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The objective of this article is to describe a new family of microwave bandpass filters in the rectangular waveguide based on resonant apertures, which can be used to implement both single- and dual-band transfer functions. The use of capacitive stubs and a staircase configuration is also discussed in order to enhance the out-of-band response and the selectivity of the filter with respect to the state of the art. Finally, simulations are compared with measured results, showing very good agreement, thereby fully validating both the new filter topologies and the design procedure. [ABSTRACT FROM AUTHOR]

The objective of this article is to describe the design of a new family of wideband filters in a rectangular waveguide based on hybrid couplings and a staircase configuration. The use of E-plane T-junctions and E-plane folded structures is also discussed, in order to enhance the out-of-band response and the selectivity of the filter with respect to the current state of the art. The design of several hybrid filter prototypes is discussed in detail, including manufacturing sensitivity and high-power analysis. Finally, simulations and measurements for an eight-pole filter prototype are also compared, showing very good agreement, thereby fully validating both the design procedure and the new filter topology that we propose. [ABSTRACT FROM AUTHOR]

In this article, we describe several alternative inline implementations for combline filters with transmission zeros (TZs) located both below and above the passband. A systematic design procedure is also presented using a lumped-element equivalent circuit. Following the design procedure that we propose, up to $N+1$ TZs can be implemented with an inline filter of order $N$. The generation of the TZs is explained physically in terms of mixed inductive and capacitive couplings. Several filters are also manufactured and tested. Good agreement between the measured and simulated results is demonstrated, thereby fully validating the new filter concepts. [ABSTRACT FROM AUTHOR]

In this letter, we propose a new device that integrates the functions of a microwave filter and switch (F&S). The key component of the F&S is a modified tuning pin (MTP) that can be used to tune or to detune a cavity or an aperture. In addition to theory, a prototype is also manufactured and tested, showing how the switching function of the new device can be easily controlled remotely. [ABSTRACT FROM AUTHOR]

In this article, we show how the multimode equivalent network (MEN) technique can be extended to the analysis of multilayer boxed planar microwave circuits that are built using a thick metallization. This analysis is carried out considering the thick metallic circuit as a length of the uniform waveguide. The problem is then divided into two waveguide steps (or junctions). We first obtain the equivalent network of the two junctions. Then, we cascade them to obtain the MEN of the complete circuit, thereby including the effect of finite thickness rigorously. A key aspect of the formulation that we propose is that it includes ports in the transverse plane of the circuit. In addition to theory, several shielded microwave filters using a thick metallization are also analyzed. An in-depth study of the numerical convergence is also performed for two practical examples. Simulation results are shown to be in good agreement with both commercial simulation tools and measurements, thereby fully validating our theoretical formulation. [ABSTRACT FROM AUTHOR]

In this article, we describe a new family of multiband waveguide filters based on a folded topology. The folded topology allows to use the filters of different orders and the introduction of transmission zeros. The design of the multiband filter is based on the aggressive space mapping (ASM) technique and is able to take into account manufacturing details, such as round corners and tuning elements. The filter structure is validated by designing, manufacturing, and measuring a triband filter. The agreement between simulations and measurements is shown to be excellent, thereby fully validating both the filter topology and the design process. [ABSTRACT FROM AUTHOR]

The multimode equivalent network (MEN) formulation has been originally developed for the efficient and accurate analysis of waveguide devices. In this article, we extend the use of the MEN to the analysis of zero-thickness, planar printed circuits in a metallic enclosure. The formulation is developed for metallic areas of arbitrary shape and includes both internal and external ports in the transverse plane to model connections to external components, and coaxial input/output ports. The boundary integral resonant mode expansion (BI-RME) method is used for the analysis of the arbitrary shape metallizations. On this basis, shielded multilayered microstrip circuits of complex geometry are analyzed in the common frame of the MEN technique. To validate the theoretical formulation, several boxed microstrip structures are analyzed, including multilayered configurations with several metallization interfaces, showing good agreement with respect to both other commercial tools, and measurements. [ABSTRACT FROM AUTHOR]

Space mapping (SM) and aggressive SM (ASM) techniques are widely used in the synthesis and design of microwave filters. Their popularity stems from the inherent simplicity of the procedures and from their effectiveness. The objective of this article is to extend the state of the art of these techniques by discussing how they can also be used very effectively to tune microwave filters. In addition to the theory, the successful tuning of a six-pole inductive waveguide filter is discussed in detail, thereby fully validating the proposed SM techniques. [ABSTRACT FROM AUTHOR]

The objective of this paper is to advance the state of the art of aggressive space mapping (ASM) by demonstrating how, for resonant structures, and microwave filters in particular, an ASM-based optimization procedure may converge to the desired target performance in just one step. This behavior is first justified in physical terms, using the electromagnetic cavity perturbation theory, and is then investigated numerically. Several practical filter design demonstrations are also presented. This paper is concluded with a conceptual definition of Space Alignment in the context of ASM. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a technique for the efficient design of bandpass waveguide microwave filters using a segmentation technique applied to an equivalent circuit. The technique is based on first developing an equivalent circuit that synthesizes the desired transfer function. Then, the different parts of the real physical structure are optimized by segmenting this equivalent circuit. The technique was originally developed for in‐line filters, and the main contribution of this paper is in the combination of this technique with the coupling matrix formalism. In this way, we adapt for the first time this design strategy to the design of complex coupling topologies, beyond the in‐line configuration. As an example, a complex sixth‐order dual‐mode filter, implemented in all‐inductive waveguide technology, is designed using the new coupling matrix segmentation technique, showing the effectiveness of the presented theory. A prototype of the filter has been manufactured, and the accuracy of the design technique is verified by measurements on the real prototype. [ABSTRACT FROM AUTHOR]

This paper provides the guidelines for the practical development of novel advanced test beds for passive intermodulation (PIM) measurements. The proposed test beds show high performance and are flexible, allowing for the measurement of several PIM signals of different orders, with two or more input carriers. In contrast to classic test beds for satellite hardware, based on the cascaded connection of several elements, an integrated solution involving the minimum number of hardware pieces is proposed. The result is a lower number of flanged interconnections, thus reducing residual PIM level and insertion losses. In addition, return loss degradation and harmful spurious generation in the interconnections are also avoided. Measurement test beds for conducted and radiated PIM, in both transmitted and reflected directions, are discussed, highlighting the benefits and drawbacks of each configuration. Design guidelines for the key components are fully discussed. Illustrative application examples are also reported. Finally, excellent experimental results obtained from low-PIM measurement setups, working from C-band to Ka-band, are shown, thus fully confirming the validity of the proposed configurations. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to use electromagnetic-based computer-aided design (CAD) tools to investigate the maximum tuning range of channel filters, typically used in satellite payloads. Both circular and rectangular waveguide technologies are investigated. The results of the investigation show that single-mode rectangular waveguide implementations offer substantially wider tuning range, as opposed to classical dual-mode circular waveguide implementations. In addition to simulations, measurements are also presented indicating very good agreement with theory, thereby fully validating the CAD procedure. [ABSTRACT FROM PUBLISHER]

This letter proposes a simple procedure to implement low-passive intermodulation (PIM) terminations in waveguide technology to measure conducted backward PIM. The procedure consists in inserting a filter before the waveguide termination of the test bench. This approach reduces the PIM contribution from the load and, consequently, lowers the residual PIM noise floor of the test bench. To validate the procedure, a conducted backward low-PIM setup working in $K$ -band has been assembled and tested. The PIM performance improvement obtained fully confirms the validity of the proposed solution. [ABSTRACT FROM AUTHOR]

A third paper is also included, showing the main results of an ESA-funded project on dielectric-loaded filters for L-band satellite diplexers. This special issue is focused on the latest practical developments of microwave filters and multiplexers for satellite communication systems, where they are key elements in the high-frequency front-end for both on-board payloads and Earth stations, giving support to a large number of advanced services. Advanced solutions for passive devices in the Ku- and Ka-band (using low-cost and fast-fabrication techniques) will be required by mega-constellation satellites, whereas reconfiguration capabilities and increasing operational bandwidths are needed by up-coming large Ka-band satellites. [Extracted from the article]

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with channel filters based on transmission-line resonators, the method is specialized for the design of classic multiplexers with circular-waveguide dual-mode filters. As a further application example, the same methodology is also used for the design of a nonconventional tuningless wideband multiplexer with a new type of rectangular waveguide filters. This paper is concluded with a comparison between simulation and measurements for the wideband multiplexer. Excellent agreement between measurements and simulations are demonstrated, thereby validating the complete design procedure. [ABSTRACT FROM AUTHOR]

This paper presents a capacitive obstacle for rectangular waveguide filters capable of realizing multiple transmission zeros (TZs). By combining a capacitive window with multiple thin stubs, a filter designer has the ability to control the total coupling implemented by the obstacle, and the frequency location of the TZs generated. The resulting structure is compact, and can be employed at the input/output and intermediate stages of direct-coupled-resonator filters. This letter includes a parametric analysis of the obstacle and practical design guidelines. To validate its practical application, an in-line five-pole filter realizing three TZs has been successfully realized. [ABSTRACT FROM PUBLISHER]

In this paper, the design of a novel planar narrowband microstrip filter is presented. The structure is designed and manufactured in microstrip technology, and it is formed by set of pairs of resonators of different lengths. The length of one resonator in each pair is adjusted so that a suitable odd resonance is tuned to the center frequency of the filter. The length of the other resonator is adjusted so that the next even resonance is tuned again to the center frequency of the filter. The different path of the signal in each resonator produces a cancellation of energy at a given frequency, therefore implementing a transmission zero in the insertion-loss response of the filter. First, this paper presents a design example of a single set of resonators (basic unit cell) working at the fifth and sixth resonances. Then, two basic unit cells working at the first and second resonances are first optimized, and then they are cascaded to show how higher-order filter responses can be implemented. The measured results confirm the theoretical predictions, and validate the new structures for high-selectivity applications. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 450–455, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20499 [ABSTRACT FROM AUTHOR]

This paper describes a number of broadside-coupled microstrip structures and their use for the implementation of high-selectivity multilayered filters. The broadside configuration allows for the introduction of cross couplings between nonadjacent resonators. The cross couplings can then be used to implement transmission zeros that can significantly increase the selectivity of the filters. Furthermore, the investigation shows that the amount of coupling can be considerably increased if the resonators are broadside coupled, thus easily allowing the implementation of broadband filters. Measured results are shown to agree with predictions, thereby fully validating the new structures described. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 295–302, 2001. [ABSTRACT FROM AUTHOR]

Examines a full-wave computer-aided design (CAD) of a microwave filter with integrated coaxial excitation. Uses of coaxial waveguide in microwave subsystems; Elements required in the implementation of a CAD tool; Composition of the filter structure.

Low-loss performance is one of the main drivers in the design of microwave filters and diplexers. In this paper, we propose a simple, low-cost solution to this problem. Measured responses of specific designs are also included, indicating that the solution proposed is indeed practical and cost effective. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 7–9, 2000. [ABSTRACT FROM AUTHOR]

In this contribution, we describe the design of bandpass filters using evanescent mode waveguides and dielectric resonators implemented with additive manufacturing techniques. Two C-band Chebyshev evanescent mode waveguide filters of order five have been designed using a low cost commercial dielectric material (ABSplus), widely used by Fused Deposition Modeling (FDM) 3D printers. The housings of the filters have been manufactured using traditional computer numerical control (CNC) machining techniques. Practical manufacturing considerations are also discussed, including the integration of dielectric and metallic parts. We first discuss two breadboards using two different resonator geometries. We then demonstrate how different transfer functions can be easily implemented by changing the 3D printed parts in the same metallic housing. Breadboards show fractional bandwidths between 3% and 4.6% with return losses better than RL = 18 dB, and spurious free ranges of SFR = 1 GHz. Insertion losses are better than IL = 4.3 dB. Even though dielectric losses from the plastic material are shown to be high, the measured results are quite satisfactory, thereby clearly showing that this strategy maybe useful for the fast production of low cost microwave filters implementing complex geometries. [ABSTRACT FROM AUTHOR]

In this work, we propose an integral equation technique for the efficient analysis of capacitive step discontinuities in rectangular waveguides. The method allows for the inclusion of a number of arbitrarily shaped posts in the vicinity of the step discontinuity. The posts can be both metallic or composed of homogeneous dielectric materials. The integral equation formulation is based on the Surface Equivalence Principle, and uses the parallel plate Green's functions that take into account for the boundary conditions imposed by the host waveguide. The formulation is written in the mixed spatial-spectral frequency domain, and takes advantage of the symmetry of the problem by reducing the original three dimensional (3D) problem to a so called 2.5D problem. The numerical technique has been validated with simulation examples, namely, two lowpass filters that use conducting and dielectric posts of different shapes as impedance inverters. The results provided by the method that we propose have been also compared to those obtained with a commercial full-wave software tool (ANSYS HFSS), showing in all cases a very good agreement with substantially higher computational efficiency. [ABSTRACT FROM AUTHOR]