Allt

Question 1

What is the typical fractional bandwidth and gain of a resonant dipole antenna?

Answer 1

FBW: 15%
Gain: 2,2 dB

Question 2

What happens to the frequency and fractional bandwidth as we increase the length of the dipole antenna?

Answer 2

f: decreases
FBW: roughly stays the same

Question 3

What is the relationship between directivity and gain?

Answer 3

Gain includes losses; G = e*D

Question 4

What are the main disadvantages of patch antennas?

Answer 4

Narrow bandwidth
Limited efficiency (cancelation)

Question 5

List the main advantages of patch antennas

Answer 5

Easy and cheap to manufacture
Low profile (height)
Somewhat directive
Not very sensitive, for example when put on body

Question 6

What is the impedance at the edge of a patch antenna?

Answer 6

Very high

Question 7

What is the impedance at the center of a patch antenna?

Answer 7

Near 0

Question 8

Describe 4 methods of achieving circular polarisation for patch antennas

Answer 8

Rotate 90 degrees and feed from two edges with a delay
Feed along diagonal
Cut a slot (rectangle) tilted 45 degrees in the patch
Cut off two perpendicular edges and have one feedpoint

Question 9

Describe two benefits of using antenna arrays

Answer 9

Increase gain
Adjust phase (steer beam)

Question 10

Name three applicants for antenna arrays

Answer 10

Base stations
Radar (space, plane, detecting)
5G

Question 11

Discuss the factors that dictate whether a radar system should operate at high or low frequencies

Answer 11

Long distance -> Low freq
Available space
Better resolution -> Higher freq
Avoid absorbance
Avoid other freqs

Question 12

What is σ?

Answer 12

Conductivity (or Radar cross section)

Question 13

What is ε?

Answer 13

Permittivity

Question 14

What is µ?

Answer 14

Permeability