EXPERIMENT 4 – ANTENNA ARRAYS

Question 1
Does the dipole radiate equally in all directions? ______________________________________.
Where is the concentration of radiation? ______________________________________________.
Question 2

What is the maximum gain of the dipole, in dB? _______________________________________.

How does your dipole gain compare with the theoretical value? ________________________
______________________________________________________________________________
Question 4

What is the percentage difference? _________________________________________.

What is the equivalent gain as a ratio to 2.15dB? ______________________________.

What is the aperture of a dipole (in square meters) at 1500MHz? _________________.

What is the minimum range distance for a dipole at 1500MHz? __________________.

Is the range distance that we are using greater than this minimum? ____________________.

Explain the reason why the separation between the transmitter and the receiver must be greater than
the minimum. ____________________________________________________________
________________________________________________________________________

Question 9

How does the VSWR vary with frequency (see right-hand-side-scale)? __________________
_____________________________________________________________________________________

Question 10

How does the VSWR vary with frequency, now? ________________________________________

Transmission Media and Antenna Systems Laboratory

With an open or a short circuit load, is the VSWR high, or low? ___________________________

Question 12

How does the VSWR vary with frequency, now? ________________________________________

Question 13

With a 50Ω load, is the VSWR high, or low? _____________________________________________

Question 14

Does the VSWR change abruptly or gradually with frequency about this minimum? ______

Question 15

Over what range of frequencies is t he VSWR below 2:1 about this minimum? ____________
_____________________________________________________________________________________

Question 16

What is the approximate equivalent return loss, in dB, to a VSWR of 2:1? _________________

Question 17

Has the polar pattern changed by adding the second element? ________________________

Describe the plot _____________________________________________________________________

Question 18

Has the gain changed by adding the second element? ________________________________

Question 19

Has the directivity changed by adding the second element? ___________________________

Question 20

What changes has the alteration in spacing made to the gain and directivity?
____________________________________________________________________________________.

Question 21

What changes has the alteration in length made to the gain and directivity?
_____________________________________________________________________________________

Transmission Media and Antenna Systems Laboratory

Describe the significant change in the radiation pattern /plot when the length of the dipole was
reduced. ________________________________________________________________
_____________________________________________________________________________________

Question 23

How do these theoretical, simulated plots compare with the ‘real’ plots obtained from Part B?
______________________________________________________________________________.

Give your observation ________________________________________________________________

Question 24

Give the significant difference between the two plots? ______________________.

Question 25

Give the significant difference between the plots, now? _____________________.

Question 26

Is there any significant difference between the two plots? ______________________________.

Question 27

How does the new plot compare with the previous two? _______________________.

Question 28

How do the gains and directives compare? ___________________________________________.

Question 29

Does the driven element – reflector spacing have much effect on the gain or directivity of the
antenna? ________________________________________________________________________.

Question 30

Between which frequencies is the VSWR 2:1, or less, for the 2.5cm reflector spacing?
____________________________________________________________________________________.

Question 31

Between which frequencies is the VSWR 2:1, or less, for the 5cm reflector spacing?
____________________________________________________________________________________.

Transmission Media and Antenna Systems Laboratory

Does the narrow or the wide spacing give the greater VSWR bandwidth? _______________.

Complete the given table below

Sketch the azimuth plot using the available polar graph sheet.

Transmission Media and Antenna Systems Laboratory

Do the software plots agree, give you observation _____________________________________.

Question 34

How do the gains and directives compare? ___________________________________________.

Question 35

Are the plots as directive in the elevation plane? ______________________________________.

Question 36

Does the log periodic antenna have gain over the dipole at 1500MHz? _________________.

Describe the plot _____________________________________________________________________

Question 37

Does the log periodic antenna have directivity at 1500MHz? ___________________________.

Question 38

Does the log periodic antenna have gain over this range of frequencies? _______________.
Record the difference ________________________________________________________________.

Question 39

Does the log periodic antenna have directivity at over this range of frequencies? _______.

Question 40

What happens to the gain of the log periodic antenna over this range of frequencies?
____________________________________________________________________________________.

Question 41

Does the log periodic antenna still have directivity at over this range of frequencies? ____________.

Question 42

Give the VSWR response of the antenna in terms of frequency? _________________________.

Question 43

Is the VSWR of the antenna good, or bad? _____________________________________________.

Question 44

What does this tell you about the impedance of the antenna? __________________________.

Transmission Media and Antenna Systems Laboratory