Transmission Lines

Question 1

Define Susceptance

Answer 1

How easy it is for alternating current to pass through a capacitance or an inductance.

Question 2

What is a Balance Line?

Answer 2

Signals are 180 degrees out of phase.

Question 3

What is an Unbalanced Line?

Answer 3

One conductor carries a data signal and another carries a reference signal.

Question 4

Is Coaxial cable balanced or unbalanced?

Answer 4

Unbalanced -> the shield carries the reference

Question 5

Is Unshielded Twisted Pair a balnced or unblanced transmission line?

Answer 5

Balanced.

Question 6

Answer 6

Question 7

What does the dielectric do in a Coaxial Cable?

Answer 7

Separates the Inner and Outer Conductor.

It is a source of attenuation.

Maximum power is limited by the breakdown voltage of the dielectric.

Question 8

Thumb
Pointer
Middle

Answer 8

Magnetic Field
Electric Field
Poynting

Question 9

Transmission Line: “Two conductors kept at constant distance by a low-loss dielectric”

Answer 9

Twin Lead

Question 10

List an advantage and disadvantage or Twin Lead transmission Lines

Answer 10

Pro: Simple Construction
Disadvantage: Vulnerable to interference

Question 11

Transmission Line: “Two insulated wires twisted together to form a flexible line without the use of spacers.”

Answer 11

Twisted Pair

Question 12

Transmission Line:

Answer 12

Power Lines

Question 13

How are frequency and attentuation related?

Answer 13

Proportional.

Question 14

What are the three mechanims of loss in a transmission line?

Answer 14

Radiation
Dielectric Heating
Conductor Heating

Question 15

“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.”

Answer 15

Radiation Loss

Question 16

“Proportional to the voltage across the dielectric material. It increases with the frequency for solid dielectrics. For air this loss is negligible.”

Answer 16

Dielectric Heating Loss

Question 17

“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.”

Answer 17

Skin Effect

Question 18

“The region towards the surface of the conductor that ocntains 63% of the current.”

Answer 18

Skin Depth

Question 19

“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.

Answer 19

Reflection Coefficient

Question 20

What does active and passive load mean wrt to Reflection Coefficient?

Answer 20

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.

Question 21

VSWR

Answer 21

The ratio between transmitted and reflected voltage standing waves.

Voltage Standing Wave Ratio

Question 22

Impedence of the transmission line

Answer 22

Characteristic Impedence

Question 23

What VSWR is an ideal case?

Answer 23

1

Question 24

What is the VSWR of a short circuit?

Answer 24

Infinity

Question 25

What is the VSWR of an Open Circuit?

Answer 25

Infinity