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DIGITAL BEAM FORMING

The absolute high end of phased-array technology employs DBF architectures. Each antenna element is equipped with a complete down-/up-converting circuit; the received/transmitted signal is digitalized at baseband and directly processed by a digital processing unit (e.g. a DSP or FPGA). This is not only the most complex system, but also the most flexible one. Because the beam forming takes place completely within the DSP unit, and all kinds of signal processing operations can be performed there. This technology can be used for any frequency band, but it is of special interest in airborne Ka-band satellite terminals for broadband multimedia services like ‘Internet in the Sky’. The terminal is divided into a separate transmit (30 GHz) and receive (20 GHz) antenna array. The frequency bands are based on future multimedia satellite systems.

    

The next figure depicts an 8x8 patch array. The basic element design is based on circularly polarized antenna patches. A key feature of the antenna concept is the modular build-up, which means the number of elements to different applications.