Tunable plasma-based microwave waveguide time delay

Design of a plasma time delay unit (TDU) for microwave waveguides is proposed. The TDU comprises a base structure with two parallel grounded metal plates and an ultra-low loss dielectric strip waveguide. To tune the phase delay of the TDU, we surround the dielectric strip waveguide with plasma of tunable density and length. Based on the dispersion diagram at W-band, plasma-induced phase delay of up to 2π can be obtained by changing the plasma density. A systematic model-based parameter study of the physical quantities of this proposed structure has been carried out. The methodology is general and could be applied to other frequency regimes, to the extent that generation of the appropriate plasma is practical. The proposed design could be potentially used in an array of individually tunable elements for a high power beam-steering lens.