An experimental demonstration of directivities exceeding the fundamental Kildal limit, a phenomenon called superdirectivity, is provided for spherical high-index dielectric antennas with an electric dipole excitation. A directivity factor of about 10 with a total efficiency of more than 80% for an antenna having a size of a third of the wavelength was measured. High directivities are shown to be associated with constructive interference of particular electric and magnetic modes of an open spherical resonator. Both analytic solutions for a point dipole and a full-wave rigorous simulation for a realistic dipole antenna were employed for optimization and analysis, yielding an excellent agreement between experimentally measured and numerically predicted directivities. The use of high-index low-loss ceramics can significantly reduce the physical size of such antennas while maintaining their overall high radiation efficiency. Such antennas can be attractive for various high-frequency applications, such as antennas for the Internet of Things, smart city systems, 5G network systems, and others. The demonstrated concept can be scaled in frequency.

1.
S. A.
Long
,
M. W.
McAllister
, and
L. C.
Shen
,
IEEE Trans. Antennas Propag.
31
,
406
(
1983
).
2.
M. W.
McAllister
,
S. A.
Long
, and
G. L.
Conway
,
Electron. Lett.
19
,
218
(
1983
).
3.
M. W.
McAllister
and
S. A.
Long
,
Electron. Lett.
20
,
657
(
1984
).
5.
R. D.
Richtmyer
,
J. Appl. Phys.
10
,
391
(
1939
).
6.
J.
Stratton
,
Electromagnetics Theory
(
McGraw-Hill
,
1941
).
7.
M.
Gastine
,
L.
Courtois
, and
J. L.
Dormann
,
IEEE Trans. Microw. Theory Tech.
15
,
694
(
1967
).
8.
M.
Shafi
,
A. F.
Molisch
,
P. J.
Smith
,
T.
Haustein
,
P.
Zhu
,
P.
De Silva
,
F.
Tufvesson
,
A.
Benjebbour
, and
G.
Wunder
,
IEEE J. Sel. Areas Commun.
35
,
1201
(
2017
).
9.
Z.
Zhang
,
Y.
Xiao
,
Z.
Ma
,
M.
Xiao
,
Z.
Ding
,
X.
Lei
,
G. K.
Karagiannidis
, and
P.
Fan
,
IEEE Veh. Technol. Mag.
14
,
28
(
2019
).
10.
W.
Lin
,
R. W.
Ziolkowski
, and
J.
Huang
,
IEEE Trans. Antennas Propag.
67
,
3670
(
2019
).
11.
H.
Tataria
,
M.
Shafi
,
A. F.
Molisch
,
M.
Dohler
,
H.
Sjöland
, and
F.
Tufvesson
,
Proc. IEEE
109
,
1166
(
2021
).
12.
J.
Van Bladel
,
IEEE Trans. Microw. Theory Tech.
23
,
208
(
1975
).
13.
15.
A. B.
Evlyukhin
,
C.
Reinhardt
,
A.
Seidel
,
B. S.
Luk’yanchuk
, and
B. N.
Chichkov
,
Phys. Rev. B
82
,
045404
(
2010
).
16.
S.
Arslanagic
,
M.
Mostafavi
,
R.
Malureanu
, and
R. W.
Ziolkowski
, in Proceedings of the European Conference on Antennas and Propagation (EUCAP) (IEEE, 2011), p. 2064.
17.
C. A.
Balanis
,
Advanced Engineering Electromagnetics
,
2nd ed.
(
John Wiley & Sons, Inc.
,
2012
).
18.
A. E.
Krasnok
,
C. R.
Simovski
,
P. A.
Belov
, and
Y. S.
Kivshar
,
Nanoscale
6
,
7354
(
2014
).
20.
S.
Arslanagić
and
R. W.
Ziolkowski
,
IEEE Antennas Propag. Mag.
59
,
14
(
2017
).
21.
R.
Li
,
X.
Zhou
,
M.
Panmai
,
J.
Xiang
,
H.
Liu
,
M.
Ouyang
,
H.
Fan
,
Q.
Dai
, and
Z.
Wei
,
Opt. Express
26
,
28891
(
2018
).
22.
I. L.
Rasskazov
,
A.
Moroz
, and
P. S.
Carney
,
J. Opt. Soc. Am. A
36
,
1591
(
2019
).
23.
Z.
Wang
,
B.
Luk’yanchuk
,
L.
Yue
,
B.
Yan
,
J.
Monks
,
R.
Dhama
,
O. V.
Minin
,
I. V.
Minin
,
S.
Huang
, and
A. A.
Fedyanin
,
Sci. Rep.
9
,
20293
(
2019
).
24.
M.
Majic
and
E. C.
Le Ru
,
Appl. Opt.
59
,
1293
(
2020
).
25.
R.
Gaponenko
,
A.
Moroz
,
I. L.
Rasskazov
,
K.
Ladutenko
,
A.
Shcherbakov
, and
P.
Belov
,
Phys. Rev. B
104
,
195406
(
2021
).
26.
K. L.
Wong
,
N. C.
Chen
, and
H. T.
Chen
,
IEEE Microw. Guided Wave Lett.
3
,
355
(
1993
).
27.
D. S.
Filonov
,
A. E.
Krasnok
,
A. P.
Slobozhanyuk
,
P. V.
Kapitanova
,
E. A.
Nenasheva
,
Y. S.
Kivshar
, and
P. A.
Belov
,
Appl. Phys. Lett.
100
,
201113
(
2012
).
28.
A. B.
Evlyukhin
,
S. M.
Novikov
,
U.
Zywietz
,
R. L.
Eriksen
,
C.
Reinhardt
,
S. I.
Bozhevolnyi
, and
B. N.
Chichkov
,
Nano Lett.
12
,
3749
(
2012
).
29.
A. I.
Kuznetsov
,
A. E.
Miroshnichenko
,
Y. H.
Fu
,
J.
Zhang
, and
B.
Luk’yanchuk
,
Sci. Rep.
2
,
492
(
2012
).
30.
J. M.
Geffrin
,
B.
García-Cámara
,
R.
Gómez-Medina
,
P.
Albella
,
L. S.
Froufe-Pérez
,
C.
Eyraud
,
A.
Litman
,
R.
Vaillon
,
F.
González
,
M.
Nieto-Vesperinas
,
J. J.
Sáenz
, and
F.
Moreno
,
Nat. Commun.
3
,
1171
(
2012
).
31.
B.
Rolly
,
J. M.
Geffrin
,
R.
Abdeddaim
,
B.
Stout
, and
N.
Bonod
,
Sci. Rep.
3
,
3063
(
2013
).
32.
A. E.
Krasnok
,
D. S.
Filonov
,
C. R.
Simovski
,
Y. S.
Kivshar
, and
P. A.
Belov
,
Appl. Phys. Lett.
104
,
133502
(
2014
).
33.
A. E.
Krasnok
,
E. A.
Krasnok
,
D. S.
Filonov
,
P. V.
Kapitanova
, and
P. A.
Belov
, in 44th EuMC Rome, Italy (IEEE Xplore, 2014), pp. 676–678.
34.
A. I.
Kuznetsov
,
A. E.
Miroshnichenko
,
M. L.
Brongersma
,
Y. S.
Kivshar
, and
B.
Luk’yanchuk
,
Science
354
,
aag2472
(
2016
).
35.
M. I.
Tribelsky
,
J.-M.
Geffrin
,
A.
Litman
,
C.
Eyraud
, and
F.
Moreno
,
Sci. Rep.
5
,
12288
(
2015
).
36.
M. I.
Tribelsky
,
J.-M.
Geffrin
,
A.
Litman
,
C.
Eyraud
, and
F.
Moreno
,
Phys. Rev. B
94
,
121110
(
2016
).
37.
Y.
Tsuchimoto
,
T.
Yano
,
T.
Hayashi
, and
M.
Hara
,
Opt. Express
24
,
14451
(
2016
).
38.
C.
Forestiere
,
G.
Miano
, and
G.
Rubinacci
,
Phys. Rev. Res.
2
,
043176
(
2020
).
39.
I.
Sinev
,
F.
Komissarenko
,
I.
Iorsh
,
D.
Permyakov
,
A.
Samusev
, and
A.
Bogdanov
,
ACS Photonics
7
,
680
(
2020
).
40.
A. W.
Powell
,
A. P.
Hibbins
, and
J. R.
Sambles
,
Appl. Phys. Lett.
118
,
251107
(
2021
).
41.
B.
Rolly
,
B.
Stout
, and
N.
Bonod
,
Opt. Express
20
,
20376
(
2012
).
42.
R. W.
Ziolkowski
,
Phys. Rev. X
7
,
031017
(
2017
).
43.
A.
Monti
,
S. H.
Raad
,
Z.
Atlasbaf
, and
A.
Toscano
,
Opt. Lett.
47
,
2386
(
2022
).
44.
P.-S.
Kildal
, in Proceedings of the 2nd European Conference on Antennas and Propagation [Institution of Engineering and Technology (IEEE), Edinburgh, UK, 2007], pp. 16–25.
45.
P.-S.
Kildal
,
E.
Martini
, and
S.
Maci
,
IEEE Antennas Propag. Mag.
59
,
16
(
2017
).
46.
C. J.
Bouwkamp
and
N. G.
de Bruijn
,
Philips Res. Rep.
1
,
135
(
1945
).
47.
A.
Uzkov
, in Comptes Rendus (Doklady) de l’Academie des Sciences de l’URSS (USSR Academy of Science, Moscow, Russia, 1946), Vol. 53, pp. 35–38.
48.
E.
Newman
and
M.
Schrote
,
IEEE Trans. Antennas Propag.
30
,
1172
(
1982
).
49.
A. D.
Yaghjian
,
T. H.
O’Donnell
,
E. E.
Altshuler
, and
S. R.
Best
,
Radio Sci.
43
,
RS3002
(
2008
).
50.
A.
Haskou
,
A.
Sharaiha
, and
S.
Collardey
,
IEEE Antennas Wirel. Propag. Lett.
15
,
24
(
2016
).
51.
S. X.
Ta
,
I.
Park
, and
R. W.
Ziolkowski
,
IEEE Access
5
,
14657
(
2017
).
52.
T.
Shi
,
M.-C.
Tang
,
R.
Chai
, and
R. W.
Ziolkowski
,
IEEE Trans. Antennas Propag.
70
,
5288
(
2022
).
54.
IEEE Std 145-2013
(Revision of IEEE Std 145-1993), 1 (IEEE, 2014).
56.
C. A.
Balanis
,
Antenna Theory: Analysis and Design
,
4th ed.
(
John Wiley & Sons, Inc.
,
Hoboken, NJ
,
2016
).
57.
IEEE Std 149-2021
(Revision of IEEE Std 149-1977), 1 (IEEE, 2022).
58.
C. F.
Bohren
and
D. R.
Huffman
,
Absorption and Scattering of Light by Small Particles
(
John Wiley & Sons
,
1998
).
59.
60.
M. I.
Mishchenko
,
Electromagnetic Scattering by Particles and Particle Groups
(
Cambridge University Press
,
2014
).
61.
Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, edited by M. Abramowitz and I. A. Stegun (U.S. Department of Commerce, National Bureau of Standards, 1964).
63.
W.
Fan
,
A.
Lu
,
L. L.
Wai
, and
B. K.
Lok
, in Proceedings of EPTC (IEEE, 2003), pp. 533–537.
64.
Rohde & Schwarz
, “Measuring balanced components with vector network analyzer ZVB” (2004), available at https://www.rohde-schwarz.com/us/applications/measuring-balanced-components-with-vector-network-analyzer-r-s-zvb-application-note_56280-15427.html.
65.
Dielectric Resonator Antennas, edited by K.-M. Luk and K.-W. Leung (SRP Ltd., Exeter, UK, 2003).
66.
S. B.
Narang
and
S.
Bahel
,
J. Ceram. Process. Res.
11
,
316
(
2010
).
67.
V. V.
Parshin
,
E. A.
Serov
,
E. E.
Chigryai
,
B. M.
Garin
,
R. N.
Denisiuk
,
D. S.
Kalyonov
,
M.
Ding
,
L.
Li
,
Y.
Lu
,
Y.
Yang
,
Y.
Liang
,
J.
Feng
, and
P. V.
Ershova
,
J. Radio Electron.
2
,
1
(
2018
).
68.
Dielectric Materials for Wireless Communication, edited by M. T. Sebastian (Elsevier, 2008), Appendix II, pp. 541–652.
69.
H.
Ohsato
,
J.
Varghese
, and
H.
Jantunen
, in Electromagnetic Materials and Devices, edited by M.-G. Han (IntechOpen, Rijeka, 2018), Chap. 1.
70.
D.
Smirnova
and
Y. S.
Kivshar
,
Optica
3
,
1241
(
2016
).
71.
D. G.
Baranov
,
D. A.
Zuev
,
S. I.
Lepeshov
,
O. V.
Kotov
,
A. E.
Krasnok
,
A. B.
Evlyukhin
, and
B. N.
Chichkov
,
Optica
4
,
814
(
2017
).
72.
D.
Tzarouchis
and
A.
Sihvola
,
Appl. Sci.
8
,
184
(
2018
).
73.
M.
Odit
,
K.
Koshelev
,
S.
Gladyshev
,
K.
Ladutenko
,
Y.
Kivshar
, and
A.
Bogdanov
,
Adv. Mater.
33
,
2003804
(
2021
).
74.
R. F.
Harrington
,
J. Res. Natl. Bur. Stan. Sect. D Rad. Prop.
64D
,
1
(
1960
).
75.
R. C.
Hansen
,
Electrically Small, Superdirective, and Superconducting Antennas
(
John Wiley & Sons, Inc.
,
Hoboken, NJ
,
2006
).
76.
M. V. Rybin, P. V. Kapitanova, D. S. Filonov, A. P. Slobozhanyuk, P. A. Belov, Y. S. Kivshar, and M. F. Limonov,
Phys. Rev. B
88(20), 205106 (2013).

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