Fig. 17 shows the complete architecture of such an antenna
element. The structure consists of eleven layers of FERRO A6
LTCC substrates. Four different functional blocks can be
identified: The antenna block (first 6 layers from the top), the
hybrid ring coupler block with 2 layers, the calibration network
(2 layers) and finally the RF-to-antenna interface (1 layer). The
different functional blocks of the antenna element and their
specific design issues are described in detail in [7] and will be
discussed in the oral presentation.