A new approach to active antenna design

Design considerations for wide-band active antenna circuits for frequencies up to 30 MHz are presented. High performance is obtained by using unusual amplifier types having a virtually grounded input electrode of the input active device, and a large amount of negative feedback over several stages. The realized antennas with a physical length of 0.5 m have a flat frequency response from 5 kHz to 30 MHz and extremely low distortion (second-order intercept >+70 dBm, third-order intercept > +50 dBm). The antennas are thoroughly protected against statics; without sacrificing the high dynamic range. Output power levels up to +28 dBm can be handled. The electric field strength may exceed 10 V/m. The equivalent input noise field strength amounts to about 25 nV/m
\sqrt{Hz}
.