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Questions and Answers
What is the primary function of a transmission line?
What is the primary function of a transmission line?
- To encode messages for transmission
- To transfer electrical energy from one point to another (correct)
- To convert satellite signals into electrical signals
- To amplify signals before transmission
Which type of transmission line consists of two conductors with equal impedances?
Which type of transmission line consists of two conductors with equal impedances?
- Microstrip Line
- Unbalanced Line
- Balanced Line (correct)
- Coaxial Cable
Which is NOT a characteristic of an unbalanced transmission line?
Which is NOT a characteristic of an unbalanced transmission line?
- Uses two conductors of the same type (correct)
- Typically involves a grounded conductor
- Has unequal impedances to ground
- Signal travels through a separate signal line
What does 'electrical length' refer to in the context of transmission lines?
What does 'electrical length' refer to in the context of transmission lines?
What is a balun used for in transmission lines?
What is a balun used for in transmission lines?
Which type of transmission line is known for utilizing two concentric conductors?
Which type of transmission line is known for utilizing two concentric conductors?
What distinguishes guided mediums from unguided mediums?
What distinguishes guided mediums from unguided mediums?
What is the main benefit of using a microstrip line?
What is the main benefit of using a microstrip line?
What is the role of primary line constants in a transmission line?
What is the role of primary line constants in a transmission line?
What is characteristic impedance in the context of transmission lines?
What is characteristic impedance in the context of transmission lines?
How is the propagation constant represented mathematically?
How is the propagation constant represented mathematically?
What defines a transverse electromagnetic (TEM) wave?
What defines a transverse electromagnetic (TEM) wave?
What happens if a transmission line is not terminated with a load equal to its characteristic impedance?
What happens if a transmission line is not terminated with a load equal to its characteristic impedance?
What does the velocity factor measure in a transmission line?
What does the velocity factor measure in a transmission line?
Which primary line constant represents the ability to conduct electricity along the line?
Which primary line constant represents the ability to conduct electricity along the line?
What does the attenuation in a transmission line refer to?
What does the attenuation in a transmission line refer to?
What does the reflection coefficient ($Γ$) represent?
What does the reflection coefficient ($Γ$) represent?
What is defined as the ratio of the maximum voltage to the minimum voltage in a transmission line?
What is defined as the ratio of the maximum voltage to the minimum voltage in a transmission line?
Which component is used to match a purely resistive load to a transmission line?
Which component is used to match a purely resistive load to a transmission line?
What does the formula $Γ= Z_L-Z_o/Z_L+Z_o$ calculate?
What does the formula $Γ= Z_L-Z_o/Z_L+Z_o$ calculate?
How do standing waves form in a transmission line?
How do standing waves form in a transmission line?
What is the primary function of a Stub Chart in transmission line applications?
What is the primary function of a Stub Chart in transmission line applications?
Which statement correctly describes an open transmission line?
Which statement correctly describes an open transmission line?
Which instrument is specifically used for time-domain reflectometry?
Which instrument is specifically used for time-domain reflectometry?
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Study Notes
Transmission Media
- Transmission media refers to the physical path that carries the signal.
- Unguided Medium: no physical media, such as radio waves, light waves, and microwaves.
- Guided Medium: requires a physical path for signal transmission.
- Examples include twisted pair, coaxial cable, and fiber optic cable.
Transmission Lines
- Metallic conductor system for electrical energy transfer.
- Types:
- Coaxial cable: two concentric conductors, excellent shielding against external interference.
- Parallel-wire transmission line: two conducting wires separated by dielectric.
- Microstrip line: conductor on a dielectric substrate.
Transmission Line Characteristics
- Physical Length: actual length of the line.
- Electrical Length: length based on the fraction of its wavelength.
Transmission Line Types
- Balanced (differential): two conductors with equal impedances to ground.
- Unbalanced (single ended): conductors have unequal impedances to ground.
- Balun: device to connect balanced line to unbalanced load.
Transmission Line Equivalent Circuit
- Primary Line Constants: physical and electrical properties that characterize the transmission line.
- Resistance (R), Inductance (L), Conductance (G), Capacitance (C).
- Secondary Line Constants: derived from primary line constants.
- Characteristic Impedance (Z₀): impedance of an infinitely long line; for maximum power transfer, the load impedance should be matched to the characteristic impedance.
- Propagation Constant (γ): represents attenuation and phase shift per unit length of a transmission line.
- γ = α + jβ, where α is attenuation constant and β is phase constant.
Transverse Electromagnetic (TEM) Wave
- Oscillatory disturbance composed of electric (E) and magnetic (H) fields perpendicular to each other and to the direction of propagation.
Velocity of Propagation
- Speed of the TEM wave propagating in a transmission line.
- Always less than the speed of light in free space.
Velocity Factor
- Ratio of actual velocity of propagation in a medium to the velocity in free space.
Reflections
- Occur when load impedance does not match the characteristic impedance.
- Incident wave (E⁺): travel from source to load.
- Reflected wave (E⁻): travel from load to source.
Reflection Coefficient (Γ)
- Ratio of reflected voltage to incident voltage.
- Γ = E⁻/E⁺ = (Z_L - Z₀)/(Z_L + Z₀).
Standing Waves
- Interference pattern created by incident and reflected waves.
Standing Wave Ratio (SWR)
- Ratio of maximum voltage to minimum voltage.
- SWR=Vmax/Vmin.
Impedance of a Section of Transmission Line
- Z = Z₀(Z_L+jZ₀tan(βl))/(Z₀+jZ_Ltan(βl)) (general formula)
- Impedance Inversion: impedance inverts every quarter-wave section.
Transmission Line Instruments
- Stub Chart: short section of transmission line used for impedance matching.
- Quarter-Wave Transformer: uses a quarter-wave section to match resistive load to transmission line.
- Smith Chart: graphical tool for transmission line calculations.
- Optical Time Domain Reflectometer (OTDR): device for measuring transmission line impairments.
- Slotted Line: section of line with a slot for measuring wavelength and standing wave ratio.
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