Wideband Bandpass Filters Using a Novel Thick Metallization Technology

TL;DR

This paper introduces a novel thick metallization technology for wideband bandpass filters using metallic bars as resonators, offering higher coupling, better quality factors, and larger bandwidths compared to traditional microstrip designs.

Contribution

The paper presents a new thick metallic bar resonator technology that enhances filter performance and enables transmission zeros, demonstrated through design, manufacturing, and testing of prototype filters.

Findings

Achieved fractional bandwidth of 32% in prototypes

Demonstrated high unloaded quality factor of 1180

Realized filters with over 20 dB return loss and no post-tuning

Abstract

A new class of wideband bandpass filters based on using thick metallic bars as microwave resonators, instead of common microstrip lines, is presented. These bars provide a series of advantages over fully planar printed technologies, including higher coupling levels between resonators, better unloaded quality factors QU, and larger bandwidths, implemented with more compact structures. Moreover, thick bar resonators can easily be coupled to an additional resonance excited in a box used for shielding, allowing to realize transversal topologies able to implement transmission zeros at desired frequencies. To illustrate the capabilities of this technology, two microwave filters with different bandwidths and one transmission zero have been designed. One of the filters has been manufactured and tested using copper bars inside an aluminum housing partially filled with Teflon. Measured data demonstrates a fractional bandwidth about FBW = 32%, spurious free range SFR > 50%, unloaded quality factor of QU = 1180 and return losses over 20 dB without requiring any post-tuning on the prototype, confirming the exciting performance of the proposed technology.