Novel low-loss delay line for broadband phased antenna array applications

The microwave propagation velocity along a nonlinear transmission line is a function of dc bias, hence, a nonlinear transmission line (NLTL) can be utilized as a broadband delay line. A hybrid NLTL has been fabricated in a proof-of-principle experimental concept test where a 1.1-ns true time delay with <4-dB insertion loss has been measured in good agreement with theory. A 2×2 NLTL-based antenna array has been utilized to demonstrate beam steering at 5 GHz. Using parameters appropriate to varactors tested by our group at 60 GHz, a monolithic NLTL is predicted to exhibit <3.4-dB insertion loss and 200 ps delay at 20 GHz