On the performance of negative impedance converters (NICs) to achieve active metamaterials

One of the main drawbacks when designing microwave circuits or antennas based on metamaterial particles is its inherent low bandwidth and not very good efficiency. An attempt to overcome this problem is based on using negative impedance converters (NICs). Although the use of NICs have been proposed as a solution to increase the bandwidth of electrically small antennas, they suffer from many problems such as stability performance, bias and the maximum frequency that can be achieved. In addition, the application of NICs has been restricted to low frequency applications in order to avoid the previous problems. This paper makes a study on the performance of NICs for active metamaterial applications. The main contributions of the present paper is that it takes into account the non-linear equivalent circuit of the NICs to find out its performance for active metamaterial applications. From that study it can be concluded that NICs can work up to a few GHz.