Abstract
Novel designs of two different negative impedance converter (NIC) circuits, one is employing bipolar junction transistors (BJTs) and the other is employing junction field effect transistors (JFETs), operating in ultra-high frequency (UHF) band are investigated. The circuits are designed for passive radio-frequency identification (RFID) tag antennas to achieve better matching characteristics. A microstrip dipole antenna with an integrated negative impedance converter designed to cancel out the input capacitance of the antenna at the resonance frequency is designed, simulated, fabricated and measured. Obtained simulation results are compared to those of the same antenna without the NIC circuit and the improvement in operation bandwidth and input reflection coefficient is observed.