Module 11 - Microwave Principles Pages
i−ix,
1−1 to 1−10,
1−11 to 1−20,
1−21 to 1−30,
1−31 to 1−40,
1−41 to 1−50,
1−51 to 1−60,
1−61 to 1−68,
2−1 to 2−10,
2−11 to 2−20, 2−21 to
2−30, 2−31 to 2−40,
2−41 to 2−50,
2−51 to 2−60,
2−61 to 2−66,
3−1 to 3−10,
3−11 to 3−20,
AI−1 to AI−6,
Index−1 to Index−2,
Assignment 1 - 1−8,
Assignment 2 - 9−16
APPENDIX I
GLOSSARY APERTURE - See slot. BOUNDARY CONDITIONS - The two conditions that
the E-field and H-field within a waveguide must meet before energy will travel down the waveguide. The E-field
must be perpendicular to the walls and the H-field must be in closed loops, parallel to the walls, and
perpendicular to the E-field. BEARING - An angular measurement that indicates the direction of an object in
degrees from true north. Also called azimuth. BUNCHER CAVITY - The input resonant cavity in a conventional
klystron oscillator. BUNCHER GRID - In a velocity-modulated tube, the grid which concentrates the electrons
in the electron beam into bunches. CATCHER GRID - In a velocity-modulated tube, a grid on which the spaced
electron groups induce a signal. The output of the tube is taken from the catcher grid. CAVITY RESONATOR - A
space totally enclosed by a metallic conductor and supplied with energy in such a way that it becomes a source of
electromagnetic oscillations. The size and shape of the enclosure determine the resonant frequency. CHOKE
JOINT - A joint between two sections of waveguide that provides a good electrical connection without power losses or
reflections. COOKIE-CUTTER TUNER - Mechanical magnetron tuning device that changes the frequency by changing
the capacitance of the anode cavities.
COPPER LOSS - Power loss in copper conductors caused by the internal resistance of the conductors to current
flow. Also called I2R loss. CROWN-OF-THORNS TUNER - See Sprocket Tuner. CUTOFF FREQUENCY - The
frequency at which the attenuation of a waveguide increases sharply and below which a traveling wave in a given
mode cannot be maintained. A frequency with a half wavelength that is greater than the wide dimension of a
waveguide. DIELECTRIC CONSTANT - The ratio of a given dielectric to the dielectric value of a vacuum. DIELECTRIC
LOSSES - The electric energy that is converted to heat in a dielectric subjected to a varying electric field. DIRECTIONAL COUPLER - A device that samples the energy traveling in a waveguide for use in another circuit. DIRECTIVITY - The narrowness of the radiated beam from an antenna. AI-1
DOMINANT MODE - The easiest mode to produce in a waveguide, and also, the most efficient mode in terms
of energy transfer. DRIFT SPACE - In an electron tube, a region free of external fields in which relative
electron position depends on velocity. DUMMY LOAD - A device used at the end of a transmission line or
waveguide to convert transmitted energy into heat so no energy is radiated outward or reflected back. E-FIELD - Electric field that exists when a difference in electrical potential causes a stress in the dielectric
between two points. E-TYPE T-JUNCTION - A waveguide junction in which the junction arm extends from the main
waveguide in the same direction as the E-field in the waveguide. ELECTRIC FIELD - See E-field. ELECTRONIC TUNING - In a reflex klystron, changing the frequency and output power of the tube by altering the
repeller voltage. ELECTROLYSIS - Chemical changes produced by passing an electrical current from one
substance (electrode) to another (electrolyte). ELECTRON ORBITAL MOVEMENT - The movement of an electron around the nucleus of an atom. ELECTRON SPIN - The
movement of an electron around its axis. ELEVATION ANGLE - The angle between the line of sight to an object
and the horizontal plane. FARADAY ROTATION - The rotation of the plane of polarization of electromagnetic
energy when it passes through a substance influenced by a magnetic field that has a component in the direction of
propagation.
FERRITE - A powdered and compressed ferric oxide material that has both magnetic properties and resistance
to current flow. FERRITE SWITCH - A ferrite device that blocks the flow of energy through a waveguide by
rotating the electric field 90 degrees. The rotated energy is then reflected or absorbed. GRID-GAP
TUNING - A method of changing the center frequency of a resonant cavity by physically changing the distance between
the cavity grids.
GROUP VELOCITY - The forward progress velocity of a wave front in a waveguide. H-FIELD - Any space or
region in which a magnetic force is exerted. The magnetic field may be produced by a current-carrying coil or
conductor, by a permanent magnet, or by the earth itself. H-TYPE T-JUNCTION - A waveguide junction in which
the junction arm is parallel to the magnetic lines of force in the main waveguide. AI-2
HELIX - A spirally wound transmission line used in a traveling-wave tube to delay the forward progress
of the input traveling wave. HORIZONTAL PLANE - An imaginary plane tangent to and touching the Earth's
surface as established by a stable element, such as a gyroscope. HORN - A funnel-shaped section of waveguide
used as a termination device and as a radiating antenna.
HOT CARRIER - A current carrier, which may be either a hole or an electron, that has relatively high energy
with respect to the current carriers normally found in majority-carrier devices. HOT-CARRIER DIODE - A
semiconductor diode in which hot carriers are emitted from a semiconductor layer into the metal base. Also called
a hot-electron diode. An example is the Schottky-Barrier diode. HYBRID JUNCTION - A waveguide junction that
combines two or more basic T-junctions. HYBRID RING - A hybrid-waveguide junction that combines a series of
E-type T-junctions in a ring configuration. IDLER FREQUENCY - In a parametric amplifier, the difference
between the input signal and the pump signal frequency. Also called the lower-sideband frequency. INTERACTION SPACE - The region in an electron tube where the electrons interact with an alternating electromagnetic
field. INTERELECTRODE CAPACITANCE - The capacitance between the electrodes of an electron tube. I2R
LOSS - See Copper Loss. IRIS - A metal plate with an opening through which electromagnetic waves may pass.
Used as an impedance matching device in waveguides.
LEAD INDUCTANCE - The inductance of the lead wires connecting the internal components of an electron tube.
LOAD ISOLATOR - A passive attenuator in which the loss in one direction is much greater than that in the
opposite direction. An example is a ferrite isolator for waveguides that allows energy to travel in only one
direction. LOOP - A curved conductor that connects the ends of a coaxial cable or other transmission line and projects into
a waveguide or resonant cavity for the purpose of injecting or extracting energy. LOOSE
COUPLING - Inefficient coupling of energy from one circuit to another that is desirable in some applications. Also
called weak coupling.
MAGIC-T JUNCTION - A combination of the H-type and E-type T-junctions. MAGNETIC FIELD - See H-field. AI-3
METALLIC INSULATOR - A shorted quarter-wave section of transmission line. MICROWAVE REGION - The
portion of the electromagnetic spectrum from 1,000 megahertz to 100,000 megahertz. MODULATOR - A device that
produces modulation; i.e., varies the amplitude, frequency, or phase of an ac signal. NEGATIVE-RESISTANCE
ELEMENT - A component having an operating region in which an increase in the applied voltage increases the
resistance and produces a proportional decrease in current. Examples include tunnel diodes and silicon unijunction
transistors. NONDEGENERATIVE-PARAMETRIC AMPLIFIER - A parametric amplifier that uses a pump signal frequency
that is higher than twice the frequency of the input signal. PHASE SHIFTER - A device used to change the
phase relationship between two ac signals. POWER GAIN - The ratio of the radiated power of an antenna compared to the output power of a standard antenna. A
measure of antenna efficiency usually expressed in decibels. Also referred to as POWER RATIO. POWER
RATIO - See Power Gain. PROBE - A metal rod that projects into, but is insulated from, a waveguide or resonant
cavity and used to inject or extract energy. PUMP - Electrical source of the energy required to vary the
capacitance of a parametric amplifier. RANGE - Distance, as measured from a point of reference, such as a
radar, to a target or other object. REACTANCE AMPLIFIER - A low-noise amplifier that uses a nonlinear
variable reactance as the active element instead of a variable resistance. Also called a parametric amplifier. RECIPROCITY - The ability of an antenna to both transmit and receive electromagnetic energy. REFLEX
KLYSTRON - A klystron with a reflector (repeller) electrode in place of a second resonant cavity to redirect the
velocity-modulated electrons back through the cavity which produced the modulation. REFRACTIVE INDEX - The
ratio of the phase velocity of a wave in free space to the phase velocity of the wave in a given substance
(dielectric). REPELLER - Sometimes called a reflector. An electrode in a reflex klystron with the primary
purpose of reversing the direction of the electron beam. ROTATING JOINT - A joint that permits one section of a transmission line or waveguide to rotate continuously
with respect to another while passing energy through the joint. Also called a rotary coupler. AI-4
SKIN EFFECT - The tendency for alternating current to concentrate in the surface layer of a conductor.
The effect increases with frequency and serves to increase the effective resistance of the conductor. SLOT - Narrow opening in a waveguide wall used to couple energy in or out of the waveguide. Also called an
aperture or a window. SPROCKET TUNER - Mechanical tuning device for magnetron tubes that changes the
frequency of the cavities by changing the inductance. Also called a crown-of-thorns tuner. STAGGER
TUNING - A method of klystron tuning in which the resonant cavities are tuned to slightly different frequencies to
increase the bandwidth of the amplifier.
STANDING WAVE RATIO - The ratio of the maximum to the minimum amplitudes of corresponding components of a
field, voltage, or current along a transmission line or waveguide in the direction of propagation measured at a
given frequency.
SYNCHRONOUS TUNING - In a klystron amplifier, a method of tuning which tunes all the resonant cavities to
the same frequency. High gain is achieved, but the bandwidth is narrow. TRANSIT TIME - The time an electron
takes to cross the distance between the cathode and anode. TRANSVERSE ELECTRIC MODE - The entire electric
field in a waveguide is perpendicular to the wide dimension and the magnetic field is parallel to the length. Also
called the TE mode. TRANSVERSE MAGNETIC MODE - The entire magnetic field in a waveguide is perpendicular to
the wide dimension ("a" wall) and some portion of the electric field is parallel to the length. Also called the TM
mode.
TUNNELING - The piercing of a potential barrier in a semiconductor by a particle (current carrier) that does
not have sufficient energy to go over the barrier. TUNNEL DIODE - A heavily doped junction diode that has
negative resistance in the forward direction over a portion of its operating range. See NEGATIVE-RESISTANCE
ELEMENT. VARACTOR - A PN-junction semiconductor designed for microwave frequencies in which the capacitance varies with
the applied bias voltage. VARIABLE ATTENUATOR - An attenuator for reducing the strength of an ac signal
either continuously or in steps, without causing signal distortion. VELOCITY MODULATION - Modification of
the velocity of an electron beam by the alternate acceleration and deceleration of electrons. VERTICAL
PLANE - An imaginary plane that is perpendicular to the horizontal plane. WAVEGUIDE - A rectangular, circular,
or elliptical metal pipe designed to transport electromagnetic waves through its interior. WAVEGUIDE MODE
OF OPERATION - Particular field configuration in a waveguide that satisfies the boundary conditions. Usually divided
into two broad types: the transverse electric (TE) and the transverse magnetic (TM). AI-5
WAVEGUIDE POSTS - A rod of conductive material used as impedance-changing devices in waveguides. WAVEGUIDE SCREW - A screw that projects into a waveguide for the purpose of changing the impedance. WINDOW - See Slot. WOBBLE FREQUENCY - The frequency at which an electron wobbles on its axis under the
influence of an external magnetic field of a given strength. AI-6
NEETS Table of Contents
- Introduction to Matter, Energy,
and Direct Current
- Introduction to Alternating Current and Transformers
- Introduction to Circuit Protection,
Control, and Measurement
- Introduction to Electrical Conductors, Wiring
Techniques, and Schematic Reading
- Introduction to Generators and Motors
- Introduction to Electronic Emission, Tubes,
and Power Supplies
- Introduction to Solid-State Devices and
Power Supplies
- Introduction to Amplifiers
- Introduction to Wave-Generation and Wave-Shaping
Circuits
- Introduction to Wave Propagation, Transmission
Lines, and Antennas
- Microwave Principles
- Modulation Principles
- Introduction to Number Systems and Logic Circuits
- Introduction to Microelectronics
- Principles of Synchros, Servos, and Gyros
- Introduction to Test Equipment
- Radio-Frequency Communications Principles
- Radar Principles
- The Technician's Handbook, Master Glossary
- Test Methods and Practices
- Introduction to Digital Computers
- Magnetic Recording
- Introduction to Fiber Optics
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