Zabdiel Brito-Brito

Microstrip Switchable Bandstop Filter using PIN Diodes with Precise Frequency and Bandwidth Control

In this paper a switchable bandstop filter able to switch between two different central frequency states while precisely maintaining a fixed bandwidth is presented. The filter topology allows precise control over the design parameters frequency and bandwidth, achieved by choosing adequate resonator sections which are switched by PIN diodes to obtain two discreet states. The central frequency control was obtained by modifying resonator length. Bandwidth control was achieved by choosing a resonator width and controlling the normalized reactance slope parameter of a decoupling resonator by means of a switchable resonator extension. The filter was designed to have center frequencies of 2 and 1.5 GHz both having an 8% fractional bandwidth. The comparison between simulations and measurements showed a central frequency deviation of 4 MHz for the 2 GHz frequency response, and a deviation of 2 MHz for the 1.5 GHz frequency response. The fractional bandwidth deviation for the 2 GHz filter response was 0.67%, while at 1.5 GHz a 0.4% deviation was observed. The simulation and measured responses are in very good agreement.

Halved Vivaldi Antenna With Reconfigurable Band Rejection

This letter presents a Vivaldi antenna having the capability of dynamically rejecting interferers, mainly aiming at multistandard communication with dynamic frequencies allocation. Only half of the Vivaldi is used and placed over a ground plane, which is suitable to vehicular communication. The rejection Alter is integrated to the antenna real estate and consists of two microstrip resonators and two varactor diodes coupled to the slot of the Vivaldi. It is simply biased by applying the control voltage at the antenna RF port. Good matching is achieved from 2.5 to 8 GHz while rejecting a band whose central frequency can be tuned from 1.8 to 5.8 GHz. Simulated and measured return loss, gain, and radiation patterns are presented. The measured gain rejection in the direction of the radiation maximum is about 20 dB or better in the entire tuning range.

Characterizing a Tune All Bandstop Filter

In this paper a reconfigurable bandstop filter able to reconfigure central frequency, bandwidth and selectivity for fine tuning applications is presented. The reconfigurable filter topology has four poles and a quasi-elliptic bandstop filter response. The filter is tuned by varactor diodes placed at different locations on the filter topology. The varactors are voltage controlled in pairs due to filter symmetry for central frequency and bandwidth control. An additional varactor is placed on a crossing line to move a pair of transmission zeros, closer or farther to the filter central frequency, which tunes filter selectivity. The filter has a tuneable fractional bandwidth range from 11.51 to 15.46%, a tuneable central frequency range from 1.346 to 1.420 GHz and a selectivity tuning range from 0.37 to 0.40 dB/MHz.

Return-loss minimization of package interconnects through input space mapping using FEM-based models

Highly efficient CAD methodologies based on full-wave EM analysis, for the design of package interconnects are necessary due to the increased frequencies of operation and a desire of faster time-to-market. In this work, we exploit a Broyden-based input space mapping (SM) algorithm with both fine and coarse models implemented with the finite-element method (FEM), to efficiently optimize design parameters of a modern package interconnect. This optimization algorithm has been applied to a single-ended package line resulting in a significant decrease of the return loss in the 5-10 GHz range, requiring just a few fine model evaluations.

Systematic configuration of coarsely discretized 3D EM solvers for reliable and fast simulation of high-frequency planar structures

Accurate simulation of microstrip and other planar structures at very high frequencies usually requires employing full-wave electromagnetic (EM) solvers. For planar circuits, 2.5D EM solvers are especially suited and easy to configure. However, in some cases, planar circuits are required to be simulated in 3D solvers. On the other hand, low-resolution discretization in 3D solvers is necessary when coarse models are employed for direct EM optimization, for instance, in space mapping methodologies, or in surrogate-based modeling techniques. In this work, we propose a systematic methodology to find a suitable 3D EM solver configuration when low-resolution meshing is needed for reliable and fast simulation of planar structures. We illustrate how improper configuration of the 3D EM solver might lead to significant alteration of the inherent structures EM response, as well as to numerical noise that affects the parameterized usage of these models, such as in direct EM optimization. Our technique is illustrated by a couple of classical microstrip filters simulated with a commercially available 3D full-wave EM solver.

Impact of 3D EM model configuration on the direct optimization of microstrip structures

We apply the classical Nelder-Mead optimization algorithm to a low fidelity EM model, using different mesh and bounding-box configurations. We demonstrate that the interaction of the coarse mesh with the bounding box size can determine whether the optimization is successful or not.

Recent advances in reconfigurable microwave filters

In today´s communication systems the demand for tunable filters with high performance and with independent control of the filter parameters have been growing. In this paper an overview of several tunable filters that have been proposed over the last years is presented, focused on recent developments involving independent frequency, bandwidth and selectivity control, and high resonator Q filters.

Reconfigurable Microwave Filters

Reconfigurable microwave filters make microwave transceivers adaptable to multiple bands of operation using a single filter, which is highly desirable in today’s communications with evermore growing wireless applications. Tunable filters can replace the necessity of switching between several filters to have more than one filter response by introducing tuning elements embedded into a filter topology. Microwave tunable filters can be divided in two groups, filters with discrete tuning, and filters with continuous tuning. Filter topologies presenting a discrete tuning generally use PIN diodes or MEMS switches. On the other hand, filter topologies using varactor diodes, MEMS capacitors, ferroelectric materials or ferromagnetic materials are frequently used to obtain a continuous tuning device. Filter topologies can mix continuous and discrete tuning by combining tuning elements as well, e.g. the use of switches and varactors on a filter topology can form part of a discrete and continuous tuned device. Center frequency is the most common filter parameter to reconfigure. Fewer designs reconfigure other parameters, such as the bandwidth or selectivity. When deciding which technology is adequate for a given application, the designer must consider the following issues: cost, power consumption, size, performance and operating frequency. This chapter intends to provide a broad view of the microwave reconfigurable filters field, where different technologies used to reconfigure filters are discussed through different chapter sections, and finally an overall view of the field is given in the conclusions section at the end of the chapter. This chapter starts discussing filters that use active devices as tuning elements in section 2; these include the PIN diode, the varactor diode, the transistor and Monolithic Microwave Integrated Circuit (MMIC) implementation. Section 3 discusses the use of Micro Electro Mechanical Systems (MEMS) as tuning elements on filter topologies; the section discusses the use of MEMS switches and MEMS varactors. Section 4 contains tunable filters using ferroelectric materials, where devices using the most common ferroelectrics are discussed. Section 5 contains filters that use ferromagnetic materials as tuning elements, the section discusses circuits using Yttrium-Iron-Garnet (YIG) films and other ferromagnetic tuning mechanisms. Section 6 describes devices that combine some of the technologies discussed in previous sections to achieve reconfigurable filter parameters. Section 7 contains a discussion of

Enhanced formulation for polynomial-based surrogate modeling of microwave structures in frequency domain

Practical formulations for EM-based modeling of microwave structures using simple polynomial surrogate functionals are described in this paper. A new polynomial surrogate formulation is proposed and compared against a previously published formulation. Both formulations calculate the surrogate model weighting factors in closed form, yielding global optimal values in the least squares sense. These formulations are suitable for EM-based design problems with no equivalent circuital models available. Our new formulation exhibits smaller learning errors and better generalization performance than the original formulation. Both methodologies are illustrated by the EM-based modeling a SIW interconnect with microstrip transitions on a standard FR4-based substrate implemented in a 3D full-wave FEM simulator.

Impedance matching analysis and EMC validation of a low-cost PCB differential interconnect

This work analyzes a USB differential pair transmission line achieved in an inexpensive standard PCB laminate that is aimed for the Internet of Things ecosystem. An initial simulation in Sonnet EM simulator of the most basic structure is presented, along with a preliminary electromagnetics-based design as well as a basic EMC analysis under the IEC 61000-4-2 standard. In addition, the analysis of a known and well characterized differential structure is presented in order to set its response as a calibration reference. These initial simulations are intended to set the foundations for a more accurate model in a future work.