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Design of FSS for Wideband and Wide-Angle
Coverage—Challenges and Possible Solutions
Raj Mittra1,2
and Nathawut Homsup1
1EMC Lab, University of Central Florida, Orlando, FL, USA
2EE Department, KAU, Saudi Arabia
Abstract – This paper examines the challenges
encountered in the process of designing Frequency
Selective Surfaces (FSSs) for applications that call for
simultaneous coverage over very wide frequency band
as well as wide angle. The paper begins with a review of
existing literature and concludes that none of them can
provide, even with the suggested modifications, a design
that meets our needs of 3:1 bandwidth over an angular
range of 60deg or higher. Next, we propose some new
designs and examine how well we can meet the stated
goals Index Terms — Frequency selective surfaces; Wideband
FSS; FSS with wide-angle coverage.
1. Introduction
Even though there are literally hundreds of publications,
both journal papers and books which provide the theory of
operation of Frequency Selective Surfaces (FSSs),
designing them remains a challenging task when the
specifications call for coverage over a wide band of
frequencies, say 3:1, and over a wide range of angles going
up to 700, as is sometimes desired. What makes the design
problem even more challenging is that while many
publications describe FSS designs over a relatively wide
band, say 2:1, which cover angles up to 30 0r 40 degrees (at
most), they do not provide a clue as to how to extend these
limits of their designs. In this work we describe the results
of parametric studies that we have carried out of a number
of existing wide-band and wide-angle FSS designs in an
attempt to cover the following specifications:
a. Passband: Frequency range f1 to f2 (ratio of f2/f1
equal to 3:1)
b. Coverage up to 60 deg., or higher TE and TM
polarizations
c. Low ripple in the passband
d. Better than 10 dB in the stopbands, at both low
and high ends, past the shoulder regions.
It is interesting to note that the strategies followed in
these works, whose designs we have investigated, are quite
different from each other and, hence, the proposed physical
structures are also somewhat unique to these designs,
despite the fact that their stated goals for meeting the
wideband and wide-angle coverage are the same. We did
find several papers which proposed a universal approach
(see [1], for instance), based on filter theory, which has
been well developed for microwave circuits, and has been
extensively used for waveguide filters for satellite
communication. However, we found that it is not possible,
in general, to transition from lumped circuits to distributed
circuits representing FSSs, especially in designs where the
higher-order Floquet modes are considered, as they must be
in the FSS designs we have studied. Thus, while the filter
theory was somewhat helpful in leading us to the right
direction, we found that it was quite inadequate for our
designs; hence it was necessary to develop new design
strategies, which we will describe in the presentation, and
which enabled us to extend the boundaries of the existing
designs to help our stated goals.
Fig. 1. Third Order Frequency Selective Surface (FSS).
(a)
(c)
(b)
Fig. 2. A unit cell of Frequency Selective Surface (FSS) (a)
Top view, (b) Bottom View, and (c) Isometric view.
2018 International Symposium on Antennas and Propagation (ISAP 2018)October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea
[ThG1-1]
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Fig. 3. Transmission (TE) with incidence angle is at 30
degrees
Fig. 4. Transmission (TM) with incidence angle is at 30
degrees
The paper will present the details of the design strategy,
together with a summary of the results that will show how
well we are able to meet our goals. We will also describe
some of the future directions that we consider worthwhile
to explore in order to systematically design FSSs for both
wide-angle and wide frequency coverage. Additional
references to related works [2-16] are also included in the
paper.
References
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2018 International Symposium on Antennas and Propagation (ISAP 2018)October 23~26, 2018 / Paradise Hotel Busan, Busan, Korea
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