David Gonzalez-Ovejero

Multibeam by Metasurface Antennas

We explore various possibilities for designing multibeam antennas using a single metasurface (MTS) aperture. Both single-source and multisource feeding schemes are considered. For the single-source case, two approaches are investigated. In the first one, the MTS aperture is divided into several angular sectors, each one devoted to the formation of a beam in a given direction. In the second approach, the whole aperture is shared by a superposition of individual modulations, which correspond to those required to obtain beams in the desired set of directions. It is shown that the latter solution provides beams with a higher gain. The configuration based on a multisource feeding scheme is also tailored by a superposition of modulation patterns. The main advantage of the latter approach is the possibility of having one independent beam at a time when each of the sources are active, as opposed to the single-source case where all the beams coexist at the same time. Closed-form expressions are provided for the MTS surface impedance in each of the proposed solutions. The design equations include appropriate amplitude tapering to improve the beam efficiency. Numerical results based on the method of moments are presented for validation.

A class of silicon micromachined metasurface for the design of high-gain terahertz antennas

We explore the use of a class of metasurface (MTS), which consists of metalized cylinders arranged in a square lattice and placed on a ground plane, for the realization of antennas at terahertz (THz) frequencies. This MTS is particularly appropriate for being micromachined out of a silicon wafer by means of deep reactive ion etching (DRIE).

Multiple beam shared aperture modulated metasurface antennas

This paper discusses the possibility of obtaining multiple beams with a single aperture by adding up the surface reactance functions that provide the desired scattering patterns for a set of given feed points. An example is presented which consists in a shared aperture antenna with two independent circularly polarized pencil beams.

Terahertz Antennas and Feeds

Terahertz antennas present a different set of challenges to the antenna designer typically striving for very high performance while at the very limit of the chosen fabrication process. Many of the same design techniques used at lower frequencies are still applied, but fabrication constraints impose significant limitations on the type of structure that can be used, forcing the designer to consider unique fabrication processes or completely new antenna structures. Through advances in fabrication and computational techniques, the variety of terahertz antennas is growing. This chapter presents a range of antennas applied at these frequencies from 1.9 THz horn antennas to superconducting planar arrays. The chapter will cover different antenna technologies and feeds such as corrugated horn antennas, smooth-walled profiled horn antennas, multi-flare angle horn antennas, lens antennas, microlens leaky wave antennas, metasurface antennas, antenna arrays, off-chip antennas, and others. It will detail theory, simulation, fabrication techniques, and state-of-the-art antenna results in all these different technologies at millimeter and terahertz frequencies. The chapter will also provide details for terahertz antennas in the context of terahertz systems.

High-power terahertz emitter arrays

This manuscript proposes the combination of several photomixing THz sources for overcoming the power limitations of this technology. Each element is placed in the gap of a balanced antenna. All the elements conform a 2D rectangular array. For avoiding issues related to having out-of-focus sources when using one electrically large silicon lens, two different strategies are considered: increasing the density of elements by using a compact design and using an array of dielectric rod waveguide antennas instead of the lens. Experimental considerations are also provided for two prototypes manufactured in the 1550 nm window. Measured power level will be shown at the conference.

Study of free-space coupling into mm-wave whispering-gallery mode resonators for a radioastronomy receiver

In this paper, the coupling mechanism of a free-space Gaussian beam into a whispering-gallery mode resonator through a dielectric lens is mathematically modeled and numerically solved by means of the Schelkunoff-Waterman method (the so called T-matrix method). This approach allows in principle, to quickly analyze the performance of different near-field coupling mechanisms with arbitrary excitations. The aim is to efficiently excite a WGM into a nonlinear dielectric resonator in order to detect the weak mm-wave radiation from the cosmic microwave background (CMB) by up-converting the signal into the optical domain via the nonlinearity of the medium.

Efficient analysis of metasurfaces in a planar layered medium

Gaussian ring basis functions (GRBFs) are proposed for the method of moments (MoM) analysis of metasurfaces (MTSs) in a planar layered medium. We solve the relevant integral equation for the homogenized problem, accounting for the MTS layers as impedance boundary conditions. The closed-form spectra of the GRBFs allows an efficient computation of the MoM impedance matrix using the spectral-domain approach and asymptotic expansions. Moreover, these basis functions represent the global evolution of the surface current density in an effective manner, which leads to a significant reduction of the number of unknowns.