Mariano Baquero

Gap Waveguides Using a Suspended Strip on a Bed of Nails

This letter discusses the feasibility of a new type of waveguide consisting of a strip suspended on a bed of nails. The bed of nails enforces a stopband, while the strip opens a propagating path that can be used to design circuits and feeding networks for the microwave and millimeter-wave bands. Advantages and drawbacks with respect to existing ridge gap waveguide are discussed. Experimental demonstration is also given.

Design of microwave circuits in ridge-gap waveguide technology

This paper presents recent advances is a new waveguiding technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and submillimeter waves. In these waveguides there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high impedance (ideally a perfect magnetic conductor) through the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear within the band of operation. The paper studies the characteristic impedance of the line and presents simulations and measurements of circuits designed using this technology.

Study of the characteristic impedance of a ridge gap waveguide

This paper presents a study of the characteristic impedance of a ridge gap waveguide. Ridge gap waveguides belongs to a new metamaterial-based waveguide technology for millimeter and submillimeter waves which emerged recently. A formula for the characteristic impedance of an ideal PEC-over-PMC ridge gap waveguide has been derived. A preliminary numerical study of the characteristic impedance of a real ridge gap waveguide where the PMC is realized by a bed of nails is also presented.

Novel UWB antennas with switchable and tunable band-notched behaviors

The objective of this paper is to further improve the antenna filtering capability by making this band- notched behavior switchable. Depending on whether interference from other systems is present or not, the antenna filtering feature can be activated. This work was initiated in F. Antonio-Daiu et al. (2006), but evolved designs with more promising results will be presented here. An antenna with similar performance was presented in V. A. Shameena et al. (2006), but some important differences exist, which will be discussed later. Moreover, using a similar configuration to that of the switchable antenna, a further improvement can be introduced to the band-notched UWB antenna by making the rejected frequency tunable.

A new Fast Physical Optics method for very large PEC surfaces

A new 3D Fast Physical Optics method is presented for computing backscattered fields at high frequencies of PEC parabolic surfaces. This method can be easily extended to more complex surfaces. By virtue of Cauchy theorem a suitable surface deformation is used to convert a double highly oscillatory integral into a double slow varying integral, easily calculable by means of Gaussian quadrature.

Barium titanate (BaTiO 3 ) RF characterization for application in electro-optic modulators

Barium titanate (BaTiO3 or BTO) is currently one of the most promising ferroelectric materials for enabling Pockels modulation that is compatible with silicon photonic circuits. The relative permittivity of BTO has been characterized in thin films deposited on a silicon-on-insulator (SOI) substrate. High values between 800 and 1600 have been estimated at 20 GHz. Furthermore, no substantial difference has been obtained by using BTO grown by molecular beam epitaxy and sputtering. The obtained permittivity has been used to properly design the RF electrodes for high-speed modulation in hybrid BTO/Si devices. Electrodes have been fabricated and the possibility of achieving modulation bandwidths up to 40 GHz has been demonstrated. The bandwidth is limited by the microwave propagation losses and, in this case, different losses have been measured depending on the BTO growth process.

Practical Derivation of Slot Equivalent Admittance in Periodic Waveguides

This communication describes a procedure for obtaining the equivalent-admittance representation of a slot in a waveguide. The approach is general, but it is particularly interesting for periodic waveguides, because it does not require knowing the Greens function of the wave guides or properly defining the ports in such waveguides. The procedure is demonstrated on a well-known rectangular waveguide. It is later applied to a periodic waveguide and used to design a small array. Measurements of the array performance are shown so as to validate the approach.

Fast physical optics using piecewise quadratic approximation

The physical optics (PO) approximation is a well-known technique used to analyze very large conducting structures. In scattering problems and radiation of large reflectors, the PO technique provides acceptable accuracy [1] for some applications. This technique allows avoiding the hard solution of the Method of Moment (MoM) linear system by approximating this solution by the explicit PO current.