Variable permittivity dielectric material loaded stepped-horn antenna

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4from improving the gain, dielectric loading enables the reduction of the physical size of thestepped-horn antenna.
CHAPTER 2MATHEMATICAL MODELTypical pyramidal horn antenna geometry is shown in Figure 2.1. Analysis of this radiatingstructure is done by separating the antenna into two parts. The first part is the taperedsection of the horn starting at the feed waveguide and ending at the aperture. This sectionis modelled by a set of NI cascaded dielectric loaded uniform waveguide sections as shownin Figure 2.2. The mode matching method is performed to obtain the generalized scatteringmatrix at each step discontinuity. The overall scattering matrix of the tapered region is thencomputed by cascading the scattering matrices of the junctions involved in the model.The second part of the problem is an aperture radiating into the half-space assumingthe horn to be terminated by an infinite metallic plane as shown in Figure 2.3. The methodof moments is then invoked to determine the generalized reflection matrix of this apertureand then the unknown aperture field distribution.2.1 Mode MatchingThe tapered region of the horn antenna is approximated in terms of NI rectangular waveguidesections each of length A/ LINT filled with dielectric material of permittivity, εi εriεo ,i 1, 2, . . . , NI. Each section begins at zi (i — 1)A/ where z = 0 corresponds tothe junction adjacent to the feed waveguide (i 1), and the aperture plane is located atz = L. The cross-sectional dimensions of the i-th waveguide section, ai and bi being thewaveguide dimensions in the transverse (x, y) plane, are defined as5
Page 1 and 2: Copyright Warning & RestrictionsThe
Page 4 and 5: VARIABLE PERMITTIVITY DIELECTRIC MA
Page 6 and 7: APPROVAL PAGEVARIABLE PERMITTIVITY
Page 8 and 9: To my parents, ..Tahsin and Güler
Page 10 and 11: TABLE OF CONTENTSChapterPage1 INTRO
Page 12 and 13: LIST OF FIGURESFigurePage2.1 Geomet
Page 14 and 15: FigureLIST OF FIGURES(Continued)Pag
Page 16 and 17: 2field uniformity and this results
Page 20 and 21: Figure 2.1 Geometry of pyramidal a
Page 22 and 23: 84Figure 2.4 Step discontinuity bet
Page 24 and 25: 10section asFrom (2.4), the transve
Page 26 and 27: 12and for the magnetic fieldIn the
Page 28 and 29: 14where * shows complex conjugate.
Page 30 and 31: 16where D is a diagonal matrix of t
Page 32 and 33: 18Figure 2.6 Generalized reflection
Page 34 and 35: 20aperture region and 11Ps is the m
Page 36 and 37: 22where T; (x) and T: (y) are trian
Page 38 and 39: 24where Γwghnk and r wg enk are th
Page 40 and 41: tiTo determine the unknown coeffici
Page 42 and 43: 28An electric vector potential F an
Page 44 and 45: 30Using midpoint rule to evaluate i
Page 46 and 47: 32whereGreen function integrals, 4,
Page 48 and 49: 34taper and the phase distribution
Page 50 and 51: 36Even though, TE10 mode is an inci
Page 52 and 53: 38satisfy the amplitude ratio of 1/
Page 54 and 55: 40would be slight deviation from th
Page 56 and 57: 42increased to 15. Scattering matri
Page 58 and 59: 44Table 4.4 Amplitude and Phase of
Page 60 and 61: 46Figure 4.3, it is obvious that th
Page 62 and 63: 48al = 0.73A, b1 = 0.34A and apertu
Page 64 and 65: 50Table 4.7 Optimization Values of
Page 66 and 67: Figure 4.3 Input reflection coeffic
Page 68 and 69:
Figure 4.5 Aperture efficiency vers
Page 70 and 71:
Figure 4.7 Input reflection coeffic
Page 72 and 73:
Figure 4.9 Aperture efficiency vers
Page 74 and 75:
Figure 4.11 E-plane pattern versus
Page 76:
62Figure 4.13 Input reflection coef
Page 79 and 80:
Figure 4.16 Aperture efficiency ver
Page 81 and 82:
Figure 4.18 Amplitude of aperture m
Page 83 and 84:
Figure 4.20 Amplitude of aperture m
Page 85 and 86:
Figure 4.22 Input reflection coeffi
Page 87 and 88:
Figure 4.24 Cross-polarization leve
Page 89 and 90:
751Figure 4.26 Amplitude of apertur
Page 91 and 92:
770.8Figure 4.28 Amplitude of apert
Page 93 and 94:
Figure 4.30 Amplitude of aperture e
Page 95 and 96:
81Dielectric materials of various p
Page 97 and 98:
The indefinite integrals associated
Page 99 and 100:
BIBLIOGRAPHY[1] P. Clarricoats, A.
Page 101 and 102:
87[26] T. Bird and S. Hay, "Mismatc
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Variable permittivity dielectric material loaded stepped-horn antenna

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