A Narrowband 3-D Printed Invar Spherical Dual-Mode Filter With High Thermal Stability for OMUXs

Lu Qian, Yi Wang, Sheng Li, Abd El Moez A. Mohamed, Moataz M. Attallah, Talal Skaik, Paul Booth, Laurent Pambaguian, Cesar Miquel Espana, Petronilo Mart

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A 3-D printed narrowband bandpass filter based on spherical dual-mode resonators is presented in this article. It is designed for output multiplexers (OMUXs) using high-Q spherical dual-mode resonators. Realization is by laser powder bed fusion (L-PBF) technology of Invar alloy chosen for its low coefficient of thermal expansion (CTE). Using PBF circumvents the alloy's manufacturability issues associated with its hardness in machining and free forming. Compared with polymer-based vat photopolymerization technology, PBF allows for direct metal manufacture of complex monolithic microwave components with better thermal-mechanical properties and higher power-handling capability. Using Invar can further help achieve high temperature stability of the filter in high-power operation. To demonstrate the proposed solution, detailed thermal-RF test at different temperatures was carried out. The experimental results of a 0.47% fourth-order silver-plated Invar filter with two transmission zeros verify the design and manufacturing. An insertion loss of 1 dB and an effective temperature coefficient of less than 2 ppm/K were achieved.

Original languageEnglish
Pages (from-to)2165-2173
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number4
Publication statusPublished - 9 Mar 2022

Bibliographical note

Publisher Copyright:


  • 3-D printing.
  • Couplings
  • Electronic mail
  • High-power filter
  • Invar
  • Iris
  • Laser stability
  • Powders
  • Resonators
  • Thermal stability
  • novel materials
  • output multiplexer (OMUX)
  • spherical resonators

ASJC Scopus subject areas

  • Radiation
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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