Stability Analysis of Superluminal Waveguides Periodically Loaded With Non-Foster Circuits

Transmission lines periodically loaded with non-Foster circuits have been shown to have superluminal propagation in the prior literature. They were proposed for applications such as broadband leaky-wave antennas and true-time-delay lines for series feeds of antenna arrays. This letter presents results of an investigation on superluminal waveguides with periodic non-Foster loads. Such waveguides are found to be stable for small line lengths, but have stability problems for practical line lengths containing many unit cells.