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and wireless interoperability microwave access (WiMAX) applications for hand held devices. The radiating elements consist of planar inverted F-antenna (PIFA) ...

2017 International Conference on Electrical and Computing Technologies and Applications (ICECTA)

A Compact Mobile Handsets MIMO/Diversity Antenna for GSM1800 and WiMAX Applications Hari Shankar Singh1, Kunal Singh1* and Vinamrata2# 1

Department of Electronics and Communication Engineering, Thapar University Patiala-147 004, Punjab, India 2 Department of Electronics and Communication Engineering, SSET, SHIATS Allahabad, U.P., India [email protected] and *[email protected] # [email protected] Abstract—A compact MIMO/Diversity antenna mobile handsets is presented with two radiating elements for GSM1800 and wireless interoperability microwave access (WiMAX) applications for hand held devices. The radiating elements consist of planar inverted F-antenna (PIFA) loaded with L and J-shaped slot. The L-slot is responsible for WiMAX frequency band and the J-slot along with L-slot is responsible for GSM1800 frequency band as well WiMAX frequency band. The proposed MIMO antenna covers GSM1800 (1740 – 1885 MHz) and WiMAX (3250 – 3805 MHz). The defected ground structure (DGS) is used to enhance the isolation between multi antenna elements. The proposed antenna provides low envelope correlation coefficient (ECC) i.e. 0.002. The results S-parameters, envelope correlation coefficient (ECC), and radiation patterns are presented in the manuscript. Keywords— DGS; ECC; multiple-input multiple-output (MIMO); PIFA; WiMAX

I. INTRODUCTION Now-a-days, the MIMO has became key technology for the fourth generation wireless communication devices like, tablet, smart mobile phones, and laptops. The demand of modern wireless technology is provide high data rate with better quality of services. Therefore, MIMO is one of the solutions by mitigating the multipath fading and provide high date speed and channel capacity [1]. In the recent years, wireless communication systems have increased rapidly. Therefore, the wireless communication system required high data rate and increased channel capacity and also required to reduce multipath fading. All these requirements are fulfilled by the MIMO technology. In the current technology anybody can access the internet wirelessly from anywhere in the world. The common wireless standard is used to access the internet are GSM, WLAN, and WiMAX systems. Further, IEEE approved the 802.16m standard as an IMT-Advanced technology [2-3]. Consequently, with the embedding of MIMO technology along with WiMAX system provide high speed transmission rate. Thus, WiMAX technology has become potential mainstream to access wireless internet. Nowadays, many hand held devices operating over frequency bands like GSM, DCS, and the PCS. So many researches has been carried out over multiband PIFA to cover the above said

978-1-5386-0872-2/17/$31.00 ©2017 IEEE

Raed M. Shubair Research Laboratory of Electronics Massachusetts Institute of Technology (MIT) Cambridge, MA, USA [email protected]

operating bands and are available in the literature [4-11]. Most of the antennas have larger footprint as compared to the modern mobile handsets. However, the demand of the MIMO antennas in hand held devices is increased in the above frequency band. The MIMO antenna is demonstrated for WLAN used in the personal computer memory card international association (PCMIA) of a laptop [12-13]. All the diversity techniques can not implement within the limit space of the mobile handset. Moreover, closely placed multi element antenna cause mutual coupling result in reduction in total antenna efficiency. To avoid this problem, a combination of rectangular slot ring along with inverted T-shaped slot between the two MIMO antenna elements are proposed by Meshram et al. for mobile handsets [14]. To reduce mutual coupling, [14], a connecting line between two antennas have been reported [15-18]. Some of the diversity antenna has been designed to improve the isolation between antenna systems using DSG [19-21]. Here, we present a PIFA antenna loaded with two different slot narrow L and J-shaped slots for MIMO applications in a mobile handset. Two different slots are responsible for two different resonating frequencies. The Lslot is responsible for WiMAX frequency band and the J-slot along with L-slot is responsible for GSM1800 frequency band as well WiMAX frequency band. The proposed diversity antennas having isolation -10dB over both frequency band of operations. The meandered line slot is created on the ground plane to reduce the mutual coupling between multi antenna elements. The proposed antenna shows lower ECC of value is 0.002 which meet the good diversity performances. The computer simulation microwave studio (CST MWS) [22] is used to characterize the proposed diversity antenna. II. ANTENNA CONFIGURATION The antenna is designed on FR4 substrate of thickness 0.8mm with dielectric constant 4.4 and loss tangent is 0.018. The designed MIMO antennas are suspended at 4.8mm from the ground plane of the dimension 50 × 100 × 0.8 mm3 and the dimension of radiating element are 13 × 17 × 0.8 mm3. The large ground plane is chosen as a system ground plane which incorporates the other electronic circuitry along with audio

2017 International Conference on Electrical and Computing Technologies and Applications (ICECTA)

video and other devices. In this design, two radiating elements are symmetrically back to back placed at both upper corners of the ground plane as shown in Fig. 1(a) and Fig. 1(b). The separation between two radiating elements is 24mm i.e. 0.14Ȝ0 (at frequency 1.8 GHz). The antenna elements are fed by 50-ȍ SMA (Sub Miniature version A) connector. Fig. 2(a) shows the front view along with details dimension of the proposed MIMO antenna which is mounted on the ground plane and Fig. 2(b) shows the back view along with details of defected ground structure which is used for isolation improvement. All the designed parameters of the proposed MIMO antenna are given in Table I. III. RESULTS AND DISCUSSIONS A. S-parameters Analysis Fig. 3 shows the variation of S-parameters with frequency. It is noted that the impedance bandwidth (|S11|< −6

dB) can cover the GSM1800 from 1740–1885 MHz and WiMAX from 3250–3805 MHz band and the isolation between two elements is well below -10dB over entire operating bands. Fig. 4 shows the effect of defected ground structure on S-parameters. It is observed that the decoupling between two antenna elements is improved at a lower frequency band (GSM1800) whereas the higher frequency band (WiMAX) is unaffected. Fig. 5 shows the effect of the different slot on Sparameters. It is observed that when antenna loaded with only J-slot it resonates at 2.6 GHz and when loaded with only Lslot it resonates at 1.8 and 3.5 GHz but not having a good matching condition for both the operating bands. When the antenna is loaded with J-slot along with L-slot then proposed antenna resonates at 1.8 GHz as well as 3.5 GHz centre frequency of GSM1800 and WiMAX band respectively with the good impedance matching. B. Diversity Parameters Analysis The scattering parameters are used to calculate the envelope correlation coefficient (ECC) rather than the far-field data [2324]. The envelope correlation coefficient of multi antenna system can be determined using the following equation [24].

ρe = (a)

* S + S S* S11 11 22 21

2

§¨1 − 2 ·§ 2 2 · S11 + S 2 21 ¸¹¨©1 − S 22 + S12 ¸¹ ©

From the Fig. 6, it is observed that the calculate ECC is well below 0.002 for the GSM1800 and WiMAX bands that is practically acceptable for the mobile handset. TABLE I. (b) Fig. 1. (a) Configuration of proposed MIMO antenna (b) side view of antenna.

(a) (b) Fig. 2. (a) Front view along with details dimension (b) Rear view along with DGS.

Antenna parameters Lsub Wsub Lant Want L1 W1 Lw L2

OPTIMIZED VALUE OF SHAPE PARAMETERS Value (mm) 100 50 13 18 10.75 12 0.75 8.25

Antenna parameters W2 L3 W3 W4 L4 L5 Sw Sw1

Value (mm) 9.5 6 3 5.5 2 5.25 2.5 1.25

Antenna parameters Sw2 Xf Yf w Ldg a b

Value (mm) 1 1 7 1 8 0.5 1.5

Fig. 3. Variation of optimized S-parameters of the MIMO/diversity antenna.

2017 International Conference on Electrical and Computing Technologies and Applications (ICECTA)

radiation patterns of the Antenna 2 by keeping the matched termination antenna, respectively at 1.8GHz and 3.5 GHz. It is observed that the radiation pattern is nearly Omni-directional in all planes. It is also noted that the radiation patterns of the two antenna elements are complimentary in space which satisfy the diversity criteria of the MIMO antenna. Moreover, the radiation patterns are distorted at the high frequency due to higher order modes.

Fig. 4. Effect of defected ground structure on S-parameters.

(a)

(b)

Fig. 5. Effect of the different slot on S-parameter.

Fig. 7. (a) 3D Radiation pattern when antenna 1 is excited (b) 3D radiation pattern when Antenna 2 is excited.

IV. CONCLUSION A compact PIFA antenna has been presented which is suitable for GSM1800 and WiMAX operating bands. The proposed antenna covers the GSM1800 from 1740–1885 MHz and WiMAX from 3250–3805 MHz. The DGS between two antennas element provide below -10dB isolation. The correlation between multi elements are well below 0.002 which meet the diversity performances. The size of the proposed antenna is comparable to handheld devices which is suitable candidate for the compact mobile handsets. REFERENCES [1] Fig. 6. Variation of ECC with frequency. [2]

C. Simulated 3D far-field radiation patterns Fig. 7 shows the simulated 3D far field radiation patterns of the proposed antenna at two different resonating frequencies 1.8 GHz and 3.5 GHz of GSM and WiMAX bands, respectively. At a time, one port of the MIMO antenna is excited while other port will be matched terminated with 50-ȍ load. Fig. 7(a) and 7(b) shows the radiation patterns of the antenna 1 by keeping matched termination antenna 2 and

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2017 International Conference on Electrical and Computing Technologies and Applications (ICECTA)

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