High-impedance amplifier for a novel 14 cm short AM/FM automotive active antenna

The design of an ultra short capacitive coupled helical AM/FM active automotive antenna with a length of only 14 cm (5.6") is investigated and its performance is presented. The antenna element produces very sharp resonances and is therefore difficult to use for broadband radio reception. The proposed high impedance amplifier concept flattens the frequency response of the very short resonant antenna, while maintaining a low noise level and a good linearity. The design has been realized and the measurements show that the new 14 cm active antenna has comparable sensitivity with 40 cm (15.8") long active monopole antennas. Field measurements indicate good performance in comparison to common passive rod antennas of 90 cm (35.4") length, both in AM and FM range.