Liquid Crystal Tunable mm Wave Frequency Selective Surface

Design and Measurement of Reconfigurable Millimeter Wave Reflectarray Cells With Nematic Liquid Crystal

“…The permittivity value of the tunable layer was varied between e// -3.2 (biased state) and e± -2.8 (0 V state), and for each state tan 6 -0.02 was used in the computer model. These values were obtained previously for Merck BL037 LC mixture [5], by data fitting computed results to experimental data over the frequency range 110-170 GHz [1]. The construction method that was used to fabricate the two structures is described and the amplitude and phase of the reflected signals, which were obtained from a novel quasi-optical measurement set up, are shown to be in close agreement with numerical results.…”

Spiral antenna with reconfigurable HIS using liquid crystals for monopulse radar application

“…THEORY OF OPERATION Liquid crystals (LC) are widely used for display applications such as flat screen televisions, personal computer monitors and mobile phones [2]. Lately, this technology has also been employed to create reconfigurable microwave and millimeter wave devices and antennas by exploiting the unique dielectric anisotropic behavior of the nematic phase, which enables the permittivity of LC material to be varied when a small voltage is applied to the structure [3][4][5][6]. This is attributed to the orientation of the molecules in relation to the RF field direction; 1) perpendicular, ε⊥ to the electric field (unbiased state), or 2) parallel, ε// to the electric field (biased state), as stated in [4] for reflectarray antennas.…”

A millimeter-wave quasi-optical grid phase shifter using liquid crystal

“…Recent advances in microwave and millimeter-wave devices which exploit the dielectric anisotropy of liquid crystal (LC) materials have mainly been accomplished using planar waveguide structures [1,2] and quasi-optical structures [3,4,5]. In the former, a microstrip delay line using dual-frequency switching mode LC [1] and a microstrip phase shifter using polymer-dispersed LC [2] have been developed to improve insertion loss and time response.…”

“…In the former, a microstrip delay line using dual-frequency switching mode LC [1] and a microstrip phase shifter using polymer-dispersed LC [2] have been developed to improve insertion loss and time response. Quasi-optical devices utilizing LC materials have been proposed to realize reconfigurable optics [3,4] and to generate an electronically tunable bandpass filter [5].…”