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Liquid crystal dual-mode band-pass filter with improved performance

Torrecilla J., Marcos C., Urruchi V., Sánchez-Pena J. M., Chojnowska O.

Opto-Electronics Review

2015

Vol. 23, No. 2

121-125

Over the last twenty years, there has been a growing interest in the design of tunable devices at microwave frequencies by using liquid crystals technology. In particular, the use of liquid crystals with high dielectric anisotropy allows manufacturing voltage-controlled devices to operate in a wide frequency range. In this work the frequency response of a liquid crystal band-pass filter with dual-mode microstrip structure has been studied in depth by using a simulation software tool. A reshaping of a conventional dual-mode square patch resonator band pass filter with a square notch, studied in the literature, has been proposed with the goal of improving the filter performance. The main features achieved are a significant increase in the return loss of the filter and a narrowing of a 3-dB bandwidth. Specifically, a reduction in the filter bandwidth from 800 MHz to 600 MHz, which leads to a return loss increase from 6 dB to 12.5 dB, has been achieved. The filter centre frequency can be tuned from 4.54 GHz to 5.19 GHz.

Lenticular arrays based on liquid crystals

Urruchi Del Pozo V., Algorri Genaro J. F., Sánchez-Pena J. M., Geday M. A., Arregui X. Q., Bennis N.

Opto-Electronics Review

2012

Vol. 20, No. 3

260-266

Lenticular array products have experienced a growing interest in the last decade due to the very wide range of applications they can cover. Indeed, this kind of lenses can create different effects on a viewing image such as 3D, flips, zoom, etc. In this sense, lenticular based on liquid crystals (LC) technology is being developed with the aim of tuning the lens profiles simply by controlling the birefringence electrically. In this work, a LC lenticular lens array has been proposed to mimic a GRIN lenticular lens array but adding the capability of tuning their lens profiles. Comb control electrodes have been designed as pattern masks for the ITO on the upper substrate. Suitable high resistivity layers have been chosen to be deposited on the control electrode generating an electric field gradient between teeth of the same electrode. Test measurements have allowed us to demonstrate that values of phase retardations and focal lengths, for an optimal driving waveform, are fairly in agreement. In addition, results of focusing power of tuneable lenses were compared to those of conventional lenses. The behaviour of both kinds of lenses has revealed to be mutually similar for focusing collimated light and for refracting images.