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This paper presents a novel formulation to efficiently analyze aperiodic arrays using the NUFFT and considering the amplitude of the unit cell radiation pattern. This formulation is extended to consider a smooth-varying incident field within each unit cell. Finally, it is employed in the optimization of an aperiodic array, obtaining excellent results.
A technique for the efficient computation of the radiation patterns of reflectarray antennas in an adaptive grid for speed improvement is presented. It relies on the use of the Non-Uniform Fast Fourier Transform (NUFFT) to efficiently compute the spectrum functions. This new application of the NUFFT improves computing times and memory usage, with regard to the use of the FFT, for very directive reflectarrays...
This paper presents several advanced techniques for the design of reflectarray antennas for far field applications, including the crosspolar optimization, which is a very recent research topic for this type of antenna. After a brief introduction to reflectarray antennas, the Phase-Only Synthesis (POS) technique for far field is presented, which is the most widely used optimization technique for reflectarrays...
In this work, the Intersection Approach algorithm is adapted to perform near field synthesis of reflectarray antennas. First, a brief description of how the near field radiated by the reflectarray is presented. Then, the algorithm is detailed, in particular, the definition of the forward and backward projectors. Unlike as the far field version of the Intersection Approach, for near field synthesis...
Two techniques are compared for the crosspolar optimization of reflectarray antennas using a full-wave analysis technique based on local periodicity directly in the optimization process within acceptable computing time. The first one is based on the Levenberg-Marquardt Algorithm (LMA) while the second technique is based on the generalized Intersection Approach framework using the LMA as backward projector...
Two dual reflectarray antennas able to provide an European coverage and beam scanning over 8° respectively have been presented. An accurate technique has been proposed for the analysis of dual-reflectarray antennas, which takes into account the angle of incidence of the field impinging on main reflectarray cells. Two 50-cm antenna demonstrators with the same geometry have been manufactured and measured...
A 1.1-m reflectarray antenna has been designed, manufactured and tested to fulfil the requirements of a satellite antenna in Ku-band that provides South American coverage in Tx and Rx. The reflectarray cells consist of four dipoles for each polarization in two dielectric layers, which were selected because of their simplicity and high performance. The dipole dimensions are optimized in all the reflectarray...
A method for the optimization of the crosspolar component of dual-polarized reflectarrays using the Method of Moments (MoM) is described. It is based on the Levenberg-Marquardt Algorithm (LMA) and it exploits several optimization techniques to accelerate the computations in order to be able to use MoM within acceptable computing times. Since MoM is used to analyze the reflectarray unit cell, it accurately...
The near field of a reflectarray at 100GHz is optimized in order to increase the size of the quiet zone for its use in compact antenna test ranges. In order to compute the radiated near field, a simple model of the reflectarray is used in which the field is obtained as contributions of the far field radiated by each unit cell, modeled as a small aperture by means of the second principle of equivalence...
In this paper we study the behaviour of event based PID controllers implemented with two different events based sampling strategies: Symmetric Send on Delta (SSOD) and Regular Quantisation (RQ). The effect of the derivative filter coefficient of the PID in the overall system response is also analysed. The study is carried out in an electro-mechanical experimental platform with CD brushless motors...
This work presents the recent developments of reflectarray antennas for space applications carried out by Universidad Politecnica de Madrid, which includes analysis and design techniques for single and dual reflector configurations, design procedures for contoured beams and bandwidth improvement and some practical realizations. Several reflectarray demonstrators are described for Direct Broadcast...
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...
In this work, the quiet zone achieved by a reflectarray antenna is evaluated. The study is focused on obtaining the near field generated by the reflectarray and the evaluation of the quiet zone in terms of the design parameters of the reflectarray antenna is presented. Then, the most critical parameters in the design of the quiet zone are identified. Finally, the quiet zone generated by the reflectarray...
A printed array antenna is defined to focus the beam in the near-field zone. The field radiated by the array elements should be sum in phase at the focusing point. The synthesis process to obtain the suitable feeding phase distribution is described. The array elements are designed to work in dual polarization. Thus, the entire antenna generates two independent and simultaneous near-field spots.
Aperiodic arrays are very interesting when room for active devices could be achievable. In this paper, a deterministic strategy to generate the aperiodicity, based on three geometric taper distributions, is studied and validated. The method is applied to arrays with inter-elements spacing greater than a wavelength. The arrays exhibit a reduction of the grating lobe level. One of these arrays has been...
A reflectarray antenna that provides a focused beam in Ka band has been designed, manufactured and tested. The antenna demonstrator has been made up using two layers of patches printed on Kapton, which are bonded to low-loss prepreg quartz materials. The effect of the manufacturing tolerance errors in the dimensions and dielectric properties of the materials have been evaluated. A good concordance...
In this paper, a dual-reflectarray antenna is proposed to generate a contoured beam for a DBS European coverage. The antenna optics is based on a compact range dual-reflector antenna, which produces low crosspolar radiation. The phase distribution of the subreflectarray is defined to simulate an equivalent hyperbolic subreflector with negative eccentricity. The phase distribution on the main reflectarray...
This paper presents a general modular technique to analyse different types of dual-reflector configurations, where the main, the sub, or both reflectors can be a flat or a curved reflectarray. The technique has been applied to two particular cases: a parabolic reflectarray with a flat sub-reflectarray, which was previously designed to produce a South American coverage; and a dual-reflectarray designed...
This paper describes the preliminary design of a Ku-band antenna based on a dual planar reflector configuration that provides electronic beam scanning in a limited angular range. The antenna is characterized by its compact optics and simplicity to be folded and deployed. The system comprises a passive reflectarray as sub-reflector and a reconfigurable reflectarray with 1-bit electronic control as...
In this paper we present an overview of liquid crystal based reflectarray technology which has been developed over the past five years at Queen's University Belfast, Universidad Politecnica de Madrid and Universidad de Oviedo. This new active control strategy requires precise characterisation of the permittivity, dielectric anisotropy and loss tangent of the liquid crystals. The electrical parameters...
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