Ultra Geniş Bant Uygulamaları için Çift Band Çentikli Karakteristik ile Yeni Bir Dikdörtgen

Mikroşerit Anten A Novel Rectangular Microstrip Antenna for

Ultra-Wideband Applications with Dual Band-Notched Characteristic

Negin Manshouri1, Mehdi Najafpour1, Ayhan Yazgan2, Masoud Maleki1, Haydar Kaya2

Elektrik - Elektronik Mühendisliği Bölümü Avrasya Üniversitesi1

Karadeniz Teknik Üniversitesi2 {negin.manshouri, mahdinajafpur, masoud.maleki}@avrasya.edu.tr

{ayhanyazgan, hkaya}@ktu.edu.tr

Özetçe—Bu çalışmada geniş band haberleşme sistemleri için baskılı mikroşerit anten çift band çentik özelliği ile sunulmuştur. Önerilen anten iki farklı band içerisinde çalışmak üzere tasarlanmıştır. Anten üzerinde 2 adet simetrik boşluk oluşturarak elde edilen birinci çentik band 5-6GHz arasında WLAN uygulamalarını etkilenmemek için oluşturulmuştur. Ayrıca C-band uydu habeleşmesi ile girişim oluşmaması için de toprak düzlemi içinde M şeklinde ikinci çentik band 8-9 GHz aralığında oluşturulmuştur. Anten benzetimleri HFSS ve CST yüksek frekans simülatörleriyle gerçekleştirilmiştir.

Anahtar Kelimeler — Ultra geniş band antenler, çentik band, mikroşerit antenler

Abstract—In this study, a printed microstrip monopole antenna with band-notched property for wide band communication systems is presented. The antenna is intended to operate in two bands. By using two symmetric rectangular slots on the radiating patch, a notched band 5-6GHz, not to interfere with WLAN, is obtained. Additionally, an M-shaped slot to acquire another notch band at 8-9GHz is formed on the microstrip feed line not to be affected by C-band satellite communication system. Antenna simulations are realized using HFSS and CST high frequency simulators.

Keywords — Ultra wideband antennas, notches band, microstrip antennas.

I. GİRİŞ Ultra wideband (UWB) antennas become an appealing

topic for wireless communications. UWB microstrip antennas have become extremely common because of their simple and compact structure, and low cost properties. To obtain the wideband property in the limited surface, different multiband or wide band antenna designs have been proposed in literature [1]. In the design of a UWB antenna, the form of the radiation patch, and the model of the ground plane have an important role. Therefore, this topic is further investigated to acquire the optimum planar shape. In [2, 3], two small planar monopole antennas with partial ground plane and notches in the lower corner of the patches are suggested to attain the maximum bandwidth. Moreover, other strategies such as radiating patch with tapered steps [4-6] and wide-slot antenna with coplanar waveguide (CPW) feed line [7] are also proposed for large bandwidth. One of the UWB antenna types is the planar inverted cone antenna (PICA) proposed by Suh [8, 9]. In order to increase the operating frequency range, several methods have been implemented so far. One of them is to use the truncated slot on the ground plane or the propagating patch [10]. Different methods are applied so as to reach large impedance bandwidths [11, 12]. Furthermore, some research groups investigate the effect of feed line and slot size to obtain the reasonable impedance bandwidth. [13, 14]. In this paper, we suggest a novel microstrip antenna with dual-band notched characteristic. In this model, the microstrip

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antenna can function from 3-11 GHz and unlike other antennas reported in the literature, the proposed antenna displays a good omnidirectional radiation pattern even at higher frequencies [15]. Most of these antennas have large sizes or narrow bandwidth. Conversely, the small size and good omnidirectional radiation pattern in the frequency band of interest of the proposed antenna may be a desired antenna for UWB communications. By choosing a suitable combination of feed line and slot shape, and adjusting their dimensions, to impede interference with existing wireless systems, two notch bands can be acquired in our design. These notches are obtained by using a pair of narrow rectangle-slots and an M-shaped slot. In order to figure out the effect of parameter size, a parametric study has been published [16]. The simulation and experimental results are in a good agreement.

II. ANTENNA DESIGN AND CONFIGURATION The geometry and configuration of the prototype

microstrip antenna is illustrated in Fig.1 (a), (b) respectively. The suggested antenna is fabricated on the FR4 substrate with a thickness of 0.8 , relative permittivity (ε ) of 4.4, dielectric loss tangent of (tan δ) 0.02. This slot antenna consists of a thin metal rectangular patch, with two narrow rectangular slots, a partial ground plane in shape of a rectangle, and a microstrip line with an M-shaped slot on it. In fact, by cutting the two notches of fitting dimensions (W × L ) at the two sides of the monopole, the impedance bandwidth can be improved [17]. The reason of this finding is the notches which cause the electromagnetic coupling effect between the ground plane and radiating surface [18]. As a result, the extra role of the novel ground plane is the impedance matching of the square monopole [19].

Fig. 1. Geometry of the proposed antenna, side view, top view, and the details of slot.

50-Ω SMA connector is connected to the antenna for measurement processes [20]. The 50-Ω impedance of the

microstrip feed line is achieved by tuning the width (w ) of the inner conduct. This kind of feeding is the easiest way of excitation techniques, and also directly connecting a strip to the edge of a radiation patch is approvingly applicable. Obtained optimized dimensions of the proposed antenna are given in Table 1.

Fig. 1. Photograph of the fabricated antenna.

Table 1: Optimal values of parameters

Parameter Size (mm) Parameter Size (mm) h 0.8 0.4

18 8.2 20 1.8 11 0.5 1.48 6.2 0.5 3.3 0.5 0.2 0.1 2

III. RESULTS AND ANALYSIS The entire dimension of the antenna fills small space.

The antenna shape is designed to improve the overall performance and the dimensional efficiency. According to the results, the proposed antenna has a bandwidth of 3- 11 GHz under the condition of VSWR<2, with two band notches. The proposed microstrip antenna is fabricated on the FR4 substrate. This antenna has omnidirectional and good radiation pattern in both elevation and azimuth plane with low cross polarization. In this paper a simple 50 Ω microstrip line is used to excite the radiation patch. The final prototype antenna is attained after the investigation of different adjustments of the parameters. Optimum geometrical parameters of the proposed antenna is obtained using Ansoft high-frequency structure simulator (HFSS) and CST Microwave studio [21]. As expected, same results are obtained by using HFSS and CST. The simulated voltage standing wave ratio (VSWR) curves with different values of L and L are plotted in Fig. 4, and 5.

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Fig.3 Simulated VSWR for different values of L4.

Fig. 4: Simulated VSWR values for for different values of L6.

Fig. 5: Simulated and measured VSWR characteristic of the proposed antenna.

As shown in these Figures, the notch frequencies are controllable by changing the interior height of the rectangular slots [22] and also the height of slot. Since the dimension of the ground plane strongly affects the performance of the antenna, the length and the width of the rectangle-shaped ground plane is also optimized to obtain better results. By little variation of these parameters, the height or the location of the band-stops can be changed. Fig. 5 displays the simulated and measured VSWR of the fabricated antenna. It is obvious that the simulated and measured results are in good agreement. In Fig. 5, there are two band-stops at the desired band which are resulted of using two slots which

perturb the resonance response [22]. The measured VSWR< 2 bandwidth ranges from 3-11 GHz, except two band-stops. Fig. 6 shows the gain and group delay of the prototype antenna. As shown in this Figure, it can be seen that the variation of the group delay is approximately less than 0.5ns except two band-stops. Also this Figure presents the simulated antenna-gain response of the proposed antenna [23]. It can be seen that the gain is flat at the lower and higher frequencies except notch-bands. Fig.7-9 show the simulated radiation patterns at three frequencies as 4 GHz, 7 GHz and 10 GHz. In UWB antenna design, the group delay is an important parameter which is given in Fig.6 [23].

Fig. 6: Simulated gain and group delay.

Fig. 7. Measured radiation patterns at 4 GHz on the E and H planes.

Fig. 8. Measured radiation patterns at 7 GHz on the E and H planes.

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Fig. 9. Measured radiation patterns at 10 GHz on the E and H planes.

IV. CONCLUSION In this paper, we have designed and constructed a

novel compact microstrip antenna that demonstrates dual band-notched characteristic at the center frequency of 5.5 GHz and 8.5 GHz in the desired UWB band. The planar antenna includes a rectangle shape patch, and a dual-band resonator to make a good notch at 5.5GHz of WLAN band, and 8.5GHz of C band communications. The proposed antenna exhibits that the experimental results have good agreement with the simulated results. This antenna also maintains the omni-directional radiation patterns with admissible gain and less changes in group delay. This antenna can be a good candidate for UWB applications.

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[21] M. Naser. Moghadasi, S. Faraji Gotolo, and G. Dadash Zadeh, “Compact monopole antenna with two bands-notched characteristic for ultra-wideband applications”, Microwave and Optical Technology Letters, Vol. 54, No. 12, 2011.

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