An active artificial transmission line for squint-free series-fed antenna array applications

A transmission line periodically loaded with an active circuit generating a non-Foster negative capacitance is presented. As a result of this loading, a special true time delay line is obtained over a broad frequency range. The remarkable attribute of this line is that its phase velocity exceeds the speed of light in vacuum and remains linear with frequency which is impossible for passive true time delay lines. The design procedure along with simulation results are presented. This line can be employed in squint-free series-fed antenna arrays as well as in squint-free leaky-wave antennas and in delay control circuits.