Juan E. Page

Simulation of negative permittivity and negative permeability by means of evanescent waveguide Modes-theory and experiment

In this paper, the theoretical foundations of the equivalence between waveguide propagation below cutoff and artificial plasmas are carefully analyzed through the derivation of the propagation constants of normal modes in waveguides filled with anisotropic plasmas. The equivalence between waveguide and dielectric plasma proposed by Marquees et al., which is valid for evanescent TE modes, has a dual counterpart for magnetic plasmas and evanescent TM modes. This new equivalence states that a negative magnetic permeability medium can be simulated by means of TM modes below their cutoff frequencies. The need of an anisotropic filling of the waveguide for the equivalence between plasmas and evanescent modes is also highlighted. To exemplify the applicability of this new equivalence, a structure that implements a double-negative medium has been proposed. Full-wave simulations of the proposed structure and measurements from an experimental setup are presented, both of which corroborate the new equivalences validity.

Fullwave analysis of three and four-port rectangular waveguide junctions

An efficient and accurate technique for the analysis of three- and four-port rectangular waveguide junctions is presented. The technique is based on a generalization of the admittance matrix concept of circuit theory and yields a multimodal description of junctions by means of their generalized admittance matrix. The elements of this matrix are analytically obtained. The multimodal description of three- and four-port junctions allows us to link them with other junctions and/or discontinuities by considering the interactions of the fundamental and higher order modes, thus achieving a fullwave characterization of composite structures. The technique is verified by comparing its results with available measurements of E- and H-plane T-junctions. The E-/H-plane three-port junction which is seldom used, is also analyzed. Finally, the four-port structure magic-T is considered and an analysis of the relative convergence problem for this structure is presented. >

Electronic controllable reflectarray elements in X band

This paper shows the design and measurements of two types of reflectarray (RA) elements with electronic control for pattern reconfigurability in X band (10.5 GHz). The radiating element consists of a patch which is coupled to a microstrip line through a slot. This structure can produce a wide range of phase shift in the re-radiated signal with a very linear response. By adding a proper electronic controllable phase-shifter to the line section it is possible to control the reflected signal allowing the pattern reconfigurability through a proper design. Two different phase-shifters have been studied: one is based on PIN diodes and allows a phase change by discrete steps. The second uses a varactor diode which allows a continuous phase-shift in the range of 120o, which would be valid for some cases of reconfigurable antennas. These elements have been validated using a Waveguide Simulator. Index Terms – Reflectarray antennas, reconfigurable antennas.

Analytical model of the wire-bonded interdigital capacitor

The wire-bonded interdigital capacitor (WBIDC) is an interdigital capacitor with short circuits across the end of alternate fingers that result in an improved frequency response. This paper presents the analytical and circuital models of the WBIDC, which are useful to design and to incorporate into an electromagnetic or circuit analysis computer-aided design program. Design equations of the WBIDC are also presented. The analytical model and design equations have been validated with numerical analysis and experimental work.

A Switchable Multiple Beam Antenna for GSM-UMTS Base Stations in Planar Technology

A broadband antenna for GSM1800-UMTS base stations with multiple switchable beams in azimuth is presented in this paper. The multiple beams are obtained by means of a broadband Butler matrix. The radiating element is broadband and consists of two stacked patches. The elevation pattern is shaped with null filling and upper lobe reduction that has been achieved by means of a broadband corporate feed network implemented in microstrip technology. Photographs and measurements of the manufactured prototypes are presented confirming that the design of all of the elements is correct

Lattice Equivalent Circuits of Transmission-Line and Coupled-Line Sections

A lattice network with branches made up of open- and short-circuited transmission-line sections is proposed as an equivalent circuit for a wide range of so-called coupled-line filter sections. The proposed lattice equivalent circuits have proven to be an advantageous alternative to the equivalent circuits found in the technical literature (when available) as they are exact, useful in wide frequency bands, and take into account the different phase velocities of even and odd modes.

DERIVATION AND GENERAL PROPERTIES OF ARTIFICIAL LOSSLESS BALANCED COMPOSITE RIGHT/LEFT-HANDED TRANSMISSION LINES OF ARBITRARY ORDER

A circuit theory-based approach for systematically deriving all possible lossless balanced composite right/left-handed transmission lines is described. To illustrate the usefulness of the proposed approach, novel artiflcial transmission line unit-cells with tri- and quad-band behaviour are proposed. It is shown that the number of right-handed or left-handed frequency bands exhibited by such transmission lines is determined by the order of its unit-cell. It is explained why artiflcial lossless balanced transmission lines exhibit a stop-band around each pole of their associated continuous transmission line that can not be closed up. Since this approach allows for the systematic derivation of such transmission line unit-cells of arbitrary order, multi-band components based on metamaterial transmission lines are envisaged.

Planar Broadband Slot Radiating Element Based on Microstrip-Slot Coupling for Series-fed Arrays

A novel planar slot radiating element with applications in series-fed arrays and significant bandwidth enhancement is presented in this communication. The structure is based on the microstrip-slotline coupling and simply consists of a microstrip-fed slot with a symmetrically-arranged strip conductor superimposed onto it. The broad impedance bandwidth (up to 16 GHz) lies in the resulting all-pass section that the strip and the slot make up. A theoretical study of the structure in terms of even and odd modes as well as a straightforward equivalent circuit are provided, which offer the required analytical tools to state the design methodology. Experimental and simulated results corroborate that the strip acts as a mere matching element that does not practically alter the slot radiation characteristics.

Exact Analysis of the Wire-Bonded Multiconductor Transmission Line

In this paper, the exact model of a multiconductor transmission line with bonding wires is presented. The model is based on the multiport admittance matrix, and is valid for any number of conductors in the structure. The model shows how to compute the two-port admittance matrix of the wire-bonded structure with direct application to the wire-bonded interdigital capacitor. The model has been validated by means of method-of-moments-based numerical simulation and by experimental work.

Design of Broadband Transmitarray Unit Cells With Comparative Study of Different Numbers of Layers

A generalized methodology to design low-profile transmitarray (TA) antennas made of several stacked layers with nonresonant printed phasing elements is presented. A study of the unit cell bandwidth, phase-shift range and tolerances has been conducted considering different numbers of layers. A structure with three metalized layers with capacitive and inductive elements enabling a phase range of nearly 360° and low insertion loss is introduced. A study of the four-layer structure shows improvement in the performance of the unit cells in terms of bandwidth from 2% to more than 20% and a complete phase coverage. Implementations on a flexible substrate of TAs with progressive phase shift operating at 19 GHz are used for validation.