G-patch Dualband Printed Monopole Antenna for GPS and WLAN Application

Nani Daniati, Hardi Nusantara, Achmad Munir* School of Electrical Engineering and Informatics

Institut Teknologi Bandung Bandung, Indonesia

*munir@ieee.org

Abstract—This paper discusses numerical design and experimental characterization of dualband printed monopole antenna with center frequency of 1.6GHz and 2.4GHz. The antenna that takes a shape of G letter is proposed to overcome the special need of GPS and WLAN application. The antenna which is fed by microstrip line extended from a center pin of 50Ω connector type has 2 distinct arms in different length arrangements to obtain the desired different resonant frequencies. After obtained the appropriate numerical design, the antenna is then deployed on an FR4-Epoxy dielectric substrate with the dimension of 50mm x 50mm and the thickness of 1.6mm. From the measurement results, it shows that the characteristics of realized antenna have good agreements each other with the numerical design. The realized antenna is able to operate at dual frequency bands where the working bandwidths for lower and higher frequency band are up to 220MHz and 150MHz, respectively.

Keywords-dualband; G-patch; GPS; monopole antenna; printed antenna; WLAN

I. INTRODUCTION In recent years, wireless communication that usually uses

high speed data communication such GPS (Global Positioning System) and WLAN (Wireless Local Area Network) is putting a higher challenge to antenna designer to create smaller and high performance antenna. The antenna which has capability to handle more than single frequency band is also being considered as an important feature, since it can simplify antenna system for a single device with ability to connect to different networks. For this purpose, the microstrip patch antenna has been one of solutions to be considered due to its small dimension, light weight, low profile, easy and cheap fabrication. Furthermore, the microstrip patch antenna sometimes can also be designed to have dual frequency bands response. Unfortunately, the dimension of antenna cannot be made any shorter than half wavelength at the desired operating frequency, since the antenna only resonates at the patch length of the order of half wavelength [1]-[3]. Moreover, some techniques emphasized for reducing the dimension of microstrip patch antenna have been proposed and developed by the antenna designer, such as by implementing short circuiting stub, cutting slot at the ground plane and using substrate with higher dielectric constant [4]-[6]. The proposed techniques, however, sometimes have to be paid by sacrificing other important features, such as gain and bandwidth [7].

In this paper, therefore, to overcome the special need of GPS and WLAN application, a G-patch printed monopole antenna with dual frequency bands capability for those applications is proposed. The monopole type of antenna is chosen due to its advantageous feature such as small, light in weight, nearly omnidirectional radiation pattern and ease of integration to the circuit board. The proposed antenna is designed to have center frequency of 1.6GHz and of 2.4GHz for GPS and WLAN application, respectively. An FR4-Epoxy dielectric substrate is applied for deploying the proposed antenna. While the basic parameters including reflection coefficient, VSWR (Voltage Standing Wave Ratio), gain, and radiation pattern are used for performance indicators both in the design and realization. Moreover, the experimental characterization results for each parameter will be compared to the design results to evaluate the performance of realized proposed antenna.

II. DESIGN OF DUALBAND PRINTED MONOPOLE ANTENNA Basically, a microstrip antenna with dual- and multiband

capability developed from single- and double-U-slot has been investigated [8]. In this development, the antenna is intended to have a bandwidth with some enhancement. Inspired from this shape of antenna, a G-patch printed monopole antenna is proposed with the additional feature in the dualband capability. Figure 1 illustrates the final design of proposed antenna. It comprises of 2 side deployed on an FR4-Epoxy dielectric substrate. The dimension, thickness, and tanδ of dielectric substrate are 50mm x 50mm, 1.6mm, and 0.002 respectively.

The top side consists of radiating element as the most important part which is fed by microstrip line extended from the center pin of 50Ω connector type. Besides as a feeding line, the microstrip line also serves as a λ/4 transformer to match the impedance of radiating element and the connector. The radiating element which is made of metal copper has 2 distinct arms in different length arrangement yields a shape of G letter. The longer arm is designed to resonate at lower resonant frequency for GPS application, i.e. 1.6GHz, whereas the shorter one is addressed to work at higher resonant frequency for WLAN application, i.e. 2.4GHz. Furthermore in the bottom side, a ground plane is printed only under the microstrip line feeding network. The thickness of metal copper for G-patch radiating element, as well as feeding line network and ground plane is 0.035mm.

2012 7th International Conference on Telecommunication Systems, Services, and Applications (TSSA)

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Figure 1. Rough sketch of dualband printed monopole antenna (unit in mm)

In the numerical design, to obtain an accurate design, metal copper conductive losses for G-patch radiating element, feeding line network and ground plane as well as its dielectric substrate loss are accounted for. The geometry of design shown in Fig. 1 is obtained after conducting some parametrical studies to acquire the optimum dimension of arm length of G-patch, feeding line network and ground plane in order to have the antenna satisfied to the requirement. It should be noted that the metal copper is peeled off from the substrate in bottom side under the G-patch radiating element.

III. REALIZATION, CHARACTERIZATION AND DISCUSSION After obtained the appropriate numerical designed, the

proposed antenna is then fabricated through wet etching technique. Figure 2 shows the pictures of realized printed monopole antenna on an FR4- Epoxy dielectric substrate as prescribed in the numerical design. To obtain the characteristics of realized antenna especially the dualband capability, the parameters are measured experimentally where the results will be verified and compared to the numerical design results. The measured results for reflection coefficient, VSWR, gain and radiation pattern are plotted in Figs. 3-6, respectively, in which the simulated results are depicted together as comparison.

Figure 2. Picture of realized dualband printed monopole antenna

From Figs.3 and 4, although there are some slight differences occur at the frequency band higher than 2.1GHz, however, it seems that the characteristics of realized antenna for resonant frequency and VSWR have good agreements qualitatively with the numerical design result. The results show that the proposed antenna can operate at 2 resonant frequencies, i.e. around 1.6GHz and 2.4GHz, demonstrating the dual frequency band capability.

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2012 7th International Conference on Telecommunication Systems, Services, and Applications (TSSA)

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The resonant frequencies of realized antenna for the lower and higher frequency band are 1.64GHz and 2.46GHz, respectively. The resonant frequency for the lower frequency band is shifted 40MHz higher than the simulated one, while for the higher frequency band is shifted 60MHz. This difference is mostly evoked by the assumed value of relative permittivity in the simulation that is bigger than of in the realization. In addition, the differences that occur at the frequency band higher than 2.1GHz are probably affected by the value of relative permittivity in the realization which has frequency-dependent, hence in the simulation was set to be frequency-independent. Therefore, the difference will be bigger for higher frequencies response.

Furthermore, from Fig. 4, the working bandwidths of realized antenna for VSWR < 2 are 220MHz for lower frequency band and 150MHz for higher frequency band. These results are also slightly different with the simulated result where the simulated working bandwidths for VSWR < 2 are 190MHz for lower frequency band and 410MHz for higher frequency band. These differences are also addressed to the relative permittivity of dielectric substrate in the simulation and realization. Hence in Fig. 5, although the overall gain of realized antenna is worse than the simulated one in some frequency responses due to the difference value of substrate dielectric loss used in the simulation and the realization,

however, the measured result has similar tendency as shown by the simulated one for all frequency responses. Here, the measured gain is 0.43dB at center of lower frequency band and 0.88dB at center of higher frequency band. While the simulated result, the gain is 0.05dB at center of lower frequency band and 1.31dB at center of higher frequency band.

Figure 6 shows the measured radiation pattern for frequency of 1.6GHz and of 2.4GHz with the simulated results depicted together as comparison. From the results, it should be noted that both results are coincided each other qualitatively. It seems that the radiation pattern of proposed antenna has the characteristics that comply to omnidirectional pattern with no major lobe and minor lobe. This is one of characteristic advantages of monopole antenna compared to the conventional microstrip antenna that has unidirectional radiation pattern.

Figure 6. Measured and simulated results for radiation pattern

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2012 7th International Conference on Telecommunication Systems, Services, and Applications (TSSA)

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IV. CONCLUSION The design and characterization of G-patch dualband

printed monopole antenna for GPS and WLAN application has been investigated numerically and experimentally. The antenna that has been designed to work at around resonant frequency of 1.6GHz and of 2.4GHz has been realized using an FR4-Epoxy dielectric substrate with the dimension of 50mm x 50mm and the thickness of 1.6mm. From the characterization results, it has been demonstrated that the proposed antenna has been able to show dual frequency band capability required for the application. Although there were some slight different achievement between the numerical and experimental characterization in term of resonant frequencies, working bandwidth, and overall gain due to the difference value of material properties used in the design and realization, i.e. relative permittivity and loss of dielectric substrate, however, in general the realized antenna has shown good agreements qualitatively with the design results.

REFERENCES [1] J. R. James and P. S. Hall, Handbook of Microstrip Antennas, London:

Peter Peregrines, 1989. [2] R. Garg, P. Bhartias, I. Bahl and A. Ittipiboon, Microstrip Antenna

Design Handbook. Norwood: Artech House, 2001. [3] J. D. Kraus and R. J. Marhefka, Antennas for all applications, 3rd

edition. New York: Mc. Graw Hill, 2002. [4] R. M. Vani, Dr. S. F. Farida, Dr. P. V. Hunagund, “A shorted

rectangular microstrip antenna with slots in ground plane”. IE(I) Journal ET, vol .87, Jul. 2006.

[5] W. Geyi, Q. Rao, S. Ali, and D. Wang, “Handset antenna design : Practice and theory”, Progress In Electromagnetics Research, PIER 80, pp. 123–160,.2008,

[6] P. Kumar, G. Singh, “Microstrip antennas loaded with shorting post”, Published online in SciRes (http://www.SciRP.org/journal/eng/). SciRes, Jun. 2009.

[7] H. Jiwei and D. Weiping, A novel printed monopole antenna for dual-band WLAN application. Institute Communications Engineering of PLA, University of Science and Technology, Nanjing, 2009.

[8] R. Bhalla and L. Shafai “Resonance behaviour of single U slot and dual U slot antenna,” IEEE Antennas and Propagation Society International Symposium,,vol 2, pp 700- 703, 2001.

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