Development of Circularly Polarized Microstrip ... - CEReS - åèå¤§å¦

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The absolute value of the axial ratio can be formulated as (Warren L., 1993) |R| = major axis length minor axis length = OA OB ≥ 1 (3.4) As can be seen from Figure 3.4, the value of OA and OB are indicating the maximum and minimum value of the electric field amplitude of the microwave signal. The R is equal to 1 for perfect circular polarization and infinite for linear polarization. In the between of 1 and infinite, electromagnetic wave is classified as elliptical polarization. Practically, R is represented in decibel (dB) unit as R(dB) = 20 log |R| (3.5) Here, factor 20 is used since |R| is the ratio of field quantities. The sign of R describes the sense of the microwave signals. Here, sense is the rotation direction of electric field vector over time while it propagates. In terms of polarization sense, the sign of R is positive for RHCP and negative for LHCP. 3.2.5 Bandwidth The bandwidth of an antenna refers to the range of frequencies over which the antenna can properly radiate or receive energy. The bandwidth can also be described in terms of percent bandwidth, because the percent bandwidth is constant relative to frequency. In linear antennas, the bandwidth of an antenna is measured from the reflection coefficient characteristic. For circularly polarized antennas, the antenna bandwidth is determined by both the reflection coefficient and the axial ratio. The bandwidth of an antenna can be defined as Bandwidth(%) = f 2 − f 1 f c × 100 (3.6) where f 2 is the upper frequency, f 1 is the lower frequency, and f c is the center frequency. 35
3.2.6 Radiation pattern In the field of antenna, the antenna radiation pattern is a measure of its power or radiation distribution with respect to a particular type of coordinates. This power variation as a function of the arrival angle is observed in the far field. It is typically represented by a three dimensional graph, or polar plots of the horizontal and vertical cross sections. The pattern of an ideal isotropic antenna, which radiates equally in all directions, would look like a sphere. Many nondirectional antennas, such as monopoles and dipoles, emit equal power in all horizontal directions, with the power dropping off at higher and lower angles (omnidirectional pattern). Based on the radiation pattern, the beamwidth (usually in 3dB) and side lobe level of the antenna can be obtained. 3.2.7 Current density and distribution The performance designed antenna can be evaluated using average current density on the surface of the antenna. The degradation color in the antenna shows the distribution intensity and a good antenna has a high intensity around the center of the antenna. The vector electric current distribution on the surface of the antenna also aid in design by displaying the animation and different size of vectors. In array configuration, the current distribution can be used to observe the power distribution to each elements of the antenna. 3.3 Circularly polarized microstrip antenna Nowadays, circular polarization is very important in the antenna design industry. It eliminates the importance of antenna orientation in the plane perpendicular to the propagation direction. It gives much more flexibility to the angle between transmitting and receiving antennas, also it enhances weather penetration and mobility (Hayt and Buck, 2001 and Rahmani et al., 2009). The quality of the circularly polarized wave is generally specified by an axial ratio value (Hall and Dahele, 1997). It is used in a bunch of commercial and militarily applications. However, it is difficult to build good circularly polarized antenna (Milligan, 2005). For circular polarization to be generated in microstrip antenna two modes equal in magnitude and 90 out of phase are 36
Page 1 and 2: Development of Circularly Polarized
Page 3 and 4: Abstract The discussion about devel
Page 5 and 6: Acknowledgements First and foremost
Page 7 and 8: CONTENTS 3 Circularly Polarized Mic
Page 9 and 10: List of Figures 1.1 Electric field
Page 11 and 12: LIST OF FIGURES 5.13 Photograph of
Page 13 and 14: List of Tables 2.1 Parameters of CP
Page 15 and 16: in linear polarization has some fla
Page 17 and 18: polarization (RHCP) and left-handed
Page 19 and 20: BIBLIOGRAPHY Bibliography [1] Birk
Page 21 and 22: Chapter 2 Circularly Polarized Synt
Page 23 and 24: generates all the necessary timing
Page 25 and 26: line platform flight trajectory is
Page 27 and 28: Figure 2.6: Range ambiguities: Port
Page 29 and 30: Substituting (2.12) and (2.13) into
Page 31 and 32: Figure 2.9: Basic principle of aper
Page 33 and 34: CP-SAR geometry, the slant range ,
Page 35 and 36: Figure 2.12: The required (a) θ EC
Page 37 and 38: 2.5.2 Design of CP-SAR system 2.5.2
Page 39 and 40: BIBLIOGRAPHY Figure 2.15: Design of
Page 41 and 42: BIBLIOGRAPHY [14] Steven Z., Unmann
Page 43 and 44: developments of novel microstrip an
Page 45 and 46: to feed or excite a microstrip patc
Page 47: defines as the ratio of the power g
Page 51 and 52: Figure 3.6: Rectangular patch arran
Page 53 and 54: diagonals axis. The area of the per
Page 55 and 56: By substitute eq. (3.7-3.9) to (3.1
Page 57 and 58: 3.4.1 Linear array Among the differ
Page 59 and 60: provide additional variables which
Page 61 and 62: The beam area or solid angle or Ω
Page 63 and 64: 2005). An array of even number of i
Page 65 and 66: BIBLIOGRAPHY m = 8 cos(mu) = 128z 8
Page 67 and 68: BIBLIOGRAPHY [21] Rahmani M., Tavak
Page 69 and 70: Figure 4.1: Design methodology. 56
Page 71 and 72: Figure 4.2: Flow chart of the anten
Page 73 and 74: Figure 4.3: Diagram of required ant
Page 75 and 76: easy if you have the right equipmen
Page 77 and 78: Chapter 5 Results and Discussion 5.
Page 79 and 80: Figure 5.2: Geometry design of prop
Page 81 and 82: terminals during the radiation proc
Page 83 and 84: 5.1.4 Radiation characteristic The
Page 85 and 86: Figure 5.11: Measured and simulated
Page 87 and 88: the physical length, L, and the eff
Page 89 and 90: Figure 5.13: Photograph of the fabr
Page 91 and 92: Figure 5.15: Simulated and measured
Page 93 and 94: In Figure 5.18, the antenna gain wi
Page 95 and 96: Figure 5.20: Array antenna characte
Page 97 and 98: Figure 3 shows the design and photo
Page 99 and 100:
Figure 5.24: Simulated and measured
Page 101 and 102:
5.4 Broadband circularly polarized
Page 103 and 104:
Figure 5.29: Axial ratio (AR) plott
Page 105 and 106:
Figure 5.33: A 3D beam pattern of t
Page 107 and 108:
Figure 5.34: Dolph-Chebyshev array
Page 109 and 110:
measurement, respectively. Such deg
Page 111 and 112:
Figure 5.40: Relationship between a
Page 113 and 114:
Figure 5.42: Array antenna characte
Page 115 and 116:
BIBLIOGRAPHY single-feed circular m
Page 117 and 118:
antenna for CP-SAR sensor. In the c
Page 119 and 120:
List of Publications Peer-reviewed
Page 121 and 122:
Curriculum Vitae YOHANDRI He was bo
Page 123 and 124:
To perform an electromagnetic simul
Page 125 and 126:
are integrated into MGRID. PATTERN
Page 127 and 128:
properly. After a rectangle is draw
Page 129 and 130:
Figure B.5: Frequency sweep in simu
Page 131 and 132:
Figure B.8: Three-dimensional far-f
Page 133 and 134:
Figure C.1: (a) Seven Mini PCB Prot
Page 135 and 136:
Figure C.3: Etching tank and chemic
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