Showing papers by "Luca Perregrini published in 2019"

Partially Air-Filled Substrate Integrated Waveguide Filters With Full Control of Transmission Zeros

Abstract: This paper presents the investigation and testing of novel substrate integrated waveguide (SIW) bandpass filters, based on air-filled cavity resonators. Removing the lateral parts of the dielectric substrate in SIW rectangular cavities enables the use of the TM120 and TM210 modes to implement a dual-mode resonator. In addition, the fundamental TM110cavity mode is adopted to implement a transmission zero. This paper demonstrates the complete control of the central operation frequency, the pass bandwidth, the spurious-free bandwidth region, and the location of the transmission zeros. After a comprehensive theoretical investigation, design rules are derived and applied to the implementation of a variety of dual-mode cavities, which have been manufactured and tested. Moreover, these basic structures have been used as building blocks to design higher order filters: simulations and measurements of four-pole filters are reported for validation.

Tunable Phase Shifter Based on Few-Layer Graphene Flakes

Abstract: This letter presents a voltage-controlled tunable phase shifter based on few-layer graphene. The phase shifter consists of a stub-loaded line, composed of a microstrip line with a stub attached to it through a taper and graphene pad. The bias voltage applied to the graphene pad determines a variation of graphene resistance, which eventually causes the phase change. Without any voltage bias, graphene exhibits high resistance, thus isolating the stub and leading to a low phase shift. As the bias voltage is increased, graphene resistance is lowered, the effect of the stub is more pronounced, and the phase shift is increased. A prototype operating in the frequency range from 5 to 6 GHz has been designed and tested. The measured maximum phase shift obtained is 40°, and the corresponding degradation of the insertion loss is 3 dB.

Evaluation of the Dispersion Diagram of Inhomogeneous Waveguides by the Variational Meshless Method

Abstract: This paper presents an extension of the variational meshless method to the calculation of the dispersion diagram of metallic waveguides including inhomogeneous dielectric regions. The method is based on the combination of the variational formulation of a 2-D boundary problem and of the meshless method using radial basis functions. The problem requires a vector representation of the field, and it leads to a well-conditioned, real, and symmetric eigenproblem, where the matrices depend on the propagation constant $\beta $ . By solving the eigenproblem for several values of $\beta $ , a spurious-free dispersion diagram of the guiding structure is obtained. Several structures are studied to demonstrate the accuracy and reliability of the proposed technique. The simulation results are compared with the analytical ones, when available, and with those given by a commercial FEM code, always showing a very good agreement with a smaller number of unknowns.

A Review of Compact Substrate Integrated Waveguide (SIW) Interconnects and Components

Abstract: This paper presents a review of the most common strategies to miniaturize substrate integrated waveguide (SIW) structures, and their application to the implementation of microwave components and antennas. The folded SIW, half-mode SIW, ridge SIW and substrate integrated slab waveguide (SISW) are presented and discussed. Most of these structures allow to reduce the footprint of regular SIW interconnects, and in some cases they exhibit broader single-mode bandwidth. These structures have been adopted for the implementation of microwave components and antennas with smaller size and comparable performance, including compact cavity filters and cavity-backed antennas: the design and realization of these components is described through examples and applications.

Mode Matching Analysis of Waveguide Components Exploiting the Variational Meshless Method

Abstract: This letter presents the analysis of waveguide components comprising a cascade of step junctions by mode matching in conjunction with the variational meshless method (VMM). In particular, a large number of modal fields of the waveguides are calculated very efficiently by the VMM. Moreover, the collocation points are randomly distributed in each waveguide cross section, and the coupling coefficients are obtained regardless of their mutual distribution. The presented technique is validated through the analysis of two junctions reported in the literature and by comparison with an finite element method (FEM) full-wave software.

A New Class of Doublet Based on Slotted Slant Ridge in Additive Manufacturing Technology

Abstract: Additive Manufacturing (AM) technology is becoming very popular for the manufacturing of electromagnetic components. In this paper the flexibility of the AM is exploited to obtain compact waveguide filters. Filters are based on transverse slant ridge resonators inside a rectangular waveguide. The ridge incorporates a slot, possibly folded. The resonance of the slot is exploited in addition to the resonance of the transverse slanted ridge to obtain a compact dual mode resonator. Therefore, a single slotted ridge can produce two poles and two transmission zeros (TZs). Control of couplings to ridge resonance is obtained by using the slant angle, while control of couplings to slot resonance is obtained by folding the slot in different points. The structure realizes a transversal topology allowing the control of the transmission zero by controlling the ratio between coupling to ridge resonance and coupling to slot resonance.

Miniaturized SIW Filters Based on Shielded Quarter-Mode Cavities

Abstract: This paper presents a modified quarter-mode cavity in substrate integrated waveguide (SIW) technology, which combines miniaturized dimension and fairly good quality factor, and its application to the design of SIW cavity filters with improved performance. The modeling of the quarter-mode SIW cavity to get maximum quality factor and the design of a bandpass filter to minimize insertion loss are presented, along with the experimental verification of the proposed approach.

Different Strategies for the Additive Manufacturing of Slotted Slant Ridge Filtering Doublet

Abstract: In this paper, the slotted slant ridge resonator together with different strategies for their manufacturing with 3D printing technology is illustrated The slant ridge resonator consists of a ridge with a slot inserted in a rectangular waveguide Both ridge and slot resonant modes are exploited to obtain a second order filter response (doublet) capable of two poles and two transmission zeros The structure allows an excellent control in terms of both bandwidth and transmission zero positioningThe manufacturing strategies considered in the paper consists in the 3D printing of the slotted ridge with different supports Ridge and support are then electroplated and finally inserted in a metallic rectangular waveguide ensuring the metal contact between support and waveguide Measured results demonstrating the feasibility of the method are shown

Analysis of Inhomogeneous Rectangular Cavities Using the Variational Meshless Method

Abstract: The variational meshless method (VMM) has been proposed and demonstrated as a very effective tool for the analysis of 2D structures. In this work, the VMM is extended to 3D eigenvalue problems. In particular, the calculation of the eigenmodes of a rectangular cavity filled with inhomogeneous dielectric material is addressed. The theory is outlined, and the method is validated through the analysis of three different structures. The results are compared with analytical values, when available, and by comparison with a commercial software based on the finite element method. In all cases a good accuracy is obtained for a large number of modes using a limited number of unknowns. Finally, the method proved to be spurious-free.

Innovative Filters in Partially Air-Filled in Substrate Integrated Waveguide Technology

Abstract: This paper presents a novel class of substrate integrated waveguide filters, based on partially air-filled rectangular cavities. These partially-air filled cavity implements a doublet, that exhibits a frequency response with two poles and two transmission zeros. Two different topologies are proposed: in the first one, the partially air-filled region is located in the center of the rectangular cavity and this allows to locate two zeros below the pass band; in the second topology, two partially air-filled regions are located at the sides of the rectangular cavity and this allows to locate arbitrarily the two zeros, either both below, or both above, or one below and one above the pass band. Prototypes of the two topologies have been designed and experimentally verified.

Analysis of Dielectric Waveguides With the Variational Meshless Method

Abstract: The Variational Meshless Method (VMM) is extended to simulate open dielectric waveguides, with the aim to find the dispersion diagram of the propagating modes. This is done by truncating the domain with a magnetic wall condition, which leads to a good approximation of the open boundary in the range of frequencies where the field is almost confined in the dielectric with higher permeability. The advantage of this approach is to lead to a linear eigenproblem, thus avoiding the need of time consuming root search. Moreover, adopting the magnetic wall boundary condition reduces the number of unknowns with respect to other closing boundary conditions. Some examples demonstrate the effectiveness of the proposed approach.

Engineering the Resonant Cavities in Substrate Integrated Waveguide Technology

Abstract: This paper presents a review of the major applications of substrate integrated waveguide (SIW) cavities and of the various techniques proposed in the last years to engineer the resonant cavities in SIW technology The aim of engineering the SIW cavities is multifold, and includes the size reduction, the loss minimization, and the optimization of the resonant modes pattern A variety of topologies of modified SIW cavity resonators are presented, together with their advantages and disadvantages, and several applications are described and discussed

The Variational Meshless Method: an Overview of the Theory and Applications

Abstract: This paper presents an overview of the variational meshless method (VMM), from his inception to the more recent developments. The VMM is an hybridization of the meshless method with the variational technique, which lead to an accurate and efficient algorithm. The theoretical aspects of the VMM implementation for the analysis of 2D and 3D waveguide structures and cavities will be addressed, and the some results will be reported to demonstrate te effectiveness of the proposed algorithm.

Stacked Substrate Integrated Waveguide Filter with Air-Holed Cavities

Abstract: This paper presents a novel filter in substrate integrated waveguide (SIW) technology, based on stacked identical rectangular cavities, where the readjustment of the resonance frequency of the cavities is performed by using air holes in the center of the cavities. The coupling between two overlapped cavities is obtained by a slot in the common metal plane. The proposed topology leads to an easier fabrication of the filter, as the metal via holes are identical and aligned for all stacked cavities. To allow the connection with input/output coplanar waveguides, the use of SIW below cutoff is adopted, thus avoiding the need of blind vias. The design, the fabrication, and the experimental testing of a three-pole filter are presented to validate the proposed solution.