Flexible Active Antenna

A target application of the High Speed, High Frequency Electro-Photonic Analog-to-Digital Converter (PHASER) technology has been identified in electronically steerable multibeam antenna (active antenna) for future communication satellites.

The general trend in the satellite telecommunication business is the demand for an ever increasing capacity (or bandwidth). The next generation of broadband Internet satellite is often called as High Throughput Satellites (HTS) or Terabit satellites. To achieve an higher throughput, future satellites shall operate in Extremely High Frequencies (typ. above 20 GHz in Ka-band and Q/V-band) at high speed (typ. hundreds of Mbps per carrier) and over a large multibeam (or cellular) coverage (typ. hundreds of spot beams or cells). The utilization of multibeam active antenna seems an attractive solution for generating a cellular coverage while allowing some flexibility in the management of coverage and traffic. Active antennas, also called electronically steerable antennas require a special piece of equipment: a Beam Forming Network (BFN). Among the available technologies (microwave, optical) for BFN, the digital technology is the most promising. Nevertheless, there is a technological bottleneck: the analog to digital conversion prior to the digital processing. The PHASER technology should be able to break free this bottleneck.

Furthermore, various types of digital processing implemented in the digital BFN will allow new services and will increase performances. For examples, the Spatial Division Multiple Access (SDMA) technique allows doubling the data rate and increasing the frequency reuse factor (and consequently the satellite capacity); Anti-jamming processing could reduce the interference levels between users or with other satellite systems.

The applications of flexible active antenna range from GEO mobile satellite (similar to Inmarsat), to broadband multispot beam satellites (Ka-Sat next generation), to military satellites… DBFN are already used in the active antenna of GEO mobile satellite (Inmarsat 4 for example) operating in the SHF (L/S-band).