Thin-Film HTS Planar Antennas
Michael J. Lancaster, Member, IEEE, Hanyang Y. Wang, and Jia-Sheng Hong, Member, IEEE
Fig. 1. The “H” antenna and feed network. The dimensions of the antenna used in the examples below are a = 5:5 mm, b = 1:5 mm, c = 2:5
mm, and d = 0:5 mm, and the aperture is 5.5 by 2.5 mm. For the copper antenna t = 1:27 mm, "r = 10:8; and for the YBCO superconducting
antenna the upper substrate has t = 1 mm and "r = 9:8.
Abstract—The “H” microstrip antenna is suitable for use as
an efficient small antenna when it is constructed out of superconducting
thin-film materials. An aperture feed and matching
network is described which provides a convenient enhancement
of the capabilities of the “H” antenna. Methods of prediction
of the center frequency are given. In addition, an analytical
expression is developed for the farfield radiation pattern of the
“H” antenna and the efficiency and Q of superconducting and
copper antennas are described using this expression. It is likely
that superconducting antennas will only have significant application
when they are used in arrays. Three arrays are described
demonstrating multiband self-diplexing multifrequency-enhanced
bandwidth and multifrequency beam forming.
Index Terms— High-temperature conductors, patch antenna,
superconductor.
I. INTRODUCTION
ASUPERCONDUCTING antenna was one of the first
microwave components to be demonstrated as an application
of high-temperature superconducting material [1].
Since then, there has been considerable work on new types
of superconducting antennas, with patch antennas looking like
an interesting possibility for a number of applications [2]–[7].
The advantage of using superconducting materials in the
development of antennas is the increase in efficiency or
Manuscript received December 8, 1997; revised October 8, 1998. This work
was supported by the U.K. EPSRC. The work of M. J. Lancaster was supported
by the Nuffield Foundation.
The authors are with the School of Electronic and Electrical Engineering,
The University of Birmingham, Edgbaston, Birmingham, B15 2TT U.K.
Publisher Item Identifier S 1051-8223(98)09646-8.
gain. There are a number of ways for this improvement in
efficiency to occur [2]: 1) For small antennas, the power
losses in the metallic parts of conventional metallic antennas
can dominate over the power radiated. Hence reducing these
losses by using a low surface resistance material, such as a
superconductor, increases the efficiency. 2) Losses are not
only important in the antenna element itself, but also the
losses in the matching network can contribute to the overall
efficiency. A superconducting matching network reduces the
matching network loss. 3) Superdirectional antenna arrays
become more efficient with the use of superconductors [2].
4) In complex high-frequency ( 20 GHz) arrays, losses in the
feed network may contribute to reduced efficiency, but making
the network out of superconductors effectively removes this
problem. and 5) There are now many applications, other
than antennas, in which superconductors are used. Integrating
antennas with additional functionality within these systems can
offer significant additional benefits.
A potential problem for elect