Ring Antenna Arrays for 1.25 GHz
M. Tecpoyotl-Torres1,3*, J. G. Vera Dimas1, J. A. Damián-Morales1, A. R.
Lopez.Alva2, E. D. Garcia-Garcia2, O. Kolokoltsev3, and A. Ochoa O. Zezzati2
1 Centro
de Investigación en Ingeniería y Ciencias Aplicadas, UAEM (Mexico)
2 Universidad Autónoma de Ciudad Juárez (Mexico)
3 Centro de Ciencias Aplicadas y Desarrollo Tecnológico, UNAM (Mexico)
{tecpoyotl, gvera}@uaem.mx
Abstract. The use of antennas is very useful not only for commercial purposes,
but also for research activities. In these cases, not licensed range frequencies are
also of special interest, nevertheless some licensed ranges are commonly used.
In this paper, annular and rectangular antenna arrays are developed in order to
couple it to a magnetic oscillator, which operates at 1.25 GHz. The material to
fabricate the antenna arrays, in order to maintain also low cost is FlameRetardant 4 (FR-4). These arrays are proposed in order to obtain a reduced
bandwidth, which is one of the design conditions to reduce the interference
effects in the resonator. A comparison on the permformance of these arrays is
also realized.
Keywords: Patch Antennas, Flame Retardant-4, Antenna Arrays, Short Circuit
Point.
1 Introduction
1.25 GHz frequency has been widely used in many electronic systems since
many years ago. As it is well-known, Hertz developed the first radio transmitter
generating frequencies between 31 MHz and 1.25 GHz.
Currently, several commercial electronic devices operate at 1.25 GHz, among
them frequency doublers, frequency counters, integrated circuits such as devices
dedicated to clock distribution, hard drivers, and so on. Also, there are dipole
antennas at this frequency [1], with a gain greater than 1 dBi.
Research publications are also developed devices operating at these
frequencies, such as the CMOS frequency synthesizer presented in [2]. A fully
integrated 1.25 GHz CMOS phase-locked-loop clock generator that incorporates
the proposed voltage-controlled oscillator topology was designed and
implemented for a data transceiver [3].
About microstrip antennas at this frequency, research results can be also
found. A microstrip antenna in the application for a military band short range
radio communication system, at a frequency range of 1 GHz – 1.5 GHz is shown
in [4], where it is also mentioned that most military aviation platforms are
equipped with Ultra-High Frequency (UHF) communication system.
In Mexico, Federal Telecommunication Commission has the responsibility
since 1996, of planning, management and monitoring the radio-electric spectrum
[5]. This dependency also realizes the actualization of the National Frequencies
Board attribution. For us, the frequency range from 1.215 GHz to 1.3 GHz
corresponds to radio navigation and earth exploration by satellite, radiolocation,
spatial research, and the range from 1.24 Ghz to 1.3 GHz corresponds to
amateurs [6].
In this paper, two antenna arrays fabricated on FR-4 to operate at 1.25 GHz are
presented. They were designed to couple them to a magnetic oscillator for
research purposes, but, as it can be observed they could be useful to other
applications. The antenna arrays are based on annular geometries.
As it is well-known, the Bandwidth (BW) of the Microstrip Antennas (MSA)
is directly proportional to the substrate thickness and inversely proportional to the
square root of its dielectric constant [7]. As a result, one of the commonly used
substrates for microstrip antennas is fiberglass-reinforced synthetic substrate,
whose dielectric constant value is typically between 2.1 to 2.6.
A description of Annular Ring Microstrip Antennas (ARMSA) is presented in
[7], where the ARMSA can be considered as a removal of a smaller inner
concentric circle from the outer circle. Rectangular Ring MSA (RRMSA) is
formed when a rectangular slot is cut in the center of the RMSA. Several
variations in geometries and in material have also been developed. In [8], it is
established that the gap-coupled ARMSA can be used for dual band operation
and especially in mobile communication; the interest is focused on the effect of
the gap length and feed point on the radiation pattern of the gap-coupled
ARMSA. Measurements on printed annular rings are realized in [9], where it is
also found that they have certain advantages over circular and rectangular
microstrip antennas.
In [10], it was demonstrated that the width of this ring conforms one of the
elements that determines the BW response of the antenna and the tuning of the
desired BW responses is also supported by the location of the feed point and the
shorting pin. This technique allows obtaining antennas of narrow BW.
As it is known, loading by an electrical short pin has been used as a convenient
means of reducing the size of the antenna [11], to obtain dual operation frequency
[12], to change the resonant frequency [7] (changing the position and the number
of shorting posts in the patch), to change of polarization and so on [13]. A review
of shorting post loaded microstrip antenna, as well as its need can be found in
[14].
This paper is organized as follows: The antenna array designs are provided in
Section 2. In Section 3, the simulation and experimental results are shown. In
section 4, a discussion of the results is developed and finally, in Section 5 some
concluding remarks are given.
2
Antenna Arrays Design
The substrate used is FR-4, which has a dielectric constant of 4.2, and a thickness of
1.6 mm. The equations used for the corresponding designs are the common ones used
for rectangular and circular patch antennas [13, 15].
The obtained sizes for the RRMSA are given in Table 1. The coordinates of the
feed point are (0, 0.6) cm. The used scaling factor is 0.5.
Table 1. Sizes of the RRMSA
Patch
Ring
Substrate
Design frequency
[GHz]
1.25
0.8
1.25
Length [cm]
Width [cm]
3.71
5.81
6.77
5.998
9.308
10.26
The obtained sizes for the ARMSA are given in Table 2. The coordinates of the
feed point are (0.2, -0.38) cm. In this case, there were also implemented a shorting
pin, with Cartesian coordinates (0.435, -0.535) cm.
Table 2. Sizes of the ARMSA
Patch
Ring
Substrate
Radio [cm]
0.5273
0.9416
Side [cm]
2.8431
In figures 1 and 2, the implemented geometries of both antenna arrays are shown.
Fig. 1. RRMSA geometry
3
Fig. 2. ARMSA geometry
Simulation and Experimental Results
Simulations were realized with the FEKO. For transmission/reception tests the
experimental setup showed in figure 3 was implemented. Distance d was established
of 15 cm, since the calculation of the corresponding radio of far field
( R  0.62 D /  ), where D is the biggest side of the antenna and  is the
corresponding wavelength [15]. In order to compare the power measurements the
same distance was also used for ARMSA.
2
Fig. 3. Experimental set-up
For RRMSA: The simulated gain and S11 parameter are shown in Figures 4 and
5, respectively. The BW of this antenna array is of 8.056 MHz.
Fig. 4. Gain of the RRMSA
Fig. 5. S11 parameter of the RRMSA (1.214 GHz, -26.23 dB)
The experimental S21 parameter is presented in figure 6. Two prototypes of each
antenna were fabricated in order to realize the corresponding tests; they are referred as
antenna1 and antenna2 for each case. Figure 7 shows pictures of the implemented
antennas.
Fig. 6. S21 parameter of the RRMSA.  Line Wire represents the cable losses,  Line
Antenna2 shows the received power with the cable noise, and  Line Antenna22
corresponds to the received power without the noise produced by the cable
(a)
(b)
Fig. 7. (a) Frontal and (b) rear view of the RRMSA
For the case of ARMSA: The simulated gain and the S11 parameter are shown in
figures 8 and 9, respectively. The BW of this antenna array is of 6.26 MHz.
Fig. 8. Gain of the ARMSA
Fig. 9. S11 parameter of the ARMSA
As it can be noted, the operation frequency was established very near to the
operation frequency required.
The experimental S21 parameter is presented in figure 10. Figure 11 shows
pictures of the implemented ARMSAs.
Fig. 10. S21 parameter of the ARMSA. Blue line represents the cable losses.
Black line shows the received power with cable noise, and Red line shows the
received power without the noise produced by cable
(a)
(b)
Fig. 11. (a) Frontal and (b) rear view of the ARMSA
In figure 12, a size comparison between the two arrays is shown. Their physical
sizes are also compared with a Mexican peso coin with a diameter of 2 cm.
Fig. 12. Size comparison of antenna arrays
4
Discussion
As it can be observed in figures 5 and 8, a well-defined reception band is located
around 1.25 GHz. The reception levels in ARMSA give a wider frequency response
range of approximately 105 MHz, against 60 MHz for the RRMSA, considering as
the limit reception power to -35 dBm. This fact can be attributed to the radiation
pattern of the ARMSA and the higher directivity of the RRMSA.
The ARMSA and RRMSA show a bigger peak in their frequency response at 1.24
GHz, but the power levels are different. At 1.25 GHz, in the RRMSA the received
power is -35 dBm and in ARMSA is of -27 dBm.
Additionally, the area of the ARMSA is approximately only one sixth of the
RRMSA area.
In [16], it was experimentally demonstrated that using an epoxy resin radome, the
antennas frequency response presents a lightly shift downwards the operation
frequency of the antenna without radome and a lightly increment in the corresponding
BW. Then, the RRMSA or the ARMSA can be covered with this resin without affect
seriously their performance.
5
Conclusions
Two alternatives obtained on the base of ring structures were analyzed and fabricated.
Their main differences are their physical sizes, BWs and radiation patterns.
Although, ring arrays are considered as common geometries, the scaling and the
use of a shorting pin make to these approximations totally personalized. The used
materials for their implementation make them low cost alternatives, especially to the
ARMSA for its reduced sizes, which produces very easy handling, and the higher
power received levels.
From the obtained results, it is suggested to use the ARMSA with the oscillator for
magnetic field detection due to its performance and the easier manipulation obtained
by its more reduced sizes compared with the RRMSA.
Additionally, both antenna arrays can be used for other applications in accordance
to the BW requirements.
Acknowledgements
J. G. Vera-Dimas and J. A. Damián-Morales gratefully acknowledge financial
support from CONACYT scholarship under grant 270210/219230 and
336781/235572, respectively . A. R. Lopez.Alva and E. D. Garcia-Garcia acknowledge
to UACJ for the economic support during the summer staying in CIICAp-UAEM.
References
1. BK M402 Dipolo antena (1,25 GHz a 1,65 GHz) para 2650A/2652A/2658A. Available on
line at http://www.tequipment.net/BKM402.html. July 2012.
2. Soyuer, M. Un totalmente monolítico CMOS sintetizador de frecuencia 1,25 GHz. Circuitos
VLSI, 1994. Recopilación de Documentos Técnicos., 1994 Simposio sobre.1994. Available
at: http://ieeexplore.ieee.org/xpl/login.jsp?reload=true&tp=&arnumber=586249&url=http%
3A%2F%2Fieeexplore.ieee.org%2Fiel2%2F4485%2F12729%2F00586249.pdf%3Farnumbe
r%3D586249. July 2012.
3. Lizhong Sun and Tadeusz A. Kwasniewski. A 1.25-GHz 0.35-m Monolithic CMOS PLL
Based on a Multiphase Ring Oscillatr. IEEE Journal of Solid-State Circuits, Vol.36, No. 6,
JUNE 2001. PP. 910-916. Available at: http://web.doe.carleton.ca/~tak/publications/
journal/00924853.pdf.
4. Aruna Rani. Design and Analysis of Rectangular and U Slotted Microstrip Patch using
Optimization Program in Java for UHF Application. International Journal of Computer
Applications (0975 – 8887). Volume 3 – No.5, June 2010. Available on line at
http://www.ijcaonline.org/volume3/number5/pxc3871021.pdf
5. Salma Jalife Villalón. Las bandas de uso libre… no tan libre. 29 Agosto 2011. Inteligencia
Mediatelecom.
Available
at:
http://www.mediatelecom.com.mx/index.php?option
=com_content&view=article&id=12412:las-bandas-de-uso-libre-no-tanlibre&catid=80:inteligencia-media-telecom&Itemid=9
6. COFETEL. Available at http://www.cft.gob.mx/wb/Cofetel_2008/Cofe_imagenes_del_
cnaf_2007. July 2012.
7. Girish Kumar and K. P. Ray. Broadband Microstrip Antennas. Artech House. ARTECH
HOUSE, INC.
8. Binod Kumar Kanaujia and Anil Kumar Singh. Analysis and Design of Gap-Coupled
Annular Ring. Microstrip Antenna. Hindawi Publishing Corporation, Street. Norwood, MA
02062. 2003, International Journal of Antennas and Propagation, Volume 2008, Article ID
792123, 5 pages, doi:10.1155/2008/792123.
9. Kokotoff, D.M.; Aberle, J.T.; Waterhouse, R.B. Rigorous analysis of probe-fed printed
annular ring antennas. Antennas and Propagation, IEEE Transactions on. 1999. Vol47 Issue 2; pp. 384 - 388
10.M. Tecpoyotl-Torres, J. G. Vera-Dimas and R. Cabello-Ruiz. Antenna Arrays of Adjustable
Bandwidth Based on Rings Containing Microstrip Antennas. Mexican Journal of Scientific
Research. Vol 1, No 1: Jul-Dec 2012. Pp. 10-23. Editorial Académica Dragón Azteca
(Editada.Org).
11.Wong Kin-Lu. Compact and broadband microstrip antennas. Wiley Series in Microwave
and Optical Engineering. Danvers MA. Chapter 1 (2002).
12.Wang, B. F., and Y. T. Lo, “Microstrip antennas for dual operation frequency, IEEE”,
Trans. Antennas and Propagation, Vol. AP-32, 938-943 (1984).
13.Ramesh Garg, Prakash Bhartia, Inder Bahal and Apisak Ittipibon. Microstrip Antenna
Design Handbook. Artech House. Norwood MA. Chapter 8 (2001).
14.Pradeep Kumar, G. Singh. “Microstrip Antennas Loaded with Shorting Post”. Engineering.
Papers 1, 1-54 (2009), Avalilable on line at: http://www.SciRP.org/journal/eng/. July 2012.
15.Balanis, Constantine. (2005). Antenna Theory. Third edition. Wiley-Interscience, Hoboken,
ISBN: 047166782X, New Jersey.
16.Vera-Dimas José Gerardo, Tecpoyotl-Torres Margarita*, García Limón J. A. and Ochoa
Ortiz Zezatti C.A. Experimental test of epoxy resin as a radome for patch antennas.
International Meeting of Electrical Engineering Research. ENIINVIE-2012. Procedia
Engineering 35 (2012) 155–164.