IEEE - Aerospace and Electronic Systems - February 2022 - 35

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waves with better directivity from spherical waves after
reflected by parabolic reflector antenna. In this part,
antenna configuration discussed is single offset-parabolic
reflector antennas.
Feeds with proper edge illumination taper will be better
to achieve higher antenna efficiency, which lead to
higher gain level and relatively low sidelobe level.
Figure 2 shows
3 dB and
12 dB taper horns illuminating
an equal parabolic reflector antenna, respectively. The
apertures of
3 dB taper horns are smaller than that of

12 dB taper horns. The directivity pattern of a
3dB
and a
12 dB taper horn illuminating the same reflector is
presented in Figure 3. The
12 dB taper horn has lower
sidelobe and higher aggregate gain than that of the
3dB
taper horn. This is due to that the
3 dB taper horn has
higher aperture efficiency, which causes narrower beams
but higher level of sidelobes due to more spillover losses.
A
12 dB taper can achieve the best antenna efficiency
and low sidelobe levels. Theoretically
12 dB taper horns
should be used in multibeam antenna systems. However,
the spacing between adjacent
12 dB taper horns is larger
in applications, which might be hard to get proper crossover
level usually 3-5 dB below the peak gain to achieve
seamless cover on the earth. To illustrate this, directivity
patterns of two adjacent horns with
3 dB and
12 dB
taper, respectively, are calculated in Figure 4. The crossover
level of two adjacent
3 dB taper horns is about

4 dB, while that of two adjacent
12 dB taper horns is
only
18 dB. To solve this problem, it is better to use
multiple reflectors fed by various corresponding clusters
of big horns rather than one reflector with small horns in
SFPB scheme.
Figure 1.
Single shaped wide beam method (left) and the multibeam
antenna method (right) covering China.
Figure 3.
Pattern of a
3 dB and a
12 dB taper horn illuminating
reflector.
Figure 2.
Comparison of
3 dB taper horns (left) and
12 dB taper horns
(right) illuminating equal reflector.
FEBRUARY 2022
Figure 4.
Patterns of two adjacent horns of
3 dB taper (left) and
12 dB
taper (right).
IEEE A&E SYSTEMS MAGAZINE
35

IEEE - Aerospace and Electronic Systems - February 2022

Table of Contents for the Digital Edition of IEEE - Aerospace and Electronic Systems - February 2022

Contents
IEEE - Aerospace and Electronic Systems - February 2022 - Cover1
IEEE - Aerospace and Electronic Systems - February 2022 - Cover2
IEEE - Aerospace and Electronic Systems - February 2022 - Contents
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