Module 3 Flashcards
The _______ determines the design of the transmitter.
final power amplifier (FPA)
A properly functioning radar system should be able to accurately reproduce a rectangular pulse. T/F
True
what is the waveform obtained when the DC pulse amplitude is plotted as a function of time, such as on an oscilloscope.
Pulse Shape
What is the energy of the pulse calculated by multiplying the pulse voltage and the pulse current.
Pulse Power
What is the power which would equal the power delivered during the pulse if power were delivered at a steady rate throughout one complete pulse interval
Average Power Output
What is the number of times per second that the pulse repeats, as controlled by the synchronizer. It is expressed in Hz, and can be calculated by taking the inverse on the pulse repetition time
Pulse Repetition Frequency
What is the ratio of the pulse width (tp) to pulse repetition time (PRT), as expressed as a fraction or a percentage.
Duty Ratio
What is the process of ensuring that the impedance of the modulator components equals that of the FPA components. If there is an impedance mismatch between the modulator and the FPA, energy will be reflected back to the source.
Impedance Matching
The main difference between a solid-state FPA and a tube type FPA is that the solid-state FPA _____.
lacks the ability to amplify in the range of megawatts
A stationary target may be perceived as a moving target if the amplitudes of the transmit pulses vary. T/F
True
The radar with the longest listening period is the _____
ARSR-4
Transmitter design depends upon the construction of the _____.
FPA (Final Power Amplifier)
RF signals undergo _____ shaping in the RF section of an ASR-8/9
Final
The FPA receives _____ power from the modulator section
High Voltage DC Power
The PFN (Pulse Forming Network) is also called _____
Energy Storage Device
The DC power supply section in a solid-state transmitter provides _____ voltage, _____ current power to the transmitter’s RF drivers and power amplifier modules.
Low High
The _____ is inhibited during transmission to prevent recharging
DC Power Suppily
Why must a transmitter’s input remain stable
To prevent displaying moving targets as fixed ones
Which input must remain stable to ensure stable FPA outputs
Coherent oscillator
A trigger from the _______ controls a charge/discharge switch in the modulator
synchronizer
A crowbar circuit is used in a(n) _____ to protect the load
active-switch modulator
The PFN (Pulse Forming Network) is also known as the _______.
energy storage device
The _____ provides isolation between the energy storage device and the HVPS (High Voltage Power Suppily).
charging circuit
The _____ must be biased on to allow energy to flow through it
SCR (Silicone Controlled Rectifier)
_____ circuits retain DC pulse power.
Diode
The modulator delivers high-powered DC pulses to the _____.
FPA (Final Power Amplifier)
The ________ discharges stored up energy
Energy Storage Device
A _____ can be used to smooth out irregular voltage and power levels in the modulator.
capacitor bank
what is it called when the SCR is unable to properly reset after firing
Hangfire
The _____ transforms ac power to continuous DC power in order to enable the FPA
HVPS (High Voltage Power Suppily)
The _____ determines the width of the high-powered pulse that is delivered to the FPA
PFN (pulse forming network)
The _____ resets every time the energy storage device discharges
charging switch
When the trigger voltage exceeds the critical voltage of the _____, it is forced into conduction.
RBDT (reverse-blocking diode thyristor)
_____ circuits generate high impedance to oppose the DC pulse during discharge
Saturable reactor
A _____ circuit absorbs unwanted ringing by dissipating high amounts of DC power.
resistor
The modulator charging path begins with the _____.
DC power supply
It is important to understand the _____ requirements of modulator components in order to troubleshoot radar systems.
timing
Impedance mismatch can be used to assist the charging cycle in the _____.
PFN (pulse forming network)
The charging choke and the charging diode double the charge that is stored on the _____.
PFN (pulse forming network)
_______ allows air traffic controllers to communicate with pilots
Amplitude modulation
_______ occur when the side lobes drop to zero and contain no energy.
Crossover frequencies
_______ is the circuit’s ability to pass a signal without distortion.
Fidelity
An adequate pulse reproduction occurs when the bandpass is equal to the _____ crossover frequency.
third
The FAA uses _____ pulse compression techniques for transistor radars
non-linear FM
Harmonics are based on the _____ of the transmitted pulse
fundamental frequency
The number of harmonics that can pass through a network depends on the _____.
bandwidth
Most radar systems use a microwave _____ diode that is Foward biased to achieve the desired pulse width
PIN (positive-intrinsic barrier-negative)
What does pulse width affect
A. Aircraft range resolution
B. Average transmitted RF energy
C. Fundamental frequency
D. Intelligence riding on the carrier frequency
E. Number of harmonics passed through a network
Aircraft range resolution
Average transmitted RF energy
Spectral analysis allows us to examine a transmitted pulse by plotting _____ versus _____.
Frequency Amplitude
Achieving bandwidth fidelity varies by the number of _____ components that an amplifier must pass within a given pulse.
harmonic
The FAA uses pulse compression techniques with _____ FPAs to achieve adequate average power. (ASR-11)
solid-state
The _____ uses a dual sub-pulse transmission technique to send out a 150 μs transmit pulse. (Radar system)
ARSR-4
The _______ and ______ are vacuum tube amplifiers.
klystron, TWT (traveling wave tube)
Pulse klystron amplifiers have a low _______ due to their cavities.
bandwidth
FAA radars use a ______ to focus the electron beam
solenoid
The RF input and output are connected by a helical delay line, which reduces the _______ to match the _________
RF signal velocity , electron beam
_______ occurs as the bunched electrons interact with the electric field of the RF signal
Amplification
The divider/combiner is the dominant method used in _______ radars(s). (3 answers)
ARSR-4
ASR-11
CARSR
Microwave transistors require a _______ and _______ pulse for proper functioning
low peak power, longer time duration
Transistor amplifiers are advantageous over vacuum tube amplifiers because they ______. (3 answers)
have a longer life expectancy
have a more reliable power supply
have a simpler construction
The FAA uses _____ (modulation) on the transmit pulse frequency
NLFM(non-linear frequency modulation)
Vacuum tube amplifiers must produce _____ peak, _____ RF pulses.
high, short
The RF output device must produce a pulse width at the _____ possible within average power limitations.
highest PRF
Which part of the klystron is nicknamed the “buncher?”
first cavity
Electrons in the electric field will slow down when the RF signal varies from_____ to ____.
181° to 359°
The TWT uses a _____ to focus the electron beam
permeant magnet
The first sub-pulse in an ARSR-4 is transmitted at _____ μs and the second is transmitted at _____ μs
90, 60
The _____ in a TWT slows down the RF pulse to correspond to the velocity of the electron beam
Helix Coil
What prevents oscillations by isolating the RF input and output in a TWT?
Attenuator
The high voltage demands of the _____ often lead to component degradation
transmitter
Pulse power requirements are listed in the _____ section of the maintenance handbook
Standards and Tolerances
The voltage standing wave ratio can be calculated from the _______.
forward and reverse power readings
Transmitted pulse characteristics determine the aircraft’s _____.
range resolution
RF pulse width is measured from the _____ of the directional coupler
forward port
Unless otherwise specified, pulse width is measured at the _____ point of the RF pulse.
70%
Bandwidth is typically measured at the _____ down position on the transmitted pulse. (2 answers).
40 dB
50 dB
Which devices can be used to measure carrier frequency and transmitter stability? (2 answers)
frequency counter
Spectrum analyzer
Which pulse-shape characteristics could cause the FPA to not work properly if they are out of tolerance? (3 answers)
Fall time
Pulse width
Rise time
FAA equipment standards and tolerances can be found in Chapter _____ of the maintenance handbooks
3
Radar parameters preceded by which symbol must fall within the stated tolerances to meet key performance parameters?
Arrow
Which parameters are used to measure peak power? 3 answers
Peak power
Pulse width
Pulse repetition time
Digital average power readings are measured from the_____ on the directional coupler
forward port
Range resolution is calculated with the speed of light and _____.
RF pulse Width
Variations in the ____ effect the range resolution
pulse width
Rise time is measured from the ___ - ___ points on the pulse’s leading edge
10%-90%
Radar technicians must verify the spectrum by calculating the _____.
bandwidth
The _____ function sets the power level to 0 dB.
Mkr –> CF
What are some actions that can be taken to troubleshoot the FPA?
Fine tune its cavities
Make sure the output device is within tolerance
Replace it
The measured carrier frequency should fall within tolerance of the _____.
transmitting frequency
Deviations in the ____ from pulse-to-pulse transmission can cause interference to adjacent radar sites.
carrier frequency
