Reconfigurable Folded Reflectarray Antenna Based Upon Liquid Crystal Technology

Abstract

A reconfigurable antenna based on the liquid crystal technology is presented in this paper. The antenna comprises a planar lower reflector with an incorporated feed at its center and a polarizing grid on top as an upper reflector. The lower reflector is utilized to collimate the beam and to twist the polarization. The polarizing grid selects the polarization for the transmission and reflects the orthogonally polarized waves toward the lower reflector. Combining reflector elements with a polarizing grid allows performing additional phase adjustment on the upper reflector for beam steering. Reconfigurability is maintained by the upper reflector, in which a liquid crystal mixture is used as a tunable substrate. The liquid crystal layer is tuned with a bias voltage configuration to obtain an appropriate phase adjustment for the beam steering. As a proof of concept, the beam steering capability of the antenna is demonstrated by steering the main beam to , 0 , and 6 at 78 GHz. The measured gain at 78 GHz is 25.1 dB. The proposed antenna configuration is a promising candidate for reconfigurable, high-gain, low-profile, and low-cost antennas.Index Terms-Beam steering, liquid crystals, microstrip antenna arrays, microwave antennas, millimeter wave technology, reflectarrays.

Liquid crystal based beam scanning reflectarrays and their potential in SATCOM antennas

“…In [7], a reconfigurable folded reflectarray antenna configuration based on LC was experimentally demonstrated for beam scanning in one plane at 78 GHz. In this architecture, the LC-based reflectarray is employed as sub-reflector, and introduces a reconfigurable phase-shift to one polarization of the incident electric field but is transparent to the orthogonal field vector.…”

“…As an example, Fig. 4 shows preliminary computed results of amplitude and phase of the reflection coefficient versus frequency for several permittivity tensors [5] of a multi-resonant cell (size P x =5 mm and P y =4.4 mm) composed of five unequal length dipoles, that operates in Ka-band and uses commercially available LC GT3-23001 (used at 100 GHz in [4]- [7]). A phase range of 600º is achieved within a bandwidth of 10 % that covers the uplink band of SATCOM (from 27.5 GHz to 31 GHz).…”

Design and Demonstration of an Electronically Scanned Reflectarray Antenna at 100 GHz Using Multiresonant Cells Based on Liquid Crystals

“…In the literature, several unit cell geometries based on this tunable material have been designed and experimentally evaluated [2]- [8], which have led to the development of several different LC-based antenna arrangements [4]- [8]. In [4], 1-bit phase quantization was used to produce a switchable radiation pattern shape from sum to difference, whereas a continuous phase variation was used to implement a LC reflectarray with scanning capabilities in one plane at 35 GHz [5] and 77 GHz [6]- [7].…”

“…In [4], 1-bit phase quantization was used to produce a switchable radiation pattern shape from sum to difference, whereas a continuous phase variation was used to implement a LC reflectarray with scanning capabilities in one plane at 35 GHz [5] and 77 GHz [6]- [7]. A LC-reconfigurable reflectarray at 78 GHz has been proposed in a folded configuration [8] to provide beam scanning in one plane with higher gain (25dBi). This arrangement uses a passive reflectarray to collimate the beam and to twist the electric field.…”

“…Furthermore, the bias voltage applied at each LC cell is obtained in [5]- [7] by using an algorithm based on measuring the received power and varying sequentially the voltages until maximum received power is obtained. In [4] and [8], the voltages are obtained by measuring the voltage dependence of the cells at one angle of incidence and for fixed cell dimensions. These procedures were employed because of the impossibility of measuring the phase curve versus voltage at each frequency, angle of incidence and for different cell dimensions, which is required to configure the appropriate phase-shift at each cell across the reflectarray surface.…”