Dual-Reflector Antenna with a Reflectarray Subreflector for Wide Beam Scanning Range at 120GHz

A dual-reflector antenna composed by a small reconfigurable reflectarray subreflector and a large parabolic main reflector is proposed for beam scanning application in the 120 GHz frequency band. The beam scanning is achieved by changing the phase distribution on the reflectarray surface which is supposed to contain reconfigurable cells. The phase distribution for the different beam deflecting states is obtained with a synthesis technique based on the analysis of the antenna in receive mode.

Frequency selective surface using nested split ring slot elements as a lens with mechanically reconfigurable beam steering capability

The design is described of a double layer frequency selective surface which can produce a differential phase shift of 180 ° as the wave propagates through it at normal incidence. The hand of an applied circularly polarized signal is reversed due to the 180° phase shift, and it is demonstrated that the exit circularly polarized output signal can be phase advanced or phase retarded by 180 ° upon rotation of the elements comprising the structure. This feature allows the surface to act as a spatial phase shifter. In this paper the beam steering capabilities of a 10 × 10 array of such elements are demonstrated. Here the individual elements comprising the array are rotated relative to each other in order to generate a progressive phase shift. At normal incidence the 3 dB Axial Ratio Bandwidth for LHCP to RHCP conversion is 5.3% and the insertion loss was found to be -2.3 dB, with minimum axial ratio of 0.05 dB. This array is shown to be able to steer a beam from -40 ° to +40 ° while holding axial ratio at the pointing angle to below 4 dB. The measured radiation patterns match the theoretical calculation and full-wave simulation results. © 2010 IEEE.

Reconfigurable beam forming using phase-aligned Rotman lens

The authors describe how a standard Rotman lens design can be readily adapted in order to allow reconfigurable beam
forming. This is achieved by applying concurrent excitations to the modified Rotman lens. A rationale for the design and
underlying behaviour of the modified, phase-aligned, Rotman lens as well as the deficiencies of a conventional Rotman lens
in this mode of operation are provided. Simulated and measured results are provided in order to illustrate the feasibility of the
approach suggested.

Pilot Tone Actuated Antenna Array Pattern Reconfiguration

A new strategy for remote reconfiguration of an antenna array far field radiation pattern is described. The scheme uses a pilot tone co-transmitted with a carrier signal from a location distant from that of a receive antenna array whose far field pattern is to be reconfigured. By mixing the co-transmitted signals locally at each antenna element in the array an IF signal is formed which defines an equivalent array spacing that can be made variable by tuning the frequency of the pilot tone with respect to the RF carrier. This makes the antenna array factor hence far field spatial characteristic reconfigurable on receive. For a 10 x 1 microstrip patch element array we show that the receive pattern can be made to vary from 35 to 10 degrees half power beam width as the difference frequency between the pilot and the carrier at 2.45 GHz varies between 10 MHz and 500 MHz carrier.

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

The design, fabrication, and measured results are presented for a reconfigurable reflectarray antenna based on liquid crystals (LCs)which operates above 100 GHz. The antenna has been designed to provide beam scanning capabilities over a wide angular range, a large bandwidth,and reduced side-lobe level (SLL). Measured radiation patterns are in good agreement with simulations, and show that the antenna generates an electronically steerable beam in one plane over an angular range of 55◦ in the frequency band from 96 to 104 GHz. The SLL is lower than −13 dB for all the scan angles and −18 dB is obtained over 16% of the scan range. The measured performance is significantly better than previously published results for this class of electronically tunable antenna, and moreover, veri-fies the accuracy of the proposed procedure for LC modeling and antenna design.

Liquid-crystal-based reflectarray antenna with electronically switchable monopulse patterns

A printed rcflectarray antenna, which generates a beam that can be electronically switched from a sum to a difference radiation pattern, is presented. This is achieved by applying a bias voltage of 20 V to one-half of the aperture, which is constructed above a 500 mu m cavity containing liquid crystals. Simulated results are shown to be in good agreement with measurements at X-band.

Design and measurement of reconfigurable millileter wave reflectarray cells with nematic liquid crystal

Numerical simulations are used to study the electromagnetic scattering from phase agile microstrip reflectarray cells which exploit the voltage controlled dielectric anisotropy property of nematic state liquid crystals (LC). In the computer model two arrays of equal size elements constructed on a 15?m thick tuneable LC layer were designed to operate at centre frequencies of 102 GHz and 130 GHz. Micromachining processes based on the metallization of quartz/silicon wafers and an industry compatible LCD packaging technique were employed to fabricate the grounded periodic structures. The loss and phase of the reflected signals were measured using a quasi-optical test bench with the reflectarray cells inserted at the beam waist of the imaged Gaussian beam, thus eliminating some of the major problems associated with traditional free-space characterisation at these frequencies. By applying a low frequency AC bias voltage of 10 V, a 165o phase shift with a loss 4.5 dB-6.4 dB at 102 GHz and 130o phase shift with a loss variation between 4.3 dB – 7 dB at 130 GHz was obtained. The experimental results are shown to be in close agreement with the computer model.