Matching electrically small antenna using non-Foster circuit in the FM-band

This paper presents a non-Foster circuit design to match electrically small monopole in the FM band. This matching circuit uses Linvill´s floating negative impedance converter, to generate a negative capacitor to cancel the large reactance component in the input impedance of small monopole. This overcomes the conventional gain-bandwidth limitation of electrically small antenna (less than 0.1λ). Several aspects of the circuit stability are considered, such as the biasing network, and the PCB layout to reduce parasitic effect. Both the frequency-and time-domain analyses are carried on to predict the potentially unstable points of the designed network before fabrication. When the non-Foster matched monopole is employed as receiver, measurement results demonstrate both received power gain increment and SNR improvement. Detailed design procedures, fabrication issues and measured data are provided.