Raphaël Gillard

The Phoenix Cell: A New Reflectarray Cell With Large Bandwidth and Rebirth Capabilities

This letter presents a new phase-shifting cell for linearly polarized reflectarray applications. It provides a nearly 360° phase range and naturally comes back to its initial geometry after the phase cycle has been achieved. A complete analysis of the resonating mechanism is given, and a low dispersion (<;30°/GHz) is demonstrated over a large bandwidth (18%) in simulation.

A steerable reflectarray antenna with MEMS controls

A reflectarray antenna in Ka-band is currently developed under the French research project ARRESAT. Reflectarrays become attractive for satellite telecommunications, as long as they exhibit low losses. Due to the emergence of the MEMS technology, such features may be obtained. This communication presents a potential application mission, and the development of low losses phase shift elements, using MEMS switches. The technological and electrical considerations that govern the accommodations of these switches within the reflectarray are detailed. Measurements of the active phase shift elements are shown.

Dual function radar communication Time-modulated array

This paper introduces the use of Time-modulated array methods to realize a dual function array. It is able to do a radar function in the mainlobe, while realizing a communication in the side lobe.

A general treatment of matched terminations using integral equations modeling and applications

This paper presents an original approach to simulate a broadband matched load in planar structures. Theoretically, the formulation appears as an additional boundary condition in the rigorous integral equations technique, and results in a partial rearrangement of the generalized impedance matrix in the moment method resolution. Practically, it enables the whole characterization of any planar multiport discontinuity in a procedure particularly realistic in regards to experimental measurement procedures. This new refinement is demonstrated to provide a versatile and powerful tool. Some typical applications are given which illustrate its numerous capabilities. The analysis of structures as different as a shielded microstrip step and an active receiving microstrip antenna is presented and successfully compared to experiments. >

The Antenna Software Initiative (ASI): ACE Results and EuRAAP Continuation

The results of four years of work within the Antenna Software Initiative (ASI) of the European Network of Excellence on Antennas (ACE) are reported. The primary goal of the ASI was to build a European framework that allows research groups, active in the development of antenna analysis and design software, to intensify and optimize cooperative research. The ASI community worked on three concrete questions: what software do we have, how good is it, and how can we make it better? This work was performed in close cooperation with ESA-ESTEC. At the last EuCAP conference (March 2009, Berlin), the EuRAAP Working Group on Software was inaugurated. The goal of this Working Group is to continue the work of the ASI community. It has to be emphasized that the ASI structure is a structure set up in a democratic way, to cope with the most important bottlenecks encountered towards European antenna-software cooperation.

Dual Linearly-Polarized Unit-Cells With Nearly 2-Bit Resolution For Reflectarray Applications In X-Band

A fully reconfigurable dual linearly-polarized phase-shifting unit-cell for reflectarrays is proposed in X-band. It consists of two orthogonal and symmetrical cross-type printed triangular dipoles loaded by 2 × 4 pin diodes. To keep independent phase responses both in vertical and horizontal polarizations and to minimize cross-polarization (by preserving the cell symmetry), the diodes are driven by pairs, leading to a maximum possible phase resolution of 2 bits per polarization. Two alternative solutions are described to bias the diode pairs. The corresponding phase responses of the unit-cell are compared for symmetrical and non-symmetrical diode loading of the dipole arms. The numerical results show that the biasing solution with no central via is more robust. They are validated experimentally around 8 GHz. The measured average loss and equivalent bit resolution at the central frequency equal 1.25 dB and 1.8 bit respectively.

A Multi Facets Composite Panel Reflectarray Antenna for a Space Contoured Beam Antenna in Ku Band

A 1.3m piecewise re∞ectarray demonstrator has been designed, manufactured and tested, that radiates a contoured beam coverage over North America. A very good agreement is obtained between the theoretical and measured radiation patterns. Many innovative techniques and processes were developed in order to meet the challenging speciflcations of a space telecommunication antenna.

An efficient analysis of planar microwave circuits using a DWT-based Haar MRTD scheme

A new wavelet-based technique to generate multiresolution time-domain schemes is presented in this paper. By using symbolic calculus, a rigorous and general formulation of subgridding at every level of multiresolution is obtained. As it is rigorously equivalent to a finer finite-difference time-domain (FDTD) scheme, it does not require any particular treatments for boundary conditions. This technique has been successfully applied to the study of microstrip structures. The near- and the far-field computation can be both improved in terms of CPU time and memory storage, while maintaining the same accuracy as the classical FDTD computation.

A multi-resolution MoM analysis of multiport structures using matched terminations

This paper presents the modeling of microstrip structures involving matched terminations with multi resolution 1-D method of moment (MoM). Semi-orthogonal (SO) spline wavelets are used to obtain a sparse system while a modeling of matched terminations enables a full multiport characterization. Theoretical results involving microstrip dipoles are presented and compared with experiments.

Design and Characterization of a CPSS-Based Unit-Cell for Circularly Polarized Reflectarray Applications

A CPSS-based unit-cell is proposed as a building block of future reconfigurable dual-CP reflectarrays illuminated by a dual CP primary feed. It is based on an enhanced version of the original Pierrots cell with multiple wires bent in a crank-like shape. It provides a 2-bit phase resolution in reflection for the left hand circular polarization (LHCP) and is nearly transparent in right hand circular polarization (RHCP). The main design steps and measurement procedure of the optimized cell are described in detail. The simulated and measured characteristics are in good agreement. The experimental results demonstrate a 6.4% bandwidth for a phase resolution better than 1.9 bits and an insertion loss of 0.5 dB at resonance.