Quadrature hybrid for feeding DVB-T antenna arrays transmitting circular polarized waves

In this paper a feeding network for DVB-T transmitting antenna arrays is presented, which provides twelve outputs from a single source with six of them being phase shifted by 90 degrees. This allows the feeding of six circular polarized transmitting antennas or alternatively an antenna array. The network is purely passive and operates in a frequency range from 470MHz to 1 GHz. It is composed of a quadrature hybrid, whose two outputs are each split by a directly connected power divider into six branches. The network is characterized by its planar structure which makes it easy to fabricate and insensitive against process variations due to its relaxed geometry parameters. Moreover the network provides a high power capability qualifying it for use in transmitter systems. The deviation of the phase difference from its design value of 90 degrees has been measured to be less than 2.7 degrees while the amplitudes of an in-phase branch and the corresponding ninety degree branch differ by less than 0.6 dB. The measured insertion loss within the DVB-T band does not exceed 0.9 dB.