Active Network Techniques for Improving Antenna Performance

Abstract : This study was concerned with improving the performance of electrically small antennas through the use of active-network techniques. Only antennas for the range 30-80 MHz were considered, and means were sought for reducing the noise figure of a receiving system employing such an antenna. Two types of active coupling networks were studied: negative-immittance converters (NIC), and feedback amplifiers. The results obtained show that an FET with feedback appears useful, whereas a NIC is impractical because of its excessive noise and its high sensitivity to changes in circuit and bias parameters.