首页|High-Efficiency Circularly Polarized Phased Array Based on 5 μm-Thick Nematic Liquid Crystals:Design,Over-The-Air Calibration,and Experimental Validation
High-Efficiency Circularly Polarized Phased Array Based on 5 μm-Thick Nematic Liquid Crystals:Design,Over-The-Air Calibration,and Experimental Validation
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This paper presents a systematic investigation and demonstration of a K-band circularly polarized liquid-crystal-based phased array(LCPA),including the design,over-the-air(OTA)in-array calibration,and experimental validation.The LCPA contains 16 phase-shifting radiating channels,each consisting of a cir-cularly polarized stacked patch antenna and a liquid-crystal-based phase shifter(LCPS)based on a loaded differential line structure.Thanks to its slow-wave properties,the LCPS exhibits a maximum phase-shifting range of more than 360° with a figure of merit of 78.3(°)·dB-1 based on a liquid crystal layer with a thickness of only 5 pm.Furthermore,an automatic OTA calibration based on a state ergodic method is proposed,which enables the extraction of the phase-voltage curve of every individual LCPA channel.The proposed LCPA is manufactured and characterized with a total profile of only 1.76 mm,experimentally demonstrating a scanned circularly polarized beam from-40° to+40° with a measured peak gain of 12.5 dBic and a scanning loss of less than 2.5 dB.The bandwidth of the LCPA,which satisfies the require-ments of port reflection(|S11|)＜-15 dB,an axial ratio(AR)＜3 dB,beam squinting＜3°,and a gain vari-ation＜2.2 dB,spans from 25.5 to 26.0 GHz.The total efficiency is about 34％,which represents a new state of the art.The use of the demonstrated low-profile LCPA to support circularly polarized scanning beams,along with the systematic design and calibration methodology,holds potential promise for a vari-ety of millimeter-wave applications.
Circularly polarizedLiquid crystalLiquid-crystal based phased array(LCPA)Phase shifterOver-the-air(OTA)calibration
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