Passive devices for UWB systems

Postprint (published version

Microstrip to Double Ridge Empty Substrate Integrated Waveguide Transitions Based on Exponential and Superelliptical Dielectric Taper

[EN] The Empty Substrate IntegratedWaveguides (ESIW) maintain the advantages of the Substrate Integrated waveguide (SIW) (i.e. low-volume, low profile, lightweight, easy manufacturing, and integration in a planar circuit board), and present lower losses and higher quality factors in resonators due to the propagation of the fields through air, instead of through lossy dielectric as in SIW. The operational (monomode) bandwidth of the ESIW can be increased with the Single Ridge ESIW (SRESIW). However, the bandwidth can be further increased with the Double Ridge ESIW (DRESIW). In this paper, a brief study of possible DRESIW geometries has been performed, and two transitions from microstrip line (MS) to DRESIW with a dielectric taper geometry based on different equations are proposed. The new wideband transitions present simulated return losses in back-to-back configurations greater than 20 dB in more than a 95% fractional bandwidth. The transition that presents a better compromise between return losses, bandwidth and ease of fabrication is manufactured. The measured return and insertion losses are better than 19.7 dB and 1.5 dB, respectively, in a 96.4% fractional bandwidth.This work was supported by the Ministerio de Ciencia e Innovacion, Spanish Government, under Project PID2019-103982RB-C44 and Project PID2019-103982RB-C41.Herraiz Zanón, D.; Esteban González, H.; Herraiz, D.; Vidal Pantaleoni, A.; Belenguer, Á.; Boria Esbert, VE. (2021). Microstrip to Double Ridge Empty Substrate Integrated Waveguide Transitions Based on Exponential and Superelliptical Dielectric Taper. IEEE Access. 9:165745-165753. https://doi.org/10.1109/ACCESS.2021.3134089165745165753

SIW/HMSIW Bandpass Filters for Ka Frequency Band Serving Wireless Applications

This paper describes a novel Substrate Integrated Waveguide (SIW) bandpass filter using Chebyshev approximation and Half Mode Substrate Integrated Waveguide (HMSIW) modeling technique. The developed 3rd order filter structure uses an inductive iris and an inductive post station in a way it resonates in Ka frequency band serving wireless applications. The paper presents in details steps of the filter design formed by specific analytical equations to extract its different synthesizable parameters including coupling matrix, quality factor and initial geometric dimensions. The ideal frequency response of the filter is determined from an equivalent circuit that uses localized elements developed by AWR Microwave Software. High Frequency Structure Simulator (HFSS) is then employed to model the proposed filter structure and optimize its initial parameters until meeting the target specifications initially fixed in order to provide a high frequency response for the proposed filter design. Finally, the obtained results display a good performance for the proposed filter design and demonstrate a high usefulness for the employed technology that allows a low design volume

Reconfigurable Devices using Liquid Crystal at Microwave Frequencies in Substrate Integrated Waveguide

[ES] La cantidad de servicios de telecomunicación se ha incrementado signiticativamente en las últimas décadas. El uso de teléfonos inteligentes, así como el Internet de las Cosas, está generando una saturación del espectro electromágnetico. Por tanto, los requisitos de los sistemas de microondas han cambiado para adaptarse a estos nuevos avances. Para satisfacer estas necesidades, se busca el desarrollo de dispositivos de bajo coste, volumen, peso y consumo. Además, interesa que sean espectralmente eficientes y fácilmente integrables con otros dispositivos. Entre todos los dispostivos de microondas, los filtros son elementos clave dentro de los sistemas de comunicaciones móviles e inalámbricas. Es por ello que el diseño de filtros que cumplan con los requisitos mencionados se ha convertido en un tema de gran interés. Para dar respuesta a este problema ha surgido la tecnología de Guía de Onda Integrada en Sustrato (Substrate Integrated Waveguide (SIW)), que permite la implementación de filtros con un reducido tamaño y fácilmente integrables con otros dispositivos en tecnología planar. Dicha tecnología presenta unas prestaciones en cuanto a manejo de potencia y pérdidas mejores que la tecnología de circuito impreso (Printed Circuit Board (PCB)), aunque no llegan a ser iguales que las de la guía de onda clásica. Por otro lado, la saturación espectral también lleva al estudio de filtros con respuestas variables en frecuencia, es decir, que puedan cambiar su frecuencia central y ancho de banda con el fin de adaptarse a las necesidades del sistema. Por ello, el objetivo general de esta Tesis es el análisis y diseño de nuevos filtros reconfigurables en tecnología integrada. El trabajo empieza con el estudio de los fundamentos de los filtros de microondas hasta llegar al diseño de resonadores reconfigurables en tecnología SIW usando el cristal líquido como material de reconfiguración. En primer lugar, se ha estudiado la influencia que los cambios en el valor de la permitividad dieléctrica en el interior de las estructuras filtrantes pueden tener en la respuesta de las mismos. En particular, se desarrollan filtros alternando secciones de línea con y sin dieléctrico dentro de una SIW vacía, Empty Substrate Integrated Waveguide (ESIW). Una vez hecho esto, se procede al estudio de materiales que tengan un valor de permitividad dieléctrica variable de alguna forma. En concreto, se ha realizado la caracterización de diferentes mezclas de cristal líquido a la frecuencia de microondas. Dicho material cambia su valor de permitividad cuando se le aplica un campo eléctrico o magnético. Dado que para la reconfiguración de la respuesta de los filtros se requiere de una estructura desacoplada en baja frecuencia, es decir, con más de un conductor, se ha desarrollado una estrategia para el desacoplo de la estructuras ESIW, la tecnología Decoupled Empty Substrate Integrated Waveguide (DESIW). Por último, se han diseñado resonadores en dicha tecnología DESIW, que se han llenado de cristal líquido y aplicado unos campos de polarización, consiguiendo variar su respuesta en frecuencia. Dichos resonadores constituyen el elemento básico para el desarrollo de filtros de microondas. Es por ello que el conocimiento obtenido en la Tesis es una buena base para futuros trabajos esta tecnología que permitan conseguir filtros de altas prestaciones.[CA] La quantitat de serveis de telecomunicació s'ha incrementat significativament en les últimes dècades. L'ús de telèfons intel$\cdot$ligents, així com la internet de les coses, està generant una saturació de l'espectre electromagnètic. Per tant, els requisits dels sistemes de microones han canviat per a adaptar-se a aquests nous avanços. Per a satisfer aquestes necessitats, se cerca el desenvolupament de dispositius de baix cost, volum, pes i consum. A més, interessa que siguen espectralment eficients i fàcilment integrables amb altres dispositius. Entre tots els dispositius de microones, els filtres són elements clau dins dels sistemes de comunicacions mòbils i sense fil. És per això que el disseny de filtres que complisquen els requisits esmentats s'ha convertit en un tema de gran interès. Per a donar resposta a aquest problema ha sorgit la tecnologia de Guia d'Ona Integrada en Substrat (Substrate Integrated Waveguide (SIW)), que permet la implementació de filtres amb una reduïda grandària i fàcilment integrables amb altres dispositius en tecnologia planar. Aquesta tecnologia presenta unes prestacions quant a maneig de potència i pèrdues millors que la tecnologia de circuit imprès (Printed Circuit Board (PCB)), encara que no arriben a ser iguals que les de la guia d'ona clàssica. D'altra banda, la saturació espectral també porta a l'estudi de filtres amb respostes variables en freqüència, és a dir, que puguen canviar la seua freqüència central i l'amplada de banda amb la finalitat d'adaptar-se a les necessitats del sistema. Per això, l'objectiu general d'aquesta tesi és l'anàlisi i el disseny de nous filtres reconfigurables en tecnologia integrada. El treball comença amb l'estudi dels fonaments dels filtres de microones, fins a arribar al disseny de ressonadors reconfigurables en tecnologia SIW usant el cristall líquid com a material de reconfiguració. En primer lloc, s'ha estudiat la influència que els canvis en el valor de la permitivitat dielèctrica a l'interior de les estructures filtrants poden tenir en la resposta d'aquestes. En particular, es desenvolupen filtres que alternen seccions de línia amb dielèctric i sense dins d'una SIW buida, Empty Substrate Integrated Waveguide (ESIW). Una vegada fet això, es procedeix a l'estudi de materials que tinguen un valor de permitivitat dielèctrica variable d'alguna forma. En concret, s'ha realitzat la caracterització de diferents mescles de cristall líquid a la freqüència de microones. Aquest material canvia el seu valor de permitivitat quan se li aplica un camp elèctric o magnètic. Atès que per a la reconfiguració de la resposta dels filtres es requereix una estructura desacoblada en baixa freqüència, és a dir, amb més d'un conductor, s'ha desenvolupat una estratègia per al desacoblament d'estructures ESIW, la tecnologia Decoupled Empty Substrate Integrated Waveguide (DESIW). Finalment, s'han dissenyat ressonadors en aquesta tecnologia DESIW, que s'han omplit de cristall líquid i aplicat uns camps de polarització, i s'ha aconseguit variar la seua resposta en freqüència. Aquests ressonadors constitueixen l'element bàsic per al desenvolupament de filtres de microones. És per això que el coneixement obtingut en la tesi és una bona base per a futurs treballs d'aquesta tecnologia que permeten aconseguir filtres d'altes prestacions.[EN] The number of telecommunication services has increased significantly in recent decades. The use of smartphones, as well as the Internet of Things, is generating a saturation of the electromagnetic spectrum. Therefore, the requirements of microwave systems have changed to adapt to these new developments and related challenges. For achieving these needs, the development of devices with low cost, volume, weight and power consumption is sought. In addition, it interests to be spectrally efficient, to offer high performance, and to be easily integrated with other devices. Among all microwave devices, filters are key elements within mobile and wireless communication systems. In this context, the design of filters that meet the aforementioned requirements has become a topic of great interest. For solving this problem, Substrate Integrated Waveguide (SIW) technology has emerged, which allows the implementation of filters with a small size and to be easily integrated with other devices in planar technology. This technology has better power handling and loss performance than Printed Circuit Board (PCB) technology, although they do not have the performance of the classic waveguide counterpart. On the other hand, the spectral saturation also leads to the study of filters with tunable frequency response, that is, they can change their central frequency and bandwidth, in order to fulfil the changing system requirements. Therefore, the general objective of this PhD Thesis work is the analysis and design of new reconfigurable filters in integrated technology. The work begins with the study of the basics of microwave filters until the design of reconfigurable resonators in SIW technology, using Liquid Crystal (LC) as reconfiguration material. Firstly, the influence that the change of the dielectric permittivity value inside the filtering structures have on the frequency response has been studied. Particularly, filters have been obtained by alternating line sections with and without dielectric material inside an empty SIW (Empty Substrate Integrated Waveguide (ESIW)). Once this is done, it is proceed to the study of materials that have a variable dielectric permittivity value. Specifically, the characterization of different LC mixtures at microwave frequencies has been carried out. This material changes its permittivity value when an electric or magnetic bias field is applied. A low-frequency decoupled structure is required for the reconfiguration of filters, that is, structures with more than one conductor. For that, a strategy for decoupling ESIW structures has been developed, i.e, the Decoupled Empty Substrate Integrated Waveguide (DESIW) technology. Finally, some resonators have been designed in DESIW technology, which have been filled with LC. The use of LC allows to tune their frequency response. These resonators are basic elements for the development of microwave filters. So that, the knowledge obtained in this Thesis work is a good basis for future works in this technology that allow for achieving high performance filters.Sánchez Marín, JR. (2019). Reconfigurable Devices using Liquid Crystal at Microwave Frequencies in Substrate Integrated Waveguide [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/132183TESI

SIW/HMSIW Bandpass Filters for Ka Frequency Band Serving Wireless Applications

This paper describes a novel Substrate Integrated Waveguide (SIW) bandpass filter using Chebyshev approximation and Half Mode Substrate Integrated Waveguide (HMSIW) modeling technique. The developed 3rd order filter structure uses an inductive iris and an inductive post station in a way it resonates in Ka frequency band serving wireless applications. The paper presents in details steps of the filter design formed by specific analytical equations to extract its different synthesizable parameters including coupling matrix, quality factor and initial geometric dimensions. The ideal frequency response of the filter is determined from an equivalent circuit that uses localized elements developed by AWR Microwave Software. High Frequency Structure Simulator (HFSS) is then employed to model the proposed filter structure and optimize its initial parameters until meeting the target specifications initially fixed in order to provide a high frequency response for the proposed filter design. Finally, the obtained results display a good performance for the proposed filter design and demonstrate a high usefulness for the employed technology that allows a low design volume

Novel empty substrate integrated waveguide for high performance microwave integrated circuits

"(c) 20xx 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."Abstract Over the last years, a great number of substrate integrated circuits has been developed. These new circuits are a compromise between the advantages of classical waveguide technologies, such as high quality factor and low losses, and the advantages of planar circuits, such as low cost and easy compact integration. Although their quality factor and losses are better than for planar circuits, these characteristics are worse than in the case of waveguides, mainly due to the presence of the dielectric substrate. In order to improve the performance of the integrated circuits, a new methodology for manufacturing empty waveguides, without a dielectric substrate, but at the same time completely integrated in a planar substrate, is proposed in this work. A wideband transition with return losses greater than 20 dB in the whole bandwith of the waveguide allows the integration of the empty waveguide into the planar substrate so that the waveguide can be directly accessed with a microstrip line. Therefore, a microwave circuit integrated in a planar substrate, but at the same time with a very high quality factor (measured quality factor is 4.5 times higher than for the same filter in the substrate integrated waveguide), and very low losses is successfully achieved.This work was supported by the Ministerio de Ciencia e Innovacion, Spanish Goverment, under Research Project TEC2010-21520-C04-03 and Research Project EC2010-21520-C04-01, and by the Autonomous Government of Castilla-La Mancha under Research Project PPII10-0047-0220.Belenguer Martínez, Á.; Esteban González, H.; Boria Esbert, VE. (2014). Novel empty substrate integrated waveguide for high performance microwave integrated circuits. IEEE Transactions on Microwave Theory and Techniques. 62(4):832-839. https://doi.org/10.1109/TMTT.2014.2309637S83283962

Compact differential-fed planar filtering antennas

This paper proposes novel low-profile differential-fed planar antennas with embedded sharp frequency selectively. The antennas are compact and easy to integrate with differential devices without matching baluns. The antenna design is formulated as a topology optimization problem, where requirements on impedance bandwidth, directivity, and filtering are used as the design objectives. The optimized antennas operate over the frequency band 6.0-8.5 GHz. The antennas have reflection coefficients below -15 dB, cross-polarization levels below -42 dB, a maximum gain of 6.0 ± 0.5 dB, and a uniform directivity over more than 130° beamwidth angle in the frequency band of interest. In addition, the antennas exhibit sharp roll-off between the operational band and frequencies around the 5.8GHz WiFi band and the 10 GHz X-band. One antenna has been fabricated with a good match between simulation and measurement results. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Wideband Watt-Level Spatial Power-Combined Power Amplifier in SiGe BiCMOS Technology for Efficient mm-Wave Array Transmitters

The continued demand for high-speed wireless communications is driving the development of integrated high-power transmitters at millimeter wave (mm-Wave) frequencies. Si-based technologies allow achieving a high level of integration but usually provide insufficient generated RF power to compensate for the increased propagation and material losses at mm-Wave bands due to the relatively low breakdown voltage of their devices. This problem can be reduced significantly if one could combine the power of multiple active devices on each antenna element. However, conventional on-chip power combining networks have inherently high insertion losses reducing transmitter efficiency and limiting its maximum achievable output power.This work presents a non-conventional design approach for mm-Wave Si-based Watt-level power amplifiers that is based on novel power-combining architecture, where an array of parallel custom PA-cells suited on the same chip is interfaced to a single substrate integrated waveguide (to be a part of an antenna element). This allows one to directly excite TEm0 waveguide modes with high power through spatial power combining functionality, obviating the need for intermediate and potentially lossy on-chip power combiners. The proposed solution offers wide impedance bandwidth (50%) and low insertion losses (0.4 dB), which are virtually independent from the number of interfaced PA-cells. The work evaluates the scalability bounds of the architecture as well as discusses the critical effects of coupled non-identical PA-cells, which are efficiently reduced by employing on-chip isolation load resistors.The proposed architecture has been demonstrated through an example of the combined PA with four differential cascode PA-cells suited on the same chip, which is flip-chip interconnected to the combiner placed on a laminate. This design is implemented in a 0.25 um SiGe BiCMOS technology. The PA-cell has a wideband performance (38.6%) with both high peak efficiency (30%) and high saturated output power (24.9 dBm), which is the highest reported output power level obtained without the use of circuit-level power combining in Si-based technologies at Ka-band. In order to achieve the optimal system-level performance of the combined PA, an EM-circuit-thermal optimization flow has been proposed, which accounts for various multiphysics effects occurring in the joint structure. The final PA achieves the peak PAE of 26.7% in combination with 30.8 dBm maximum saturated output power, which is the highest achievable output power in practical applications, where the 50-Ohms load is placed on a laminate. The high efficiency (>20%) and output power (>29.8 dBm) over a wide frequency range (30%) exceed the state-of-the-art in Si-based PAs

Advanced infrared laser modulator development

A parametric study was conducted to develop an electrooptic waveguide modulator for generating continuous tunable sideband power from an infrared CO2 laser. Parameters included were the waveguide configurations, microstrip dimensions device impedance, and effective dielectric constants. An optimum infrared laser modulator was established and was fabricated. This modulator represents the state-of-the-art integrated optical device, which has a three-dimensional topology to accommodate three lambda/4 step transformers for microwave impedance matching at both the input and output terminals. A flat frequency response of the device over 20 HGz or = 3 dB) was achieved. Maximum single sideband to carrier power greater than 1.2% for 20 W microwave input power at optical carrier wavelength of 10.6 microns was obtained

Wideband bandpass filters using a novel thick metallization technology

A new class of wideband bandpass filters based on using thick metallic bars as microwave resonators is presented in this work. These bars provide a series of advantages over fully planar printed technologies, including higher coupling levels between resonators, higher unloaded quality factors QU , and larger bandwidths implemented with compact structures. In comparison to dielectric and waveguide resonators filters, higher bandwidths together with lower weight and footprint reduction are achieved with the proposed thick bars technology. Moreover, thick bar resonators can easily be coupled to an additional resonance excited in a box used for shielding, allowing to realize transversal topologies able to implement transmission zeros at desired frequencies. To illustrate the capabilities of this technology, three microwave filters with different topologies have been designed. One of the designed filters has been manufactured and tested using copper bars inside an aluminum housing partially filled with Teflon. Measured data demonstrates a fractional bandwidth of FBW = 32%, spurious free range SFR > 50%, unloaded quality factor of QU = 1180, insertion losses over 0.16 dB and return losses over 20 dB, without requiring any post-tuning operation on the prototype. This result confirms the exciting performance of the proposed technology for wideband applications.This work was supported in part by the National Science Foundation with CAREER under Grant ECCS-1749177, in part by the Spanish Government, Ministerio de Educación, Cultura y Deporte under Grant FPU15/02883, and in part by the Ministerio de Economía y Competitividad through the Coordinated Project under Grant TEC2016-75934-C4-R and Grant PRX18/00092