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Abstraction in Assumption-based Argumentation

Apostolakis, Iosif

A Semantical Approach to Abstraction in Answer Set Programming and Assumption-based Argumentation

Lehtonen, Tuomo

Complexity Results and Algorithms for Preferential Argumentative Reasoning in ASPIC+

Popescu, Andrei

Advancing Algorithmic Approaches to Probabilistic Argumentation under the Constellation Approach

Robins, Luke

Bartlett, Chad

Arsanjani, Arash

Teschl, Reinhard

Bösch, Wolfgang

Höft, Michael

IEEE MICROWAVE AND WIRELESS TECHNOLOGY LETTERS, VOL. 33, NO. 11, NOVEMBER 2023 1517
A 3-D-Printed Dielectric Resonator for
Triple-Mode Applications
Luke Robins , Member, IEEE, Chad Bartlett , Member, IEEE, Arash Arsanjani , Member, IEEE,
Reinhard Teschl, Member, IEEE, Wolfgang Bösch , Fellow, IEEE, and Michael Höft , Senior Member, IEEE
Abstract— This work presents a novel 3-D-printed triple-mode
dielectric resonator for microwave filter applications. The design
demonstrates the use of an odd number of periodic rings placed
along a dielectric combline resonator to create a miniaturized
filter structure capable of creating a quasielliptic triple-mode
filter response. A new approach suitable for 3-D-printing of the
periodic rings is presented using support structures that take
the form of struts. The resonator is fabricated using alumina
with lithography-based ceramic manufacturing and housed in
a compact single-cavity structure. The filter is designed for
operation with a center frequency of 10.78 GHz, fractional
bandwidth (FBW) of 2.13%, and a measured quality factor of
approximately 1700.
Index Terms— Additive manufacturing (AM), alumina, band-
pass filter, dielectric resonator, stereolithography, triplet.
I. INTRODUCTION
MICROWAVE filters are a critical part of moderntelecommunications systems. In some circumstances,
the technology chosen to implement the structure can result
in bulky, heavy products or in formats that are difficult to
integrate. Therefore, it is important to investigate miniatur-
ization methods for these types of filters while working to
maintain high-quality factors and dynamic filtering responses.
Many approaches to miniaturization exist, such as the use of
dielectric resonators, which reduce the structural size by com-
pressing the electromagnetic fields [1], metamaterials [2], and
multimode monoblock filters [3]. In a recent work on utilizing
ceramic additive manufacturing (AM) for dielectric combline
resonators [4], the quality factor performance of higher modes
was increased and dual-mode operation was achieved through
changes in the geometry. In this work, the concept of periodic
changes in the geometry is expanded to triple-mode operations.
A filter that utilizes the combination of the TM010 and the two
orthogonal TE111 modes and operates at 10.78 GHz with a
fractional bandwidth (FBW) of 2.13% is designed. It features
Manuscript received 21 April 2023; revised 21 June 2023 and 15 August
2023; accepted 24 August 2023. Date of publication 19 September 2023;
date of current version 8 November 2023. This work was supported by
the European Union’s Horizon 2020 Research and Innovation Program
under the Marie Skłodowska-Curie Grant 811232-H2020-MSCA-ITN-2018.
(Corresponding author: Luke Robins.)
Luke Robins, Arash Arsanjani, Reinhard Teschl, and Wolfgang Bösch are
with the Institute of Microwave and Photonic Engineering, Graz University
of Technology, 8010 Graz, Austria (e-mail: lrobins.p@gmail.com).
Chad Bartlett and Michael Höft are with the Department of Electrical and
Information Engineering, Kiel University, 24143 Kiel, Germany.
Color versions of one or more figures in this letter are available at
https://doi.org/10.1109/LMWT.2023.3311812.
Digital Object Identifier 10.1109/LMWT.2023.3311812
Fig. 1. Alumina (εr = 9.5 and tanδ = 8·10−5 [6]) resonator comparison:
(a) post, (b) solid-ring, and (c) five-ring.
Fig. 2. Solid-ring E-field distributions middle cut. (a) TM010. (b) TE111.
(c) TE111⊥. (d) Side on view.
increased distance to the next spurious mode while decreasing
the material and weight at the same time, highlighting the
flexibility in resonator design possibilities enabled through the
use of ceramic stereolithography-based 3-D-printing.
II. TRIPLE-MODE RESONATOR DESIGN
To demonstrate the build-up of the 3-D-printable resonator
structure, a progression of the resonators is presented in Fig. 1.
The most basic resonator configuration, consisting of a dielec-
tric post placed in a cylindrical cavity, is shown in Fig. 1(a).
The first four modes in this configuration are: TM010, TM011,
TE111, and TE112. It is important to mention that these modes
are not purely TM or TE due to the asymmetric placement
of the resonator. However, the respective longitudinal field
components are small. The addition of a solid ring (SR)
on the post, as demonstrated in Fig. 1(b), can influence the
positions of these modes relative to each other. The simulated
field concentrations of the first two modes are illustrated in
Fig. 2. From these, it can be observed that the TM mode has
more field concentrated at the center of the cavity along the
central post, while the TE mode is most concentrated near
the outside edge of the introduced ring. These areas of field
concentration can be exploited to, somewhat independently,
shift the resonant frequency of the TM010 and TE111 modes,
allowing the modes to be close enough together to be useful
in a dual-mode configuration. Additionally, the TE111 has an
© 2023 The Authors. This work is licensed under a Creative Commons Attribution 4.0 License.
For more information, see https://creativecommons.org/licenses/by/4.0/
1518 IEEE MICROWAVE AND WIRELESS TECHNOLOGY LETTERS, VOL. 33, NO. 11, NOVEMBER 2023
Fig. 3. Resonant frequency study for the SR and FR resonators, demonstrating the (a) triple-mode operation ratio while keeping a fixed height
(Hsr1 = 4.25 mm), (b) mode separation improvement with a fixed ratio (Dsr1/Hsr1) = 1, and (c) further mode separation using the FR resonator and
sweeping the central post diameter with (Dsr1 = Dr1 = 5.6 mm).
identical orthogonal mode at the same resonant frequency [see
Fig. 2(b) and (c)], and, therefore, a triple-mode implementation
is possible. The effect of the ratio of ring height (Hsr1) to the
outside diameter (Dsr1) is shown in Fig. 3(a). Interestingly,
for the desired triple-mode operation point, the optimal ratio
was found to be approximately 1. Parameter sweeps with
this ratio fixed are shown in Fig. 3(b). Keeping the outside
diameter of the SR fixed while sweeping the diameter of
the central post (Dsr) is demonstrated in Fig. 3(c). These
results demonstrated that the resonator can be optimized for
both triple-mode operations and situated at a point where the
distance to the next mode is a maximum, ultimately moving
the TE111 away from the spurious TM011 and TE112 modes.
Similar results can be achieved using a five-ring (FR) structure
as shown in Fig. 1(c). A comparison of the respective shifts
in resonant frequency, between SR and FR, can be seen in
Fig. 3(c) and it highlights that the TE112 mode is shifted
to higher frequencies when using the FR profile and gives
approximately 60% (1 GHz) of additional separation to the
desired modes.
III. FABRICATION CONSIDERATIONS
Fabrication of the FR configuration would require approxi-
mately 22% less material and result in an 18% lighter resonator
when compared to the SR resonator. Due to these advantages
and the fact that the FR resonator has a higher degree of
complexity, lithography-based 3-D-printing was chosen for
fabrication. Using the principles outlined previously, a triple-
mode resonator specified for 10.8-GHz operation was designed
for fabrication. The model of the FR resonator is depicted in
Fig. 1(c), where the dimensions are given as: Hr0 = 5.62,
Hr1 = 1.5, Hr = 18.6, Dr = 1.6, Dr1 = 5.6, and Hs =
0.5 (mm).
The resonators were fabricated using a Lithoz CeraFab
7500 printer, with an XY resolution of 40 µm and a
printing-layer height of 50 µm. Multiple fabrication rounds
were required to enable successful printing. The large differ-
ence between the central post and outside ring radius created
overhangs too large to be easily printed without support.
The transition areas from the post to the ring were prone to
breakages during printing due to sheer stress.
To overcome this, supporting struts were introduced in
between the rings as shown in Fig. 4. However, it should be
Fig. 4. Modified triple-mode resonator for printing. (a) Side view. (b) Per-
spective view. (c) Fabricated resonator.
Fig. 5. Input coupling: (a) TM010, (b) TE111, and (c) simulated results.
noted that the addition of material can cause the TM modes
to shift to lower frequencies, and therefore, keeping the struts
as thin as possible was critical for the design to succeed. The
final strut-adapted resonator design is shown in Fig. 4 with
the following dimensions: Hr0 = 9, Hr1 = 1, Hr = 18.51,
Dp = 1.6, Dr = 6.05, Hs = 0.5, R = 1, St = 0.12 (mm), and
θ = 30◦. The resonators have a simulated Qu of approximately
11 000 in a copper cavity and 6000 in brass.
IV. TM010 AND TE111 TRIPLE-MODE FILTER
A third-order filter centered at 10.78 GHz with a return
loss of 20 dB and an FBW of 2.13% was designed to verify
the resonator concept and show an application of dynamic
alumina-based 3-D-printing. The triplet uses a cylindrical
cavity with a radius of 7.5 mm and a height of 21.8 mm and
encompasses the 3-D-printed resonator specified in Section III.
SMA probes were chosen as a simple approach to feeding,
where the input coupling can be controlled by the length
of the probe into the cavity. Horizontal placement of the
probes was used as more space was available on each wall
to accommodate both feeds for the triplet case. The probe
feeding provides a challenge, as in this case, the TM010 and
TE111 electric fields are almost entirely orthogonal to each
other. The field configurations are shown in Fig. 5(a) and (b),
highlighting a small area toward the top of the resonator where
some of the electric field components are oriented horizontally
ROBINS et al.: 3-D-PRINTED DIELECTRIC RESONATOR FOR TRIPLE-MODE APPLICATIONS 1519
Fig. 6. Designed triple-mode filter: (a) side view, (b) top view, (c) simulated and measured performance, and (d) alternate zero configuration.
for both modes. Placing the feeds at this position enables
the simultaneous excitation of both modes. Fig. 5(c) shows
the feasible input coupling achieved by varying the probe
depth. The coupling can be further increased by a deliberate
misalignment of the resonator with respect to the center of the
cavity, as further demonstrated in Fig. 5(c), allowing for wider
bandwidths and more gradual changes in regard to the input
coupling.
To achieve triple-mode operation, the ports were placed
at 90◦ relative to one another. A metallic screw was placed
at 45◦ between the ports to excite both orthogonal TE111
modes and a metallic screw controlling TM010 was placed
next to the resonator on the floor of the cavity. The screws are
positioned close to the maximum electric field of the respective
mode for the most impact. Two additional screws for each
TE111 mode were included to allow for the tuning of each.
The final filter responses and layout are provided in Fig. 6.
Extraction of the exact coupling parameters in this triple-mode
configuration is difficult due to innate parasitic and loading
effects. Therefore, a simplified analogous transversal coupling
matrix, which excludes the cross-coupling, is included to aid
the initial filter design: MS1 = 0.59, M1L = 0.54, MS2 =
0.59, M2L = 0.54, MS3 = −0.81, M3L = 0.83, M11 =
−1.6, M22 = 1.54, M33 = −0.135, and MSL = −0.039.
The dimensions are given as: PL = 3.7, S1 = 1.1, S2 = 0.8,
S3 = 1.83, S4 = 3.35, L1 = 4.5, Hp = 11.4, and Hs = 9 (mm).
The transmission zero (TZ) appearing below the passband
is generated by the relationships between the input coupling
to each mode with the source to TE111⊥ having the opposite
phase. In this case, the TZ position can be moved by keeping
coupling into mode TE111⊥ fixed and adjusting the coupling
of TM010 and TE111. As the coupling into TM010 is decreased
and into TE111 is increased, the TZ moves downward away
from the passband. The selected probe-feeding setup limits
the flexibility in positioning the TZs, as changes in input
coupling influence at least two of the modes at a time. There
is, however, a way to keep the TZ below the passband and
create an additional TZ above the passband; this is done by
reducing the source-to-load coupling. This can be achieved by
rotating one of the inputs by 25◦ clockwise from the position
in Fig. 6(b), thus reducing the coupling between the ports.
While the input coupling of the TM mode is independent of
the rotation of the feeds, the coupling for the two TE modes
changes based on the rotation of the feeding. This allows
the response illustrated in Fig. 6(d), whereby the second TZ
above the passband is caused by the higher-order TE112 mode
interacting with the TE111 which bypasses the resonator. The
TABLE I
COMPARISON TO RECENT WORKS ON THE DIELECTRIC RESONATOR AND
CERAMIC 3-D-PRINTED FILTERS
simplified analogous transversal coupling matrix: MS1 = 0.52,
M1L = 0.41, MS2 = 0.51, M2L = 0.52, MS3 = −0.87,
M3L = 0.83, M11 = −1.5, M22 = 1.43, M33 = −0.17, and
MSL = −0.017.
V. FABRICATION AND MEASUREMENT
The designed resonator and filter cavity were fabricated
using Lithalox 350 and brass, respectively, with a resonator
shown in Fig. 4(c). The resonator was glued to the bottom
lid by hand using superglue and, as such, makes achieving an
exact alignment difficult, leading to slight shifting in frequency
and quality factor degradation. However, this simple process
is accurate enough for a proof-of-concept filter and allows
for the verification of the performance of the 3-D-printed
resonator. The measured filter performance is compared to the
simulated S-parameter in Fig. 6(c) and largely matches that
of the simulation, aside from a 40-MHz shift. The extracted
quality factor is approximately 1700, while the simulated value
is in the range of approximately 3600. These deviations are
attributed to the manual assembly process and additional losses
introduced by the superglue and the tuning screws. Table I
provides a comparison of this work to recent 3-D-printed
filters and demonstrates the overall compactness while still
maintaining quality factor performance.
VI. CONCLUSION
This work introduces a novel 3-D-printed triple-mode
dielectric resonator that enables the use of the TM010 and
the two orthogonal TE111 modes together in a triplet imple-
mentation. Additionally, the work presents a thin strut-like
support geometry to enable the printing of alternating ring-
type structures. The resonator was fabricated and demonstrated
for a triplet filter implementation operating at 10.78 GHz,
highlighting potential applications of 3-D-printed ceramic res-
onator structures.
1520 IEEE MICROWAVE AND WIRELESS TECHNOLOGY LETTERS, VOL. 33, NO. 11, NOVEMBER 2023
REFERENCES
[1] V. Nocella, L. Pelliccia, C. Tomassoni, and R. Sorrentino, “Miniaturized
dual-band waveguide filter using TM dielectric-loaded dual-mode cavi-
ties,” IEEE Microw. Wireless Compon. Lett., vol. 26, no. 5, pp. 310–312,
May 2016, doi: 10.1109/LMWC.2016.2549181.
[2] A. Arsanjani, C. Bartlett, L. Robins, R. Teschl, W. Bösch, and
M. Höft, “Metasurfaces for filter miniaturization and out-of-band rejec-
tion improvement,” IEEE Microw. Wireless Technol. Lett., vol. 33, no. 3,
pp. 271–274, Mar. 2023, doi: 10.1109/LMWT.2022.3221467.
[3] D. Miek et al., “Ceramic additive manufactured monolithic X-shaped
TM dual-mode filter,” IEEE J. Microw., vol. 2, no. 3, pp. 496–506,
Jul. 2022, doi: 10.1109/JMW.2022.3167250.
[4] L. Robins et al., “3D-printed dielectric resonators for quasi-TE112
mode singlets, doublets and dual-mode filters,” IEEE Access, vol. 10,
pp. 130326–130338, 2022, doi: 10.1109/ACCESS.2022.3228764.
[5] X. X. Yuan, L.-H. Zhou, and J.-X. Chen, “Triple-mode bandpass filter
based on silver-loaded ring-shaped dielectric resonator,” IEEE Microw.
Wireless Compon. Lett., vol. 28, no. 9, pp. 789–791, Sep. 2018, doi:
10.1109/LMWC.2018.2853568.
[6] Lithoz. Materialübersicht LCM-Technologie. Accessed: Jul. 25, 2022.
[Online]. Available: https://lithoz.com/wp-content/uploads/2022/04/
LITHOZMaterialfolder DE web.pdf
[7] C. Carceller, F. Gentili, D. Reichartzeder, W. Bösch, and
M. Schwentenwein, “Development of monoblock TM dielectric
resonator filters with additive manufacturing,” IET Microw., Antennas
Propag., vol. 11, no. 14, pp. 1992–1996, Nov. 2017, doi: 10.1049/iet-
map.2016.1051.
[8] A. Perigaud, O. Tantot, N. Delhote, S. Verdeyme, S. Bila, and
D. Baillargeat, “Bandpass filter based on skeleton-like monobloc
dielectric pucks made by additive manufacturing,” in Proc.
48th Eur. Microw. Conf. (EuMC), Sep. 2018, pp. 296–299, doi:
10.23919/EuMC.2018.8541710.
[9] A. Widaa, F. Cacciamani, L. Pelliccia, C. Tomassoni,
V. T. di Crestvolant, and M. Höft, “Compact ultra-wideband bandpass
filter using additively manufactured TM-mode dielectric resonators,” in
Proc. 52nd Eur. Microw. Conf. (EuMC), Sep. 2022, pp. 115–118, doi:
10.23919/EuMC54642.2022.9924504.
[10] E. López-Oliver, C. Tomassoni, F. Cacciamani, L. Pelliccia, and
V. T. D. Crestvolant, “Bandpass filter based on 3-D-printed ceramic
resonators,” in Proc. 24th Int. Microw. Radar Conf. (MIKON), Sep. 2022,
pp. 1–5, doi: 10.23919/MIKON54314.2022.9924680.
[11] A. Widaa, C. Bartlett, and M. Höft, “Design of compact quasi-
elliptic bandpass filters based on coaxial inset resonators,” IEEE
Access, vol. 11, pp. 18739–18749, 2023, doi: 10.1109/ACCESS.2023.
3247137.


English

A 3-D-Printed Dielectric Resonator for Triple-Mode Applications

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