  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.
