2015 IEEE 2015 International Conference on Computer, Communication, and Control Technology (I4CT 2015), April 21 - 23 in Imperial Kuching Hotel, Kuching, Sarawak, Malaysia
Design of Circular Patch Microstrip Ultra Wideband Antenna with Two Notch Filters Raed A. Abdulhasan, R. Alias, A. A. Awaleh, A. O. Mumin Faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia Johor, Malaysia
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Abstract—This paper presents a small size UWB patch antenna with two notch filters. U-shaped and J-shaped slots are loaded in the patch of the antenna for WiMAX and WLAN frequency band rejection. The antenna is simulated using the commercially available CST Microwave Studio software. The slots dimensions are systematically adjusted and optimized to achieve the desired band rejection responses. The achieved results demonstrate that the antenna has good performance over the entire working frequency band (3.1 GHz to 10.6 GHz) except WiMAX (3.15-3.7 GHz) and WLAN (5.15-5.85 GHz) notched frequency bands. Moreover, the antenna was fabricated and the simulation results are experimentally validated. The measured results demonstrate a good agreement with the simulations.
Some UWB applications require the rejection of unwanted frequency bands by means of discrete band-stop filters in order to overcome the problem of electromagnetic interference (EMI). The primary challenge in UWB antenna design is achieving the wide bandwidth while maintaining high gain and good radiation efficiency with a less manufacturing complexity. For the last decade, researchers have approached the subject area in a number of different ways. A numerous slot configurations embedded in the radiation patch or the ground plane are the most common approaches to realize the rejection of unwanted frequency bands and to reduce the antenna size[5]-[8]. The UWB antenna design comes with a few other challenges as well. Some segments of the UWB bandwidth (which have been assigned by the FCC) are also shared by other current narrowband services, such as the wireless local area network (WLAN) IEEE 802.11a and the HIPERLAN/2 WLAN, which are functioning within the 5-6 GHz band. Another service, known as the Worldwide Interoperability for Microwave Access (WiMAX), which is used in some countries in Europe and Asia, uses a frequency band of 3.3 - 3.6 GHz.
Keywords-UWB patch antenna; slots; band-stop filter; WiMAX; WLAN;
I.
INTRODUCTION
Ultra Wide Band (UWB) technology is the basis of different methods of wireless communications. In 1896, the first UWB communications system was set up in London to connect two post offices, which were more than a mile apart [1]. Since then, a contemporary UWB system was introduced in 1960 and the U.S. armed forces made use of pulse transmissions to conceal imaging, radar and stealth communication [2]. And as a result of this, UWB has triggered a huge investment in antenna design with new opportunities and challenges for antenna architects.
However, each notch structure can achieve only one rejected band. Therefore, to yield multiple notched bands, multiple slots structures are required. Thus, the intention of this study is to design two notch structures (J-shaped and Ushaped slots) to realize band rejection characteristics at 3.4 GHz [9] and at 5.5 GHz [5] respectively.
According to the Shannon-Hartley theorem, the main benefit of the UWB system is that it is channel capacity corresponds to the bandwidth. The UWB can handle a large capacity of hundreds of Mbps because of it is ultra-wide frequency bandwidth. In addition, UWB systems function at exceedingly low levels of power transmission. Hence, it is able to offer an extremely safe and dependable communications system because of the low energy density. Moreover, the impulse radio UWB is cheap and simple because of the baseband character of the signal transmission [3]-[4]. In February 2002, the Federal Communications Commission (FCC) allocated the UWB applications from 3.1 GHz to 10.6 GHz. Based on the FCC's decision, any signal that takes up at least 500 MHz of spectrum can be employed in UWB systems. Thus, UWB is no longer confined to impulse radios alone, but also includes any technology that utilizes 500 MHz of spectrum and fulfils all the other prerequisites for UWB. Since impulse radio-based UWB systems deliver pulses of energy,
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II. ANTENNA DESIGN Fig. 1(a) illustrates the geometry of the conventional UWB design for circular patch antenna without notch filter [10]. Besides, the proposed UWB circular patch antenna with two notch filters is sketched in Fig. 1(b). The patch antenna was printed on a standard FR4 substrate having relative permittivity (εr) of 4.4, dielectric loss tangent (tan δ) of 0.019 and substrate thickness of 1.6 mm. The antenna substrate and ground plane sizes equal 47×40 mm2 and 19.3× 40 mm2 respectively. The circular patch has a microstrip feed line with dimensions 20.3 × 2.6 mm2 to achieve the impedance matching 50 Ω between the patch antenna and the SMA connector.
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TABLE I.
To determine the overall dimensions of a patch antenna structure. In general, the mathematical equuations of circular patch antenna at a specific resonance frequenncy can used [11].
IMPORTANT DESIGN D PARAMETERS OF THE ANTE ENNA. Value
Parameter Frequency range
3.1 GHz to 10.6 GHz 47 mm,W= 40 mm, Lg = 19.3 mm, W 40 mm, W 2.6 mm, Lf = 20.3 mm, r = 10 mm 8 m, y1 = 3.8 mm, x1 = 2.8 mm, x11 = 8.5 t1= 0.5 mm, x2 = 11 mm, y2 = 4.2 mm, t2 = 0.8 mm. FR4: = 4.4, h = 1.6 mm, tan δ = 0.019 L
Antenna dimensions Optimised slot dimensions Substrate
III.
(a)
(b)
Figure 1. Geometry of the UWB antenna (a) conventionnal UWB circular patch antenna (b) Proposed UWB antenna configgurations.
Table I summarizes the optimized antenna physical parameters and main features. Two notches were w loaded on the circular patch of the antenna as an unwanteed frequency band filter mechanism. This is to avoid interferennce between UWB and other wireless services (in this case WiM MAX and WLAN bands). The two slots (J-shaped and U-shapped) were adjusted by varying their lengths. The dimensions of the slots are optimized to obtain the desired frequency baand rejections with VSWR> 2 and S11> -10 dB, using the followiing equations.
( x 1 + x 11 + y 1 – 2t1 ) = L1 ≈ 4 f
c e notch εeff
(1)
10
Where L1 in the above equation is thee length of the Jshaped notch, fnotch is the notch frequency, c is the speed of light, and εeff is the effective dielectric constant of the substrate.
λg =
=
c f notch εeff
λg 2
X2 = 10 mm X2 = 10.5 mm X2 = 11 mm
VSWR
8
For the U-shaped slot length, the follow wing relationships are used:
( x 2 + 2 y 2 – 2t 2 ) ≈ L 2
PARAMETRIC STUDY AND ANALYSIS
The performances of the prroposed UWB patch antenna are thoroughly studied. The sloots lengths (L1 and L2) are systematically varied and optim mized to achieve notched-band over WiMAX (3.4 GHz) and WLAN W (5.5 GHz). The antenna is designed and simulated using CST Microwave Studio software. First, the conventionnal UWB circular patch antenna was simulated and a VSWR off less than 2 and value of S11 less than -10 dB are obtained oveer the whole design frequency range (3.1 – 10.6 GHz). Secoondly, the U-shaped slot length was adjusted by varying the approximated a value determined from using equation (2). Thiis is to achieve the best slot dimensions for WLAN (5.5 GH Hz) band reject. Fig. 2 compares the VSWR performances among conventional patch (without notch) and three U-shaped slot lengths. It can be seen from the figure that the obtained VSWR R results are above 2; hence, the antenna has shown a notcheed-band over WLAN. Further, increase of the slot length (x2) causes frequency shift from the desired notched band.
6 4 2
(2)
0 2
(3)
3
4
5
6 7 8 Frequ uency (GHz)
9
10
11
Figure 2. Effect of the U-shaped slot leength (x2) on the VSWR performance.
Where is the guided wavelength of the desired notch frequency and L2 is the approximated lengthh of the U-shaped slot [5].
Thirdly, the J-shaped approoximated slot lengths determined from using equation (3) are adjusted to obtain the most optimized slot dimensions forr WiMAX frequency rejection. Fig. 3 presents the simulated VSWR V of the designed antenna on different slot lengths. Simillarly, the results show a VSWR of more than 2, meaning that thhe designed antenna has shown a notched-band over WiMAX (3..4 GHz).
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Figure 5. Measured and Simulated return loss curves.
Figure 3. Effect of the J-shaped slot length (x11) on the VSWR performance.
IV.
RESULTS AND DISCUSSION
The proposed antenna is fabricated on the selected dielectric substrate as shown in Fig. 4. The scattering parameters of the antenna are measured using Vector Network Analyzer. The antenna return loss and VSWR are recorded and sketched with the comparison of the simulated results.
Figure 6. Measured and Simulated VSWR curves (with and without notches).
However, the adjustable lengths of these two-notched filters were optimized for a good band reject performance, which can be an ultimate solution for electromagnetic interference problems between WLAN/WiMAX and UWB systems.
Figure 4. Fabricated UWB circular patch antenna with U and J shape notches.
It is shown in Fig. 5 that the return loss performance of the antenna is better than -10 dB for the entire working frequency range except WiMAX and WLAN notched frequency bands. Additionally, the obtained results show that the antenna input impedance had good matching over all the desired bands. It is also observed that the adjusted U-shaped slot length is larger than the J-shaped slot length, hence achieves better band reject (5.15 GHz – 5.85 GHz). Figure 7. Gain of the band-notched UWB circular patch antenna.
The gain of the UWB patch antenna decreases to 2 dB at 5 GHz (see Fig. 7), due to the effect of the notch at this particular band. This means the notch filter parameters were optimized to give a good band-reject on the WLAN bandwidth
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for the entire working frequenncy range except WiMAX and WLAN notched frequency bands.
(5.15 to 5.85 GHz) and WiMAX bandwidthh (3.2 to 3.7 GHz). The antenna gain drastically increases after thhis band.
ACKNOWLLEDGMENT The authors would like to thank t to University Tun Hussein Onn Malaysia (UTHM), shorrt-term grant (STG) U116 and (EMC) for sponsoring this workk. REFER RENCES [1]
H. Nikookar and R. Prasad, "Intrroduction to ultra wideband for wireless communications," Springer,vol. 200, 2 2009. [2] H. G. Schantz, “A brief history of o UWB antennas,” IEEE Aerospace and Electronic Systems Magazine, vool. 19, pp. 22-26, 2004. [3] J. Liang, "Antenna study and design for ultra wideband communication applications," PhD thesis, universsity of London, 2006. [4] Y. S. Hu, M. Li, G. P. Gao, J. S. S Zhang, and M. K. Yang, "A doubleprinted trapezoidal patch dipolee antenna for UWB applications with band-notched characteristic," Proogress In Electromagnetic Research, vol. 103, pp. 259-269, 2010. [5] J. R. Panda and R. S. Kshetrimayyum, "A Compact CPW-Fed Monopole Antenna With An U-Shaped Slott For 5 GHz/6 GHz Band-Notched Ultra wideband Applications," India Annual A IEEE Conference (INDICON), 2009. CPW–fed triangular antenna with am [6] W.C. Liu and P. C Kao, “C frequency-band notch functioon for ultra-wideband application,” Microwave Opt. Technol. Lett., vol. v 48, no.6, pp.1032-1035, 2006. [7] A. A. Awaleh, S. H. Dahlan, M. M Z. M. Jenu, “A Compact Flat Lens Antenna with Aperture-Coupledd Patch Elements,” IEEE Asia-Pacific Conference on Applied Electrom magnetics, APACE 2014, Johor Bahru, Malaysia, 20 – 23, 2014. N “Bandwidth enhancement of [8] R. Zaker, C. Ghobadi, and J. Nourinia, novel compact single and dual band-notched b printed monopole antenna with a pair of L-shaped slotss,” Antennas and Propagation, IEEE Transactions on, vol. 57, pp. 3978-3983, 2009. [9] S. Kalraiya, H.S. Singh, G. K. Pandey,A. K. Singh, A.K. and M. K. Meshram, “CPW-fed fork shapeed slotted antenna with dual-band notch characteristics,” Engineering andd Systems Students Conference (SCES), 2014. [10] B.Allen, M. Dohler, E. E. Okonn, W. Q. Malik, A. K. Brown, “Ultrawideband Antenna and Propagaation: for Communications, Radar and Imaging,” John Wiley & Sons Lttd., 2007. [11] C. A. Balanis, “Antenna Theory, Analysis and Design,” 3rd edition, John Wiley & Sons, Inc., 2005.
Figure 8. Far-field radiation patterns for the antenna’s E-plane E and H-plane at (a) 4 GHz, (b) 7 GHz and (c) 9.6 GHz. G
The far-field radiation for the propoosed UWB patch antenna was plotted by using CST Microwavve Studio software at 4 GHz, 7 GHz and 9.6 GHz frequencies. Fig. F 8 shows the Eplane and H-plane radiation patterns for these frequencies. At 4 GHz, the obtained H-plane pattern for the proposed antenna is nearly Omni-directional and has a gain of 2.5 dB (at 266°) where was at 7 GHz, the E-plane has a gainn magnitude of 3.5 dB (at Theta = 90°). Finally, a gain of 7.2 dB d was shown for E-plane at 9.6 GHz (at Theta= 90°). It can be summarised that the gain increased when the frequency increase for the proposed UWB antenna. V.
CONCLUSION
A small size UWB patch antenna wiith a good bandrejection performance have been designed annd measured. Two different slots were embedded in the patch of the antenna as notch filters. The slots dimensions werre optimized for WiMAX and WLAN frequency band rejecttion. The achieved results show that the proposed antenna has good g performances in terms of radiation patterns, gain and refl flection coefficient
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