Design of an Additively-Manufactured Self-Supported All-Metal Coaxial-Line X-Band Bandpass Filter

Alejandro Pons-Abenza; Ivan Arregui; Miguel Angel Gomez Laso; Txema Lopetegi; Petronilo Martin-Iglesias

doi:10.1109/ACCESS.2024.3399745

IEEE Access (Jan 2024)

Design of an Additively-Manufactured Self-Supported All-Metal Coaxial-Line X-Band Bandpass Filter

Alejandro Pons-Abenza,
Ivan Arregui,
Miguel Angel Gomez Laso,
Txema Lopetegi,
Petronilo Martin-Iglesias

Affiliations

Alejandro Pons-Abenza: ORCiD; Department of Information and Communication Technologies, Technical University of Cartagena (UPCT), Cartagena, Murcia, Spain
Ivan Arregui: ORCiD; Department of Electrical, Electronic, and Communications Engineering, Institute of Smart Cities (ISC), Public University of Navarre (UPNA), Campus Arrosadia, Pamplona, Spain
Miguel Angel Gomez Laso: ORCiD; Department of Electrical, Electronic, and Communications Engineering, Institute of Smart Cities (ISC), Public University of Navarre (UPNA), Campus Arrosadia, Pamplona, Spain
Txema Lopetegi: ORCiD; Department of Electrical, Electronic, and Communications Engineering, Institute of Smart Cities (ISC), Public University of Navarre (UPNA), Campus Arrosadia, Pamplona, Spain
Petronilo Martin-Iglesias: ORCiD; Department of Electrical, Electronic, and Communications Engineering, Institute of Smart Cities (ISC), Public University of Navarre (UPNA), Campus Arrosadia, Pamplona, Spain

DOI: https://doi.org/10.1109/ACCESS.2024.3399745
Journal volume & issue: Vol. 12
pp. 68171 – 68183

Abstract

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In this contribution, the design and manufacturing of an all-metal coaxial-line X-band bandpass filter is discussed. The device is 3D-printed as a self-supported structure without any dielectric inside the coaxial. The mechanical support between the inner and outer coaxial-line conductors is provided by means of $\lambda /4$ short-circuited stubs, which are also used in the bandpass filter design. The real transmission zeros (TZs) produced by the short-circuited stubs are responsible for a high filter selectivity. In order to enhance the filter performance, a second stage consisting in a coaxial-line stepped-impedance low-pass filter is integrated in the design to provide the rejection level required for the out-of-band behaviour. Following our design method, the bandpass and low-pass filters are designed separately, and a final matching step is performed to connect both and to achieve the aimed frequency specifications. In this way, a monoblock coaxial filter with very good in-band and out-of-band performance can by obtained by using an additive manufacturing (AM) procedure. Only the input/output (I/O) coaxial connectors will need to be assembled to the filter to perform the frequency measurements. The filters in this work can be seen as a first proposal towards more complex multi-functional monoblock structures using additively-manufactured coaxial technology, for highly-integrated RF chains. Other expected benefits beyond the compactness or lightweight are an increased RF shielding, electrostatic discharge risk reduction, and Passive Intermodulation (PIM) protection. In the paper, a prototype with a passband between 8 and 12 GHz is designed and manufactured, using a bandpass filter with three stubs and an integrated 15th-order low-pass filter, providing rejection for spurious frequencies up to 30 GHz. The filter is manufactured using Selective Laser Melting (SLM) and measurements show an excellent agreement with the simulations.

Published in IEEE Access

ISSN: 2169-3536 (Online)
Publisher: IEEE
Country of publisher: United States
LCC subjects: Technology: Electrical engineering. Electronics. Nuclear engineering
Website: https://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=6287639

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