Integrated Ultra-Low-Loss 4-Bit Tunable Delay for Broadband Phased Array Antenna Applications

We demonstrate the design, fabrication, and characterization of a 4-bit tunable delay in an ultra-low-loss ${\rm Si}_{3}{\rm N}_{4}$ planar platform. Temporal delays up to 12.35 ns with resolution of 0.85 ns are measured, for a total of 2.407 meters of propagation length. The TE waveguide propagation loss is measured to be $(1.01\pm 0.06)~{\rm dB}/{\rm m}$ at a wavelength of 1550 nm with the lowest loss of $(0.57\pm 0.08)~{\rm dB}/{\rm m}$ at 1591 nm.