Influence of Load Resonance on Operation of Negative Impedance Converter Circuits

In an ideal case, a negative impedance converter (NIC) transforms the load impedance or admittance into its negative image. However, due to non-idealities present in electronic circuitry of NIC, there will always be some conversion error. On the other hand, conversion of resonant load is, among others, important for the use in recently introduced self-oscillating antennas based on negative immittance conversion. Namely, it was noticed that operation of such transmitter is limited by the resonant nature of the antenna. Therefore, in this paper, we investigate the influence of NIC dispersion on the conversion of generic resonant load. The effect is analysed both for short circuit stable (SCS) and open circuit stable (OCS) grounded NIC based on operational amplifiers. Transient and S-parameter simulations were performed with the help of circuit theory simulator. It was noticed that both NIC types show lower conversion errors for the frequencies at which the load has capacitive character.