WHY A COST PROJECT ON ACTIVE ANTENNAS ?

Active antennas for broadcasting and fixed communications

For broadcasting and fixed communications, complex antennas are required on board broadcast satellites to concentrate the limited power avaible into the desired coverage regions without interference to neighbouring areas (fig.1), which use the same frequencies for different programmes.

Fig.1 Satellite TV and fixed communications : antenna contoured beams footprint (Courtesy ESA/ETEC)

Contouring antenna beam footprints for direct TV broadcasting requires large reflectors with optimum surface shaping or with many feed elements and complex microwave circuits. The same applies to communication space systems where, in addition, satellites can be moved to a different geostationary orbit location, and beams must be reconfigured to serve other regions. Fig. 2 shows an example of contoured beam satellite antenna developed in Germany for the INTELSAT VIII communication satellite.

Fig.2 DASA array fed reflector antenna for the satellite INTELSAT VIII (Courtesy DASA)

With the advent of multimedia interactive communications, satellite antennas will require even more flexibility to change coverages and possibly operators during the 10 to 15 year lifetime of the satellite. Home users will require sophisticated transmitting and receiving antennas capable of fast access to multiple satellites. These will be active or semi-active arrays or array-fed reflectors based on the types investigated in the COST project 245.

COST-245 Summary report

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Mars 1997 Content Responsible : Technical Manager : Webmaster@lema.epfl.ch