Module 11 - Microwave Principles
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
, 2−31 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
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.
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.
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.
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.
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).
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.
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
- Introduction to Amplifiers
- Introduction to Wave-Generation and Wave-Shaping
- 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