Daniel Llorens del Río

Three-dimensional ray-tracing to model internal reflections in off-axis lens antennas

A three-dimensional ray tracing technique for internally reflected rays is developed and applied to compute the radiation pattern of an integrated lens antenna architecture with a twin arc-slot printed feed. The feed is represented in simulation by equivalent currents computed by the method of moments. The simulated results are compared against measurements at 30.2 GHz, including the case of an offset feed, in which internal reflections lead to pattern contributions of up to 20 dB that cannot be predicted by first-order physical optics (PO) techniques described in prior work. The twin arc-slot design reduces undesired sensitivity in diagonal lateral directions with respect to a comparable rectangular slot feed. Low-directivity feed model basis functions are shown to reduce discretization noise in the simulated patterns with respect to an array factor model. A frequency sweep analysis is introduced to test the sensitivity of individual sidelobes to the fabrication tolerances of the dielectric lens.

Sparse Array Antenna for Ku-Band Mobile Terminals Using 1 Bit Phase Controls

This paper presents a new architecture for low-cost mobile terminal antennas suitable for linear-polarized satellite communications systems. It is based on a sparse phased array that uses 1-bit phase controls. In this way it is possible to reduce the array cost by employing simpler and fewer controls. Measurements of a prototype demonstrate the feasibility of the approach.

On the interaction between electric and magnetic currents in stratified media

The presence of both electric and magnetic current elements embedded in stratified media is necessary to model many problems of interest in current integrated circuit and printed antenna technology. The integral equation formulation as applied to these problems is reviewed. Special attention is given to the Greens dyadic for the electric field generated by a magnetic current element. The fact that spectral-domain transmission line Greens functions for a multilayered structure are closed form integrable along the axis normal to the stratification is exploited to greatly improve the efficiency and the accuracy of the method. Theory and implementation are demonstrated in two practical problems: 1) arbitrarily shaped apertures in thick conducting screens, and 2) a metallic airbridge over a slot line.

Phased arrays with reduced number of phase shifter bits for polarization and pointing control

This paper presents two electronically steered phased array approaches allowing to reduce the number of phase shifter bits required to control steering and polarization. The first approach is based on particular combination of the phase shifters arrangement and elements rotation, while the second introduces a different approach with a combination of simplified phasing approach and aperiodic lattice allowing the number of bits to be reduced to one only. Both approaches have been validated through full scale implementation and measurements results are presented in this paper.

On the Coupling Integrals Arising in the Method of Moments Formulation of Laterally Bounded Structures

A generic integral equation and method of moments formulation is presented for laterally bounded stratified media including planar metallization. The main asset of the developed approach is its flexibility, as it encompasses generic lateral boundary conditions and explicitly applies to any linear subsectional basis functions with constant surface divergence. This includes the rooftop functions on rectangular and triangular supports currently proposed in standard method of moment meshers. This approach provides closed expressions for the coupling integrals appearing in the method of moments matrix elements. These formulas are based of Greens functions modal expansions and in the possibility, conclusively demonstrated in this paper to transform the surface integrals into contour integrals allowing an efficient and systematic implementation of the procedure. Full derivations are presented for several lateral boundary conditions, including rectangular and circular metallic cavities and periodic structures. Numerical examples including the analysis of real-life planar boxed circuits are presented. In all cases the obtained results compare favourably with other existing techniques.

A New Aperture for Switched-Beam Low-Profile Ku-Band Mobile Terminal Array Antennas [EurAAP Corner]

This paper presents an innovative switched-beam architecture for a low-cost mobile-terminal antenna, suitable for linear-polarized satellite communications systems. This antenna concept can produce twelve adjacent sector beams that cover the full azimuth field of view with a directivity of 11 dB, using the same physical aperture. This radiating aperture consists of slot-coupled patch antennas arranged in a specific lattice, inspired by the so-called tri-hexagonal tiling of the plane. An innovative beamforming-network layout, based on series feeding, is devised to reduce the circuit-board real estate required by the different beams. A prototype producing two beams has been built, and its radiation pattern has been measured, in order to demonstrate the feasibility of the approach.

Small-scale prototype of a Ku-band phased array for mobile satellite communications

This paper describes a demonstrator with a small size, incorporating the concepts developed in the ESA-funded project NATALIA. This demonstrator is a smaller version (16 patches) of the final prototype (156 patches). The small prototype is described in detail and measurement results of the farfield, nearfields, power consumption and thermal behaviour are presented. It is shown that the performance is according to expectation and that the design is very robust. The outcome of all experiments verifies the NATALIA concepts.

Low-profile Ku-band array antenna for broadband mobile satellite communications

This paper presents the design of a planar array antenna for Ku-band mobile satellite communications systems. 12The antenna is low-profile and is designed for integration in small aircrafts and ground vehicles. The antenna allows simultaneous transmit and receive operations taking advantage of the complete available aperture surface for both transmit and receive functions. The beam steering is electronic for the elevation and polarisation angles and mechanical for the azimuth scan. The paper presents the main characteristics of the antenna architecture and the design of the radiating aperture with emphasis on isolation between transmit and receive channels. A first sub-array module of the antenna has been realized and measured. The results of network parameters and radiation patterns are presented.