Generalized Director Approach for Liquid-Crystal-Based Reconfigurable RF Devices

Alex‐Amor, Antonio; Palomares‐Caballero, Ángel; Palomares, Antonio; Tamayo‐Domínguez, Adrián; Fernández-González, José-Manuel; Padilla, Pablo

doi:10.1109/lmwc.2019.2939553

Cited by 9 publications

(8 citation statements)

References 19 publications

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“…That is, θ m = θ m (k 11 , k 22 , k 33 , ∆ε b , V, θ p ). A detailed study particularized to LCs enclosed in parallel-plate waveguides, showing the relation between θ m and the parameters presented above, can be found in [39,40].…”

Section: Liquid Crystalmentioning

confidence: 99%

“…In order to form the permittivity tensor (5) and then compute the S-parameters of the structure in CST, a conversion between the polarization voltage V and the average tilt angle θ m has to be done. This conversion has been carried out with the formulas of [40], originally intended for application in parallel-plate waveguides. If fringing-field effects are neglected, the formulas of [39,40] approximate well the relation between V and θ m in microstrip structures.…”

Section: Microstrip-like Linementioning

confidence: 99%

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Dispersion Analysis of Periodic Structures in Anisotropic Media: Application to Liquid Crystals

Alex‐Amor

Palomares‐Caballero

Mesa

et al. 2022

IEEE Trans. Antennas Propagat.

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This paper presents an efficient method to compute the dispersion diagram of periodic structures with generic anisotropic media. The method takes advantage of the ability of full-wave commercial simulators to deal with finite structures having anisotropic media. In particular, the proposed method opens new possibilities with respect to commercial eigenmode solvers: (i) anisotropic materials with non-diagonal permittivity and permeability tensors can be analyzed; (ii) the attenuation constant can easily be computed and lossy materials can be included in the simulation; (iii) unbounded and radiating structures such as leakywave antennas can be treated. In this work, the proposed method is particularized for the study of liquid crystals (LCs) in microwave and antenna devices. Since LCs show promising capabilities for the design of electronically reconfigurable elements, the dispersion properties of a great variety of LC-based configurations are analyzed, from canonical structures, such as waveguide and microstrip, to complex reconfigurable phase shifters in ridge gap-waveguide technology and leaky-wave antennas. Our results have been validated with previously reported works in the literature and with the Eigenmode solver of commercial software CST.

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Section: Liquid Crystalmentioning

confidence: 99%

Section: Microstrip-like Linementioning

confidence: 99%

Dispersion Analysis of Periodic Structures in Anisotropic Media: Application to Liquid Crystals

Alex‐Amor

Palomares‐Caballero

Mesa

et al. 2022

IEEE Trans. Antennas Propagat.

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“…W ITH the advent of 5G, cognitive radio and ultrawideband systems, demand for the reconfigurable radio frequency (RF) front ends is on the rise [1]- [4]. Devices that can adapt themselves to a controlled input are getting popular [5]- [8]. This calls for devices that are multifunctional and offer multiband operation.…”

Section: Introductionmentioning

confidence: 99%

A Compact Reconfigurable 1-D Periodic Structure in GaAs MMIC With Stopband Switching, Dual-Band Operation and Tuning Capabilities

Shahid¹,

Thalakotuna

Karmokar

et al. 2021

IEEE Access

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This paper presents a systematic study of a compact and reconfigurable periodic structure in GaAs MMIC technology. Compactness is achieved by the introduction of spiral inductors in a conventional unit cell without disturbing the reactive loading mechanism. The proposed architecture exhibits a 28.3% wider stopband with 62.6% smaller footprint compared to a conventional structure. The compactness and bandwidth improvement in the proposed structure is explained with the help of dispersion and circuit analysis. The reconfigurability built into the design using PIN diodes allows stopband switching, dual-band operation and tuning capabilities with the mere use of a single reactive load in its unit cell. To the best of the authors knowledge, it is the first time a reconfigurable MMIC implementation is realized using the proposed structure or even the conventional design. As a guide to design, sensitivity analysis to filter performance is presented for important structure parameters. Switching element parasitics are discussed in two ways: firstly, with the design and measurement of structures with idealized switching conditions and in second, with the circuit and full-wave EM modelling of the finite periodic structure with the actual PIN diodes. The on-chip measurements of the fully reconfigurable filter show excellent agreement with simulations.

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“…Nevertheless, PIN diodes suffer from high losses in mm-wave regime. Some reconfigurable material such as liquid crystals [13]- [17] or ferroelectrics [18]- [20] are also used to vary the phase shift. These approaches are currently attractive but present some drawbacks such as complex implementation in waveguide and high insertion losses incurred when the frequency increases.…”

Section: Introductionmentioning

confidence: 99%

Low-Loss Reconfigurable Phase Shifter in Gap-Waveguide Technology for mm-Wave Applications

Palomares‐Caballero

Alex‐Amor

Escobedo

et al. 2020

IEEE Trans. Circuits Syst. II

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In this brief, we present a low-loss mechanically reconfigurable phase shifter implemented in gap-waveguide technology for mm-wave frequencies. The proposed design gives a practical implementation of tuning elements inside the waveguide providing alternatives to the use of the E-plane split waveguide at high frequencies in order to avoid leakage losses. The depicted phase shifter design is based on a H-plane split waveguide. The phase shift is controlled by means of a tuning screw, which exerts pressure on a flexible metallic strip inserted inside the waveguide. The flexible strip bends with different curvature radii and determines the phase shift at the output port. Costeffective manufacturing and simple implementation of the flexible metallic strip are achieved by means of the gap-waveguide design. A prototype has been manufactured for validation purposes. Good impedance matching is achieved from 64 GHz to 75 GHz providing a 15.8% impedance bandwidth. The results show a maximum phase shift of 250 o with a maximum and mean insertion loss (IL) of 3 dB and 1.7 dB, respectively.

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Generalized Director Approach for Liquid-Crystal-Based Reconfigurable RF Devices

Cited by 9 publications

References 19 publications

Dispersion Analysis of Periodic Structures in Anisotropic Media: Application to Liquid Crystals

Dispersion Analysis of Periodic Structures in Anisotropic Media: Application to Liquid Crystals

A Compact Reconfigurable 1-D Periodic Structure in GaAs MMIC With Stopband Switching, Dual-Band Operation and Tuning Capabilities

Low-Loss Reconfigurable Phase Shifter in Gap-Waveguide Technology for mm-Wave Applications

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