Millimetre-wave beam steering with analog-resolution and minimised distortion based on liquid crystals tunable delay lines with enhanced signal-to-noise ratios

Millimetre-wave beam-steering distortions are due mainly to unbalanced feeding amplitudes among the delay lines network. To compensate for this, active amplifiers or attenuators are employed, increasing the circuit complexity and costs, whilst compromising the passive array advantage. This work presents a passive millimetre-wave distortion-free beam steering solution with analog resolution in liquid crystal planar delay line technology. Enclosed coplanar waveguide (ECPW) tunable delay lines with 0-180 degrees and 0-360 degrees phase-shifting ranges are prototyped respectively. A novel impedance matching and mismatching approach for amplitude compensation is proposed and verified, as evidenced by the 67 GHz measured maximum insertion loss of -4.37 dB (variation up to 5%) for the 0-180 degrees delay line, and -8.28 dB (variation up to 8%) for the 0-360 degrees device. Based on a smart combination of the 0-180 degrees and 0-360 degrees ECPW, an optimised delay lines deployment scheme is proposed for two-dimensional beam steering with a fault tolerance capability and a minimised systematic insertion loss in total on the feeding network.