Millimeter-wave beam former using liquid crystal

By using liquid crystal, a beam former is fabricated and evaluated that can electrically steer the beam direction at millimeter wave frequencies. The beam former is constructed by alternately stacking liquid crystal and copper foil layers. By using a membrane impregnated with liquid crystal as the liquid crystal layer, a simple configuration is realized that does not require a solid substrate or spacer. In the experiment, it is found that the maximum phase shift is about-420° at 60 GHz and the beam steering angle is about ±13°. The structure works in a broad bandwidth from 50 to 75 GHz. The structure is also used as a dielectric lens to correct the phase distribution of electromagnetic waves fed from a pyramidal horn antenna. It is therefore demonstrated that various beam forming functions can be obtained. On the other hand, the insertion loss is 5 to 8 dB. To reduce the loss, it may be necessary to reduce the dielectric loss of the liquid crystal at millimeter wave frequencies.