Transactions on Antennas and Propagation

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Transactions on Antennas and Propagation
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the similar distribution as incident angle, whereas for inho- mogeneous radome, interval of
H
and
V
has different length (the former, 0.042 rad, much less than the latter, 0.105 rad) and separate with each other, which, again, lead to a similar phenomenon in Fig. a) and (b, that is,
H
nearly constant with blue color and
V
, with more than one color, not as constant as
H
, and thus again,
M
has a similar distribution as polarization angle. The only difference with the former case is that as the maximum polarization angle is just about 66°, not as large asunder scan angle,
M
is smaller than
V
in the area of maximum polarization angle, due to the effect of
H
which is very small. Once more, with CTR as a reference, VTR still reduces BSE by changing the
IPD distribution (the distribution of incident angle, whereas inhomogeneous radome decreases BSE by the introduction of anew distribution (the distribution of polarization angle, and the reduction of IPD interval length (from 0.296 rad to 0.145 rad, as shown in Table II. Under 16° scan angle, the distribution of polarization angle is abetter one in the behalf of restraining
BSE than that of incident angle, opposite to the phenomenon under 6° scan angle. Table II also gives the jg of inhomoge- neous radome, CTR and VTR, which is -0.2, 0.94 and 1.68, respectively. Similar with the case under 6° scan angle, with the increase of jg, the distribution of
M
varies gradually from being similar with polarization angle
(cf. Fig. 14) to being similar with
H
and
V
(cf. Fig. 13). ab) c) (d) Fig. 13 IPD of optimum CTR and incident angle distribution under 16° scan angle. (a) Parallel polarization -
H
. (b) Perpendicular polarization -
V
. (c)
Co-polarization -
M
. (d) Incident angle distribution. ab) c) (d) Fig. 14 IPD of inhomogeneous radome and polarization angle distribution under 16° scan angle. (a) Parallel polarization -
H
. (b) Perpendicular polarization-
V
. (c) Co-polarization -
M
. (d) Polarization angle distribution. TABLE II
IPD
VARIATION INTERVAL UNDER
16°
SCAN ANGLE INTERVAL UNIT RAD)
Inhomo. radome CTR
VTR Interval of
H
[0.211, 0.253]
[2.171, 2.409]
[2.049, Interval of
V
[0.276, 0.381]
[2.257, 2.485]
[2.029, Interval of
M
[0.211, 0.356]
[2.171, 2.467]
[2.049, Interval length of
H
0.042 0.238 0.247 Interval length of
V
0.105 0.228 0.279 Interval length of
M
0.145 0.296 0.256 Overlap ratio
-0.14 0.48 0.89 Range ratio
0.4 0.96 0.89
jg
-0.2 0.94 1.68 ab) (c) Fig. 15 Interval of
H
,
V
and
M
under 16° scan angle corresponding to Table II (a) Inhomogeneous radome. (b) CTR. (c) VTR. Therefore, a key factor in determining the insertion phase delay (IPD) distribution is the interval characteristics of

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