already scarce available radio frequency spectrum it also needs a lot of effort of coordination and agreement from all involving countries and institutions.

4) Design complicate nonlinear antenna amplifiers

The antenna beam lit elements are carefully arranged and designed so that every antenna beam generated from the combinations of these beam lit will have desired radiation patterns. This involves not only a lot of non-linear processing it also requires a lot of trial and error implementation efforts.

5) Determine every operating frequency from a lengthy look up table

For every possible transmitting frequency it evaluates the resulting system interference levels from all possible combinations of signal frequencies existing in the system at that time. For all transmitting frequencies considered it then selects the one that generates the least interference level. Repeat this operation, a table is then created to list the desired transmitting frequency for any possible combination of transmitting frequencies.

6) Generate a uniform number of channels in each satellite switch entity

It tries to generate a uniform radio interfe...