Carsten Fritzsch

Reconfigurable Folded Reflectarray Antenna Based Upon Liquid Crystal Technology

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 -6°, 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.

Compact tunable Ka-band phase shifter based on liquid crystals

This paper presents the design and realization of a compact phase shifter based on a tunable dual-mode ring filter at 35 GHz. The tunability is achieved by employing a thin liquid crystal layer as a tunable dielectric substrate. By applying a bias voltage in the range of 0… 40V, a tunable phase range of 117° is measured. The figure of merit of the realized phase shifter is 30.6 °/dB at 34.3 GHz.

Ka-band frequency tunable patch antenna

In this paper we present a frequency tunable patch antenna working in the Ka-band. Liquid Crystals are used as a tunable dielectric layer between a ground plane and an inset feed microstrip patch. Measurements show, that the resonance frequency of the antenna can be tuned continuously from 34.1 GHz to 37.7 GHz with bias voltages between 0 and 90 V.

Temperature investigations of liquid crystal based reconfigurable reflectarrays

The effects of temperature variations on liquid crystal based reconfigurable reflectarrays are investigated. A Ka-band reconfigurable reflectarray that is made of microstrip patch elements has been used for this purpose. Measured far-field patterns and gain of the reflectarray antenna are presented at different temperatures at 36 GHz. Beam steering time measurements are also carried out at different temperatures, i.e., between 15 °C and 35 °C, for the 0° to -20° beam steering case.

Monolithic SU-8 based hollow waveguide with integrated electro thermally tunable iris filter for W-band applications

This paper reports the design and fabrication of a new generation of micromechanically fabricated hollow waveguides for the W-band (75-110 GHz). It is based on UV high aspect ratio lithography for 1.27 mm SU-8 thick films on PCB substrates. The epoxy based negative resist provides the means to monolithically integrate electro thermal actuators. This enables the realization of tunable waveguide components like the described iris filter design.

Novel Reflectarray Antenna with Quasi-Dipole Unit Cells

This letter presents a novel reflectarray design based on quasi-dipole unit cells. The substrate of the quasi-dipoles is oriented perpendicular to the array surface, giving the advantage of sufficient large area for phase-shifter circuits behind the antenna element. In order to prove the concept at 10 GHz, unit cells are characterized in a waveguide simulator, and far-field measurements of two 8 × 8-element antenna demonstrators are presented. One demonstrator, pointing in a broadside direction, has shown a half-power beamwidth of 15 ° and a sidelobe level of -12 dB in the E-plane. The other demonstrator is pointing toward 20 ° and has shown a sidelobe level of -7 dB with a half-power beamwidth of 20 °.

MEMS and combined MEMS/LC technology for mm-wave electronic scanning

This paper proposes two innovative solutions for the exploitation of MEMS and Liquid Crystal (LC) technology in mm-wave electronic scanning reflectarrays: a MEMS-only approach, where the switches are used to obtain reconfigurable elementary cells with 1-bit of phase resolution and a LC/MEMS combined solution, able to provide a continuous phase-shift up to 180°.