The document discusses and compares the performance of various antenna designs through return loss/VSWR plots and radiation patterns sourced from several research papers. Key findings include that bicone and monocone antennas have bandwidths over 7 GHz but are difficult to fabricate. A helix antenna with a capacitive coupling has the best performance of the helix designs with a bandwidth of around 4 GHz. Square planar monopole antennas with trident or double feeding strips have bandwidths of around 10 GHz. Vivaldi antennas and circular/elliptical dipole antennas also achieve bandwidths greater than 9 GHz. LPDA and monopole antennas have more varied performance depending on specific dimensions.

1. Appendix A
Abstract –
The s11 parameter is defined as the reflected voltage divided by the incident voltage
and is the same as the return loss which is equal to –
RL = −20 log( s11 )
It is desirable to have as little reflected voltage as possible and hence a return loss of
-∞. Practically this is not possible however, if the Voltage Standing Wave Ratio
(VSWR) is less than 2, the antenna performs acceptably. In terms of return loss, a
VSWR of less than 2 compares to a return loss less than -9.54dB (common practice is
to use -10dB for simplicity).
The results obtained from research papers and displayed in this report are used
determine which antenna will be used for experimentation. However, there are also
other factors which are taken into consideration such as ease of fabrication and also as
not all data was able to be obtained for all antennas, some data may be extrapolated
from certain antennas for other antennas.
It is also worth noting that the group delay and phase response are related by –
∂θ (ω )
Groupdelay = −
∂ω
where θ (ω ) is the phase angle dependent on frequency. Hence a linear phase
response gives a constant group delay.

2. Bicone, Monocone, LPDA, F-probe, Simulated Horn
Figure 1 – Images of simulated antenna from [1]
Figure 2 – s11 parameter results and radiation pattern of antennas in Figure 1 from [1]
Discussion –
Figure 2 shows the return loss of the different antennas from figure 1 between
frequencies of DC and 10GHz. It can be seen from figure 2 that the best performers
are the bicone (with a bandwidth of >7GHz) and the monocone (with a bandwidth of
approximately 7GHz). The horn antenna performed the worst with a bandwidth of
approximately 500MHz and the LPDA and f-probe antennas performed rather
similarly with the LPDA having a rather poor return loss over certain frequencies and
a good return loss over others due to the design of the antenna.
The radiation patterns depicted in figure 2 are for the monocone antenna (top) and the
f-probe antenna (bottom). Because the f-probe antenna and the horn antenna are both
directional antennas, it is assumed that the horn antenna with have a similar radiation
pattern to that of the f-probe antenna. The radiation pattern for the monocone shows
an omnidirectional pattern which is expected due to the symmetry of the antenna’s
design. It is assumed that the radiation pattern for the bicone will be similar to that of
the monocone due to the similarities of design. The radiation pattern of the LPDA
however is unknown from figure 2 although figure 15 does show the radiation pattern
for a different LPDA and hence this can be used as a comparison.
Although the cone antennas have the best performance, these are harder to fabricate
than say the LPDA antenna and hence must be taken into consideration.

3. Section 2 - Helix Antennas
Figure 3 – Helix antenna and s11 parameter results from [2]
Figure 4 – Helix antenna with cone feed and s11 parameter results from [2]
Discussion –

4. The helix antenna shown in figure 3 performs particularly well at certain frequencies
but poorly over the range of 2 – 6GHz. The helix antenna shown in figure 4 (with a
capacitive coupling) performs the best out of all the helix antennas with a bandwidth
of slightly less than 4GHz. All other antennas have relatively poor bandwidth
compared to the capacitive coupled helix antenna. Although the radiation pattern is
not given, it can be assumed that due to the symmetrical design of the antenna that the
radiation pattern will be omnidirectional. Also, due to the complex shape of the
antenna, it will be harder to fabricate than an average planar antenna.

5. Square Planar Monopole
Figure 5 – Square Monopole antenna and s11 parameter results from [3]
Figure 6 – Radiation pattern of square monopole antenna at 5GHz from [3]
Discussion –
Figure 5 shows the square planar monopole antenna having a large bandwidth of
approximately 10GHz. The radiation pattern is also shown at 5GHz and can be seen
to be omnidirectional. Figure 1 however does show that this large bandwidth is
dependent on the notches in the design however this does not make the fabrication
much more difficult.

6. Square Monopole with various feeding strips
Figure 7 – Square monopole antenna with various feeding strips and results of s11
parameter from [3]
Figure 8 – Radiation pattern of square monopole antenna with various feeds from [3]
Discussion –
Figure 7 shows that a square monopole antenna with a trident shape or 2 branch
feeding strip performs better than that of a simple feeding strip. The trident and
double feeding strip antennas perform very similarly however the trident feeding strip
does have a slightly larger bandwidth of approximately 10GHz. Once again the
radiation pattern is omnidirectional and is rather simple to fabricate.

7. Step shaped Planar Monopole
Figure 9 – Step shaped planar monopole antenna and results of s11 parameter from [3]
Figure 10 – Radiation pattern of step shaped planar monopole antenna from [3]
Discussion –
The step shaped planar monopole antenna performs quite poorly over the UWB
frequency range with a bandwidth of only 4.4GHz. The radiation pattern is similar to
that of the previous monopole antennas and it is simple to build however the
bandwidth is rather poor.

8. U shaped Planar Monopole
Figure 11 – U shaped planar monopole antenna and results for s11 parameter from [3]
Discussion –
The U shaped planar monopole antenna performed slightly better than the step planar
monopole antenna with a bandwidth of approximately 5GHz however this is still
rather poor over the UWB frequency range.

9. Cylindrical planar monopole
Figure 12 – Dimensions of cylindrical planar monopole antenna from [3]
Figure 13 – s11 parameter results for cylindrical planar monopole antenna from [3]
Discussion –
The cylindrical planar monopole antenna performs very similarly to the U shaped
planar monopole antenna which has a rather poor bandwidth over the UWB frequency
range.

10. Cross plate Monopole
Figure 14 – Cross plate monopole antenna and s11 parameter results from [3]
Discussion –
The cross plate monopole antenna can be seen to have a bandwidth of approximately
10GHz which is good for a UWB application. The antenna performs better with a
bent cross plate rather than a planar cross plate.

11. LPDA
Figure 15 – Dimensions for LPDA and s11 parameter results from [4]
Figure 16 – Radiation pattern for LPDA from [4]
Figure 17 – Plot showing the group delay for LPDA from [4]
Monopole Antenna

12. Discussion –
Figure 15 shows that the LPDA has a bandwidth of approximately 10GHz which is
suitable for a UWB application however the return loss does vary significantly with
frequency as shown by all the downward spikes in the plot. Figure 15 also shows that
the original design (shown in figure 15) performs better than the band-notched design
(not shown). The radiation pattern of the LPDA can be seen to be omnidirectional,
although it is not the best radiation pattern of antenna previously looked at. Figure 17
does show the LPDA to have a relatively constant group delay over the UWB
frequency range which is a desirable characteristic of an antenna.

13. Monopole Antenna
Figure 17 – Dimensions of monopole antenna from [5]
Figure 18 – s11 parameter results for monopole antenna with various dimensions from
[5]
Discussion –
It can be seen in figure 18 that the monopole antenna has a poor return loss between
approximately 5 and 7 GHz which is rather poor compared to some of the previous
antennas. It can also be assumed that the radiation pattern of this antenna will be
rather similar to that of previous planar monopole antennas and hence has no stand
out characteristics above other antennas.

14. Planar Dipole
Figure 19 – Dimensions of planar dipole antenna from [6]
Figure 20 – s11 parameter results and radiation pattern of the planar dipole antenna
from [6]
Discussion -
Figure 20 shows a poor return loss over the UWB frequency range (particularly above
6GHz). Its radiation pattern is very similar to that of other planar monopole antennas.

15. Planar Monopole
Figure 21 – Dimensions of planar monopole antenna from [7]
Figure 22 – s11 parameter results of planar monopole antenna from [7]
Discussion –
Figure 22 shows that the monopole antenna shown in figure 21 has a bandwidth of
approximately 10GHz; this is an acceptable bandwidth for an UWB application.

16. Vivaldi Antenna
Figure 23 – Dimensions of Vivaldi antenna from [8]
Figure 24 – VSWR plot and group delay plot of Vivaldi antenna from [8]
Figure 25 – Dimensions of a second Vivaldi antenna from [8]

17. Figure 26 – VSWR plot and group delay plot of second Vivaldi antenna from [8]

18. Discussion –
Unlike previous antenna data shown, the data for the Vivaldi antenna gives a plot of
the VSWR rather than the return loss. As stated in the abstract, having a return loss of
less than 10dB is approximately the same as having a VSWR of less than 2. Figure
24 shows that the first type of Vivaldi antenna has a simulated bandwidth of >9GHz
and a measured bandwidth of 7.5GHz and a relatively constant group delay (except at
9GHz where strange things happen for reasons unknown). Figure 26 shows that the
second type of Vivaldi antenna has a simulated bandwidth of >9GHz and a measured
bandwidth of approximately 8GHz and a relatively constant group delay.

19. Planar Dipole Antennas
Figure 27 – Circular, bow-tie and elliptical dipole antennas from [9]
Figure 28 – VSWR plot and frequency response of dipole antennas from [9]
Figure 29 – Radiation patterns of dipole antennas from [9]
Discussion –
Figure 28 shows that both the circular and elliptical dipole antennas have large
bandwidths while that of the bow-tie dipole is slightly worse. Figure 28 also shows
the phase response of the antennas and shows that the elliptical antenna has a
nonlinear phase response (and hence not a constant group delay) whereas the circular

20. and bow-tie antenna have rather linear phase responses with that of the bow-tie being
slightly better than that of the circular. The radiation patterns appear to be similar to
those of previous planar antennas.

21. Circular Monopole Antenna
Figure 30 – Circular monopole antenna from [10]
Figure 31 – s11 parameter results of circular monopole antenna from [10]
Discussion
Figure 31 shows that the bandwidth of the circular monopole antenna to be less than
7.5GHz over the UWB frequency range. The impedance bandwidth is from 3.1GHz
to approximately 10GHz and hence does not cover the entire UWB frequency range.

22. Microstrip Antenna
Figure 32 – Microstrip antenna from [11]
Figure 33 – s11 parameter results of microstrip antenna from [11]
Discussion
The microstrip antenna shows a relatively poor impedance bandwidth being
approximately 6GHz between 4.5GHz and 10.5GHz.

23. Conclusion –
Firstly, because there were many antennas which had a suitable bandwidth for UWB,
all of the others can be disregarded. This leaves the bicone, monocone, helix with
capacitive coupling, square planar monopole, cross plate monopole, LPDA, planar
monopole, Vivaldi and circular and elliptical dipole antennas. All of these antennas
have very similar (omnidirectional) radiation patterns so this does not have an effect
on the choice of antennas.
Secondly, the bicone, monocone and helix antennas are the most difficult antennas to
fabricate and do not provide much, if any, difference compared to other, easier to
fabricate antenna designs. This leaves the square planar monopole, cross plate
monopole, LPDA, planar monopole, Vivaldi, circular monopole, microstrip and the
circular and elliptical antennas.
From this point, the major determining factor has become the phase response or group
delay of the antenna. Because all of the antennas have very similar radiation patterns
and bandwidths, the antennas that phase responses were unable to be obtained for will
be disregarded hence leaving the LPDA, Vivaldi, circular monopole, microstrip and
the circular and elliptical dipole antennas. Also, because the elliptical dipole has a
non-linear phase response, it can also be disregarded. This leaves a choice between
five antennas, the LPDA, Vivaldi and the circular dipole. It was determined that the
LPDA and circular dipole were too difficult to simulate hence the Vivaldi, circular
monopole and microstrip antennas will be simulated.

24. Bibliography
[1] – Sibbile, A 2005, ‘Modulation Scheme and Channel Dependence of Ultra-
Wideband Antenna Performance’, IEEE Antennas and Wireless Propagation Letters,
vol. 4
[2] – Yang, Y, et al. ‘The Design of Ultra-wideband Antennas with Performance
Close to the Fundamental Limit’, Virginia Tech Antenna Group, Blacksburg, VA,
USA
[3] – Wong, K.L. ‘High-Performance Ultra-Wideband Planar Antenna Design’, Dept.
of Electrical Engineering National sun Yat-Sen University Kaohsiung, Taiwan.
[4] – Chen, S.Y., et al. 2006, ‘Unipolar Log-Periodic Slot Antenna Fed by a CPW for
UWB Applications’, IEEE Antennas and Wireless Propagation, vol. 5
[5] – Xiao-Xiang, HE, 2009, ‘New band-notched UWB antenna’, College of
Information Science and technology, Nanjing University of Aeronautics and
Astronautics, Nanjing, P.R. China
[6] – Zhao, CD, 2004, ‘Analysis on the Properties of a Coupled Planar Dipole UWB
Antenna’, IEEE Antennas and Wireless Propagation Letters, vol. 3
[7] – Choi, SH, 2003, ‘A new Ultra-Wideband Antenna for UWB Applications’,
Microwave and Optical Technology Letters, vol. 40, no. 5, Mar 2004
[8] – Mehdipour, A. 2007, ‘Complete Dispersion Analysis of Vivaldi Antenna for
Ultra Wideband Applications’, Progress in Electromagnetics Research, pp 85-96.
[9] – Hecimovic, N. ‘The Improvements of the Antenna Parameters in Ultra-
Wideband Communications’, Ericsson Nikola Tesla, d.d., Croatia.
[10] – Liang, J. 2005, ‘Study of Printed Circular Disc Monopole Antenna for UWB
Systems’, IEEE Transactions on Antennas and Propagation, vol. 53, no. 11.
[11] – Lim, K.-S. 2008, ‘Design and Construction of Microstrip UWB Antenna with
Time Domain Analysis’, Progress in Electromagnetics Research, vol.3 pp 153 – 164.

25. Appendix B
9m Coaxial Cabling Magnitude 9m Coaxial Cabling Phase
0 0
-500
-5
-1000
-10
-1500
Magnitude, dB
Phase, rad
-15 -2000
-2500
-20
-3000
-25
-3500
-30 -4000
2 4 6 8 10 12 2 4 6 8 10 12
Frequency, GHz Frequency, GHz
(a) (b)
Figure 1. Cable magnitude and Phase response for 9m of cables
Figure 2. Cable magnitude and Phase response for 9m of cables

26. Project Management Plan – Ultra Wideband Antennas
OFFCDT Andrew Spear
School of Engineering and Information Technology
UNSW@ADFA
Purpose
The project will focus on antennas suitable for a typical Ultra Wideband (UWB) of
3.1GHz to 10.6GHz. The purpose is to research existing UWB antenna technology,
identify key features of UWB antennas, analysing, characterising and constructing
particular antenna designs and to give a comparison of the relative performance and
trade-offs between fabrication, cost and performance.
Objectives
The aim of the project was to develop a diagnostic tool in order to produce an Ultra
Wideband (UWB) antenna with a linear phase response in order to give a constant
group delay using a passive equalisation network.
Milestones
The milestones for the project are –
1. To obtain one or two UWB antenna designs which can be simulated and
constructed for testing.
1.1. Draft a document on UWB antenna technology, highlighting the particular
requirements for UWB systems and applications.
1.2. Have construction details and published performance characteristics/
targets for antenna designs.
2. To simulate the antenna designs and obtain data which can be manipulated
using MATLAB.
2.1. Draft a document detailing the process to be used for simulation of the
antenna designs and also the desired data which is to be extracted.
2.2. Draft a report detailing the data obtained from simulation and a
comparison of this data to what theory predicts.
3. To characterise the permittivity of the antenna substrate over the frequency
range of 3.1GHz – 10.6GHz.
3.1. Have constructed test boards.
3.2. Obtain an accurate simulation model for the antenna substrate.
4. To construct the antenna design and conduct real life testing of the system.
4.1. Have constructed the antenna.
4.2. Draft a report detailing the data obtained from the real life testing and a
comparison of this to theory/data obtained from simulation.
5. To develop a diagnostic tool in order to determine whether a particular antenna
can be equalised to have a constant group delay over the UWB frequency
spectrum.

27. 5.1. Draft a document detailing the requirements for a system to give a linear
phase response.
5.2. To produce the diagnostic tool to be operated in MATLAB.
5.3. To adapt the diagnostic tool in order to simulate equalisation networks of
varying complexity.
5.4. To draft a report detailing the data obtained and a comparison to what is
predicted by theory/simulation (if simulation is possible).
Key Dates
• Week 25/26 – VIVA
• Week 40 – 15 minute seminar
• Week 44 – Thesis due

28. Projected Timeline
Task Task Start (Week No.) Finish Total time Remarks
No. (Week spent
No.) (Weeks)
1 Research antenna theory and UWB antenna 11 13 3 Completed
and systems
2 Milestone 1.1 11 13 3 Completed
3 Milestone 1.2 11 13 3 Completed
4 Practice using simulation software 13 13 1 Completed
5 Conduct simulations 14 20 5 Completed
6 Milestone 2.1 13 13 1 Completed
7 Milestone 2.2 16 16 1 Completed
8 Milestone 3.1 20 20 1 Completed
9 Conduct testing on test boards 21 21 1 Completed
10 Milestone 3.2 22 24 3 Completed
11 Milestone 4.1 20/29 20/30 3 One antenna built
12 Conduct real life testing of antenna 23 32 6 Completed 1-port
testing for the 1
antenna
13 Milestone 4.2 33 33 1
14 Milestone 5.1 29 30 2
15 Milestone 5.2 31 32 2
16 Simulate system to give linear phase response 32 33 2
17 Milestone 5.3 34 35 2
18 Test system to give linear phase response 36 37 2
19 Milestone 5.4 37 37 1
20 Collaborate work/write thesis 40 44 4

29. 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

30. The above matrix works as follows –
• The numbers across the top represent the week number in the year
• The numbers down the left represent the task number given in the projected timeline -
Anticipated Obstacles –
The construction time of the antenna is unknown and hence in the event that the fabrication takes significantly longer than expected the system
to give a linear phase response can begin to be designed based on the results of simulations.
Obstacles Encountered –
It took a lot longer than expected to get an accurate simulation result from the simulation software (CST Microwave Studio) and hence that
pushed back the construction of the antennas. However, the time taken to construct the antennas was not as long as expected and hence helped
me catch up some time.
The construction time of the antennas was approximately 1 week hence it was not a significant issue in terms of time constraints.
The biggest obstacle encountered was obtaining the 2-port measurements of the antenna network. This process took much longer than expected
due to the several iterations of testing which had to be done in order to achieve accurate results. The testing was first conducted outside the
anechoic chamber and it was found that there was too much backscatter in the transmission results to do any manipulation of the data in
MATLAB. The test was then moved inside the anechoic chamber but in order to do this 9m of cable had to be used to connect the antennas to
the network analyser. These cables introduced a significant amount of attenuation in the results which was reducing the magnitude of the
transmission down to the threshold of the network analyser. The next iteration involved a setup similar to the first (outside of the anechoic
chamber) but using the anechoic chamber foam tiles in an attempt to reduce the amount of backscatter. It was found that this did not work
particularly well and finally the network analyser was moved closer to the anechoic chamber to reduce the amount of cable used to connect the
antennas to the network analyser which gave accurate results.

31. Scope Changes –
The scope of the project began as investigating UWB antennas and technologies and developing a system to linearise the group delay of the
antennas hence giving it a constant group delay. This shifted to producing a tool to take in the 2-port parameters of an antenna and determine the
effect of equalisation on the antennas using a passive network of varying complexities.