Practical_Antenna_Handbook_0071639586

I n d e x 755
maximum effective length (MEL), 334–335
maximum useable frequency (MUF), 53, 54–55,
61–64
MUF control points, 61, 64
Maxwell, James Clerk, 3, 9, 90–91
displacement current, 91–92
prediction of electromagnetic waves, 9,
90–91, 93
Maxwell’s equations, 9, 13, 88, 91, 92–93
medium (media), 12–13
megahertz (MHz), 11–12
Mercator projection, 65
meteor scatter propagation, 76
micromatch SWR bridge, 606–607
microwave antennas, 471–489
aperture, 478
arrays, 485–487
branch feed, 485–486
corporate feed, 485–486
flatplate array, 488–489
phase shifters, 485–487
slot array, 487–488
solid-Âstate, 486–487
back lobes, 477
beamwidth 476–477
Cassegrain feed geometry, 483–484
cavity antenna, 480
corner reflector, 480–481
dipole elements, 473–474
directivity, 474–477
directivity gain (G d ), 477–478
directrix (of a parabola), 481–482
dish antennas (see parabolic antennas)
effective radiated power (ERP), 477
efficiency, 473, 477
feed illumination, 482
gain, 477–478, 483
gain vs. aperture, 478
horn radiators, 479
impedance, 471, 473
interference, 477
isotropic radiator, 471–472
monopulse feed system, 484–485
near field vs. far field, 472
phase shifter, 485–487
radiation loss, 473
radiation patterns, 475–476
radiation resistance, 473
reflector, 480–481
splash plate, 483
microwave waveguides, 447–470
analyzed as Âquarter-Âwavelength shorted
stub, 450–451
attenuation, 377
boundary conditions, 452
characteristic impedance, 461–463
coupling methods, 468–470
aperture (slot), 470
capacitive (probe), 468–469
inductive (loop), 470
choke joints, 466–467
coordinate system, 453–454
cutoff frequency (f C ), 458–461
dominant mode, 453–454
dummy loads, 463–466
effective aperture (A e ), 478
electric fields, 449, 452–453, 461
end plate, 463, 466
feedpoint impedance and matching,
473
free-Âspace velocity (c), 454–458
frequency spectrum, 447
graphite-Âsand, 463–464
group velocity (V g ), 455–458
joints and bends, 466–468
light pipe analogy, 448
losses, 447–449
magnetic fields, 452–453, 461
materials, 449
permanent joints, 466
phase velocity (V p ), 455–458
power gain (G p ), 477–478
probe coupling, 468–469
propagation modes, 451–454
radiating vs. nonradiating slots, 470
rotating joints, 468
safety issues, 447
semipermanent joints, 466–467
side lobes, 476, 477
terminations, 463–466
transverse electric (TE) mode, 452,
453–454, 459–460, 462
transverse electromagnetic (TEM) mode,
452
transverse magnetic (TM) mode,
453–454, 461, 462
velocities, 454–458
wavelength, 454–458
millimeter waves, 12
MiniNEC modeling software, 546