Liquid Crystal Tunable Stripline Phase Shifter

A continuously tunable phase shifter based on liquid crystal from 10 GHz to 60 GHz is presented. In this design, a larger portion of the waves propagate inside the LC mixture by making use of the stripline structure instead of the commonly used inverted microstrip line structure and thus the tunability brought by the liquid crystal is fully functioned. To demonstrate the effectiveness of the proposed structure, two delay line phase shifters based on inverted microstrip line and stripline structures are designed and simulated. The results show that, while the two structures have reflection coefficients less than −20 dB, the proposed structure achieves figure of merit values ranging from 66.4°/dB to 88.5°/dB which is on average 86 % higher than those achieved by the inverted microstrip line structure over the same band. In other words, the proposed structure can provide 86 % more phase shift while maintaining the same insertion loss.