Manuel Sierra Pérez

Phased Array for UAV Communications at 5.5 GHz

This letter presents the design and manufacturing of a phased array at 5.5-GHz band. The antenna application is the communications with unmanned aerial vehicles (UAVs) in a wildfire. The antenna is controlled through a WiMAX station. The vertical radiation pattern is a shaped beam. This shaped beam has the maximum at broadside and a smooth gain decay in positive

SIW Antenna With Polarizer at ku-Band

\theta

Linear polarization parallel plate slot antenna

. This way, the differences in the free-space losses of the UAVs are compensated. The antenna is steered in the horizontal plane through phase shifters. It also includes amplifiers and digital attenuators to calibrate the antenna performance. A calibration method is also proposed in the letter.

3×3 Microstrip beam forming network for multibeam triangular array

This communication presents the design and manufacturing of a small size SIW array antenna at ku-band with circular polarization. The antenna consists of eight standing-wave slotted array plus a polarizer to obtain the circular polarization. There is some tapering among slots to reduce the SLL. The distribution network is done in a different layer than the radiating elements to reduce the antenna size. To couple the power between layers, a coupling H-slot is used. The design and measured results of each element are presented in this communication. Possible manufacturing problems are also explained.

Study of a new 4×3 beam forming network for triangular arrays of three radiating elements

We show the design of a linearly polarised flat antenna. The main goal is getting a low cost antenna to use for the reception of Hispasat satellite emissions in the 12 GHz band. The gain needed for the antenna is around 30 dBi. A rectangular array of slots in the upper side of a parallel plate waveguide form the main antenna structure. The guide is excited by one planar feeding structure consisting of an array of rectangular microstrip patches. We also modify the feeding network the design procedure and the materials used to build of the radiation surface.

Analysis and design software for radial slot antennas

The design of a beam forming network (BFN) for a triangular cell of three elements is considered. A useful relation between phase excitation of the elements of the cell, beam direction, wavelength and distance is given. The BFN is studied based on a Butler matrix, using balanced and unbalanced hybrid couplers to obtain a three inputs and three outputs network which is used to develop a multibeam structure. A system of three equations is also presented to calculate the lengths of the transmission lines which connect the couplers of the network. These equations allow a flexible design of the network depending on the needed specifications. Finally, a microstrip BFN circuit that demonstrates the utility of the design has been developed.

A Robust Adaptive Beamformer Based on an Iterative Subspace Projection with Conjugate Gradient Method

An innovative dissipative multi-beam network for triangular arrays of three radiating elements is proposed. This novel network provides three orthogonal beams in θ0 elevation angle and a fourth one in the broadside steering direction. The network is composed of 90° hybrid couplers and fixed phase shifters. In this paper, a relation between network components, radiating element distance and beam steering directions will be shown. Application of the proposed dissipative network to the triangular cells of three radiating elements that integrate the intelligent antenna GEODA will be exhibited. This system works at 1.7 GHz, it has a 60° single radiating element beamwidth and a distance between array elements of 0.57 λ. Both beam patterns, theoretical and simulated, obtained with the network will be depicted. Moreover, the whole system, dissipative network built with GEODA cell array, has been measured in the anechoic chamber of the Radiation Group of Technical University of Madrid, demonstrating expected performance.

Geoda: Unitary Cell Distribution, Composition and Working Properties

A software for the analysis and design of radial slot antennas excited by one or several coaxial probes is presented. This tool has two main different blocks: analysis and design. The software has been improved with a file input/output options and a graphic display of radiation patterns, impedance, directivity and other antenna parameters. Everything is compiled in C++ for Windows. The second part of the paper includes some designs and results.

T/R module design for GEODA antenna

Adaptive arrays have traditionally used in two applications: beamforming and direction of arrival (DOA) estimation. Several techniques making use of a certain reference are utilised to form a particular beam. One of them that is inherent to any spatial filter is the spatial reference beamformer. However, spatially beamformers suffer from two disadvantages such as the slowness of convergence under bad circumstances when gradient algorithms are used and its hypersensitivity to calibration and pointing errors (perturbation errors) (Jablon [11]). Conjugate Gradient Methods have been proposed to alleviate these drawbacks. CG methods (Fletecher-Reeves [3]) provides the minimisation of a quadratic function via a set of conjugate directions instead of only one direction such as in gradient methods reaching the minimum in fewer iterations with a little increase in computational cost Besides by using projection on signal subspace and due to the relation of parameters present in CG iteration and corresponding eigenvectors via Lanczos connection a robust beamformer to calibration can be obtained without increasing considerably the computational cost (Feldman [2]). A second independent way to obtain signal subspace is proposed based on a minimisation of the distance between the corresponding snapshot and its projection on signal subspace. The minimisation of a non quadratic function is done via CG method instead of the traditional batch processing.