A feed structure for a radio frequency antenna, comprising: a plurality of radio frequency antenna elements; and a plurality of detectors, each one of the detectors being coupled to a corresponding one of the radio frequency antenna elements. In the ceramic member, an index of orientation degree is not less than 0. A second electrically conducting connection, which may comprise sliding contacts, is provided for transmitting the electrical measurement signals. The elastomeric material has a gap at the seat to allow electrical connection of the conductive connecting structure with a semiconductor die. The second stage has symmetrical pull-up and pull-down circuits.