Quarter-wavelength three-section coaxial stepped impedance resonators (SIRs), having two degrees of freedom, allow independent control of the first resonance and antiresonance. Utilizing an original interconnection and based on polarity inversion, it is possible with this kind of resonator to design the nth-order bandpass filters offering n distinct transmission zeros in the upper stopband. To validate the principle, we designed and fabricated a demonstrator three-section fourth-order filter in aluminum at L-band, for which we also simulated the multipactor threshold. The experimental results are presented and discussed.

This paper presents several designs and implementations of filters based on SIR coaxial resonators. These high-power filters have been specifically developed for space applications, where constraints related to electrical performance, dimensions and multipactor effects are significant. Various solutions based on iris and direct couplings are presented and discussed.

This paper focus on a single-stage half-wavelength short-ended three-section coaxial stepped impedance resonators (SIRs) for the design of Tx bandpass filters with high multipactor thresholds. Through the design and manufacture of a fourth-order filter in the L-band, this solution is compared with other coaxial configurations in terms of, dimensions, electrical performance and multipactor threshold. The addition of a cross-coupling is also examined.

This paper presents a method of making tubular narrowband short-circuited stub filters using coaxial technology. This is achieved using an original interconnection technique, based on polarity crossing, enabling both inverters and several resonators in parallel to be integrated in a coaxial configuration. The filter consists of independent, well-isolated blocks that incorporate an inverter and an equivalent resonator, arranged vertically one above the other in a tubular configuration. To demonstrate this, two examples of 4th order filters, working in the L band with center frequency, f0 = 1.5 GHz and relative bandwidths of 6% and 12%, are described. Multipactor simulated performances and experimental S-parameters are presented.

This paper presents a method of making shortcircuited stub filters using coaxial technology. This is achieved using an original interconnection technique, based on crossing the polarities of coaxial lines, enabling both inverters and resonators to be integrated in coaxial configuration. To demonstrate this, two examples of 4th order filters, with relative bandwidths of 24% and 39%, are described. Multipactor simulated performances and experimental S-parameters are presented.

This paper presents a new solution for the interconnection of N coaxial waveguides through a quarterwavelength resonator. The proposed solution is narrowband, but greatly simplifies the interconnection of a large number of coaxial waveguides, by reversing the polarity of the lines coming from one side with those coming from the other. To illustrate the idea, a two-way Wilkinson divider/combiner is presented. Multipactor simulated performances and experimental S-parameters are presented.

This paper presents the implementation of two-section coaxial stepped impedance resonators (SIRs) solution to control the attenuated band of Tx bandpass filters. This type of resonator has two degrees of freedom, in the transverse and longitudinal dimensions. At a fixed fundamental frequency, this allows the dimensions of the resonators to be modulated to control both the location of the harmonics and the power handling for space applications. It is therefore possible to design a filter for which the harmonic frequencies of the resonators are not the same, leading to destructive recombinations in the attenuated band. This is illustrated through the design of a 6th order narrowband L-band bandpass filter with controlled attenuation up to 6.6 × F 0 and a multipactor threshold of around 30 W. This filter was fabricated in aluminum and tested. The experimental results are presented and discussed. Finally, a comparison is made with the state-of-the-art.

This letter presents a novel geometrical implementation of the quarter-wavelength coaxial stepped impedance resonator (SIR). Based on the inversion of the location of the coaxial sections in the resonator, this topology increases the distance between conductors, thus improving the multipactor threshold and fabrication tolerances. To demonstrate these advantages, we designed an L-band 4th-order filter. This filter was fabricated in aluminum and measured. The experimental results are presented and compared with their two- and three-section quarter-wavelength counterparts.

Different ways of synthesis were studied to tune physical properties of MXene. Depending on the synthesis method (etching, heat treatment), a wide range of electromagnetic properties can be achieved due to their abundant functional groups. MXene powders are thereafter incorporated into a polymer matrix and processed into thin films. The microwave characterization of the so-fabricated MXene-based composites showed that both high permittivity materials with medium loss tangent and high permittivity resistive materials can be obtained. Simulation suggests that these unusual properties can be used to decrease the absorption frequency of a Salisbury screen without increasing its thickness. In the light of these findings, a MXene-based composite was used to manufacture a Salisbury absorber that showed an absorption of 27.4 dB at 6.57 GHz. The resonance frequency is reduced by over 41% compared with a standard Salisbury screen, thanks to the high permittivity of MXene composites. These results pave the way for the design of thin, efficient microwave absorbers.

This article focuses on the comparison of quarter-wavelength and open-end half-wavelength four-section coaxial stepped impedance resonators (SIRs) for the design of Tx bandpass filters with high multipactor thresholds. To obtain a half-wavelength configuration with open ends in an enclosed space, the coaxial sections are stacked on two levels. Despite the strong geometrical difference between the two structures, the same analytical formalism can be used to model their frequency behavior. The synthesis equations show that the first three frequencies (fundamental, first transmission zero, and second harmonic) are independent, making the three impedance ratios between two adjacent coaxial sections, very practical degrees of freedom. They impact sensitivity to technological variations in manufacture and misalignments, power handling, and quality factors. Moreover, the two-level topology makes it possible to obtain another shape factor, and thus, push back size and performance limitations. A comparison was made of the values of the quality factor, obtained with eigenmode and a numerical method. To compare the two configurations, we designed a quarter-and a half-wavelength four-section fourth-order filter in the L -band. These two four-section filters were also compared with their two-and three-section quarter-wavelength counterparts in terms of electrical performances, bulk, and multipactor threshold. Finally, a comparison with the state-of-the-art is given.

This article presents a novel two-section coaxial stepped impedance resonator (SIR) based on the integration of parallel coaxial sections in the central part of the structure. Compared with the classical approach, this topology adds a new degree of freedom to the design, allowing an improvement of the quality factor, multipactor threshold, and fabrication tolerances. To demonstrate these advantages, we designed an example of a fourth-order filter in the $L$ -band. This filter was fabricated in aluminum and measured. The experimental results are presented and discussed.

This paper proposes a method to develop an analytical model and/or numerical resolution of the quality factor of quarter-wavelength n-section coaxial stepped impedance resonators (SIRs). The topology is based on cascaded coaxial sections nested within each other. Thanks to the SIR effect, this type of geometrical arrangement offers practical degrees of freedom to modulate the size of the resonator in both longitudinal and transverse dimensions. Moreover, in an air-filled configuration, it provides interesting quality factor, although this depends on its shape factor at any given frequency. In this paper, we show the added value of using an analytical model or numerical resolution for the quality factor, to be able to optimize the topology. To demonstrate the advantages of this model and the numerical method, comparisons of two- and three-section coaxial SIRs at two different frequencies are proposed and discussed. To validate the analytical model and numerical resolution, the values are compared with ones obtained in eigenmodes ANSYS HFSS with electromagnetic simulation tool.

This paper presents the design of a sixth-order cross-coupled L-band filter, specifically intended for space applications. The solution was based on the principle of stepped impedance coaxial resonators (SIRs), which allowed us to fulfill several electrical and size specifications and more particularly a high multipactor threshold. The degrees of freedom afforded by the proposed topology offer a wide choice of design configuration possibilities. Whatever the central frequency and required specifications, several compromises can be made in terms of volume, height, footprint, quality factor, multipactor threshold, harmonic rejection, etc. For instance, SIR coaxial topology is very well suited to small L-band filters when moderate quality factors and multipactor thresholds of around 4000 and 400 W, respectively, are requested. The design procedure is presented and simulations and measurements are compared and discussed.

This paper focuses on the flexibility in the design of quarter wavelength coaxial stepped impedance resonators (SIRs) for space applications. For such resonators, a coaxial geometry owns one degree of freedom allowing to modulate the transverse dimensions, and the SIR effect allows to adjust the longitudinal dimension. For this later, the number of degrees of freedom depends on the number of coaxial nested sections. For these topologies, the electrical model is a cascade of coaxial sections, where the ground conductor of one section becomes the central core of the next, and vice versa. According to the transverse and longitudinal degrees of freedom, it is possible to propose several sets of dimensions, height and footprint, for the same given fundamental frequency. Obviously, this will have an impact on: the quality factor, the multipactor threshold and also the frequency behavior in the attenuated band. In this paper, on the base of 4th order filters, we illustrate this ability by presenting two sets of 1.5 GHz central frequency filters with a similar bandwidth, and different footprints. Two- and three-section configurations are considered, and for each the multipactor threshold is simulated.

This article focuses on the synthesis equations of three-section coaxial stepped impedance resonators (SIRs) for the design of Tx bandpass filters and on the benefits of adding a third section compared with using a two-section SIR. In this topology, the three coaxial structures fit inside ones another. In terms of the electrical scheme, the model is a succession of coaxial sections in a cascade, where the ground conductor of one becomes the central core of the next and vice versa. An advantageous property of SIRs is that they allow the size and the distance from the next harmonic to be controlled. The SIR effect depends on the ratio of the characteristic impedances of two adjacent coaxial TEM sections. For a resonator based on three sections, two impedance ratios need to be considered to electrically characterize the resonator in terms of fundamental resonant frequency and transmission zeros. Thanks to the equations obtained by modeling its frequency behavior, we are able to show the added value of changing such a resonator from two to three sections. This makes it possible to enlarge the minimal gap between the cylinders, decreasing the sensitivity to technological variations in manufacture and improving immunity to multipactor phenomena under constrained conditions of height and bandwidth. It also makes the first transmission zero frequency and fundamental frequency independent, as the relative proximity of these two frequencies has an impact on the quality factor and the power handling of the structure. To demonstrate the advantages, we designed an example of a three-section fourth-order filter in the L-band. This was compared with equivalent two-section filters, considering electrical performances and power handling, particularly the multipactor effect. This filter was fabricated in aluminum and tested. The experimental results are presented and discussed.

The concept of a reconfigurable 5GHz microfluidically actuated antenna with beam forming, steering and hoping in a 360° angular range, is presented in this paper. Its architecture is that of a Yagi‐Uda array. Its actuation relies on the electrically controlled vertical displacement of liquid metal slugs inside microfluidic channels without the need of any external actuator. Simulations results along two fabricated proofs of concept investigating RF and microfluidic actuation performances are presented. This paper aims at demonstrating the technical soundness and interest of this design for applications such as autonomous sensors networks.

This paper focus on one particularity of a filtering coaxial architecture, allowing to satisfy the same requirements in terms of central frequency and bandwidth with various dimensions. The filtering architecture is based on miniature two-section Stepped Impedance Resonators (SIR) built from air-filled coaxial structures fitted inside one another. The SIR effect is a freedom degree allowing to adjust on demand, the global size of the resonators and thus of the filters. In order to illustrate the concept, two UHF 2 nd -order bandpass filters, with a strong contrast of dimensions are designed, fabricated, measured and compared.

This paper describes an original topology of tunable SIR coaxial filter. The proposed solution combines, moving cylinders, and rotating shutters associated with coupling arches. This topology allows the central frequency to sweep on a large frequency range of almost one octave, while controlling the bandwidth. To illustrate the principle, a third order filter was fabricated with an additive manufacturing process. The experimental results are compared with simulated data obtained with HFSS.