Lab Fundamentals - Antenna Arrays
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Questions and Answers

What is a primary purpose of a link budget in wireless communications systems?

  • To predict how received power will change based on gain or loss factors (correct)
  • To define the frequency of operation for the system
  • To estimate the physical size of the antennas used
  • To measure the actual power output of the transmitter only
  • Which component is NOT explicitly listed as part of the TMYTEK 5G mmWave Developer Kit for measurement in the lab?

  • Cable#4
  • Power splitter, Left side
  • Power combiner, Right side
  • Antenna array (correct)
  • Why is it beneficial to measure the gains or losses associated with components in a wireless communication system?

  • To determine the overall aesthetic of the components used
  • To maximize the potential environmental impact of the system
  • To create a visual layout of the system's internal wiring
  • To ensure optimal performance and predict system changes (correct)
  • What component would you measure the gain or loss from during lab T1?

    <p>Each of the specified cables and splitters in the kit (D)</p> Signup and view all the answers

    What could a designer use the link budget to predict if a component fails?

    <p>How received power will change in response to the failure (C)</p> Signup and view all the answers

    What does measuring the gains or losses in a wireless communications system allow designers to do?

    <p>Evaluate trade-offs between different system components (A)</p> Signup and view all the answers

    During lab exercises, which combination of components would likely be evaluated for their effects on the link budget?

    <p>Power splitters and combiners (A)</p> Signup and view all the answers

    What role do power splitters play in the context of the lab assignment?

    <p>They distribute power among multiple paths, affecting the link budget (D)</p> Signup and view all the answers

    What is one method for changing the phase difference between two signals with the same amplitude and phase?

    <p>Inserting a transmission line of specified physical length (B)</p> Signup and view all the answers

    What is the primary purpose of phase calibration in the lab?

    <p>To achieve constructive or destructive interference (B)</p> Signup and view all the answers

    Which aspect makes bench tests more reliable than over-the-air tests?

    <p>Less interference from environmental factors (B)</p> Signup and view all the answers

    What is typically a drawback of conducting tests over the air compared to on the bench?

    <p>Random signal reflections causing distortions (B)</p> Signup and view all the answers

    Which device is involved in introducing discrete phase shifts in response to digital control signals?

    <p>Digital phase shifter (B)</p> Signup and view all the answers

    Why are most wireless communication system tests performed on the bench?

    <p>It limits signal reflection issues (C)</p> Signup and view all the answers

    What is a common purpose of inserting both digital and analog phase shifters?

    <p>To vary the phase difference of signals (B)</p> Signup and view all the answers

    What is a key feature of the TMYTEK antenna test fixture mentioned in T5?

    <p>It integrates a software interface for phase setting (B)</p> Signup and view all the answers

    What is one reason to measure the losses or gains in a wireless communications system component?

    <p>To confirm the component is functioning correctly (A)</p> Signup and view all the answers

    What does EIRP stand for?

    <p>Effective Isotropic Radiated Power (C)</p> Signup and view all the answers

    What can happen if loss or gain values are inaccurately reported?

    <p>Predictions of received power may be poor (B)</p> Signup and view all the answers

    What does the link margin indicate in a wireless communication system?

    <p>The difference between actual and minimum received power (C)</p> Signup and view all the answers

    What range of losses is typical for an RF connector at 28 GHz?

    <p>0.25 to 0.5 dB (C)</p> Signup and view all the answers

    What is receiver sensitivity?

    <p>The minimum received power needed for acceptable performance (B)</p> Signup and view all the answers

    What is the typical loss introduced by a short piece of coaxial cable at 28 GHz?

    <p>4.5 to 5.0 dB (D)</p> Signup and view all the answers

    What might the 'fade margin' refer to in a wireless communication context?

    <p>The amount of signal that can be lost before performance is affected (B)</p> Signup and view all the answers

    Why must high-gain antennas be automatically steered in mobile communications?

    <p>Narrow beamwidths require precise direction to maintain link quality. (B)</p> Signup and view all the answers

    What principle do phased arrays utilize to create different antenna patterns?

    <p>Constructive and destructive interference between signals. (B)</p> Signup and view all the answers

    What is a major disadvantage of measuring an antenna pattern at regular intervals?

    <p>It may lead to inaccurate measurements of peaks and nulls. (D)</p> Signup and view all the answers

    What is a compact and less expensive alternative to mechanical beam steering?

    <p>Implementing electronic amplitude and phase shifting. (D)</p> Signup and view all the answers

    Which of the following factors is crucial for phased arrays to function correctly?

    <p>Identical elements with uniform spacing. (D)</p> Signup and view all the answers

    What happens if antenna pattern measurements are taken at wider angular intervals?

    <p>The precise locations of peaks and nulls may be missed. (A)</p> Signup and view all the answers

    Which of the following best describes the effect of wavelength ( $\lambda$ ) in millimetre-wave bands on antenna design?

    <p>Smaller wavelengths necessitate high-gain antennas for effectiveness. (B)</p> Signup and view all the answers

    What is a potential improvement over traditional angle interval measurement methods?

    <p>Performing measurements based on peak detection. (A)</p> Signup and view all the answers

    Flashcards

    Link Budget Purpose

    A link budget predicts how received power changes if system gain/loss factors change.

    Link Budget Components

    A link budget accounts for all gain or loss sources between a transmitter and receiver.

    Component Gain/Loss Measurement

    Measuring the gain or loss of each component in a wireless system is beneficial for predicting signal strength.

    TMYTEK 5G mmWave Developer Kit

    A device used to experiment with 5G millimeter-wave phased arrays in communications.

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    RF/Microwave Measurement

    Measuring radio frequency and microwave signals and components.

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    Lab Memos

    Written reports documenting lab experiments, including results and procedures for projects like Link Budget

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    Lab Quiz

    Test in class to assess understanding of specific knowledge gained during a lab session.

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    Component Characterization

    Measuring the properties (like gain or loss) of a component in an electronic device

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    RF Connector Loss

    The decrease in signal strength when an RF connector is used in a wireless system, typically between 0.25 and 0.5 dB at 28 GHz.

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    Coaxial Cable Loss

    The decrease in signal strength when using a short piece of coaxial cable in a wireless system, typically between 4.5 and 5.0 dB at 28 GHz.

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    EIRP

    Effective Isotropic Radiated Power. Represents the total power radiated by an antenna in all directions, as if it were an ideal isotropic antenna.

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    Link Margin

    The difference between the received signal strength and the minimum signal strength needed for reliable communication.

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    Receiver Sensitivity

    The minimum signal strength required for a receiver to function correctly, either in terms of signal-to-noise ratio (analog) or bit error rate (digital).

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    Channel Gain Adjustment

    The process of fine-tuning the amplification of each RF channel in a multi-channel wireless system.

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    Channel Gain Difference

    The variation in signal strength between different channels in a multi-channel wireless system.

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    Constructive/Destructive Interference

    When signals from multiple sources combine, they can either reinforce (constructive) or cancel out (destructive) each other.

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    Signal Cancellation

    When two signals with the same amplitude and frequency are combined, they can cancel each other out if they are out of phase.

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    Phase Difference

    The difference in the starting point of two waves with the same frequency, measured in degrees or radians.

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    Methods for Changing Phase

    Techniques to alter the timing of a signal, affecting its phase relative to another signal.

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    Phase Calibration

    Adjusting the phase of a signal to achieve desired interference patterns (e.g., constructive or destructive).

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    Constructive Interference

    When waves combine in phase, their amplitudes add up, resulting in a larger amplitude.

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    Destructive Interference

    When waves combine out of phase, their amplitudes cancel out, resulting in a smaller amplitude.

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    OTA (Over-the-Air) Link

    A wireless communication link where signals travel through the air, as opposed to cables.

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    Bench (Conduction) Testing

    Testing electronic components or systems using cables to connect them, as opposed to OTA testing.

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    Beamforming in mmWave

    Directing the focus of a millimetre-wave antenna array to specific locations, usually done electronically for efficiency and flexibility.

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    Phased Array Advantage

    Phased arrays use constructive and destructive interference to create narrow, directional beams, allowing for efficient signal transmission and reception.

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    Why is Beamforming Needed in mmWave?

    Millimetre waves are short and require high-gain antennas to make up for signal loss. These antennas have narrow beams, needing steering for communication.

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    Beamforming vs. Mechanical Steering

    Electronic beamforming uses phase adjustments to control the beam direction, whereas mechanical steering involves physically moving the antenna.

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    Measuring Beam Patterns: Problems with Regular Intervals

    Measuring at regular intervals can miss the exact peaks and nulls of the beam pattern, leading to inaccurate results.

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    Better Alternative to Regular Intervals

    Instead of fixed intervals, a 'beam scanning' method allows for precise measurement of antenna pattern details.

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    TMYTEK Antenna Test Fixture

    A specialized device used for measuring antenna patterns in mmWave applications, including a swing arm, ruler, protractor, and software for phase control.

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    Phase Step in Adjacent Channels

    Adjusting the phase difference between signals from adjacent antenna elements to control the direction of the beam.

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    Study Notes

    Lab Fundamentals - Antenna Arrays

    • Students completed two lab sets using Keysight and TMY Technologies for RF/microwave and 5G mmWave phased array measurements.
    • Lab memos demonstrate lab completion and results.
    • Lab quizzes assess student understanding of specific knowledge.
    • A question bank is provided for TMYTEK lab review.
    • Objectives include understanding practical gain/loss measurements in systems.
    • Conduct experiments to characterize components of the TMYTEK 5G mmWave Developer Kit (PLO + Attenuator, Cable#1, Cable#2).

    Lab T2 - What is the Channel Gain?

    • Objectives include familiarization with techniques for adjusting gains and measuring the gain differences between RF channels.
    • Conduct experiments to determine the gain difference between channel pairs.

    Lab T3 - Constructive/Destructive Interference in Conduction

    • Students learn how to adjust and measure RF channel phases.
    • Determine signal cancellation between different channel pairs.
    • Conduct experiments for phase step comparison and plot results.

    Lab T4 - Constructive/Destructive Interference in Radiation

    • Redo Lab T3 using an OTA (over-the-air) link.
    • Compare results of over-the-air testing to bench-top results.
    • Explore why most communication systems test in a controlled environment vs. in open air .

    Lab T5 - How is the Beam Steered?

    • Students learn about the TMYTEK test fixture with swing arm, ruler, and protractor.
    • Learn to set the phase step of channels for antenna array beam steering.

    Lab T6 - How is the Beam Pattern Measured?

    • Students use the TMYTEK antenna test fixture.
    • Learn to measure the pattern of the mmWave antenna array.
    • Avoid using large steps to measure the antenna pattern.
    • Explore adaptive sampling techniques when measuring an antenna pattern.

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    Description

    This quiz covers the key concepts and experiments related to antenna arrays and RF/microwave measurements through lab sets using Keysight and TMY Technologies. Students will explore various topics such as link budgets, channel gains, and interference phenomena. Successful completion of lab memos and quizzes will demonstrate understanding of these advanced topics in the context of 5G technologies.

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