Giorgio Montisci

Waveguide slot antennas for circularly polarized radiated field

We present a new waveguide slot configuration able to radiate a circular polarization with a very low axial ratio. This configuration is mainly intended as a circularly polarized radiating element to be used in an array. Both left-hand and right-hand circular polarization can be independently obtained and therefore this configuration could be used to realize a polarization agile antenna. The proposed configuration consists of two very closely spaced radiating slots, so a specialized method of moments code has been developed to analyze, in a very effective way, the near-field interaction between such slots. Our method of moments code has been validated against a commercial finite-element method code, and then used to design a number of different circularly polarized radiating elements.

Design of Circularly Polarized Waveguide Slot Linear Arrays

A design procedure for circularly polarized waveguide slot linear arrays is presented. The array element, a circularly polarized radiator, consists of two closely spaced inclined radiating slots. Both the characterization of the isolated element and the evaluation of the mutual coupling between the array elements are performed by using a method of moments procedure. A number of traveling wave arrays with equiphase excitations are designed and then analyzed using a finite element method commercial software. A good circular polarization is achieved, the design goals on the far field pattern are fulfilled and high antenna efficiency can be obtained

A Wideband PET Inkjet-Printed Antenna for UHF RFID

A new antenna, designed on a polyethylene terephthalate (PET) substrate and implemented by inkjet printing using a conductive ink, is proposed as a passive tag antenna for UHF radio frequency identification (RFID). The operating bandwidth of the proposed antenna is very large since it encompasses all worldwide UHF RFID bands and extends well beyond at both edges. Moreover, it has a very simple geometry, can be easily tuned to feed many of the commercial RFID chips, and is very robust with respect to realization tolerances. The antenna has been designed using a general-purpose 3-D computer-aided design (CAD), CST Microwave Studio, and measured results are in very good agreement with simulations. The proposed passive RFID tag meets both the objectives of low-cost and size reduction.

A Rigorous Analysis of Dielectric-Covered Narrow Longitudinal Shunt Slots With Finite Wall Thickness

ABSTRACT The need for a protective dielectric cover is becoming more relevant in waveguide slot arrays, expecially in space applications. The aim of this paper is to describe a rigorous Method of Moment approach to the analysis of a dielectric-covered longitudinal shunt slot, taking into account the effect of the wall thickness. The whole procedure has been devised aiming at a time effective but precise way to compute the slot admittance, tailored to the needs of design procedures for slot arrays.

DESIGN OF A PRINTED LOG-PERIODIC DIPOLE ARRAY FOR ULTRA-WIDEBAND APPLICATIONS

A printed Log-periodic dipole array (LPDA) is presented, operating over the C, X and Ku bands. The antenna feeding structure consists of two coaxial cables, in order to realize an inflnite balun which provides the required broadband input matching. The second coaxial cable mirrors the flrst one, connected to the antenna input, and is capable of both stabilizing the antenna phase center and improving the radiation pattern. The antenna has been designed using CST Microwave Studio, with an useful frequency range of 4{18GHz. Moreover, both simulated and measured results show that the proposed LPDA can be successfully used as an Ultra Wideband Antenna in the range 4.25{13.25GHz, in which its phase center remains stable.

Design of Dielectric-Covered Planar Arrays of Longitudinal Slots

The Elliotts procedure for the design of a waveguide longitudinal slot array has been extended to the case of dielectric-covered planar slot arrays. A protective dielectric cover is required in many different applications of waveguide slot arrays, especially in aerospace and satellite applications. The results of the synthesis procedure have been validated against a commercial FEM software.

A Printed LPDA Fed by a Coplanar Waveguide for Broadband Applications

A printed log-periodic dipole array (LPDA), operating between 3 and 6 GHz and fed with a coplanar waveguide, is presented. The antenna has been designed starting from Carrels theory, optimized using CST Microwave Studio 2012, and then realized. The comparison between simulated and measured results shows that the proposed antenna can be used for broadband applications in the whole operating frequency band (3-6 GHz), with a very good input matching and a satisfactory endfire radiation pattern.

Effective Analysis of a Waveguide Longitudinal Slot With Cavity

We propose an effective and accurate analysis technique based on the method of moments (MoM) for the characterization of a longitudinal slot with a short truncated waveguide above it. This antenna has been used in the recent literature as the radiating element of large waveguide arrays. We focus our attention on some features and applications of this configuration which have not been taken into account in previous works. Then, we discuss the need for a tailored, effective and accurate analysis technique linking the radiating properties of the proposed antenna to its circuital properties according to Elliotts model. This task is easy by using the MoM with entire domain sinusoidal basis functions. The results of our procedure are compared with those of Ansoft HFSS against the computational time, showing a significant improvement.

Design of Shaped Beam Planar Arrays of Waveguide Longitudinal Slots

The Elliott’s procedure for the design of a pencil beam waveguide longitudinal slot array has been generalized to encompass the design of shaped beam planar slot arrays. An extended set of design equations, taking into account in an operative way the feeding part of the array, has been devised. From this set of equations, a general and effective design procedure has been set up, shedding light on the constraints posed by a complex aperture distribution. The results of the proposed synthesis procedure have been validated through comparison with a commercial FEM software.

Effective analysis of a microstrip slot coupler

A popular feeding technique for printed antennas is the use of a coupling slot. From a modelling point of view, we can describe the patch as a transmission line resonator and therefore consider this slot as a coupler between two microstrip lines. In this paper we propose a model for such a transverse coupling slot cut in the ground plane between two microstrip lines. Aim of this work is to give an effective and accurate characterization of the electromagnetic coupling due to the slot. The presented approach is based on the equivalence between a microstrip line and a magnetic wall waveguide. The coupling slot effect has been modelled using a full-wave method of moment analysis technique, which takes rigorouslyinto account the effect of the finite thickness of the ground plane. The proposed model has been validated through comparison with both a finite element method and a method of moment–based commercial software. A suitable circuital model has eventuallybeen derived.