Liquid crystal microwave phase shifter

Dolfi, Daniel; Labeyrie, M.; Joffre, Pascal; Huignard, Jean‐Pierre

doi:10.1049/el:19930618

Cited by 113 publications

(60 citation statements)

References 2 publications

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“…A 50-nm-thick alignment film was used to determine the initial alignment of the LC molecules without bias voltage. Dolfis group [11] made the initial alignment perpendicular to the surface of the substrate and the direction of microwave propagation, but in this variable delay line we set the direction of the initial alignment parallel to the microwave propagation direction as shown in Fig. 2.…”

Section: Design and Test Fabricationmentioning

confidence: 99%

“…Lims group reported a voltage-controlled millimeter-wave variable phase shifter implemented by filling a waveguide with nematic LC [10]. Dolfis group reported a wide-range microwave and millimeter-wave variable phase shifter that employs nematic LC as the dielectric of microstrip lines [11,12]. However, we can guess from the measured dielectric characteristics of LC materials [1013], that the insertion loss of LC microwave devices is too large for practical use.…”

Section: Introductionmentioning

confidence: 97%

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Design of a microwave variable delay line using liquid crystal, and a study of its insertion loss

Kuki

Fujikake

Nomoto

et al. 2002

Electron Comm Jpn Pt II

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SUMMARYA microwave variable delay line was designed and fabricated using a nematic liquid crystal for the dielectric substrate of the microstrip line, and the phase characteristics and insertion losses of the device were evaluated. The phase shift characteristics were found to be in close agreement with the design value, indicating the ability to implement wide-band variable delay lines over a microwave frequency range. The insertion losses of the fabricated variable delay line were found to be too high for practical applications, and it was revealed that the losses were dominated by conductor losses. It was found that one effective way to reduce losses was to increase the thickness of the liquid crystal layer, but this had the negative effect of making the response time of the liquid crystal alignment slow. It is thus critically important in designing liquid crystal variable delay lines that careful consideration be given to the trade-off between insertion losses and response time depending on the application.

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Section: Design and Test Fabricationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Design of a microwave variable delay line using liquid crystal, and a study of its insertion loss

Kuki

Fujikake

Nomoto

et al. 2002

Electron Comm Jpn Pt II

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“…There are reports of the development of a variable phase-shifter for the millimeter-wave band with a waveguide filled with a nematic liquid crystal [6], and of a variable phase-shifter for the microwave and millimeterwave band using nematic liquid crystals as the microstrip line substrate [7,8]. In the case of microstrip variable delay lines using nematic liquid crystals, it is reported that the insertion loss, which is mostly due to the conductor loss, and the response time after voltage application are in a trade-off relationship, with the thickness of the liquid crystal layer as the parameter [9].…”

Section: Introductionmentioning

confidence: 99%

Measurements of the dielectric properties of nematic liquid crystals at 10 kHz to 40 GHz and application to a variable delay line

Kamei

Utsumi

Moritake

et al. 2003

Electron Comm Jpn Pt II

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SUMMARYIn support of the application of liquid crystals to adaptive devices such as variable delay lines in the microwave and millimeter band, the complex permittivities and response times of five different nematic liquid crystals after voltage application were measured. We measured both the real part ε // g of the relative permittivity, when the long axis of the liquid crystal molecule is parallel to the high-frequency electric field, and the relative permittivity ε ⊥ g when it is perpendicular to the high-frequency electric field. The values tanδ // and tanδ ⊥ were measured. In the range from 10 kHz to 13 MHz, the capacitance and conductance of a liquid crystal cell sandwiched between ITO glass plates processed by rubbing were directly measured. For 100 MHz to 40 GHz, we propose the new cutback method, in which two coaxial tubes with different lengths are filled with the liquid crystal and the dielectric properties are measured on the basis of their respective group delay and transmission loss. Dielectric relaxation is verified in the low frequency range. In particular, in the range from 3 to 40 GHz, dielectric properties are shown for a continuous change of frequency. It is found that ε // g and ε ⊥ g are kept almost constant regardless of the frequency, taking values of approximately 3 and 2.5, respectively. ∆ε′, which is the difference between the permittivities in two orientations, exhibits a large variation, from 0.4 to 0.8, depending on the material, which provides crucial data for selecting the optimal material. The response time was measured by placing the liquid crystal cell between two polarizers with the polarizing directions set parallel. The light from a He-Ne laser (632.8 nm) is directed onto the liquid crystal cell, and the transmitted light is detected by a photodiode. Assuming that the liquid crystal is used in an adaptive device, the speed of operation is investigated. Based on the measurement results for two different nematic liquid crystals, the design of a variable delay line for 20, 30, and 40 GHz is considered, and a principle of liquid crystal material selection is presented.

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“…Figures 2(c)-(d), to millimeter-or bulkier microwave devices for tunable -delay line, -phase shifter, -wavelength selector and beam steering devices [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], to name a few. Nematic liquid crystals are uni-axial, characterized by refractive indices n and the n ⊥ , for light polarization parallel and orthogonal to the director axis, respectively.…”

Section: F Figures 2(a)-(b)mentioning

confidence: 99%

MULTIPLE TIME SCALES OPTICAL NONLINEARITIES OF LIQUID CRYSTALS FOR OPTICAL-TERAHERTZ-MICROWAVE APPLICATIONS (Invited Review)

Khoo¹,

Zhao²

2014

PIER

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Abstract-We provide a critical account of the dynamics of laser induced refractive index changing mechanisms in nematic liquid crystals which may be useful for all-optical switching and modulation applications in the visible as well as the Terahertz and long-wavelength regime. In particular, the magnitude and response times of optical Kerr effects associated with director axis reorientation, thermal and order parameter changes, coupled flow-reorientation effects and individual molecular electronic responses are thoroughly investigated and documented, along with exemplary experimental demonstrations. Emphases are placed on identifying parameter sets that will enable all-optical switching with much faster response times compared to their conventional electro-optics counterparts.

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Liquid crystal microwave phase shifter

Cited by 113 publications

References 2 publications

Design of a microwave variable delay line using liquid crystal, and a study of its insertion loss

Design of a microwave variable delay line using liquid crystal, and a study of its insertion loss

Measurements of the dielectric properties of nematic liquid crystals at 10 kHz to 40 GHz and application to a variable delay line

MULTIPLE TIME SCALES OPTICAL NONLINEARITIES OF LIQUID CRYSTALS FOR OPTICAL-TERAHERTZ-MICROWAVE APPLICATIONS (Invited Review)

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