Vol 1. Introduction To Radar Systems, Unit 1. Radar Fundamentals

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Vol 1. Introduction To Radar Systems, Unit 1. Radar Fundamentals - Quiz

These tests, four (Unit 1 - 4) in total, are designed to give you knowledge about the spectrum of equipment covered by the ground radar career field and to reinforce the information you learned in technical school. These tests are intended to help you progress from an Apprentice (3-level) to a Journeyman level (5-level) in the career field. This series of tests is focused on Volume 1 only.


Questions and Answers
  • 1. 

    What is the purpose of Aircraft control and warning (AC&W) radar?

    • A.

      To control friendly aircraft, detect hostile aircraft, and control interceptors

    • B.

      To control enemy aircraft, detect friendly aircraft, and control interceptors

    • C.

      To control friendly aircraft, detect friendly aircraft, and control interceptors

    • D.

      To control friendly aircraft, detect hostile interceptors, and control interceptors

    Correct Answer
    A. To control friendly aircraft, detect hostile aircraft, and control interceptors
    Explanation
    The purpose of Aircraft control and warning (AC&W) radar is to control friendly aircraft, detect hostile aircraft, and control interceptors. This radar system is designed to provide situational awareness and enhance air defense capabilities by monitoring and managing the airspace. It helps in identifying and tracking both friendly and hostile aircraft, allowing for effective control and coordination of friendly forces. Additionally, it enables the detection of hostile aircraft, providing early warning and enabling timely response to potential threats. The ability to control interceptors is crucial for effective air defense operations, as it allows for the interception and neutralization of hostile aircraft.

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  • 2. 

    What is used, with proper receiving equipment, to detect the presence of a distant object?

    • A.

      Reflected energy

    • B.

      Light

    • C.

      Mirror

    • D.

      Sound waves

    Correct Answer
    A. Reflected energy
    Explanation
    Reflected energy is used, with proper receiving equipment, to detect the presence of a distant object. When an object reflects energy, such as light or sound waves, it can be detected by specialized equipment. This detection allows us to sense the presence of objects that are not within our direct line of sight. Light and sound waves are forms of energy that can be reflected off objects and detected, but a mirror is simply a surface that can reflect light and does not have the capability to detect distant objects.

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  • 3. 

    At what speed do radio waves travel?

    • A.

      Speed of light

    • B.

      Speed of sound

    • C.

      Twice the speed of sound

    • D.

      Twice the speed of light

    Correct Answer
    A. Speed of light
    Explanation
    Radio waves are a type of electromagnetic wave, and all electromagnetic waves, including light, travel at the same speed in a vacuum, which is the speed of light. Therefore, radio waves also travel at the speed of light.

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  • 4. 

    How long does it take for a radar pulse to travel one radar mile?

    • A.

      12.36 microseconds

    • B.

      6.18 microseconds

    • C.

      24.72 microseconds

    • D.

      3.09 microseconds

    Correct Answer
    A. 12.36 microseconds
    Explanation
    The correct answer is 12.36 microseconds. This is because a radar mile is defined as the distance that a radar pulse travels in one microsecond. Therefore, to travel one radar mile, it would take 12.36 microseconds.

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  • 5. 

    What radar assembly supplies timing signals to coordinate the operation of the complete system?

    • A.

      Synchronizer

    • B.

      Transmitter

    • C.

      Duplexer

    • D.

      Receiver

    Correct Answer
    A. Synchronizer
    Explanation
    The radar assembly that supplies timing signals to coordinate the operation of the complete system is called a synchronizer. A synchronizer ensures that all components of the radar system are working in sync and at the correct timing intervals. It plays a crucial role in ensuring accurate and coordinated operation of the radar system.

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  • 6. 

    When a transmitter uses a high-power oscillator to produce the output pulse, what switches the oscillator on and off?

    • A.

      Modulator high-voltage pulse

    • B.

      Sine-wave oscillator

    • C.

      Multivibrator

    • D.

      Blocking oscillator

    Correct Answer
    A. Modulator high-voltage pulse
    Explanation
    The correct answer is Modulator high-voltage pulse. In a transmitter, the high-power oscillator is switched on and off by the modulator high-voltage pulse. This pulse controls the operation of the oscillator, allowing it to produce the desired output pulses.

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  • 7. 

    What radar component permits the use of a single antenna for both transmitting and receiving?

    • A.

      Duplexer

    • B.

      Receiver

    • C.

      Transmitter

    • D.

      Indicator

    Correct Answer
    A. Duplexer
    Explanation
    A duplexer is a radar component that allows the use of a single antenna for both transmitting and receiving signals. It is responsible for separating the incoming and outgoing signals, allowing the radar system to alternate between transmitting and receiving without any interference. This helps to optimize the use of the antenna and conserve space in the radar system.

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  • 8. 

    What are the functions of the antenna on transmit?

    • A.

      Concentrate energy in a predetermined beam shape and to point the beam in a predetermined directions

    • B.

      Form a beam in a particular direction to gather selectively transmitted energy

    • C.

      To concentrate energy in a predetermined beam shape and to point this beam in random directions

    • D.

      To concentrate energy in a random beam shape and to point this beam in a predetermined direction

    Correct Answer
    A. Concentrate energy in a predetermined beam shape and to point the beam in a predetermined directions
    Explanation
    The antenna on transmit functions to concentrate energy in a predetermined beam shape and to point the beam in a predetermined direction. This allows for the selective gathering and transmission of energy in a specific direction, rather than dispersing it randomly.

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  • 9. 

    What are the functions of the antenna on receive?

    • A.

      Forms a beam in a particular direction to gather selectively transmitted energy that has been reflected from various targets Received energy is sent via transmission lines to the receiver

    • B.

      Concentrate energy in a predetermined beam shape and to point the beam in a predetermined directions

    • C.

      To concentrate energy in a predetermined beam shape and to point this beam in random directions

    • D.

      To concentrate energy in a random beam shape and to point this beam in a predetermined direction

    Correct Answer
    A. Forms a beam in a particular direction to gather selectively transmitted energy that has been reflected from various targets Received energy is sent via transmission lines to the receiver
    Explanation
    The antenna on receive functions by forming a beam in a specific direction. This allows it to selectively gather transmitted energy that has been reflected from different targets. The received energy is then sent to the receiver through transmission lines.

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  • 10. 

    What does it mean if an antenna is said to be reciprocal?

    • A.

      The transmit and receive patterns of the antenna are usually identical

    • B.

      The transmit and receive patterns of the antenna are usually similar

    • C.

      The transmit and receive patterns of the antenna are usually different

    • D.

      The transmit and receive patterns of the antenna are always different

    Correct Answer
    A. The transmit and receive patterns of the antenna are usually identical
    Explanation
    Reciprocity in the context of antennas refers to the property where the transmit and receive patterns of the antenna are usually identical. This means that the antenna behaves the same way when transmitting a signal as it does when receiving a signal. In other words, the antenna exhibits the same characteristics and performance regardless of whether it is used for transmitting or receiving signals. This property is important in many applications, such as wireless communication systems, where the antenna needs to be efficient and reliable in both transmitting and receiving signals.

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  • 11. 

    Which pattern is specified and measured for a reciprocal antenna?

    • A.

      Transmit

    • B.

      Transmit and receive

    • C.

      Transmit or receive

    • D.

      Receive

    Correct Answer
    A. Transmit
    Explanation
    A reciprocal antenna is an antenna that has the same radiation pattern for both transmitting and receiving signals. Therefore, the pattern that is specified and measured for a reciprocal antenna is the transmit pattern. This pattern describes how the antenna radiates energy when it is transmitting a signal. By measuring the transmit pattern, engineers can ensure that the antenna is performing optimally and efficiently when transmitting signals.

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  • 12. 

    Why are reflector antennas extremely important and practical devices for use in radar systems?

    • A.

      Because they offer an economical method of distributing energy over a large aperture area and can produce shaped or pencil beams with high gain.

    • B.

      Because they offer an expensive method of distributing energy over a large aperture area and can produce shaped or pencil beams with high gain.

    • C.

      Because they offer an economical method of distributing energy over a small aperture area and can produce shaped or pencil beams with high gain.

    • D.

      Because they offer an economical method of distributing energy over a large aperture area and can produce shaped or pencil beams with very low gain.

    Correct Answer
    A. Because they offer an economical method of distributing energy over a large aperture area and can produce shaped or pencil beams with high gain.
    Explanation
    Reflector antennas are extremely important and practical devices for use in radar systems because they offer an economical method of distributing energy over a large aperture area. This means that they can cover a wide area without requiring excessive energy consumption. Additionally, reflector antennas can produce shaped or pencil beams with high gain, allowing for more precise and focused radar detection. This makes them highly effective in radar systems where accuracy and efficiency are crucial.

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  • 13. 

    What generally does the reflector do with its energy?

    • A.

      Redirects and reshapes it from one or more point sources located near the focal point into a desired far-field pattern

    • B.

      Reshapes it from one or more point sources located near the focal point into a desired narrow pattern

    • C.

      Redirects it from one or more point sources located near the focal point into a desired far-field pattern

    • D.

      Reshapes it from one or more point sources located near the focal point into a desired far-field pattern

    Correct Answer
    A. Redirects and reshapes it from one or more point sources located near the focal point into a desired far-field pattern
    Explanation
    A reflector redirects and reshapes energy from one or more point sources located near the focal point into a desired far-field pattern. This means that the reflector takes the energy emitted from the point sources and manipulates it in such a way that it is directed away from the reflector and into the desired pattern in the far-field. This allows for a controlled and focused distribution of energy in the desired direction.

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  • 14. 

    What is the most common reflector shape?

    • A.

      Paraboloid

    • B.

      Sphere

    • C.

      Oval

    • D.

      Flat

    Correct Answer
    A. Paraboloid
    Explanation
    A paraboloid is the most common reflector shape because it has the ability to focus incoming light or sound waves to a single point known as the focal point. This makes it ideal for applications such as satellite dishes, telescopes, and headlights, where a concentrated beam of light or sound is required. The paraboloid shape allows for efficient reflection and minimal distortion, making it a popular choice in various industries.

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  • 15. 

    How is the paraboloid formed?

    • A.

      By rotating a two-dimensional parabola about its focal axis

    • B.

      By rotating a two-dimensional parabola about its rear axis

    • C.

      By rotating a three-dimensional parabola about its focal axis

    • D.

      By rotating a three-dimensional parabola about its rear axis

    Correct Answer
    A. By rotating a two-dimensional parabola about its focal axis
    Explanation
    The paraboloid is formed by rotating a two-dimensional parabola about its focal axis. When a parabola is rotated around its focal axis, it creates a three-dimensional shape known as a paraboloid. This rotation expands the parabola in the third dimension, creating a curved surface that resembles a bowl or a satellite dish. The focal axis is the line passing through the focus of the parabola and perpendicular to its directrix.

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  • 16. 

    Why is the paraboloid shape useful?

    • A.

      Because all rays leaving the focal point and striking the reflector are reflected along a path parallel to the focal axis

    • B.

      Because all rays leaving the focal point and striking the reflector are reflected along a path perpendicular to the focal axis

    • C.

      Because half the rays leaving the focal point and striking the reflector are reflected along a path parallel to the focal axis

    • D.

      Because half the rays leaving the focal point and striking the reflector are reflected along a path perpendicular to the focal axis

    Correct Answer
    A. Because all rays leaving the focal point and striking the reflector are reflected along a path parallel to the focal axis
    Explanation
    The paraboloid shape is useful because it ensures that all rays leaving the focal point and striking the reflector are reflected along a path parallel to the focal axis. This property allows for the concentration of the reflected rays at a single point, resulting in a focused beam of light or sound. The paraboloid shape is commonly used in applications such as satellite dishes, telescopes, and parabolic microphones, where precise focusing is required.

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  • 17. 

    How is a paraboloid reciprocal?

    • A.

      Because it intercepts an electromagnetic plane wave traveling parallel to its axis and redirects it so that all of the energy passes to the focal point, where it may be collected

    • B.

      Because it avoids an electromagnetic plane wave traveling parallel to its axis and redirects it so that all of the energy passes to the focal point, where it may be collected

    • C.

      Because it intercepts an electromagnetic plane wave traveling perpendicular to its axis and redirects it so that all of the energy passes to the focal point, where it may be collected

    • D.

      Because it intercepts an electromagnetic plane wave traveling perpendicualr to its axis and reflects it so that all of the energy passes to the focal point, where it may be collected

    Correct Answer
    A. Because it intercepts an electromagnetic plane wave traveling parallel to its axis and redirects it so that all of the energy passes to the focal point, where it may be collected
    Explanation
    A paraboloid is reciprocal because it intercepts an electromagnetic plane wave traveling parallel to its axis and redirects it so that all of the energy passes to the focal point, where it may be collected. This means that the paraboloid is able to efficiently capture and focus the energy from the wave, making it a useful shape for applications such as satellite dishes and telescopes.

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  • 18. 

    What happens when you change the physical shape of a feedhorn antenna?

    • A.

      It gives you a fixed change to the radiated beam pattern, but does not give us any way to continuously control or vary the beam pattern

    • B.

      It gives you a dynamic change to the radiated beam pattern, but does not give us any way to continuously control or vary the beam pattern

    • C.

      It gives you a fixed change to the radiated beam pattern, but does give us a way to continuously control or vary the beam pattern

    • D.

      It gives you a dynamic change to the radiated beam pattern, but does give us a way to continuously control or vary the beam pattern

    Correct Answer
    A. It gives you a fixed change to the radiated beam pattern, but does not give us any way to continuously control or vary the beam pattern
    Explanation
    Changing the physical shape of a feedhorn antenna results in a fixed change to the radiated beam pattern. However, it does not provide any means to continuously control or vary the beam pattern. This means that once the shape is changed, the beam pattern remains fixed and cannot be adjusted or modified further.

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  • 19. 

    How can you provide an amount of control over the received beam pattern?

    • A.

      Use two feedhorns

    • B.

      Use one feedhorn

    • C.

      Change the shape of the feedhorns

    • D.

      Don't use feedhorns

    Correct Answer
    A. Use two feedhorns
    Explanation
    Using two feedhorns provides an amount of control over the received beam pattern. By using two feedhorns, the signals can be combined or adjusted in a way that allows for control over the pattern of the received beam. This can be done by adjusting the position, orientation, or phase of the signals from the two feedhorns. By manipulating these factors, the beam pattern can be shaped and controlled to meet specific requirements or objectives.

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  • 20. 

    What is the purpose of the active feedhorn?

    • A.

      It is the normal feedhorn; it is the horn normally used for transmitting and receiving

    • B.

      It is the normal feedhorn; it is the horn normally used for transmitting

    • C.

      It is the normal feedhorn; it is the horn normally used for receiving

    • D.

      It is the passive feedhorn; it is the horn normally receiving

    Correct Answer
    A. It is the normal feedhorn; it is the horn normally used for transmitting and receiving
    Explanation
    The active feedhorn is the normal feedhorn that is used for both transmitting and receiving signals. It is the primary component responsible for capturing and focusing signals in a communication system. By using the active feedhorn, signals can be transmitted from the antenna to the receiver and vice versa. This allows for bidirectional communication and ensures efficient signal transmission and reception.

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  • 21. 

    What is the purpose of the passive feedhorn?

    • A.

      It is used only for receiving; it is gated to the receiver only when the signal received by that horn is desired over the signal from the normal horn

    • B.

      It is used only for transmitting; it is gated to the transmitter only when the signal transmitted by that horn is desired over the signal from the normal horn

    • C.

      It is used only for transmitting; it is gated to the receiver only when the signal received by that horn is desired over the signal from the normal horn

    • D.

      It is used only for receiving; it is gated to the transmitter only when the signal transmitted by that horn is desired over the signal from the normal horn

    Correct Answer
    A. It is used only for receiving; it is gated to the receiver only when the signal received by that horn is desired over the signal from the normal horn
    Explanation
    The purpose of the passive feedhorn is to receive signals. It is only connected to the receiver when the signal received by that horn is preferred over the signal from the normal horn. This means that the passive feedhorn is used to selectively receive specific signals when needed, allowing for better control and optimization of the received signals.

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  • 22. 

    What is an advantage of using MTI?

    • A.

      It reduces clutter

    • B.

      It increases clutter

    • C.

      It increases system sensitivity

    • D.

      It filters out low-level moving clutter

    Correct Answer
    A. It reduces clutter
    Explanation
    MTI stands for Moving Target Indicator, which is a radar technique used to filter out unwanted clutter caused by stationary objects or environmental factors. By using MTI, the clutter is reduced, allowing for a clearer detection of moving targets. This is advantageous as it improves the accuracy and effectiveness of radar systems by eliminating unnecessary information and focusing on relevant moving targets.

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  • 23. 

    What is a disadvantage of using MTI?

    • A.

      It reduces system sensitivity, and cannot do anything about low-level moving clutter, such as birds

    • B.

      It increases system sensitivity, and cannot do anything about low-level moving clutter, such as birds

    • C.

      It reduces system sensitivity, and eliminates low-level moving clutter, such as birds

    • D.

      It increases system sensitivity, and eliminates low-level moving clutter, such as birds

    Correct Answer
    A. It reduces system sensitivity, and cannot do anything about low-level moving clutter, such as birds
    Explanation
    MTI, or Moving Target Indication, is a radar technique used to detect and track moving targets while filtering out stationary clutter. The given answer states that a disadvantage of using MTI is that it reduces system sensitivity, meaning it may not be as effective in detecting weak signals or targets at longer distances. Additionally, it mentions that MTI cannot do anything about low-level moving clutter, such as birds, which can cause false alarms or interfere with target detection.

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  • 24. 

    What could you expect if you’re using the clutter-reducing aspect of the dual-feedhorn system on a mountain range reaching 3 degrees above the horizon?

    • A.

      A significant reduction in the returns from ground targets

    • B.

      A significant increase in the returns from ground targets

    • C.

      A significant reduction in the returns from aerial targets

    • D.

      A significant increase in the returns from aerial targets

    Correct Answer
    A. A significant reduction in the returns from ground targets
    Explanation
    Using the clutter-reducing aspect of the dual-feedhorn system on a mountain range reaching 3 degrees above the horizon would result in a significant reduction in the returns from ground targets. This is because the clutter-reducing aspect of the system helps to filter out unwanted signals and noise from the ground, thereby reducing the returns from ground targets.

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  • 25. 

    What problem in the dual-feedhorn antenna can be eliminated by using a 12-feedhorn antenna?

    • A.

      Multipath reflections

    • B.

      Single path reflections

    • C.

      Multipath deflections

    • D.

      Singlepath deflections

    Correct Answer
    A. Multipath reflections
    Explanation
    Using a 12-feedhorn antenna can eliminate the problem of multipath reflections. Multipath reflections occur when signals bounce off objects and create multiple paths for the signal to reach the antenna. This can cause interference and signal degradation. By using a 12-feedhorn antenna, the signals can be received from multiple directions simultaneously, reducing the chances of multipath reflections and improving the overall signal quality.

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  • 26. 

    How is range gating adjusted in the 12-feedhorn system?

    • A.

      Individually in each of four azimuth quadrants, relative to the north reference.

    • B.

      In pairs in the four azimuth quadrants, relative to the north reference.

    • C.

      Individually in each of four azimuth quadrants, relative to the south reference.

    • D.

      In pairs in the four azimuth quadrants, relative to the south reference.

    Correct Answer
    A. Individually in each of four azimuth quadrants, relative to the north reference.
    Explanation
    The range gating in the 12-feedhorn system is adjusted individually in each of the four azimuth quadrants, relative to the north reference. This means that the range gating is customized and fine-tuned separately for each quadrant, taking into account the north reference as a point of comparison. This allows for precise and accurate range gating adjustments in each quadrant, optimizing the performance and functionality of the system.

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  • 27. 

    What do you call the use of contiguous beams stacked in elevation?

    • A.

      A stacked-beam radar

    • B.

      2D radar

    • C.

      Phased-array radar

    • D.

      Next Generation radar

    Correct Answer
    A. A stacked-beam radar
    Explanation
    A stacked-beam radar refers to the use of contiguous beams stacked in elevation. This technique allows for improved target detection and tracking capabilities by providing a more detailed and accurate picture of the radar environment. By stacking the beams, the radar can cover a larger area and gather more information about the targets within that area. This type of radar is commonly used in applications where high resolution and accuracy are required, such as air traffic control or military surveillance.

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  • 28. 

    Why is stacked-beam a good technique?

    • A.

      Becasue it uses simultaneous pencil-beam radiation patterns from a single aperture to cover the elevation angles of interest

    • B.

      Becasue it uses simultaneous pencil-beam radiation patterns from multiple apertures to cover the elevation angles of interest.

    • C.

      Becasue it uses consecutive pencil-beam radiation patterns from a single aperture to cover the elevation angles of interest.

    • D.

      Becasue it uses consecutive pencil-beam radiation patterns from multiple apertures to cover the elevation angles of interest.

    Correct Answer
    A. Becasue it uses simultaneous pencil-beam radiation patterns from a single aperture to cover the elevation angles of interest
    Explanation
    Stacked-beam is a good technique because it utilizes simultaneous pencil-beam radiation patterns from a single aperture to cover the elevation angles of interest. This means that multiple beams are transmitted simultaneously, allowing for efficient coverage of the desired elevation angles without the need for multiple apertures or consecutive beam transmissions. This technique offers improved performance and flexibility in beamforming for various applications.

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  • 29. 

    What is each beam considered in an array antenna?

    • A.

      A separate radar

    • B.

      A fan

    • C.

      A transmitter

    • D.

      A feedhorn

    Correct Answer
    A. A separate radar
    Explanation
    Each beam in an array antenna is considered as a separate radar because an array antenna consists of multiple individual radiating elements that can be electronically steered to create multiple beams. Each beam can be directed towards a specific target or area of interest, allowing the array antenna to function as multiple radars simultaneously. This enables the array antenna to track multiple targets or gather information from different directions at the same time.

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  • 30. 

    How does the transmitter give the desired elevation coverage?

    • A.

      It radiates a fan beam from the summation of all overlapping pencil beams

    • B.

      It radiates a single beam from the summation of all overlapping pencil beams

    • C.

      It radiates a fan beam from the summation of all pencil beams

    • D.

      It radiates a single beam from the summation of all pencil beams

    Correct Answer
    A. It radiates a fan beam from the summation of all overlapping pencil beams
    Explanation
    The transmitter gives the desired elevation coverage by radiating a fan beam that is formed by adding up all the overlapping pencil beams. This means that multiple pencil beams are combined together to form a wider beam that covers a larger area in the elevation direction.

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  • 31. 

    How many receivers are used for each pencil beam on a stacked beam radar?

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    Correct Answer
    A. 1
    Explanation
    In a stacked beam radar, each pencil beam is directed towards a specific target or area of interest. To receive the reflected signals from these pencil beams, only one receiver is used. This receiver collects the signals from all the pencil beams and processes them to extract relevant information about the targets. Therefore, the correct answer is 1.

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  • 32. 

    How is sidelobe cancellation employed?

    • A.

      Separately in each receiving channel

    • B.

      Separately in each transmitting channel

    • C.

      With automatic detection in each receiving channel

    • D.

      With automatic detection and MTI in each receiving channel

    Correct Answer
    A. Separately in each receiving channel
    Explanation
    Sidelobe cancellation is employed separately in each receiving channel. This means that each receiving channel is individually configured to cancel out the sidelobes, which are unwanted signals that can interfere with the desired signal. By addressing the sidelobes in each channel separately, the system can effectively reduce interference and improve the quality of the received signal. This approach allows for precise control and optimization of sidelobe cancellation in each channel, resulting in better overall performance.

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  • 33. 

    What is a disadvantage of using automatic detection, sidelobe cancellation, or MTI in the radar?

    • A.

      They add to the radar’s cost and complexity

    • B.

      They add to the radar’s cost

    • C.

      They add to the radar’s complexity

    • D.

      They add to the radar’s cost, complexity, and maintenance

    Correct Answer
    A. They add to the radar’s cost and complexity
    Explanation
    Using automatic detection, sidelobe cancellation, or MTI in radar systems can result in increased cost and complexity. These techniques require additional hardware, software, and processing capabilities, which can add to the overall cost of the radar system. Additionally, implementing these features may require more advanced algorithms and signal processing techniques, leading to increased complexity in the design and operation of the radar system. Therefore, the use of automatic detection, sidelobe cancellation, or MTI can have a negative impact on both the cost and complexity of radar systems.

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  • 34. 

    What is an advantage of the individual pencil beams when handling rain clutter or chaff?

    • A.

      It limits the volume of space observed

    • B.

      It limits the volume of space not observed

    • C.

      There's no limit to the volume of space observed

    • D.

      There's no limit to the volume of space not observed

    Correct Answer
    A. It limits the volume of space observed
    Explanation
    The advantage of individual pencil beams when handling rain clutter or chaff is that they limit the volume of space observed. This means that the radar system can focus on specific areas and filter out unwanted signals from rain or chaff, allowing for more accurate detection and tracking of targets.

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  • 35. 

    How does the gain of the individual pencil beams compare to the fan-beam antenna?

    • A.

      They are higher

    • B.

      They are lower

    • C.

      They are equal

    Correct Answer
    A. They are higher
    Explanation
    The gain of the individual pencil beams is higher compared to the fan-beam antenna. This means that the individual pencil beams have a stronger signal strength and can provide better coverage and reception compared to the fan-beam antenna.

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  • 36. 

    What phrase-array ability is an important advantage if the required antenna is large?

    • A.

      Its inherent ability to steer a beam without the necessity of moving a large mechanical structure

    • B.

      Its inherent ability to steer a beam by moving a large mechanical structure

    • C.

      Its inherent ability to steer a beam without the necessity of moving a small mechanical structure

    • D.

      Its inherent ability to steer a beam by moving a small mechanical structure

    Correct Answer
    A. Its inherent ability to steer a beam without the necessity of moving a large mechanical structure
    Explanation
    The correct answer is "Its inherent ability to steer a beam without the necessity of moving a large mechanical structure." This means that the phrase-array ability allows the beam to be directed without the need for physically moving a large antenna. This is advantageous because it reduces the complexity and cost of the system, as well as the potential for mechanical failures.

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  • 37. 

    What are attractive features of the phased-array antenna?

    • A.

      The capability to generate more than one beam with the same array and flexibility in the control of the aperture illumination

    • B.

      The capability to generate more than one beam with the same array

    • C.

      The capability to generate one beam with the same array and flexibility in the control of the aperture illumination

    • D.

      The flexibility in the control of the aperture illumination

    Correct Answer
    A. The capability to generate more than one beam with the same array and flexibility in the control of the aperture illumination
    Explanation
    The attractive features of the phased-array antenna include the capability to generate more than one beam with the same array and flexibility in the control of the aperture illumination. This means that the antenna can produce multiple beams simultaneously, allowing for increased coverage and the ability to track multiple targets. Additionally, the control of the aperture illumination provides flexibility in adjusting the antenna's performance, such as adjusting the beam shape or focusing the beam on a specific target.

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  • 38. 

    Which array is particularly useful in radar applications?

    • A.

      Two-dimensional planar array

    • B.

      Three-dimensional planar array

    • C.

      One-dimensional planar array

    • D.

      Four-dimensional planar array

    Correct Answer
    A. Two-dimensional planar array
    Explanation
    A two-dimensional planar array is particularly useful in radar applications because it allows for both azimuth and elevation scanning. This means that it can detect and track targets in both horizontal and vertical directions, providing a comprehensive view of the radar coverage area. This is important in radar applications where accurate target detection and tracking is crucial, such as in military surveillance or air traffic control systems. The two-dimensional planar array offers enhanced situational awareness and improves the overall effectiveness of the radar system.

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  • 39. 

    How does the two-dimensional planer array work in rectangular form; in circular aperture form?

    • A.

      In a rectangular aperture form, it can generate fan beams; in a circular aperture form, it can generate pencil beams

    • B.

      In a rectangular aperture form, it can generate pencil beams; in a circular aperture form, it can generate pencil beams

    • C.

      In a rectangular aperture form, it can generate fan beams; in a circular aperture form, it can generate fan beams

    • D.

      In a rectangular aperture form, it can generate pencil beams; in a circular aperture form, it can generate fan beams

    Correct Answer
    A. In a rectangular aperture form, it can generate fan beams; in a circular aperture form, it can generate pencil beams
    Explanation
    The correct answer states that in a rectangular aperture form, a two-dimensional planar array can generate fan beams, while in a circular aperture form, it can generate pencil beams.

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  • 40. 

    What kinds of radiators have been used in phased arrays more than others?

    • A.

      The dipole, the open-ended waveguide, and the slotted waveguide

    • B.

      The dipole

    • C.

      The open-ended waveguide

    • D.

      The slotted waveguide

    Correct Answer
    A. The dipole, the open-ended waveguide, and the slotted waveguide
    Explanation
    The dipole, the open-ended waveguide, and the slotted waveguide have been used more than other kinds of radiators in phased arrays.

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  • 41. 

    Which waveguide antenna is more suited for one-dimensional scanning than scanning in two coordinates?

    • A.

      The slot array

    • B.

      The dipole

    • C.

      The open-ended

    Correct Answer
    A. The slot array
    Explanation
    The slot array waveguide antenna is more suited for one-dimensional scanning than scanning in two coordinates. This is because the slot array antenna is designed with multiple slots along the waveguide, allowing it to radiate and receive signals in a single direction. In contrast, the dipole antenna radiates and receives signals in all directions, making it more suitable for omnidirectional scanning. The open-ended waveguide antenna also radiates in a wide pattern, making it less suitable for precise one-dimensional scanning.

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  • 42. 

    Give four reasons why it is important that minor lobes of radar antennas be small compared to the main lobe.

    • A.

      (1) Have an antenna with high directivity. (2) Reduce the susceptibility of the antenna to interfering signals.(3) Reduce the possibility of detecting a target in a minor lobe. (4) Reduce the probability of interference with other nearby systems.

    • B.

      (1) Have an antenna with low directivity. (2) Reduce the susceptibility of the antenna to interfering signals.(3) Reduce the possibility of detecting a target in a minor lobe. (4) Reduce the probability of interference with other nearby systems.

    • C.

      (1) Have an antenna with high directivity. (2) Reduce the susceptibility of the antenna to interfering signals. (3)Reduce the possibility of detecting a target in a major lobe. (4) Reduce the probability of interference with other nearby systems.

    • D.

      (1) Have an antenna with low directivity. (2) Reduce the susceptibility of the antenna to interfering signals.(3) Reduce the possibility of detecting a target in a major lobe. (4) Reduce the probability of interference with other nearby systems.

    Correct Answer
    A. (1) Have an antenna with high directivity. (2) Reduce the susceptibility of the antenna to interfering signals.(3) Reduce the possibility of detecting a target in a minor lobe. (4) Reduce the probability of interference with other nearby systems.
    Explanation
    It is important for the minor lobes of radar antennas to be small compared to the main lobe for several reasons. Firstly, having an antenna with high directivity allows for more accurate and focused signal transmission and reception. Secondly, reducing the susceptibility of the antenna to interfering signals improves the overall performance and reliability of the radar system. Thirdly, by reducing the possibility of detecting a target in a minor lobe, false alarms and unnecessary data processing can be minimized. Lastly, minimizing the probability of interference with other nearby systems ensures that the radar system operates efficiently without causing disruptions to other communication systems.

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  • 43. 

    What do we call the fictitious surface located on or near an antenna?

    • A.

      The antenna aperture

    • B.

      The antenna reflector

    • C.

      The antenna surface

    • D.

      The antenna conical

    Correct Answer
    A. The antenna aperture
    Explanation
    The fictitious surface located on or near an antenna is called the antenna aperture. The antenna aperture refers to the opening or area through which the electromagnetic waves pass. It is an important component of the antenna system as it determines the amount of energy that can be received or transmitted. By controlling the size and shape of the aperture, the antenna's performance can be optimized for specific frequencies and applications.

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  • 44. 

    How is the fictitious surface used?

    • A.

      It is often useful in computing the performance of the antenna

    • B.

      It is often useful in calibrating the antenna

    • C.

      It is often useful in computing the transmitting frequency of the antenna.

    • D.

      It is often useful in calibrating the transmitting frequency of the antenna

    Correct Answer
    A. It is often useful in computing the performance of the antenna
    Explanation
    The fictitious surface is often used in computing the performance of the antenna. This means that it helps in determining how well the antenna is functioning and how efficiently it is transmitting and receiving signals. By analyzing the performance of the antenna, engineers can make adjustments and improvements to optimize its effectiveness.

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  • 45. 

    How is the pattern of the antenna determined?

    • A.

      The distribution of electromagnetic energy from the antenna over the aperture determines the pattern of the antenna

    • B.

      The distribution of electromagnetic energy from the antenna over the conical surface determines the pattern of the antenna

    • C.

      The distribution of electromagnetic energy from the antenna over the feedhorn determines the pattern of the antenna

    • D.

      The distribution of electromagnetic energy from the feedhorn over the aperture determines the pattern of the antenna

    Correct Answer
    A. The distribution of electromagnetic energy from the antenna over the aperture determines the pattern of the antenna
    Explanation
    The pattern of the antenna is determined by the distribution of electromagnetic energy from the antenna over the aperture. The aperture is the opening through which the electromagnetic waves pass, and the distribution of energy across this aperture affects how the waves propagate and interact with the environment. Therefore, the distribution of energy over the aperture directly influences the pattern of the antenna.

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  • 46. 

    How can the antenna designer modify the shape of the pattern?

    • A.

      By altering the distribution of energy over the aperture

    • B.

      By altering the distribution of energy from the feedhorn

    • C.

      By altering the distribution of energy over the conical surface

    • D.

      By altering the distribution of energy over time

    Correct Answer
    A. By altering the distribution of energy over the aperture
    Explanation
    The shape of the pattern can be modified by altering the distribution of energy over the aperture. The aperture refers to the opening through which the energy passes. By changing how the energy is distributed across this opening, the antenna designer can change the shape of the pattern that is emitted or received by the antenna. This can be done by adjusting the size, shape, or arrangement of the elements within the aperture, or by using techniques such as beamforming to control the directionality of the energy distribution.

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  • 47. 

    What are the three primary performance parameters for an antenna?

    • A.

      Gain, beamwidth, and sidelobe level

    • B.

      Gain, beamwidth, and frontlobe level

    • C.

      Gain, beam strength, and sidelobe level

    • D.

      Beamwidth, sidelobe level, and pattern

    Correct Answer
    A. Gain, beamwidth, and sidelobe level
    Explanation
    The three primary performance parameters for an antenna are gain, beamwidth, and sidelobe level. Gain refers to the ability of the antenna to direct or focus its energy in a particular direction. Beamwidth is the angular width of the main lobe of the antenna's radiation pattern, indicating the coverage area. Sidelobe level refers to the level of radiation outside the main lobe, which should ideally be minimized to avoid interference. Therefore, the correct answer is gain, beamwidth, and sidelobe level.

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  • 48. 

    Name two basic functions of the radar antenna

    • A.

      (1) To efficiently launch and receive electromagnetic energy into the atmosphere or space. (2) To direct the energy into an appropriately shaped beam.

    • B.

      (1) To efficiently receive electromagnetic energy into the atmosphere or space. (2) To direct the energy into an appropriately shaped beam.

    • C.

      (1) To efficiently launch electromagnetic energy into the atmosphere or space. (2) To direct the energy into an appropriately shaped beam.

    • D.

      (1) To efficiently launch and receive electromagnetic energy into the atmosphere or space. (2) To receive energy from an appropriately shaped beam.

    Correct Answer
    A. (1) To efficiently launch and receive electromagnetic energy into the atmosphere or space. (2) To direct the energy into an appropriately shaped beam.
    Explanation
    The radar antenna has two basic functions. The first function is to efficiently launch and receive electromagnetic energy into the atmosphere or space. This means that the antenna is responsible for transmitting and receiving the radar signals. The second function is to direct the energy into an appropriately shaped beam. This means that the antenna is responsible for shaping the radar beam so that it can accurately detect and track targets.

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  • 49. 

    What determines the shape of the beam of radar energy and its antenna pattern?

    • A.

      The purpose of the radar

    • B.

      The shape of the radar

    • C.

      The shape of the aperture

    • D.

      The purpose of the aperture

    Correct Answer
    A. The purpose of the radar
    Explanation
    The purpose of the radar determines the shape of the beam of radar energy and its antenna pattern. Different radar systems have different purposes, such as long-range surveillance or short-range target tracking. The shape of the beam and antenna pattern is designed to optimize the radar's performance for its specific purpose. For example, a radar used for long-range surveillance may have a narrow beam and a focused antenna pattern to achieve a longer detection range, while a radar used for short-range tracking may have a wider beam and a broader antenna pattern for better coverage in close proximity.

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  • 50. 

    In the search radar what do we need to measure?

    • A.

      Range and azimuth but not height

    • B.

      Range, azimuth, and height

    • C.

      Range and height

    • D.

      Azimuth and height

    Correct Answer
    A. Range and azimuth but not height
    Explanation
    In a search radar, the two main parameters that need to be measured are range and azimuth. Range refers to the distance between the radar and the target, while azimuth is the angle between the target and a reference point. However, height is not typically measured in a search radar as it is not necessary for detecting and tracking targets. Therefore, the correct answer is "Range and azimuth but not height."

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