Transmission Lines Flashcards
Define Susceptance
How easy it is for alternating current to pass through a capacitance or an inductance.
What is a Balance Line?
Signals are 180 degrees out of phase.
What is an Unbalanced Line?
One conductor carries a data signal and another carries a reference signal.
Is Coaxial cable balanced or unbalanced?
Unbalanced -> the shield carries the reference
Is Unshielded Twisted Pair a balnced or unblanced transmission line?
Balanced.
What does the dielectric do in a Coaxial Cable?
Separates the Inner and Outer Conductor.
It is a source of attenuation.
Maximum power is limited by the breakdown voltage of the dielectric.
Thumb
Pointer
Middle
Magnetic Field
Electric Field
Poynting
Transmission Line: “Two conductors kept at constant distance by a low-loss dielectric”
Twin Lead
List an advantage and disadvantage or Twin Lead transmission Lines
Pro: Simple Construction
Disadvantage: Vulnerable to interference
Transmission Line: “Two insulated wires twisted together to form a flexible line without the use of spacers.”
Twisted Pair
Transmission Line:
Power Lines
How are frequency and attentuation related?
Proportional.
What are the three mechanims of loss in a transmission line?
Radiation
Dielectric Heating
Conductor Heating
“Transmission lines can behave as an antenna if conductor separation is close to Lamda/2. Losses increase with frequency and ususally set the upper limit of frequency for which a line can be used.”
Radiation Loss
“Proportional to the voltage across the dielectric material. It increases with the frequency for solid dielectrics. For air this loss is negligible.”
Dielectric Heating Loss
“The non-uniform density of alternating current through a conductor causes this effect. Direct current uses the entire cross sectional area equally but AC will tend to flow through the outer areas of the conductor rather than through the middle. This effectively increases the resistnac eof the conductor.”
Skin Effect
“The region towards the surface of the conductor that ocntains 63% of the current.”
Skin Depth
“The degree of signal power relfectino back towards the source due to impedence mismatch”
Quantitatively, it is a complex number that describes the change in magnitude and phase shift when a voltage is reflected.
Reflection Coefficient
What does active and passive load mean wrt to Reflection Coefficient?
Passive load: Does not generate power -> reflected voltage will be less than the incident voltage.
Active Load: Load connected to external power -> refleected voltage greater than incidident voltage.
VSWR
The ratio between transmitted and reflected voltage standing waves.
Voltage Standing Wave Ratio
Impedence of the transmission line
Characteristic Impedence
What VSWR is an ideal case?
1
What is the VSWR of a short circuit?
Infinity
What is the VSWR of an Open Circuit?
Infinity
