Systematic Design of Wideband Bandpass Filters Based on Short-Circuited Stubs and λ/2 Transmission Lines

!In this paper, a new technique to design wideband bandpass filters BPFs is proposed. It is based on the classical filter topology formed by shunt short-circuited stubs connected by transmission lines, where the λ/4 connecting lines are replaced by λ/2 lines. In this way, the connecting lines have a double functionality: to control the coupling between resonators and to add additional poles, increasing the filter order up to 2N -1, where N is the number of short-circuited stubs. In addition, their function as inverters is, theoretically, for all spectrum, avoiding the limitation of the λ/4 lines working as inverters or the coupled-line coupling mechanisms of classical configurations, which are of narrowband nature. Design equations are provided with up to N degrees of freedom, which allows for a proper selection of impedance values for the filter design. As a verification, a 5th-order BPF of fractional bandwidth 50and with a Chebyshev response is implemented, fullfiling the expections and validating, in this way, the proposed approach

Energy Recovery from Microstrip Passive Circuits

In this paper, the energy recovery in microstrip passive circuits from the power losses into heat is studied. For this purpose, a thermoelectric generator (TEG) based on the Seebeck effect principle is used, which converts part of the power dissipated into heat to dc electrical power. A solution integrating the TEG with the microstrip circuit is proposed, and design guidelines in order to optimize the recovered power keeping a good isolation between the RF signal and the TEG system are provided. As will be shown, under moderate applied signal powers of just 1–5 W, the levels of recovered power in microstrip passive circuits can be notable. As a demonstrator circuit, an integration device formed by an embedded microstrip bandpass filter for WiMAX applications and a TEG is designed, fabricated, and characterized (thermal and electrically). Different scenarios are considered, depending on frequency and thermal loads. For an applied inband CW input signal power of 2 W at 3.48 GHz, a recovered power of around 250 μW has been continuously supplied to the electrical load. Several aspects, such as efficiency and future improvements, are also discussed.This work was supported by the Euripides European Project MIDIMU-HD

Compact Dual-Mode Substrate Integrated Waveguide Coaxial Cavity for Bandpass Filter Design

This letter proposes a new compact filtering building block. It consists of two via holes embedded into a substrate integrated waveguide (SIW) cavity connected to capacitive metal patches at the top layer. This topology provides two coaxial modes performing a doublet filtering configuration. The proposed dual-mode SIW coaxial cavity is studied in detail and guidelines for the filter design are given. As will be shown, the proposed building block presents a high degree of design flexibility, which allows for the design of multiple kind of bandpass filter (BPF) responses, including both narrow- and wide-band BPFs along with transmission zero generation. As a verification, several filters are designed and implemented at 8 GHz.This work has been supported in part by MINECO (Spanish Government) under projects TEC2013-47037-C5-1-R and TEC2013-48036-C3-3-R, and by a “Juan de la Cierva” Research fellowship

Design Strategy and Considerations to Improve Corona Discharge Breakdown in Groove Gap Waveguides

Paper submitted to the 15th European Conference on Antennas and Propagation (EuCAP), 22-26 March 2021.This paper studies the corona discharge breakdown thresholds in groove gap waveguides, and proposes a design strategy to enhance its peak power handling capability (PPHC). The theoretical analysis is focused on the study of the quasi-TE 10 mode, and on the PPHC at different frequencies and multiple arrangements of the pin dimensions of the bed of nails. Next, the geometrical parameters width, length and separation of such pins are optimized for improving peak power limits. Finally, the simulated results show reasonably good performance with respect to the equivalent rectangular waveguide power limit.This work has been supported by the University of Alicante through the fellowship grant UAFPU2018-054 and by the ”Ministerio de Ciencia e Innovación” through research projects PID2019-103982RB-C41 and PID2019-103982RB-C43

In-depth Study of the Corona Discharge Breakdown Thresholds in Groove Gap Waveguides and Enhancement Strategies for Inductive Bandpass Filters

This work focuses on the study of the corona discharge breakdown in groove gap waveguides (GGWs) and inductive bandpass filters (BPFs) based on this technology. With the main aim of improving the peak power handling capability (PPHC), the location of the maximum normalized electric field strength (|Ê MAX |) as a function of the geometrical parameters is analyzed. First, the research deals with wave-guiding structures, comparing the distribution of the transverse electric TE10-like mode of a GGW to that of an equivalent rectangular waveguide (RW). Next, a design strategy based on the adjustment of the geometrical dimensions of the bed of nails is proposed, thus achieving a considerable reduction of |Ê MAX |. The second part of this paper aims for vertically polarized GGW BPFs, where the inductive irises become the most critical part of the component. By a simple modification of their dimensions, a second design criterion is suggested for improving the PPHC. Finally, several Ku-band BPFs centered at 14 GHz and 16 GHz have been manufactured and experimentally verified at the European High-Power Radiofrequency Space Laboratory. This measurement campaign shows peak power thresholds up to 1.09 kW and 3.59 kW at 600 mbar for the non- and full-optimized GGW BPFs, respectively, thereby demonstrating a PPHC enhancement up to 5.16 dB in the high-pressure range when both strategies, proposed in this work, are used.The authors would like to thank the European Space Agency (ESA) and Val Space Consortium (VSC) —Laboratories funded by the European Regional Development Fund—A way of making Europe, and the Antennas and Propagation Lab (APL – iTEAM UPV) for their contributions

Advanced Filtering Solutions in Coaxial SIW Technology Based on Singlets, Cascaded Singlets, and Doublets

(c) 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.[EN] The use of singlets, cascaded singlets and doublets in coaxial substrate integrated waveguide (SIW) technology is proposed in this paper, with the aim of implementing low-loss filters with very compact size and highly-selective symmetric, asymmetric as well as dual-band responses. Singlets based on coaxial SIW resonator structures with source-load coupling are presented and studied. Then, different filter examples based on N cascaded singlets are designed, fabricated and measured at 7.5 GHz, with up to N transmission zeros (TZs) that can be easily located below and above the passband. Moreover, the application of doublets based on a dual-mode coaxial SIW resonator with source-load coupling for achieving extremely compact dual-band filters is presented, and two examples with different bandwidth configuration for each channel are designed, demonstrating the flexibility of the proposed coaxial SIW structure. The obtained experimental results of the different implemented filters show a good agreement with simulations, thus confirming the interesting potential application of these structures for the design of very compact devices with advanced filtering responses.This work was supported by the Ministerio de Economia, Industria y Competitividad, Spanish Government, under Project TEC2016-75934-C4-3-R.Sirci, S.; Sánchez-Soriano, MÁ.; Martínez Pérez, JD.; Boria Esbert, VE. (2019). Advanced Filtering Solutions in Coaxial SIW Technology Based on Singlets, Cascaded Singlets, and Doublets. IEEE Access. 7:29901-29915. https://doi.org/10.1109/ACCESS.2019.2902956S2990129915

When Compactness Meets Flexibility: Basic Coaxial SIW Filter Topology for Device Miniaturization, Design Flexibility, Advanced Filtering Responses, and Implementation of Tunable Filters

[EN] Substrate integrated waveguide (SIW) technology [1], [2] is a well established and successful approach for implementing planar microwave filters with very stringent requirements in terms of quality (Q) factor and also with the ability to integrate into a system. Optimized SIW filters can reach a Q factor of 200-800 using low-loss substrates and standard fabrication procedures [3]. Furthermore, packaging and electromagnetic (EM) shielding, power-handling capabilities, and low-cost batch manufacturing are other broadly recognized strengths of this approach. However, SIW filters are still larger than most of their planar counterparts; in addition, advanced topologies are not always easy to accommodate, and filter reconfigurability usually leads to very complex implementation [4]-[6]Martínez Pérez, JD.; Sirci, S.; Boria Esbert, VE.; Sánchez-Soriano, MÁ. (2020). When Compactness Meets Flexibility: Basic Coaxial SIW Filter Topology for Device Miniaturization, Design Flexibility, Advanced Filtering Responses, and Implementation of Tunable Filters. IEEE Microwave Magazine. 21(6):58-78. https://doi.org/10.1109/MMM.2020.2979155S587821

Peak Power Handling Capability in Groove Gap Waveguide Filters Based on Horizontally Polarized Resonators and Enhancement Solutions

This letter studies the peak power handling capability (PPHC) in groove gap waveguide filters based on horizontally polarized resonators. Moreover, a modification of the resonant cavity is proposed, where the central pins of the original structure are replaced by a rounded metal block. As a result of this change, the TE₁₀₁-like mode can still be excited, but the maximum electric field strength is shifted to the center of the cavity, which leads to a higher PPHC. The main advantages of the original structure are maintained, and greater robustness in the manufacturing process is achieved. Next, some guidelines for the design of the coupling windows and the dimensions of the blocks are shown to minimize the electric field strength and, consequently, maximize the PPHC. Finally, two third-order bandpass filters (with pins and with blocks) centered at 16 GHz have been manufactured and tested in a measurement campaign, where a PPHC enhancement of 8.7 dB at high pressures is achieved for the novel solution presented in this work.This work was supported in part by the University of Alicante through the Fellowship Grant UAFPU2018-054 and in part by MCIN/AEI/10.13039/501100011033 through the Sub-Projects C41 and C43 of the Coordinated Project under Grant PID2019-103982RB

A novel band-pass filter based on a periodically drilled SIW structure

The design and fabrication of a band-pass step impedance filter based on high and low dielectric constant sections has been realized on substrate integrated waveguide (SIW) technology. The overall process includes the design of the ideal band-pass prototype filter, where the implementation of the impedance inverters has been carried out by means of waveguide sections of lower permittivity. This can be practically achieved by implementing arrays of air holes along the waveguide. Several SIW structures with and without arrays of air holes have been simulated and fabricated in order to experimentally evaluate their relative permittivity. Additionally, the equivalent filter in SIW technology has been designed and optimized. Finally, a prototype of the designed filter has been fabricated and measured, showing a good agreement between measurements and simulations, which demonstrates the validity of the proposed design approach.This work was supported by the Ministerio de Economía y Competitividad, Spanish Government, under the Research Project TEC2013-47037-C5-4-R

Estrategia de Diseño para Aumentar la Capacidad en Potencia en Guias de Onda Groove-Gap

[EN] This work describes a new design strategy for improving the power handling capability (PHC) of groove gap waveguides (GGW). First, a theoretical analysis is carried out to study the distribution of the quasi-TE10 mode and the variation of the PHC for different configurations and frequencies. Then, in order to minimize the strength of the maximum electric field above the pins, three of the main geometrical dimensions of the nails are optimized. Finally, the numerical results show that by using this strategy, the corona discharge power thresholds can be enhanced without degrading the electrical response.Este trabajo ha sido financiado por la Universidad de Alicante mediante la beca de investigación UAFPU2018-054, y por el Ministerio de Ciencia e Innovación a través de los proyectos de investigación PID2019-103982RB-C41 y PID2019-103982RB-C43.Morales-Hernández, A.; Ferrando-Rocher, M.; Sánchez-Soriano, MÁ.; Marini, S.; Boria Esbert, VE. (2021). Estrategia de Diseño para Aumentar la Capacidad en Potencia en Guias de Onda Groove-Gap. Íñigo Cuiñas Gómez. 1-4. http://hdl.handle.net/10251/1910731