Highly Selective Broadband mm-Wave Diplexer Design

This letter presents a novel broadband diplexer design that is capable of achieving highly stringent rejection characteristics though the use of singlets whose interconnecting irises are formulated as resonant slot-irises. The combination of these two resonant-cavity types allows for a unique filtering solution with increased filter order, wide available bandwidth, low geometric complexity and simple milling requirements which can be suitably applied to millimetre-wave and submillimetre-wave applications. A prototype is fabricated for operation in the Wband (75 GHz - 110 GHz) in order to cover a 10% fractional bandwidth in each passband. Measurement of the prototype denotes highly accurate results and exemplifies the use of all resonator and coupling elements in order to support ten poles and four transmission zeros in an elegant diplexer solution

Investigation of the cutting plane and tolerance analysis of cross-coupled W-band waveguide filters with multiple transmission zeros by source to load cross-coupling

In this paper, the influence of the cutting plane as well as the orientation of the cavities in cross-coupled W-band waveguide filters are investigated. When waveguide filters are manufactured with the commonly known CNC (computer numerical control) milling technique, at least one cutting plane is required. The position of this cutting plane has an impact on the composition of the cavities, the manufacturing accuracy, and on the maximal number of transmission zeros (TZs) introduced by a direct source to load (SL) cross-coupling. Similar filter set-ups therefore may show different performances depending on the position of this cutting plane. To examine all these effects, three similar fourth-order W-band filter set-ups are realized with distinct cutting planes and different oriented cavities. The filters are compared in terms of the sensitivity to manufacturing tolerances, the maximal number of TZs introduced by a direct SL cross-coupling as well as their spurious mode performance

Reconfigurable Bandpass Filter with Extracted Pole and Coupling Resonators

This paper presents a reconfigurable bandpass filter with an extracted pole section in the Ku-band. The filter’s center frequency and bandwidth can be controlled independently from each other by using additional resonators. The center frequency can be varied between 13.8 GHz and 14.8 GHz while the bandwidth can be varied between 100 MHz and 200 MHz in the given center frequency range. The extracted pole section provides a transmission zero close to the passband, which increases the selectivity and remains in place relative to the passband during all tuning states

Coupling Matrix Description of WR-3 Waveguide Filter with Multiple Transmission Zeros Created by Source to Load Cross-Coupling

In this paper, a fourth order source to load (SL) cross-coupled WR-3 band (220–325 GHz) waveguide filter is presented. Due to the dispersive characteristic of the SL cross-coupling, two extra transmission zeros (TZs) are obtained, which are not predicted by the common coupling matrix theory. One of these TZs can be positioned freely on the frequency axis while the position of the second one depends on the position of the first one, allowing the realization of asymmetric filter responses. It is shown that the SL coupling proposed in this filter set-up reveals a quadratic frequency dependency. Based on this observation, a coupling matrix description which agrees well with an appropriate discrete equivalent circuit as well as the simulation results can be found. A prototype is manufactured with a high precision CN C milling machine as proof of concept

Effects of Cutting Planes on Filter Performance of FDM 3D-Printed X-Band Waveguide Filters

In this paper, the impact of E-plane and H-plane cuts on filter performance of 3D-printed waveguide filters manufactured with fused deposition modeling (FDM) is examined. The employed manufacturing procedure consists of FDM 3D-printing and the subsequent electroplating process. A number of samples in both configurations are fabricated and surveyed. The measurement results are quantified and a comparison is conducted. Finally, the differing filter behaviors are discussed

X-Band 3D-Printed Metal-Insert Twist-Component for Bandpass Filter Applications

This work presents the development of an X-band twisted metal-insert bandpass filter as a monolithic 3D-printed structure. The component serves as a compact solution for the incorporation of a fourth-order bandpass filter response while simultaneously rotating the polarization by 90 degrees as a twist-component. The structure is fabricated using lowcost stereolithography 3D-printing and metallized using a simple copper electroplating method. The measured results exhibit an unloaded Q-factor of approximately 2600 and have an insertion loss better then 0.44 dB throughout the passband, ultimately demonstrating a unique use of the metal-insert filter technique and providing a novel presentation on integrated monolithic structures

Quasi-Elliptical Stub-Based Multi-Resonance Waveguide Filters With Low Manufacturing Complexity for mm-Wave Applications

In this paper, the design and realization of quasi-elliptical waveguide filters with reduced manufacturing complexity are discussed. The filters are based on TE mode cavities, which are loaded with TM mode stubs. It is shown that dual-, triple- and quadruple-resonance segments are obtained by using up to three stubs loaded on the broad side of a TE mode cavity. The structures obtained can either be used as a stand-alone filter or even as a building block suitable for the realization of higher order filters. The multi-resonance blocks reveal several advantages in the mm-wave area: The manufacturing complexity is easy to handle and comparable to simple all-pole filters, which is especially important at high frequencies. Therefore, three prototypes are manufactured as proof of concept in the D-band (110 GHz–170 GHz). Moreover, the building blocks are able to produce $n-1$ transmission zeros (TZs) with $n$ being the number of resonances. Therefore, the blocks generate between one (dual-resonance) and up to three (quadruple-resonance) TZs. Advantageously, the filters can be cut in the E-plane in order to reduce the insertion loss and hence consist of only two components. Three examples are manufactured by high precision CNC milling and reveal good agreement to the simulation by obtaining unloaded Q-factors of up to 1000