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A temperature-compensated resonator based on stacked rings is proposed in this letter. The resonator is made of several layers of machined dielectric substrates where the copper rings stand. These rings define an air-filled TE011 cavity with an unloaded quality factor better than 1800. Due to a low sensitivity of the air gap between the layers and metallic contact of the TE011 mode, a cavity with low building constraints (no vias and no connection between layers) is realized. Furthermore, a multilayer design allows the introduction of a controlled amount of dielectric material in the cavity with a negative thermal coefficient of permittivity to realize temperature compensation of the device and to counteract its natural thermal expansion. Thus, this compensation layer allows proper management of a frequency drift from of −18 to +18 MHz for a temperature range of 20 °C–80 °C. However, there is a tradeoff, and the quality factor decreases as the compensated layer is inserted. A guideline demonstrating the performance of the design and the compensation technique is thus presented in this letter.

In this work, microwave planar resonators are printed with silver nanoparticle inks using two printing technologies, inkjet printing and aerosol jet printing, on polyimide substrates. The microwave resonators used in this paper operate in the frequency band 5–21 GHz. The printing parameters, such as the number of printed layers of silver nanoparticle inks, drop spacing, and sintering time, were optimized to ensure repeatable and conductive test patterns. To improve the electrical conductivity of silver deposits, which are first dried using a hot plate or an oven, two complementary sintering methods are used: intense pulsed light (IPL) and laser sintering. This paper presents the results of different strategies for increasing the final quality factor of printed planar resonators and the trade-offs (sintering time versus final conductivity/unloaded Q) that can be reached. Improvement of the resonator unloaded quality factor (up to +55%) and of the equivalent electrical conductivity (up to 14.94 S/μm) at 14 GHz have been obtained thanks to these nonconventional sintering techniques. The total sintering durations of different combinations of sintering techniques (hot plate, oven, IPL, and laser) range from 960 to 90 min with a final conductivity from 14.94 to 7.1 S/μm at 14 GHz, respectively.

In this work, using a Drop on demand (DOD) inkjet printer, microwave resonators are printed on a polymer (polyimide) substrate with silver nanoparticle ink. To improve the electrical conductivity of the metallic deposit, two strategies are presented using sintering with pulsed light (IPL) over a broad spectrum of 190-1100 nm. The conductivity measured is improved from 50 to 138% for resonators working in range of 7-21 GHz.

This paper presents a new microwave characterisation technique to obtain the coefficient of thermal expansion (CTE) using a cylindrical resonator. This technique is non-destructive and can be applied to any kind of solid material. With the help of a metallised sample insert in the middle of the resonator, two cavities are formed, with one side made of the unknown metallisation of the sample. By monitoring resonant frequencies and the quality factor of these cylindrical sub-cavities, the dimensions of the sample and its conductivity can be extracted. Performing this technique with temperature tracking allows us to calculate a thermomechanical parameter, the coefficient of thermal expansion. The realised measurements on different samples and metallised substrates show a micrometre resolution for the thickness and a resolution of approximately 5 µm with other measurement techniques. Several electric conductivities in terms of temperature are also presented at different frequencies related to their uncertainties.

Currently, artificial satellites are extensively used for scientific, military, and civil applications, particularly for telecommunications satellites.

This paper illustrates the different possibilities given by additive manufacturing technologies for the creation of passive microwave hardware. The paper more specifically highlights a prototyping scheme where the 3D-printed plastic parts can be used as initial proofs of concept before considering more advanced 3D-printed parts (metal parts, for instance). First, a characterization campaign has been made on common plastics used by a 3D printer using the fused deposition modeling and material jetting (Polyjet©) technologies. The impact of the manufacturing strategy (high-speed or high-accuracy) on the part roughness, as well as on the dielectric material permittivity and loss tangent, has been specifically studied at 10 and 16 GHz. Based on a specifically optimized and deeply explained characterization method, the conductivity of a coating based on silver paint has also been characterized on such plastic parts at 10 and 40 GHz. These plastic materials and coating have been used for the creation of quasi-elliptic and tuning-free bandpass filters centered at 6 and 12 GHz and compared with a similar filter made of stainless steel by selective laser melting. Finally, a compact rectangularTE10to circularTE01mode converter also undergoes one prototyping step out of plastic before moving to an advanced part made out of stainless steel. This mode converter, which is made in a single part, is designed to operate from 28 to 36 GHz as a tuning-free final demonstrator.

A study on the passive microwave components made by polymer additive manufacturing (polymer jetting) is presented. Different types of components (waveguides, couplers, power dividers, filters and antennas) are designed to be made in a single part. Using a simple and cost-effective metallisation by applying silver paint, various prototypes with complex geometries have been manufactured to evaluate these proofs of concept and the robustness of the low-cost approach to make microwave components. Different measurements show that the obtained filters can provide an acceptable unloaded Q factor of 400–500 for the operating frequencies of 12–22 GHz. Waveguiding structures such as a mode converter, which is used as a broadband antenna, have also notably efficiently worked up to the Ka band (36 GHz). Due to a remarkable accuracy of nearly 80 µm, the obtained results of the proposed coupler, power divider and antennas are consistent with the full wave simulations, which prove that the currently available three-dimensional plastic printers can provide notably accurate prototypes to design original components.

Recent studies show that alumina doped with TiO2 exhibits promising dielectric properties, corresponding to low loss tangents and low temperature coefficients (or close to 0 ppmC−1). This paper aims to confirm these trends and study the dielectric properties of alumina doped with TiO2 from 0.5% to 12% wt. at high frequency, 13–73 GHz. This work demonstrates that alumina doped with TiO2 corresponds to potential materials for frequency converter devices working at a high frequency (up to 50 GHz).

In this work, microwave components were printed on a Kapton (polyimide) substrate using a Drop-On-Demand (DOD) ink jet printer with silver nanoparticle ink. Two different laser curing strategies are presented by implementing selective sintering. The measured improvement of the achieved conductivity is between 70 and 100% for such resonators from 5 to 15 GHz.

A new type of continuously tunable resonator is described here. The resonator is working on the TE011 mode which provides a good quality factor. The frequency tuning is obtained by varying its height. A K-band resonator has been fabricated, using plastic 3D printing for the housing and silver paint for the metallization. Measurements show a tuning range of 14%, with quality factors of 2 300 and above while the mechanical system that is adopted for the cavity height variation also ensures a good spurious-free region. The proposed tunable resonator and mechanical tuning system are both made into one single part thanks to additive manufacturing.

Several designs of lossy filters for receivers in satellite transponders have been investigated in order to improve the performance in terms of flatness compared to a classical hairpin filter design. Flatness and insertion loss performances for all solutions are summarized. The reference design is a microstrip filter made of coupled hairpin resonators. Two approaches have investigated for improving the flatness of the reference design. Lossy filter designs have been compared to the reference, considering the same specifications and the same technology. An in-line network with resistive cross-couplings and a transversal network with heterogeneous Q resonators have been designed and fabricated first. Theoretically, the transversal network leads to better performances in terms of flatness, but its implementation is generally difficult, especially considering the input/output junctions between multiple paths, which are naturally dispersive, causing spurious transmissions in the stopband. Moreover, a Monte Carlo analysis has been performed, showing higher sensitivity of this later solution with respect to manufacturing tolerances. Consequently, considering measured performances, in-line networks with resistive cross-couplings appear to be the best solution for implementing our receiver filter. In particular, the version with two RCCs appears as a good compromise between flatness and insertion loss. Finally, the in-line network has been transformed introducing non-resonant nodes and additional resistive cross-couplings in order to design absorptive lossy filters. The resulting filters allow attenuating the reflected wave substantially with a reduced impact on the absolute level of losses.

Dans ce papier est présentée la conception de coupleurs directifs microondes basés sur des guides d’ondes volumiques facilement imprimables en plastique par technologie FDM ou Polyjet©. La conception d’un coupleur en guides d’ondes croisés est abordée à la manière d’un projet sub-divisible en plusieurs phases, de la bibliographie à la mesure du dispositif une fois celui-ci imprimé. L’ensemble de ces phases étant relativement interdépendantes, il est possible de se concentrer uniquement sur l’une d’elles dans le cadre d’une séance de travaux pratiques, ou d’en sélectionner plusieurs dans le cadre d’un projet par exemple. Dans une seconde partie, deux topologies de coupleurs hybrides se prêtant également bien à ce type de projets sont présentées, à savoir des coupleurs Short-Slot et Ladder-Type.

This paper presents a 6th order quasi-elliptic bandpass filter working at 11.75 GHz and based on dielectric hollow resonators (pucks). The resonators and their supporting elements have been fabricated altogether in a single part using ceramic (Alumina) additive manufacturing. This part is simply placed in the filter metal housing and therefore limits the number of pieces to be assembled. An important aspect of this work is that no specific, and potentially lossy, third materials (supports, glue) are needed. This assembly route easily allows the dielectric resonators to be placed in the middle of their cavities in order to maximize their Q factor. The proposed principle has been experimentally validated using, for the fast prototyping of this proof of concept, metallized and low cost plastic 3D printing

This work presents the conformal printing of milli-meter-wave transmission lines up to 67 GHz using inks based on silver nanoparticles. Several coplanar (CPW) lines have been printed over 3D Alumina test structures such as slope, half-sphere and ridge, all of them being fabricated using a ceramic additive manufacturing technology. All of the achieved transmission lines show a return loss better than 10 dB and insertion loss better than 0.8 dB up to 60 GHz. Extensive tests have been done on the performances obtained with the Aerosol Jet Printing (AJP) technology. Minimum features (line width, lines spacing) down to 16.5 μm have been obtained on flat surfaces (24 μm on 3D ceramic objects) while obtaining a high conductivity of 2.1107S/m at 49.2 GHz for the directly printed silver layers.

This paper presents different metal deposition techniques used for the metallization of additively manufactured plastic components. Comparison between them are presented with a focus on their use with 3D printed Ka band bandpass filters. The results, in terms of conductivity, roughness and thickness, will be analyzed and measured up to 66 GHz by a resonant cavity method. The characterized metallization techniques will be applied on different 6th order bandpass filters working around 19 GHz.

This paper deals with a study on multiplexer topology based on 3dB couplers. A diplexer in Ku-band was conceived and printed using material jetting (Polyjet®) and Fused Deposition Modeling (FDM) technologies for this purpose. The different parts composing the diplexer are separately tested. In a first step, 3 dB directional couplers are printed with both technologies experimentally confirming the expected behavior. 4th order printed TE101 mode filters are tested as well, also providing sufficient performances (unloaded Q around 600) for the purpose of this paper. After assembling the different 3D printed parts composing this diplexer, the measured response confirms the reliability of the different manufacturing techniques and the robustness of this multiplexer technology.

This work presents a compact LTCC Alter hybridizing 2 resonator technologies (microstrip lines and SIW resonators). This solution makes it possible to find a compromise in terms of footprint and performance (insertion loss and flatness). The structure was synthesized and designed using an electromagnetic simulator.

International audience; This article presents a sensor based on zinc wires of different widths deposited on the surface of the ceramic resonator capable of detecting and following the evolution of the corrosion of the zinc material. Electromagnetic studies show that due to the evolution of the corrosion, the progressive degradation of the conductivity of the formed zinc grid (from 6 S/μm to 0.015 S/μm) causes a degradation of the quality factor (from Q0 = 50 to Q0

This paper presents a continuously tunable bandpass filter fully made by plastic additive manufacturing. This filter is designed to provide a constant absolute bandwidth around 5.7 GHz using a mechanical movement. A 3D spiral ribbon made of metallized plastic is designed to create a 4th order Chebyshev bandpass filter by making it rotate in a standard WR159 waveguide. The obtained filter experimentally provides a 325 MHz +/− 35 MHz bandwidth while having its operating frequency be continuously tuned from 5.45 to 5.64 GHz (7.47% tuning range). The return loss remains better than 10 dB over the whole tuning range. Even if the insertion loss are rather high (1.6 to 3.6 dB) mainly due to the low conductivity used for the plating of the plastic parts, this proof concept demonstrates the validity of such design and of the use of additive manufacturing for prototyping new concepts of tunable waveguide filters.

This paper proposes a new solution for implementing high-quality-factor tunable filters, suitable for high-power handling. The dual-mode filter is realized with a cylindrical cavity, which comprises metallic lugs and is loaded by a dielectric element. The center frequency is tuned between two states, by adjusting mechanically the position of the lugs within the cavity. The lugs allow modifying the capacitive effect between the dielectric element and the cavity for adjusting the resonant frequency.

International audience; This paper presents a concept of a tunable cavity resonator composed of a resonating cavity and a dielectric perturber. This tunable resonator is designed and measured to prove the tuning mechanism obtained by varying the angle of rotation of the perturber. A rotation from 0 to 90 produces a tuning ratio of 1:1.25, i.e., a tuning range of 22.2% around 11.5 GHz while maintaining an unloaded Q factor between 1500 and 2300. After this first experimental validation, a third-order bandpass filter is then designed and measured using the same base principle. Using a single mechanical movement, all three resonators’ perturbers are synchronously rotated to create a third-order Chebyshev bandpass filter maintaining a 516±38-MHz bandwidth (for a return loss better than 10 dB) from 9.915 to 12.189 GHz. A 20.6% tuning range is then obtained at approximately 11 GHz with an estimated Q factor from 1400 to 2150. These performances have been obtained by using specifically shaped dielectric perturbers, which have been made by a ceramic additive manufacturing (AM) process (stereolithography). This technology has enabled the perturbers’ specific geometries and embedded supporting elements to be feasible. A sixth-order Chebyshev bandpass filter has also been theoretically proposed using full wave simulations.

This paper outlines an original shape optimization library backed by a three dimensional (3D) full-wave electromagnetic (EM) simulator, combining several efficient structural optimization techniques and suitable for viable computer-aided design (CAD) of complex microwave components. The microwave components are modeled by finite element method (FEM) and their dimensions and shape are optimized using four techniques: design of experiments (DOE), level-set method (LS), topology gradient (TG) method, and genetic algorithm (GA). The various methods allow determining the optimal geometry, shape or topology of 2D or 3D objects within the microwave device, by minimizing iteratively a cost function related to the desired specifications. Typical demonstration illustrates the versatility of the proposed library based on the design of a dual mode dielectric resonator filter in order to improve its unloaded quality factor by keeping the same frequency isolation, their accuracy and efficiency are verified by the available measured results.

In this paper, the design of compact diplexers with dual-mode cavities for satellite payloads is detailed. Compact diplexers are composed of coupled resonators without additional waveguide element, leading to a more compact architecture. Two topologies are first implemented and compared with a standard manifold output diplexer, in terms of electrical performances, compactness, and power handling. Hardware prototypes are fabricated and measured for experimental verification. A third topology is finally introduced for the design of noncontiguous diplexers. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:249-258, 2014.

This paper is focused on the use of low loss alumina substrates for the creation of compact Q band bandpass filters. The proposed process flow is based on the laser micro-machining of ceramic substrates in order to create small footprint and lightweight filters. The bandpass filter proposed in this study shows a 3.3% bandwidth around 39.31 GHz. The insertion loss of 1.51 dB experimentally confirms that an unloaded Q factor of 400 is obtained at 39 GHz. The filter dimensions are 5.98 mm × 2.76 mm × 0.6mm.

For output multiplexer (OMUX) filters placed in telecommunication satellites, microwave breakdown happens in an involuntary and undesirable way during tests at atmospheric pressure. This avalanche phenomenon is due to exponential growth of the electronic density caused by thermoelectronic emission under strong electromagnetic field magnitude. In this paper, our objective is to model and characterize experimentally multipole OMUX filters composed with coupled cavities. For identifying the element responsible for the breakdown, the electric field is calculated within each cavity and each iris. In order to characterize the breakdown phenomenon, we proposed an experimental test bench and we measured the power, both at the input and at the output of the filter. The article details the theoretical breakdown prediction and the experimental setup for such a structure. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:46–54, 2014.

This paper is focused on the impact of density, average grain size, and impurity content on dielectric properties of pure alumina (

The design of 3D printed plastic modular filters is presented in this paper. The proposed principle allows the user to choose at will the order of a bandpass filter by plugging as much blocks (resonators) as needed. The conception and results of a 4-poles filter are discussed. Because of their simplicity, these filters have the potential to be used for microwave practical courses thanks to good performances, quick and easy assembly, easy tuning and maintenance and finally low cost manufacturing.

A compact dual-mode dual-band filter with widely separated passbands is proposed for possible integration in a TX/RX front-end. The basic structure is a cavity working on two distinct dual-modes. The design of this cavity realizing a 4-pole dual-band filtering function is detailed. A prototype is fabricated and measured for validating the concept.

This paper presents an overview of the possibility offered by 3D plastic printers for a quick, simple and affordable manufacturing of working filters and other passive devices such as antennas. This paper thus goes through numerous examples of passive devices made with the Fused Deposition Modeling (FDM) and material jetting (Polyjet©) technologies and will highlight how they can now be considered as a solid companion to RF designers during an optimization process up to Ku and higher bands.

In this paper, the design of compact diplexers and triplexers with dual-mode cavities is presented. Such devices are composed of coupled resonators without additional waveguide element, leading to a more compact architecture. Two topologies of compact diplexers are implemented and compared to a standard manifold diplexer. A hardware prototype is fabricated and measured for experimental verification. A compact triplexer is finally introduced for extending the concept to more than three ports.

Two compact microwave filters designed using multilayer inter-digital resonators are introduced. The first structure combines vertically and horizontally coupled interdigital resonators for optimizing the surface occupation while realizing high-order filters. A 12-pole filter centered at 18 GHz, with a 2.4 GHz passband, is designed and characterized. The second structure is composed of stepped-impedance interdigital resonators for widening the upper stopband. The filter is centered at 3 GHz with a 0.9 GHz passband, and both simulated and experimental results show an extended stopband up to 21 GHz.

As the first part of a study that aims to propose tools to take into account some electromagnetic compatibility aspects, we have developed a model to predict the electric and magnetic fields emitted by a device. This model is based on a set of equivalent sources (electric and magnetic dipoles) obtained from the cartographies of the tangential components of electric and magnetic near fields. One of its features is to be suitable for a commercial electromagnetic simulation tool based on a finite element method. This paper presents the process of modeling and the measurement and calibration procedure to obtain electromagnetic fields necessary for the model; the validation and the integration of the model into a commercial electromagnetic simulator are then performed on a Wilkinson power divider.

A novel approach for shape optimization of dielectric resonators is presented with an objective of improving their unloaded quality factor. Shape (level-set) and topology (topology gradient) optimization methods coupled with finite element method are utilized together, which as a result, relaxes the traditional trade-off made between the spurious-free band (isolation) and the high unloaded quality factor of the resonators. The defined cost function is minimized by the proposed iterative coupling between the level-set method and the topology gradient method. The optimized resonator, which improves the unloaded quality factor of about 65% compared with the reference, is then approximated for fabrication. The reference, optimized, and approximated resonators are fabricated and measured. Results from the simulated and the fabricated resonators validate the optimization approach presented in this work. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011. © 2011 Wiley Periodicals, Inc.

A gradient-based optimization method is presented for the design of packaged integrated microwave circuits. The method uses a reduced electromagnetic model resulting in a quasi-instantaneous analysis of the packaged device. A gradient-based strategy identifying parasitic effects due to circuit packaging is then deployed for optimizing the whole device. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 688–691, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23187

This paper compares several designs of lossy filters for receiver subsystems in satellite transponders. The reference design is a microstrip filter made of coupled hairpin resonators. Two approaches are investigated for improving the flatness of the reference design. The first approach combines nonuniform quality factor (Q) resonators in a transversal network. The second approach uses an inline network with resistive cross couplings. Lossy filter designs are compared to the reference, considering the same specifications and the same technology. The inline network with resistive cross-couplings is finally modified for designing absorptive filters, which protect the receiver from reflected waves. All filter configurations are fabricated and measured, showing a good agreement with electromagnetic simulations.

This paper presents compact multilayer interdigital filters for realizing general Chebyshev (i.e., quasi-elliptic) filtering functions. Several coupling elements are proposed for implementing a wide range of couplings between quarter-wavelength resonators, which are placed on a unique layer or stacked thanks to a multilayer technology. Several multipole filters are designed and fabricated using low-temperature co-fired ceramic (LTCC) technology. Designs and experimental results are detailed in order to appreciate the potential of the proposed technology. The multilayer interdigital filters proposed in this paper are designed especially for electronic warfare specifications from S- to Ku-band.

A mutual-synthesis approach is presented for the design of subsystems combining two microwave circuits. In this paper, we are focused on subsystems combining a filter and an antenna. In a first step, the methodology consists of synthesizing the global subsystem, which realizes both filtering and radiation functions, with respect to overall specifications. Considering circuits interactions within the subsystem, the resulting constraints are distributed optimally between the two circuits. The latter mutual synthesis then leads, on one hand, to a set of optimal impedances for their connection and, on the other hand, to the corresponding ideal characteristics of each circuit. A solution can then be selected by carrying out a compromise between the simplicity of achieving the characteristics of each circuit and the performances and compactness of the subsystem. In a second step, the circuits are designed independently with respect to the synthesized characteristics. Compared to a classical synthesis approach, where circuits are synthesized independently with respect to a common reference impedance (generally 50 or 75 Omega), the proposed mutual synthesis allows to simplify the global subsystem since interactions between the two circuits are considered and used optimally. The technique is illustrated with the design of a filter-antenna at Ku-band.

Three-dimensional (3-D) ceramic stereolithography has been developed and used to manufacture RF devices using periodic structures. To our knowledge, it is the first time that zirconia and high-performance Ba3ZnTa2O9 ceramics are used with that process to manufacture high unloaded quality factor resonant structures and bandpass filters working in the Ka-band. A theoretical study on the performances of periodic arrangements of high-permittivity structures has been carried out and has led to the manufacture of a high unloaded quality factor cavity and narrow three-pole filter (1% bandwidth) measured at a working frequency of 33 GHz

Particle swarm optimization (PSO) has lately become very popular in the electromagnetics domain. Although in some instances PSO shows a superior performance compared with other global optimization techniques, it is still computationally more expensive relative to classical gradient techniques. In this paper, a cooperative particle swarm optimization (CPSO) is adopted to achieve a faster convergence compared with the conventional PSO, while maintaining its main feature, which is the capability of finding global optimum. In order to deploy PSO more efficiently, the often neglected effect of the initial population on the overall convergence of PSO is discussed. It is shown that subdividing the space into grid cells and using random distribution within these cells will give the best results in terms of convergence speed. Different boundary conditions are tried on the CPSO algorithm. In order to verify the performance of the proposed algorithm, the algorithm is compared with the conventional PSO using six different objective functions. As a design example, an ultra-wide-band filter is designed. The results show a slightly faster convergence compared with the conventional PSO. The designed filter is fabricated and experimental results are also shown. Copyright © 2007 John Wiley & Sons, Ltd.

This paper deals with the microwave breakdown phenomenon that can appear in output multiplexer filters for telecommunications satellites. The first objective of this paper is to describe summarily the phenomenon. The second objective is to validate the theoretical modeling by experimental tests on a realistic example. A two-channel OMUX at Ka band has been designed and built and a dedicated measurement procedure has been proposed. As it will be shown, the experimental results agree well with the theoretical one.

This paper deals with the microwave breakdown phenomenon that can appear in output multiplexer filters for telecommunications satellites. In order to model this phenomenon a multidisciplinary approach with a combination of three fields of science was used: electromagnetism, thermal transfer theory and plasma physics. In this article we resume the theoretical study and we present our experimental validation.

This article presents an electromagnetic tool for the synthesis of manifold multiplexers — the dynamic inverter. By associating this model with the classical circuit model of the filter, the broadband behaviour of each filter can be analysed rapidly and then optimised accurately for an efficient synthesis of the manifold multiplexer. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

A quasi-planar technology is applied to the design of transversal multiple pole filters for space applications. To define the optimal dimensions of the filter, an original synthesis method is developed to yield the transversal equivalent electrical circuit. In this article, a 2nd-order and a 4th-order transversal filters are designed, built, and tested. These filters are centered around 28.5 GHz and exhibit a 3-dB bandwidth of 1.75% and 4.2%, respectively. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.