Direct Energy, 2018a

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4 ANTENNAS 77 fall in the VHF and UHF ranges. Like all sensors, antennas detect both signal and noise. Noise in a radio receiver may be internal to the receiving circuitry or due to external sources such as other nearby transmitters [49, p. 4]. An antenna with a broad bandwidth will receive more noise due external sources than an antenna with a narrow bandwidth. Noise characteristics of an antenna inuence the ability to receive weak signals, so they should be considered in selecting an antenna for an application [50]. 4.4.2 Impedance Both antennas and transmission lines have a characteristic impedance. The termtransmission line is dened in Sec. 4.3 as a long pair of conductors. If the length of the conductors is long compared to the wavelength of signal transmitted, the voltage and current may vary along the length of the line, and energy may be stored in the line. For this reason, transmission lines are described by a characteristic impedance in ohms. The characteristic impedance gives the ratio of voltage to current along the line, and it provides information on the ability of the transmission line to store energy in the electric and magnetic eld. Typical values for the impedance of transmission lines used for communications are 50 or 75 Ω. Similarly, each antenna has its own characteristic impedance, measured in ohms, which represents the ratio of voltage to current in the antenna. Why is the impedance important? Transmitting antennas are often physically removed from the signal source and connected by a transmission line. Similarly, receiving antennas are often in a dierent location than receiving circuitry and connected by a transmission line. To eciently transmit a signal between transmitting or receiving circuitry and an antenna, the impedance between the antenna and transmission line should be matched. In this case, where the characteristic impedance of the line and antenna are equal, energy ows along the transmission line between the circuitry and the antenna. Transmission lines are made from good, but not perfect, conductors. A small amount of energy may be converted to heat due to the resistance in the lines, but this amount of energy is often trivial. However, if there is an impedance mismatch between the antenna and the transmission line, reections will be set up at the transmission line antenna interface. Less energy will be transmitted to or from the antenna because energy will be stored in the line, and the amount of energy involved may be signicant. In a properly designed system were the impedances of the antenna and the transmission line are matched, no reection occurs, so as much energy as possible is transmitted to or from the antenna.
78 4.4 Antenna Characteristics Impedance of an antenna is a function of frequency. Antennas transmit and receive communications signals which are almost never sinusoids of a single frequency. Often, however, the signals contain only components with frequencies within a narrow band. For example, a radio station may have a carrier frequency of 100 MHz, and it may transmit signals with frequency components 99.99 MHz
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Direct Energy Conversion by Andrea
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CONTENTS i Contents Contents i 1 In
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CONTENTS iii 6.3.2 Energy Levels in
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CONTENTS v 9.6 Fuel Cells . . . . .
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Acknowledgements I would like to th
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2 1.2 Preview of Topics to connect
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4 1.2 Preview of Topics Math throug
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6 1.2 Preview of Topics Process Spo
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8 1.2 Preview of Topics drodynamic
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10 1.4 Measures of Power and Energy
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12 1.5 Properties of Materials 1.5
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14 1.5 Properties of Materials most
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16 1.6 Electromagnetic Waves −→
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18 1.6 Electromagnetic Waves Relate
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20 1.6 Electromagnetic Waves A unif
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22 1.7 Problems
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24 2.2 Capacitors 2.2 Capacitors 2.
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Page 41 and 42: 30 2.2 Capacitors Figure 2.3: Natur
Page 43 and 44: 32 2.3 Piezoelectric Devices Piezoe
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Page 53 and 54: 42 2.3 Piezoelectric Devices In cer
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Page 57 and 58: 46 2.3 Piezoelectric Devices tions.
Page 59 and 60: 48 2.4 Problems 2.5. A piezoelectri
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Page 63 and 64: 52 2.4 Problems 2.16. The gure belo
Page 65 and 66: 54 3.2 Pyroelectricity Material Che
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Page 73 and 74: 62 3.4 Notation Quagmire Notation i
Page 75 and 76: 64 3.5 Problems 3.5 Problems 3.1. F
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Page 81 and 82: 70 4.2 Electromagnetic Radiation In
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Page 103 and 104: 92 5.2 Physics of the Hall Eect The
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Page 107 and 108: 96 5.3 Magnetohydrodynamics This am
Page 109 and 110: 98 5.5 Applications of Hall Eect De
Page 111 and 112: 100 5.6 Problems 5.6 Problems 5.1.
Page 113 and 114: 102 6.2 The Wave and Particle Natur
Page 115 and 116: 104 6.3 Semiconductors and Energy L
Page 131 and 132: 120 6.4 Crystallography Revisited L
Page 133 and 134: 122 6.5 Pn Junctions E Indirect Sem
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Page 137 and 138: 126 6.5 Pn Junctions V x - + Energy
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128 6.6 Solar Cells to day and loca
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130 6.6 Solar Cells dot based mater
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132 6.7 Photodetectors Solar Panel
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134 6.7 Photodetectors 6.7.2 Measur
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6 PHOTOVOLTAICS 137 6.3. The gure i
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7 LAMPS, LEDS, AND LASERS 139 7 Lam
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7 LAMPS, LEDS, AND LASERS 141 Photo
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7 LAMPS, LEDS, AND LASERS 143 Absor
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7 LAMPS, LEDS, AND LASERS 145 We ca
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7 LAMPS, LEDS, AND LASERS 147 If we
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7 LAMPS, LEDS, AND LASERS 149 tube
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7 LAMPS, LEDS, AND LASERS 151 easil
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7 LAMPS, LEDS, AND LASERS 153 Power
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7 LAMPS, LEDS, AND LASERS 155 Two L
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7 LAMPS, LEDS, AND LASERS 157 but n
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7 LAMPS, LEDS, AND LASERS 159 of ec
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7 LAMPS, LEDS, AND LASERS 161 the o
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7 LAMPS, LEDS, AND LASERS 163 Ti:Sa
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7 LAMPS, LEDS, AND LASERS 165 the b
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7 LAMPS, LEDS, AND LASERS 167 Gas D
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7 LAMPS, LEDS, AND LASERS 169 categ
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7 LAMPS, LEDS, AND LASERS 171 7.8.
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8 THERMOELECTRICS 173 8 Thermoelect
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8 THERMOELECTRICS 175 Symbol Name V
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8 THERMOELECTRICS 177 per unit volu
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8 THERMOELECTRICS 179 kPa, and the
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8 THERMOELECTRICS 181 Seebeck Effec
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8 THERMOELECTRICS 183 gradient acro
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8 THERMOELECTRICS 185 thermocouples
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8 THERMOELECTRICS 187 The gure of m
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8 THERMOELECTRICS 189 or mass invol
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8 THERMOELECTRICS 191 temperatures?
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8 THERMOELECTRICS 193 Figure 8.4: L
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8 THERMOELECTRICS 195 8.9 Problems
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8 THERMOELECTRICS 197 8.8. A thermo
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8 THERMOELECTRICS 199 Figure 8.5 8.
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202 9.2 Measures of the Ability of
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212 9.3 Charge Flow in Batteries an
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214 9.3 Charge Flow in Batteries an
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216 9.4 Measures of Batteries and F
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224 9.5 Battery Types specic energi
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226 9.5 Battery Types at the anode
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228 9.5 Battery Types Figure 9.8: T
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230 9.6 Fuel Cells Fuel cell compon
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232 9.6 Fuel Cells 9.6.3 Practical
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234 9.7 Problems 9.7 Problems 9.1.
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236 9.7 Problems A E - + I B D H 2
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238 10.3 Radiation Detectors high e
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240 10.5 Resistive Sensors capacito
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242 10.6 Electrouidics However, ene
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244 10.6 Electrouidics
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246 11.2 Lagrangian and Hamiltonian
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248 11.3 Principle of Least Action
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250 11.4 Derivation of the Euler-La
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252 11.5 Mass Spring Example not in
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254 11.5 Mass Spring Example Path 1
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256 11.5 Mass Spring Example We can
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258 11.6 Capacitor Inductor Example
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260 11.6 Capacitor Inductor Example
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262 11.7 Schrödinger's Equation 11
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264 11.8 Problems 11.4. Figure 11.2
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266 11.8 Problems a famous result k
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268 11.8 Problems (c) Find the gene
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270 12.2 Electrical Energy Conversi
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276 12.3 Mechanical Energy Conversi
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282 12.4 Thermodynamic Energy Conve
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284 12.4 Thermodynamic Energy Conve
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286 12.5 Chemical Energy Conversion
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288 12.6 Problems 12.6 Problems 12.
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290 12.6 Problems 12.6. Match the d
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292 13.1 Introduction • Describe
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294 13.2 Preliminary Ideas Assuming
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296 13.3 Derivation of the Lagrangi
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306 13.4 Deriving the Thomas Fermi
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308 13.5 From Thomas Fermi Theory t
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310 13.6 Problems (a) Write the Ham
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312 14.1 Introduction damental equa
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314 14.2 Types of Symmetries be wri
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316 14.3 Continuous Symmetries and
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322 14.4 Derivation of the Innitesi
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330 14.5 Invariants and we end up w
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332 14.5 Invariants in the limit ε
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334 14.5 Invariants Next use Eq. 14
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336 14.6 Summary 14.6 Summary In th
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338 14.7 Problems 14.6. The equatio
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340 14.7 Problems
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342 Appendices Symbol Quantity Unit
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350 Appendices Prex name Symbol Val
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352 Appendices for voltage. (As an
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354 Appendices Material or Device S
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356 REFERENCES [15] E. C. Jordan an
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358 REFERENCES [45] V. K. Tikhomiro
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360 REFERENCES [73] M. G. Thomas, H
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362 REFERENCES [100] A. Ishibashi,
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364 REFERENCES [125] D. Wright, Req
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366 REFERENCES [150] J. P. Owejan,
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368 REFERENCES [175] G. K. Woodgate
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Index Absorption, 139 Action, 247 A
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372 INDEX Nernst equation, 220 Neur
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