Sensitivity of negative impedance converter circuit with respect to PCB design effects

Performance characteristics of Electrically Small Antennas are limited by fundamental physics. Using Non-Foster elements into antennas structures appears like an opportunity to overshoot those limits. In this paper, a Negative Impedance Converter circuit is designed for antenna applications at 868 MHz. These active circuits, that produce Non-Foster negative capacitance or inductance, are known as sensitive circuits due to their nonlinearities that can produce instabilities. Thus, designing Negative Impedance Converters at Ultra High Frequency bands becomes quite challenging. Accurate design is strongly recommended to predict the final behavior of the circuit. The Negative Impedance Converter sensitivity is investigated with respect to Printed Circuit Board design through both simulation and measurement results.