Cube satellite missions perform innovative scientif ic experiments on a low cost developmental platform but have an inherent limitation of size and space. This restricts the total available solar power that can be harnessed and as a result, the radio links operate on stringent power budgets. For improving the avail able margins for communication in such satellites, it is desirable to improve upon the antenna system performance at the ground station used for the esta blishment of the links with the satellite. This can be achieved by improving the forward gain, the forward to backward ratio and the directivity of the anten na. This paper describes the electrical simulations and the performance evaluation of the one unit, two un it and four unit circularly polarized crossed Yagi-Uda ant enna array designed for communication with amateur radio (HAM) satellites operating over the 434 MHz t o 438 MHz Amateur UHF band. The electro-magnetic model has been developed using the 4NEC2 software. The simulations have been validated with the practical field testing performed for estimating th e SWR, antenna gain, the forward to backward ratio and radiation pattern for the antenna system
Content may be subject to copyright.
Discover the world's research
- 20+ million members
- 135+ million publications
- 700k+ research projects
Join for free
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
DOI : 10.5121/ijwmn.2014.6512 145
D
ESIGN AND
P
ERFORMANCE
E
VALUATION OF
T
WO
-U
NIT
Y
AGI
-U
DA
A
RRAY FOR
UHF
S
ATELLITE
C
OMMUNICATION
Rupesh Lad
1
, Pritesh Chhajed
2
, Lokeshsingh Bais
3
, Shyam Dahiwal
4
, Sukhada Saoji
5
,
Vaibhav Rekhate
6
, Pushkar Chaudhari
7
, Shimoli Shinde
8
, Ketan Chitale
9
, Anjali
Mondhe
10
and Shreyas Kulkarni
11
College of Engineering Pune, Pune, India
A
BSTRACT
Cube satellite missions perform innovative scientific experiments on a low cost developmental platform but
have an inherent limitation of size and space. This restricts the total available solar power that can be
harnessed and as a result, the radio links operate on stringent power budgets. For improving the available
margins for communication in such satellites, it is desirable to improve upon the antenna system
performance at the ground station used for the establishment of the links with the satellite. This can be
achieved by improving the forward gain, the forward to backward ratio and the directivity of the antenna.
This paper describes the electrical simulations and the performance evaluation of the one unit, two unit and
four unit circularly polarized crossed Yagi-Uda antenna array designed for communication with amateur
radio (HAM) satellites operating over the 434 MHz to 438 MHz Amateur UHF band. The electro-magnetic
model has been developed using the 4NEC2 software. The simulations have been validated with the
practical field testing performed for estimating the SWR, antenna gain, the forward to backward ratio and
radiation pattern for the antenna system.
K
EYWORDS
Array Antenna, polarization, radiation pattern, stacking distance, UHF antenna, Yagi-Uda
1.
I
NTRODUCTION
Amateur cube satellites orbiting in Low Earth Orbit are categorized as pico satellites, nano
satellites based upon their size. Smaller the size of these cubesats, lesser is the power generation
capacity and thus lesser is the power of telemetry signals transmitted from such satellites.
Communication with such small cube satellites requires the establishment of an efficient ground
system. The performance of the system can be greatly increased by developing a high gain,
directional antenna. A specific gain is associated with each type of antenna based upon its
structure. A half wave dipole antenna has a nominal gain of about 2.14 dBi. It is omnidirectional
antenna and thus it has low directivity. When the reflectors and directors are added to the dipole
antenna, its gain starts increasing with each director. But the gain gets saturated at about 15 dBi,
with number of directors equal to 11 [1]. For further increase in the gain, a number of antennas
can be coupled together using proper impedance matching network. Horn antennas and parabolic
dish antennas have very high directionality but there lie structural constraints and incompatibility
with the antenna rotator system.
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
146
2.
A
NTENNA
D
ESIGN
2.1. Polarization of ground station antenna
Elliptical polarization is the most general form of polarization. The loss due to mismatch between
polarization of transmitting and receiving antenna is given by
++ ) )(1 (1
2cos)-)(1-(1+4
2
1
+
2
1
log 10=Loss
2
R
2
T
2
R
2
T
10
γγ
βγγγγ
RT
(1)
Where, is Axial ratio of transmitting antenna, is Axial ratio of receiving antenna and is
polarization mismatch angle [2].
Small satellites are equipped with linearly polarized dipole antenna transmitting linearly polarized
electro-magnetic waves [3]. This linearly polarized wave undergo Faradays rotation as it travels
across the space, hence the state of polarization received on the Earth cannot be predicted.
Theoretically the polarization loss between the two linearly polarized antennas varies from 0dB to
infinite loss depending upon the angle of mismatch given by
1
) (cos2
2
1
+
2
1
log 10=Loss(dB)
10
β
(2)
The maximum loss between linear and circularly polarized antenna obtained after substituting
values in (1) is 3dB [2]. A crossed Yagi antenna reduces the losses due to polarization mismatch.
2.2. Gain of Antenna
The satellite downlink power budgets are very stringent and operates with link margin of about
2dB. Thus to have a large link margin the gain of antenna needs to be more than 15 dBi. To
receive and extract information from the weak signals arriving at the Earth from satellites, the
power of signal must exceed the sensitivity of the receiver and the signal to noise ratio (SNR)
needs to be sufficiently higher. Both the objectives of achieving power and SNR can be fulfilled
by amplifying the received signals using an antenna and low noise amplifier. High gain antennas
also have very high directionality thus the antenna rotator system was needed to direct the main
lobe of radiation pattern towards the satellite. The Yeasu G5500
TM
antenna rotor assembly [4] is
mounted on the Antenna mast which elevates the antenna by 2 meters from the roof top.
2.3. Antenna modeling in 4NEC2
Simulations for various parameters and dimensions of antenna is carried out in 4NEC2X software
which works on Numerical Electromagnetic Codes [5]. It uses method of moments to find out
numerical solutions to the integral equation of induced current in metallic structure.
A circularly polarized cross Yagi [6] was simulated to achieve maximum gain at frequency of
437.025MHz and the corresponding wavelength is 0.6864m. The resonating length of a dipole
antenna is half of wavelength which is 0.3432m. Yagi antennas are derived from half wave dipole
antennas [7] with reflector and directors added to increase directivity and gain in a specific
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
147
direction. The length of reflector is greater than driven element and the lengths of successive
directors go on decreasing. The cross Yagi as shown in Fig. 1 are further derived from the Yagi
antennas
Boom is the important part of antenna support assembly but it is also an unintended radiating part
of antenna. It is generally preferred to electrically insulate the elements and the conducting boom.
Presence of conducting boom close to the elements of antenna shortens the electrical length of
antenna [8]. Due to this the bandwidth of antenna shifts to higher frequencies. Thus the physical
lengths of elements are added with boom correction length which makes it slightly larger than the
simulated lengths. Boom correction help to improve the performance of antenna with respect to
standing wave ratio (SWR) and gain on the frequency band for which it is designed. The
dimensions of the cross Yagi elements are as mentioned in Table I.
Figure 1. A 2 unit array of Cross Yagi Antenna with elements labelled
The circularly polarized cross Yagi antenna simulated with the above dimensions have a
gain of about 15.5dBi and HPBW of 32o. The gain could be further increased by using
multiple such
antenna and coupling those together [9].
Table 1. Dimensions of antenna elements.
Elements Length
(in metres)
Spacing from driven element
(in metres)
Reflector R1, R1' 0.3892 -0.126
Driven elements D0, D0' 0.3492 0
D2, D2' 0.306 0.171
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
148
D4, D4' 0.2988 0.504
D6, D6' 0.2918 0.884
D8, D8' 0.285 1.474
D9, D9' 0.2816 1.744
D11, D11' 0.2744 2.284
An array of units of antennas has a narrower beam width, and hence higher gain than one single
antenna. The maximum achievable gain could be N times greater than one unit fed with same
power if there are N units in an array. Stacking distance is a function of half
power beam width (HPBW) of individual antenna of an array. The optimum stacking distance for
maximum gain is given by,
2
2sin
=S
opt
φ
(3)
Where is half power beam width of individual antenna unit [1]. The signals from antennas are
combined together and fed to low noise amplifier for further amplification.
The effective gain of an antenna array depends upon the stacking distance between the units of
antenna. The optimum stacking distance for 2 unit array antenna obtained from (3) is 1.8λ. The
stacking distance was varied from 0.5λ to 3λ and the graph of gain vs stacking distance is shown
in Fig. 2. It was observed that the gain is maximum at stacking distance of 1.68λ and on further
increase in stacking distance no significant change in gain is observed. Hence the stacking
distance of 1.68λ i.e. 1.13m is optimum for the present configuration.
Simulations were carried out for 2 unit and 4 unit array using 4NEC2 software and the results are
summarized in Table II. Although the primary objective was to build a High gain antenna the
losses due to coaxial cables and connectors also have to be considered. The gain obtained from 4
unit cross Yagi antenna is increased but at a cost of physical stability of structure.
Figure 2. Gain as a function of Stacking distance for 2 unit array antenna
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
149
Table 2. Comparison between antennas
Parameter Cross Yagi antenna 2 unit array antenna 4 unit array antenna
Gain 15.5 dBi 18.6 dBi 20.9 dBi
SWR 2.8 2.78 1.49
HPBW 32° 32° 16°
Cable loss 0.5dB 1 dB 2dB
It is observed that 2 unit array antenna provides higher gain than single cross Yagi antenna and
the losses are lesser than 4 unit array antenna. The simulated radiation patterns of 2 unit array
antenna are as shown in Fig. 3 and Fig. 4
Figure 3. Simulated Horizontal Plane Radiation Pattern
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
150
Figure 4. Simulated Vertical Plane Radiation Pattern
3.
F
IELD
T
EST
The validation of these simulated results is important and is obtained by carrying out various field
tests. The 2 unit array antenna is constructed with the simulated dimensions and was mounted on
antenna rotor system. A transmitter kept in line of sight and at same height as that of antenna,
transmitted a fixed amount of power which was received by Antenna assembly and was measured
on Spectrum Analyzer [10]. The antenna was then rotated in horizontal plane and also for
different elevation angle. The power received was recorded for each angle and radiation patterns
were obtained practically.
Figure 5. Observed Horizontal Plane Radiation Pattern
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
151
Figure 6. Observed Vertical Plane Radiation Pattern
Presence of metallic bodies in reactive field [11] of antenna contributes to its output parameters
and radiation pattern. The physical construction of antenna is such that it avoids use of unintended
radiating part in its reactive field region. Use of metallic structure to mount 2 individual units of
antenna would have introduced an unintended metallic element hence PVC pipe was used to
mount the 2 units on Rotor system thus the practically obtained results are very close to the ones
simulated.
The SWR of an antenna can be lowered using matching network [12]-[14] once the antenna is
physically constructed hence the gain was given more importance while simulating the antenna.
The impedance matching was done using stubs of coaxial cables and with help of smith chart
calculations. The SWR of antenna at 437.025MHz was 2.78 in simulations but the SWR after
impedance matching is 1.13 as observed using Vector Network Analyzer [15]. The SWR is lesser
than 1.2 for amateur radio satellites frequency range of 434MHz to 438MHz with a gain of 17
dBi.
Figure 7. Observed SWR plot as a function of Frequency
International Journal of Wireless & Mobile Networks (IJWMN) Vol. 6, No. 5, October 2014
152
4.
C
ONCLUSION
The patterns obtained and the field tests are in good congruence with the model developed. Large
number of iterative simulations carried out resulted into a comparison of antennas and their
performance parameters. Mutual coupling and matching network lowered down the SWR which
was high in simulations resulting into high gain and matched antenna. Successful communication
links have been practically established with existing amateur radio satellites thus establishing the
performance of this antenna.
A
CKNOWLEDGEMENTS
This work is sponsored by College of Engineering, Pune under the Swayam Satellite project. The
authors acknowledge the valuable inputs of faculty of Electronics and Telecommunication
department and HAM club VU2COE. Authors thank Shri. Pramod Kale for his deep insights in
radio and satellite communication. Authors thank Dr. A. D. Sahasrabudhe, Hon. Director of
COEP and Dr. M. Y. Khaladkar for their constant motivation and support to the Swayam project.
R
EFERENCES
.
[1] P. Swallow, "Practical VHF/UHF antennas", in Radio communication handbook, 11th ed. London,
UK: The Radio Society of Great Britian, ch. 16.
[2] T. K. Ishii, Handbook of Microwave Technology, Hill and Smith, Volume 2, ch. 7, pp. 176-177.
[3] P. Chaudhari et al., "Performance optimization of a 1-U satellite antenna", in Proc. of 64th
International Astronautical Congress, Beijing, China, Sept 2013.
[4] Yeasu G5500 Antenna Azimuth Elevation Rotator and Controller Operating Manual, Yeasu
Musen Co., Ltd., 1998.
[5] Numerical electomagnetic code (NEC-l),"NEC User's guide", Lawrence Livermore Laboratory,
1977.
[6] C. A. Balanis, Antenna Theory Analysis and Design, John Willey& Sons, inc, New York,
Chichecter, Brisbane, Toronto, Singapore, 2003
[7] R. K. Shevgaonkar, "Antennas", in Electromagnetic Waves, New Delhi, India: Tata McGraw-Hill,
2006, ch. 8.
[8] D. Dragoslav, "Boom distance influence on yagi antenna", in Antennex, Issue 148, Serbia, August
2009.
[9] M. Pingle, B. Pingle, S. Deosarkar, "Mutual coupling in arrays and its effect on 435 MHz 4-
element Yagi-Uda antennas in array configurations", in Proc. of International Conference on
Recent Advances in Microwave Theory and Applications, Jaipur, Nov 2008; pp. 818-820.
[10] R&S FSH Handheld Spectrum Analyzers Operating Manual, Rohde & Schwarz, pp. 2.20-2.23.
[11] A. W. Rudge, Handbook of Antenna Design, Volume 1, pp. 12-14.
[12] D. Jefferies, Single stub matching of transmission lines to loads, [Online] Available:
http://personal.ee.surrey.ac.uk/Personal/D.Jefferies/jefferies-stub.html
[13] J. Staples, Impedance matching and smith charts, Available:
http://uspas.fnal.gov/materials/08UCSC/mml13_matching+smith_chart.pdf
[14] R. K. Shevgaonkar, "Transmission Lines", in Electromagnetic Waves, New Delhi, India: Tata
McGraw-Hill, 2006, ch. 2.
[15] Performing Amplifier Measurements with the Vector Network Analyzer ZVB, Rohde & Schwarz,
pp. 3-7.
... Hence TTC system requires establishment sufficient ground segment. The performance of the total system can be highly developed by utilization a high gain directional antenna [2]. Generally, satellite-ground telecommunications have been implemented in VHF/UHF bands where the required equipment (such as antenna pointing accuracy) is not as critical as for higher frequencies. ...
-
![Vahid Rasti Nasab]()
Ground station antennas are a part of TTC system, generally, Yagi-Udi antennas and Parabola dish antenna are using in Earth segment to communication with LEO small satellites, this paper uniquely presents the three huge antennas of Beihang University ground station which are communicating with some microsatellites with view window above Beijing, China. The ground station contains two Yagi-Udi antennas for VHF/UHF and an S-band dish antenna for reception of payloads data. For verification feasibility of the antennas, simulations have been accomplished according to the antennas requirements. Eventually, the simulations assisted to recognize the matched commercial ground station antennas based on comparison of the simulations with commercial antennas and the matched ones are chosen for the implementation of Beihang University ground station antennas.
... Hence TTC system requires establishment sufficient ground segment. The performance of the total system can be highly developed by utilization a high gain directional antenna [2]. Generally, satelliteground telecommunications have been implemented in VHF/UHF bands where the required equipment (such as antenna pointing accuracy) is not as critical as for higher frequencies. ...
-
![Constantine Balanis]()
The discipline of antenna theory has experienced vast technological changes. In response, Constantine Balanis has updated his classic text, Antenna Theory, offering the most recent look at all the necessary topics. New material includes smart antennas and fractal antennas, along with the latest applications in wireless communications. Multimedia material on an accompanying CD presents PowerPoint viewgraphs of lecture notes, interactive review questions, Java animations and applets, and MATLAB features. Like the previous editions, Antenna Theory, Third Edition meets the needs of electrical engineering and physics students at the senior undergraduate and beginning graduate levels, and those of practicing engineers as well. It is a benchmark text for mastering the latest theory in the subject, and for better understanding the technological applications. An Instructor's Manual presenting detailed solutions to all the problems in the book is available from the Wiley editorial department.
Practical VHF/UHF antennas
- P Swallow
P. Swallow, "Practical VHF/UHF antennas", in Radio communication handbook, 11th ed. London, UK: The Radio Society of Great Britian, ch. 16.
[5] Numerical electomagnetic code (NEC-l),"NEC User's guide Antennas
- P Chaudhari
P. Chaudhari et al., "Performance optimization of a 1-U satellite antenna", in Proc. of 64th International Astronautical Congress, Beijing, China, Sept 2013. [4] Yeasu G5500 Antenna Azimuth Elevation Rotator and Controller Operating Manual, Yeasu Musen Co., Ltd., 1998. [5] Numerical electomagnetic code (NEC-l),"NEC User's guide", Lawrence Livermore Laboratory, 1977. [6] C. A. Balanis, Antenna Theory Analysis and Design, John Willey& Sons, inc, New York, Chichecter, Brisbane, Toronto, Singapore, 2003 [7] R. K. Shevgaonkar, " Antennas ", in Electromagnetic Waves, New Delhi, India: Tata McGraw-Hill, 2006, ch. 8. [8] D. Dragoslav, " Boom distance influence on yagi antenna ", in Antennex, Issue 148, Serbia, August 2009. [9]
Handbook of Microwave Technology
- T K Ishii
T. K. Ishii, Handbook of Microwave Technology, Hill and Smith, Volume 2, ch. 7, pp. 176-177.
Performance optimization of a 1-U satellite antenna
- P Chaudhari
P. Chaudhari et al., "Performance optimization of a 1-U satellite antenna", in Proc. of 64th International Astronautical Congress, Beijing, China, Sept 2013.
Boom distance influence on yagi antenna
- D Dragoslav
D. Dragoslav, "Boom distance influence on yagi antenna", in Antennex, Issue 148, Serbia, August 2009.
Mutual coupling in arrays and its effect on 435 MHz 4-element Yagi-Uda antennas in array configurations
- M Pingle
- B Pingle
- S Deosarkar
M. Pingle, B. Pingle, S. Deosarkar, "Mutual coupling in arrays and its effect on 435 MHz 4-element Yagi-Uda antennas in array configurations", in Proc. of International Conference on Recent Advances in Microwave Theory and Applications, Jaipur, Nov 2008; pp. 818-820.
Single stub matching of transmission lines to loads
- D Jefferies
D. Jefferies, Single stub matching of transmission lines to loads, [Online] Available: http://personal.ee.surrey.ac.uk/Personal/D.Jefferies/jefferies-stub.html
Impedance matching and smith charts
- J Staples
J. Staples, Impedance matching and smith charts, Available: http://uspas.fnal.gov/materials/08UCSC/mml13_matching+smith_chart.pdf
Source: https://www.researchgate.net/publication/280929029_Design_and_Performance_Evaluation_of_Two-Unit_YAGI-UDA_Array_for_UHF_Satellite_Communication
Posted by: davedaveskagerberge0268737.blogspot.com
