EO-4 Flashcards
Modulator
A switch used to trigger the transmitter on and off to release bursts of DC energy.
Timer
Provides a stable timing source for the entire radar system. AKA the “synchronizer”.
Transmitter
High-power oscillator, generates a high-power radio frequency wave for the duration of the input pulse from the modulator. (Converts DC energy into RF energy)
Oscillator
An electronic circuit that generates periodic, oscillating signals. (Convert DC from a power supply to AC signal)
Amplifier
A device used to increase the power of a signal. (Increases the strength of the RF before transmission)
Duplexer
Protects the receiver from the high-power signals that the transmitter produces.
Reciever
Converts RF energy into electrical current to be processed. (Can consist of many different components)
Signal Processor
The part of the system which separates targets from clutter on the basis of Doppler content and amplitude characteristics.
Matched Filter
Maximizes the SNR ratio by filtering out returned energy that does not match what was transmitted.
Low-Noise Amplifier
Located at the first stage of the receiver, Increases amplitude level of the target, Sets the noise floor of the radar system.
Antenna
Focuses radio waves in a desired direction, provides the ability to measure angle to a target, gives transmitted waves a boost (Gain).
What are the 2 basic/major types of Transmitters?
Coherent, Non-Coherent
What are the 2 common categories of oscillators?
Magnetron, Solid-State
Coherent Pulse Train
The pulses generated are made from a common, underlying waveform. (All pulses are in phase with each other)
Non-Coherent Pulse Train
Do not have a common underlying sine wave, the starting phase of each recurring pulse is completely random and not influenced by previous pulses
Magnetron
Has the ability to generate high-amplitude RF signals due to the amount of electrical current they can handle.
What are the drawbacks of using magnetrons?
Generally non-coherent, systems employing them cannot use certain kinds of specialized signal processing
Exciter
A unit that generates wave forms used in the transmitted signal. (Typically don’t generate RF with enough power for radar use and, usually, must be boosted with an amplifier)
What are the 2 parts of a radar exciter?
Waveform generator, upconverter
Waveform Generator
Creates and shapes the waveform modulation
Upconverter
Translates the waveform to the transmitted carrier frequency
Name some types of amplifiers.
cross-field amplifiers, klystrons, traveling wave tubes (TWT)
What are some considerations in choosing the right amplifier for a radar system?
Power requirements, bandwidth limitations, stability, cost, size, weight, and application.
What could happen if power from the transmitter “leaked” into the receiver?
The receiver would likely be damaged or cease to function.
Duplexers are necessary in what type of radars?
They are necessary in radars using a single antenna for both transmission and reception, called “monostatic” radars.
Bistatic radars
Radars with separate antennas for transmit and receive functions.
Moving Target Indicator (MTI) Processor
System processor to display echoes from moving targets (i.e. aircraft) and to reject echoes from fixed targets (i.e. permanent echoes)
Pulse Integrator
Processing method that can achieve target detection where individual signal returns would be too low in power to be identified as a target.
Pulse Doppler (PD) Processing
Primary wat that radar systems measure relative velocity of targets.
Target Detector
Determines if a target is present in each range or Doppler bin.
Display
Component of the radar system that enables the operator to read the output of the radar
Impedance
opposition to the flow of energy
Electrical Impedance
The measure of the opposition that a circuit presents to a current when a voltage is applied.
Inductance
The induction of voltages in conductors self-induced by the magnetic fields of currents.
Capacitance
the ability of a conductor to store energy in the form of electrically separated charges
A standing wave occurs when
a wave reflects upon itself. (the effects resemble those of jitter)
Transmission Lines
The wires (overhead or underground) that take electrical current between components.
What are the 2 most common types of transmission lines?
Coaxial cables, Waveguides
Coaxial cable (coax)
Cable consisting of a hollow outer cylindrical conductor that surrounds a single inner wire conductor.
Waveguide
A thin layer or hollow structure in which electromagnetic waves are “guided” from one place to another.
What is the most common method for generating timing pulses?
The use of a crystal-controlled timer
Crystal-controlled Timer
A timer that generates the “clock ticking” with an oscillating quartz crystal.
Crystal frequency
The rate of the crystal’s oscillation, the rate of output “ticks”.
Crystal Countdown
The number of crystal periods used to create the Pulse Repetition Interval (PRI)
Master Oscillator-Power Amplifier (MOPA)
Refers to a configuration that uses an oscillator to generate a RF, followed by an amplifier to increase the power of the RF to the required output level.
False Alarm
Caused by a target detector’s threshold being set too low. (the system perceived a target when none was present)
Missed Detection
Caused by the target detector’s threshold being set too high. (the system did not perceive a target when one was present)
