Hanyang University ANTENNA THEORY by Constantine A Balanis
Hanyang University ANTENNA THEORY by Constantine A. Balanis Chapter 3. 8 – 3. 8. 2 & 4. 1 – 4. 2. 3 Yun-tae Park 2018. 01. 24 1/26 Antennas & RF Devices Lab.
Hanyang University Contents 3. Radiation Integrals and Auxiliary Potential Functions 3. 8 Reciprocity and Reaction Theorems 3. 8. 1 Reciprocity for Two Antennas 3. 8. 2 Reciprocity for Antenna Radiation Patterns 4. Linear Wire Antennas 4. 1 Introduction 4. 2 Infinitesimal Dipole 4. 2. 1 Radiated Fields 4. 2. 2 Power Density and Radiation Resistance 4. 2. 3 Radian Distance and Radian Sphere 2/26 Antennas & RF Devices Lab.
Hanyang University Patch Antenna - a type of radio antenna with a low profile, which can be mounted on a flat surface - consists of a flat rectangular sheet or "patch" of metal, mounted over a larger sheet of metal called a ground plane - mainly practical at microwave frequencies, at which wavelengths are short enough that the patches are conveniently small - widely used in portable wireless devices because of the ease of fabricating it on printed circuit boards 3/26 Antennas & RF Devices Lab.
Hanyang University Patch Antenna S-Parameter plot Solution frequency : 2. 5 GHz VSWR plot 4/26 Antennas & RF Devices Lab.
Hanyang University Patch Antenna Directivity plot Radiation Pattern Gain Phi Gain Theta 5/26 Antennas & RF Devices Lab.
Hanyang University 2. 15 Antenna Vector Effective Length and Equivalent Areas (291) (2 - 2. 15. 1 Vector Effective Length 93) (4 -36 a) (4 -36 b) (292) Figure 2. 29 Uniform plane wave incident upon dipole antennas. For linear antennas 6/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems Discuss the reciprocity theorem as it applies to electromagnetic theory. Maxwell’s equations Lorentz Reciprocity Theorem in differential form (360) (361) Lorentz Reciprocity Theorem in integral form 7/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems (362) (363) (364) (365) (361) (366) 8/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems (366) a coupling between a set of fields and a set of sources, which produce another set of fields Reaction (367) (368) For reciprocity, (369) 9/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems 3. 8. 1 Reciprocity for Two Antennas Figure 3. 4 Two-antenna system with conjugate loads. Figure 3. 3 Transmitting and receiving antenna systems. the power delivered by the generator to antenna #1 (370) the transfer admittance , the current through the load the power delivered to the load (371) 10/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems 3. 8. 1 Reciprocity for Two Antennas Figure 3. 4 Two-antenna system with conjugate loads. Figure 3. 3 Transmitting and receiving antenna systems. (3 -70) (in a similar manner, when #2 - transmitting antenna & #1 - receiving antenna) (3 -71) (3 -73) (3 -72) 11/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems 3. 8. 2 Reciprocity for Antenna Radiation Patterns Reciprocity for antenna patterns - the materials used for antennas and feed, and the media of wave propagation are lineaer - the antennas can be of any shape or size, and they do not have to be matched to their corresponding feed lines or loads provided there is a distinct single propagating mode at each port - the antennas in the transmit and receive modes to be polarization matched, including the sense of rotation - the antennas can transmit and receive the same field components, and thus total power If the antenna that is used as a probe to measure the fields radiated by the antenna under test is not of the same polarization, then in some situations the transmit and receive patterns can still be the same. ex) transmit antenna - circularly polarized probe antenna - linearly polarized Same the transmit and receive patterns (During this procedure, the power level and sensitivities must be held constant. ) 12/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems 3. 8. 2 Reciprocity for Antenna Radiation Patterns (3 -74) (3 -75) Figure 3. 5 Antenna arrangement for pattern measurements and reciprocity theorem. If the medium between the two antennas is linear, passive, isotropic, and the waves monochromatic, then because of reciprocity #1 the antenna under test #2 the probe antenna - oriented to transmit or receive maximum radiation (3 -76) (3 -77) 13/26 Antennas & RF Devices Lab.
Hanyang University 3. 8 Reciprocity and Reaction Theorems 3. 8. 2 Reciprocity for Antenna Radiation Patterns Figure 3. 5 Antenna arrangement for pattern measurements and reciprocity theorem. #1 the antenna under test #2 the probe antenna - oriented to transmit or receive maximum radiation (a) antenna #1 is held stationary while #2 is allowed to move on the surface of a constant radius sphere (b) antenna #2 is maintained stationary while #1 pivots about a point 14/26 Antennas & RF Devices Lab.
Hanyang University 4. 1 Introduction Wire antenna (linear or curved) - oldest, simplest, cheapest, versatile - most basic configurations - minimize the complexity of the antenna structure and geometry 4. 2 Infinitesimal Dipole Figure 4. 1 Geometrical arrangement of an infinitesimal dipole. (4 -1) 15/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 1 Radiated Fields Figure 3. 1 Block diagram for computing fields radiated by electric and magnetic sources. (349) (351) (350) (352) (353) (354) (4 -3) (4 -2) (4 -4) 16/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 1 Radiated Fields (4 -4) (32 a) in spherical coordinates (4 -7) (4 -5) (4 -8) (315) (3 - (4 -6) 10) (4 -9) 17/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 1 Radiated Fields (4 -6) into (4 -8) (4 -9) (410) Figure 4. 1 Electric-field components on a spherical surface. 18/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 2 Power Density and Radiation Resistance To find the input resistance for a lossless antenna, the Poynting vector is formed in terms of the E- and H-fields radiated by the antenna. By integrating the Poynting vector over a closed surface, the total power radiated by the source is found. The real part of it is related to the input resistance. for the infinitesimal dipole, (4 -8) (411) (410) (412) 19/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 2 Power Density and Radiation Resistance (413) (414) total complex power The reactive power density, which is most dominant for small values of kr, has both radial and transverse components. It merely changes between outward and inward directions to form a standing wave at a rate of twice per cycle. 20/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 2 Power Density and Radiation Resistance (413) which gives the real and imaginary power that is moving outwardly, (415) from (414) (416) (417) 21/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 2 Power Density and Radiation Resistance Since the antenna radiates its real power through the radiation resistance, For the infinitesimal dipole, (416) (412 b) (418) does not contribute to radiation resistance (419) the total radiation resistance (419) 22/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 3 Radian Distance and Radian Sphere (4 -8) (410) Figure 4. 2 Magnitude variation, as a function of the radial distance, of the field terms radiated by an infinitesimal dipole. 23/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 3 Radian Distance and Radian Sphere Figure 4. 2 Magnitude variation, as a function of the radial distance, of the field terms radiated by an infinitesimal dipole. 24/26 Antennas & RF Devices Lab.
Hanyang University 4. 2 Infinitesimal Dipole 4. 2. 3 Radian Distance and Radian Sphere 25/26 Antennas & RF Devices Lab.
Hanyang University Thank you for your attention 26/26 Antennas & RF Devices Lab.
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