Delay control via the bias field angle in YIG films

Bajpai, S. N.; Weinert, R.W.; Adam, J.D.

doi:10.1109/tmag.1983.1062689

Cited by 7 publications

(2 citation statements)

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“…Adaptive techniques using magnetic material now under study include variable delay line [1,2], variable oscillators [3,4] using static magnetic waves, and S/N enhancers [5] utilizing nonlinearity. In addition, liquid crystals are considered interesting as a medium in which the permittivity can be made variable in the microwave and millimeter-wave band.…”

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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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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“…One class of devices being studied that would further the adaptive approach is capable of electronically altering the amplitude, phase, and frequency of radio frequency signals [1]. In the microwave band for example, variable delay lines [2,3] and variable oscillators [4,5] using the magnetostatic wave mode have been studied. Reports have also described variable phase shifters [6] and variable oscillators [7] that control microwaves by varying the intensity of the light irradiating semiconductor, and a variable oscillator [8] that changes the dielectric characteristic of high dielectric materials by altering external bias voltages.…”

Section: Introductionmentioning

confidence: 99%

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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