Successful realization of Non-Foster circuits for wide-band antenna applications

Non-Foster circuits (NFCs) are promising for numerous microwave and antenna applications because they are not limited by the gain-bandwidth product. Although NFCs can be very useful in many applications, successful realization of these circuits is difficult because they suffer from several issues, including losses, noise, and instability. As a consequence, an accurate and efficient design technique is necessary to predict and correct any undesired behavior. In this paper, we introduce a successful realization of grounded NII and floating NIC for wide-band electrically small antennas. We show the effect of the transmission lines on stability and losses. Measured results of the realized gain of two antennas showing improvement of 11.5 and 15 dB is provided. Measured time-domain data also shown to demonstrate the system is stable.