Module 5 Flashcards
What are the primary functions of a signal processor? Select all that apply.
A. Accept raw target return video from the receiver
B. Condition data based on the appropriate operating mode
C. Control receiver gain
D. Present video to PPI display
E. Provide radar timing signals
F. System testing
Accept raw target return video from the receiver
Condition data based on the appropriate operating mode
Present video to PPI display
As a radar target moves away from the radar, the target echoes will _______, and their frequencies will _______.
expand, decrease
The radial velocity is _______ the ground speed velocity if the target is moving directly toward the radar.
equal to
________ signal processors place returns in a memory storage device before comparing them.
Digital
_______ creates a trend analysis of Doppler shift returns.
Doppler filtering
The Doppler shift is ________.
A. determined by the angle between the true range and the line-of-sight to the radar
B. the change in frequency as a target moves towards and away from a radar
C. the ground velocity of a target as it moves towards or away from a radar
D. the process of delaying one sample for comparison to the next sample
the ground velocity of a target as it moves towards or away from a radar
________ is the component of an aircraft’s groundspeed that is moving toward or away from the radar.
Radial velocity
When calculated the ______ using ground velocity, take the cosine of the angle between the aircraft’s true heading and its line of sight to the radar.
radial velocity
______ is the process of comparing two sequential intelligence samples to determine whether or not a Doppler shift has occurred.
Cancellation
A secondary function of radar signal processors is to _______.
provide radar timing signals
Which radar system component generates range and azimuth gates to control related functions?
Signal processor
Which of the following are secondary functions of a radar system’s signal processor? Select all that apply.
A. Accept raw target return video from the receiver
B. Control receiver gain
C. Present video to PPI display
D. Provide radar timing signals
Control receiver gain
Provide radar timing signals
If an input signal is greater than the reference signal, it moves to the _______.
subtractor
Digital to analog conversion is used for ______.
sending signals to display devices
______ is the process used to differentiate targets from noise.
Constant false alarm rate
If a target signal does not cross the detection threshold, it is called a _____.
miss
________ is the process of adding the number of pulses over several PRTs to improve target detection.
Integration
If an input signal is below the threshold for the reference signal, it moves on to the _______.
A. adder
B. canceller
C. next comparator
D. subtractor
next comparator
Modern radar converters must have which characteristics? Select all that apply.
A. They must be asynchronous.
B. They must be monotonic.
C. They must have high resolution.
D. They must have low dynamic range.
They must be asynchronous.
They must be monotonic.
They must have high resolution.
In a(n) _______, the half of the input signal that flows towards the op amplifier affects the output voltage.
R-2R ladder network
What indicates the likelihood that a signal is detected while in presence of noise?
A. Constant false alarm rate
B. Probability of detection
C. Probability of false alarm
D. Pulse repetition time
Probability of detection
If the detection threshold increases, the probability of false alarm ____ and the probability of detection ____.
A. decreases, decreases
B. decreases, increases
C. decreases, remains constant
D. increases, increases
E. increases, remains constant
decreases, decreases
Adding pulses with similar characteristics is called _____.
coherent integration
The purpose of MTI (Moving Target Indicator) processing is to _______.
suppress fixed target returns and enhance moving target returns
MTI (Moving Target Indicator) processors compare the _______ of each pulse to distinguish fixed targets from moving ones.
amplitudes and polarity
A difference in amplitudes between two compared returns indicates a _______ target
moving
An echo entering the delay line travels to the summer in how many PRTs (pulse repetition time)?
1 PRT (pulse repetition time)
_______ reduces the blind speed effects on a target.
Staggering the PRF Pulse Repetition Frequency)
The ______ is not affected by blind phases because it operates independent of the phase.
magnitude detector
An MTI (Moving Target Indicator) system uses ______ filtering to remove returns from fixed targets
band-reject
Quadrature phase detection measures a received signal’s phase and _______.
amplitude
What are the components of a delay line canceller? Select all that apply.
A. Comparator
B. Delay line
C. Magnitude combiner
D. Summer
Delay line
Summer
A moving target that produces a Doppler frequency that is an odd multiple of ½ the PRF (Pulse Repetition Frequency)has reached _______.
optimum velocity
At optimum speed, a moving target travels _______ wavelength between transmit bursts
1/4
Vector processing MTI (Moving Target Indicator) _______ delay line to process phase detector output.
uses several
What might increase in weather returns looks like in a pulsed radar system?
Extra noise in the system’s average noise
What prevents video saturation from the large amplitude of weather returns?
Logarithmic amplifier
What provides sampled range-cell signals that are applied to video input?
Digital cell averaging system
If a signal level of interest is greater than the average noise threshold, _______.
an output is generated
The _______ was designed to eliminate clutter.
MTI (Moving Target Indicator) system
SCV (Sub-Clutter Visibility) is the ratio of _______ that will just cause the canceller voltage from the signal to equal twice the clutter residue.
A. clutter phase to moving target echo initial phase
B. clutter signal strength to moving target signal strength
C. moving target echo initial phase to clutter phase
D. moving target signal strength to clutter signal strength
moving target signal strength to clutter signal strength
What is required for maximum canceller performance?
A. The STALO (stable local oscillator) and COHO (coherent oscillator) must vary.
B. The STALO (stable local oscillator) must not vary while the COHO (coherent oscillator) varies.
C. The transmitted signal cannot be stable.
D. The transmitted signal must be stable.
The transmitted signal must be stable.
What factors limit MTI (Moving Target Indicator) performance? Select all that apply.
A. Decreased clutter residue
B. Phase change caused by the Doppler Effect
C. Radar system instabilities
D. Small movements in the clutter itself
Radar system instabilities
Small movements in the clutter itself
What indicates how well a canceller is removing fixed target returns? Select all that apply.
A. Cancellation ratio
B. Clutter rejection
C. MTI (Moving Target Indicator) improvement factor
D. The transmitted signal
Cancellation ratio
Clutter rejection
________ instabilities could prevent fixed targets from being canceled, resulting in a cancellation ratio of one.
COHO (coherent oscillator)
Which of the following is a simple CFAR circuit preventing weather from interfering with target detection?
A. Log FTC Fast time Constant)
B. Phase detector
C. Pulsed
D. Microprocessor-based
Log FTC (Fast time Constant)
In a pulsed radar system, returns for weather will look like ______ in phase detector output over a ________ range than actual aircraft returns.
A. a decrease, larger
B. a decrease, smaller
C. an increase, larger
D. an increase, smaller
an increase, larger
In a ________, a cell-averaging or low pass filter determines a signal’s local average
logarithmic amplifier
In a logarithmic amplifier, what determines the time and range used to evaluate the signal’s average?
Filter cutoff frequency
Where is the test cell output applied?
Threshold detector
A return target will only appear in _______. Therefore, its output _______ increase the average enough to prevent detection.
A. one cell, will not
B. two cells, will
C. three cells, will
D. four cells, will not
one cell, will not
All ________ are assumed to be equally likely when referring to sub-clutter visibility.
A. false alarms
B. signal strengths
C. target radial velocities
D. target sizes
target radial velocities
As the clutter ________, it gets harder to see the moving target inside of it.
A. size gets larger
B. size gets smaller
C. strength gets stronger
D. strength gets weaker
strength gets stronger
SCV (Sub-Clutter Visibility) _______ to compare the performance of two radars operating in the same environment.
cannot be used
Which characteristic measures MTI (moving target indicator) system performance?
A. Cancellation ratio
B. Clutter rejection
C. MTI improvement factor
D. The transmitted signal
MTI (moving target indicator) improvement factor
Instabilities in the _______ will increase the amount of clutter residue in a different cancellation ratio.
A. radar frequencyv
B. signal-to-noise ratio
C. system’s signal
D. transmitted signal
radar frequency
What are some of the factors influencing an MTI receiver’s response to a moving target over clutter? Select all that apply.
A. A moving target’s radial velocity
B. Signal strength of a moving target echo
C. The clutter phase
D. The target’s size
A moving target’s radial velocity
B. Signal strength of a moving target echo
The clutter phase
What are the characteristics of a digital filter?
Frequency and Phase sensitive
Setting _______ tunes the multiply and accumulate algorithm. (Digital Filters)
coefficients
Pulse compression techniques let a system transmit a pulse of _______ and low peak power.
long duration
________ in the PCF represent modulation values applied in the transmitter.
Phasors
The final sampling output is obtained at a rate _____ with the desired range resolution ______ the pulse compression filter is used as a phase detector.
frequency, phase relationship
A digital filter is a(n) ________.
algorithm
The final sampling output is obtained at a rate _____ with the desired range resolution ______ the pulse compression filter is used as a phase detector.
A. consistent, if
B. consistent, regardless of whether
C. inconsistent, if
D. inconsistent, regardless of whether
consistent, regardless of whether
What tasks does the MTD processor use digital filter for? Select all that apply.
A. Batch processing
B. Filtering the Doppler shift of targets
C. Pulse compression
D. Understanding what happens once a report is generated
Batch processing
Filtering the Doppler shift of targets
Pulse compressioN
The purpose of PCF(pulse compression filter) is to remove __________ introduced in the transmitter
fm chirp
How often is I&Q data generated for the radar’s range cells?
Each PRT (pulse repetition time)
The first piece of data to enter into memory storage is the ________.
first azimuth cell of the first PRT (pulse repetition time)
The Doppler filter input is in _____ format for batch processing.
BRC (Batch Range Cells)
Doppler filters process in _____ order.
A. ascending
B. descending
C. azimuth
D. range
azimuth
Which of the following is true about the mean level threshold?
A. Each threshold must have a different amplitude
B. It eliminates magnitude data for false targets
C. It generates a new filter threshold after each comparison
D. The filter value is combined with the threshold data for comparison
The filter value is combined with the threshold data for comparison
- What is the possibility a signal will be detected when in noise?
A. Constant false alarm rate
B. Probability of detection
C. Probability of false alarm
D. Thresholding
Probability of detection
What is a disadvantage of raising the CFAR (constant false alarm rate) threshold?
It could eliminate valid targets
A clutter map allows _____ targets to be detected by storing the nominal zero-velocity returns as thresholds.
zero velocity
What is another name for clutter mapping?
Time average CFAR(constant false alarm rate)
It is possible for a single target to produce several primitive target reports extending over several BRCs that encompass multiple Doppler filters.
A. True
B. False
True
What does the primitive target report contain? Select all that apply.
A. Amplitude of origin
B. Doppler filter of origin
C. Range of origin
D. Velocity of origin
Amplitude of origin
Doppler filter of origin
Range of origin
The representation created by a Geo-Map cannot include _____.
airport grounds
What does an MTD Geo-Map do? Select all that apply.
A. Allows zero velocity targets be detected
B. Detects moving targets
C. Identifies problem areas in known geographic locations
D. Prevents road traffic from being displayed as moving targets
Prevents road traffic from being displayed as moving targets
Identifies problem areas in known geographic locations
What converts range data to batch ordered data?
Memory storage
Radar transmits and receives echoes in a range-ordered format _____, for the entire range system.
one cell at a time
What is the format used to output from memory storage?
Batch-ordered data
Coefficients in _____ compromise data that allows targets to be sorted by their radial velocity.
Doppler filters
Doppler filters operate in groups called _____, in which each filter is tuned to a progressively higher frequency.
banks
The specific _____ of each Doppler filter is determined by the selection of coefficients.
optimum frequency
When a filter produces its _____ the involvement of adjacent filters is minimized.
optimum response
What changes continuously to eliminate magnitude data that is not a valid target?
The dynamic mean threshold
The process of suppressing false alarms caused by noise, interference, or weather is _____.
CFAR (Constant False Alarm Rate)
What is the ability to maintain the false alarm rate at a predetermined level even as external conditions change?
Adaptive CFAR (constant false alarm rate)
What is the likelihood of noise being mistaken for a target?
Probability of false alarm
The probability of false alarm must be _____ to ensure the number of false alarms is as small as possible?
low
The primitives can be from _____ different PRFs and are combined in an m or n decision
2
What is meant by a tangent target?
It is a moving target that does not produce a radial velocity
What causes a zero-velocity filter to become an alarm?
A. The time-average CFAR must average the radar inputs from the zero Doppler filter
B. The magnitude of the zero-velocity target must be less than the stored threshold
C. The magnitude of the zero-velocity target must be greater than the stored threshold
D. The clutter map must average the zero velocity echoes and compare it to the stored threshold
The magnitude of the zero-velocity target must be greater than the stored threshold
A _____ target may take up several consecutive range cells.
Large
Which of the following presents an issue for MTD target processing?
A. Inclement weather
B. Moving vehicles
C. Slow moving aircraft
D. Trees
Moving vehicles
What determines the range center’s location?
Range-straddle test
Azimuth centroiding uses ________ to determine a target’s center.
algorithms
What are the four universal steps in track-while-scan processing?
A. Association
B. Correlation
C. Track initiation
D. Track updating
E. Track uploading
A. Association
B. Correlation
C. Track initiation
D. Track updating
Which step of the track-while-scan process uses the track-to-report association probability?
Conflict resolution
Which process associates completed target reports with target reports generated in a secondary radar system?
Merge function
Which process involves receiving target plot and track data as well as other data?
Formatting
Which equipment provides interface and protocol conversion for communication between radars, end users, and networking requirements for modern radar’s computer or microprocessor controlled functions?
Communications interface
What is the final functional process in sending radar data to the end-user?
Remoting
What is the process of establishing range and azimuth centers?
plot extraction
What is the purpose of the range resolution test?
To determine if other targets exist in adjacent range cells
What is the best resolution for azimuth centroiding?
CPI (coherent processing interval)
What is the process of eliminating plot characteristics for valid primitive clusters associated in azimuth and range?
Plot extraction
During which step in the track-while-scan process is an imaginary azimuth window placed around each existing track?
Association
If more than one report is in the associated window _______ associates each report with existing track in the window.
conflict resolution
Which process occurs after a new report is received and a check is performed to determine if a target is located in the window of an existing track?
Track initiation
What happens when a track initiation report finds an unassociated track that is located in the window of an existing track?
A. The unassociated track is not filed
B. The unassociated track is added to a new file
C. The unassociated track is added into a file selected at random
D. All of the tracks are combined into one file
The unassociated track is added to a new file
What is declared if a track has new reports associated with it for several antenna scans?
Correlation
During ________, a target-tracking file is made current and a check is performed to verify a target is moving.
track updating
Which of the following is true of the Legacy format?
A. The Legacy format is determined by the formatter protocol
B. The Legacy format is IP-based
C. The Legacy format keeps a complete history of targets in the target-tracking file
D. The Legacy format transfers data through a modem
The Legacy format transfers data through a modem
In which step is it decided whether a return from the primary radar and reply from the secondary radar are from the same target?
Merge function
Other remote-related functions like CARSR _________ will communicate status and control with the end-user.
A. APU (Azimuth Processing Unit)
B. RMC (Remote and Monitor Control)
C. RSC (Radar Set Control)
D. TMCT (test maintenance and control terminal)
RMC (Remote and Monitor Control)
Which CARSR component converts Ethernet data for the receiver channels?
A. CD-2 data switch
B. MPS (multi-protocol server)
C. RSC (Radar Set Control)
D. TMCT(test maintenance and control termina)
MPS
