Analysis of Hybrid Coupler Connected Circular Patch Antenna with Different Dielectric. Material for Wireless Applications

Transcription

1 MAGNT Research Report (ISSN ) Vol.2 (3): pp. 1-7 Analysis of Hybrid Coupler Connected Circular Patch Antenna with Different Dielectric Material for Wireless Applications A.Sahaya Anselin Nisha 1, T.Jayanthy 2 1 Assistant Professor, Sathyabama University, Chennai , India. 2 Principal, Panimalar Institute of Technology, Chennai , India. Abstract: A microstrip patch antenna plays a critical role in wireless communication systems because of its enormous benefits of lightweight, thin profile and of less price. This paper presents the design of circular patch antenna with hybrid coupler for wireless applications. This technique enclosed electromagnetic simulation for return loss, gain, directivity and far field pattern plot which is reported here. The comparison is ceased for circular patch antenna with hybrid coupler with high dielectric material RT/Duroid 6010 and FR4 material. For operating in the same band of frequency, RT/Duroid 6010 material with less thickness has low dimension relatively to FR4 material. Keywords: Circular Patch, Dual Feed, Hybrid Coupler, Microstrip antenna, Polarization, WLAN. 1. Introduction Antennae are the parts of modern tools of communication establishing link between communities and nations. They are nearly our electronic eyes and ears. Des champs introduced the concept of microstrip antenna at 1953, but the first microstrip antenna was developed by Howell & Munson after 20 years in the early 1970s [5]. This printed patch antennae find large applications in new wireless communications during its low profile features but its narrow bandwidth features limits the usage from many applications. For vehicle applications microstrip patch antenna is opened by Economou and Langley [1]. RT/Duroid were used as a dielectric material with circular patches printed on this, with glass laminated superstrates. Glass laminate will introduce uncertainty into the resonant frequency and bandwidth will make problem where communication bands demand bandwidths of 5% and above. To achieve required space diversity quarter wavelength patch antenna for 2.4GHz ISM band designed and is consists interdigitation of two separated patches. The application of this antenna is that it has been integrated in a high-speed wireless LAN PC card system [2]. For wide band applications microstrip line-fed L-strip patch antenna is designed. In this paper L shape strip connected to the microstrip antenna without a matching network with small step is introduced at the end of the feed line. Additionally the noncontact structure improves the fabrication of antenna arrays [4]. Small circularly polarized printed antenna which consists of synchronous sub array of shorted patches with the desired feed network inscribed on a high dielectric constant substrate situated below the ground-plane of the antenna. This circular patch antenna is very small in dimension with x x wave length [3]. The guiding principle miniaturization of patch antenna is discussed by Skrivervik et al [11]. A compact size coplanar waveguide (CPW)-fed monopole antenna with dual folded strips for the radio frequency identification (RFID) application is presented by Wen-Chung Liu and Ping-Chi Kao [13]. Probe feed stacked patch antenna for GNSS Applications, which is receiving two or more signals from GNSS [14]. Different structures of circularly polarized antenna with 3dB hybrid coupler is designed and analysed in the literature [6] [9]. In this literature to realize the circular polarization, 3dB hybrid coupler is directly connected with various structures of microstrip antenna and the parameters are investigated. Initially rectangular patch with 27.42mm width and 37.32mm length is connected with hybrid coupler antenna and simulation is done using ADS software [6]. The operating frequency is about 2.4Ghz, it is having circular polarization with gain is above 7db. Next hybrid coupler connected diagonal shaped patch antenna with slot is examined [9]. This antenna is having gain of 3.319dB and the directivity of 6.98dB. Then the gain is further increased by introducing antenna array technique [8]. Each square in array having length of 4.6mm patch is having thickness of 0.381mm and the dielectric material used FR4. The

2 designed antenna having high gain of 6.26dB and directivity of 5.11dB at the resonant frequency of 3.7GHz. Afterwards octagonal shaped hybrid coupled microstrip antenna for multiband operation is designed [7]. The design simulation is done using Method of Moment based software. The proposed antenna is resonating in the frequency range of 2-4 GHz. Hybrid coupled octagonal patch antenna having gain of 9.11 db and the directivity of 8.98 db. Power radiated by this antenna is watts. Recently, patch antenna research has been focused on reducing the size of the patch for their applications in mobile communications and monolithic microwave integrated circuits. Reduction of antenna electrical size is done by lengthening the path of current flow on its configuration and in this planate inverted-f antenna is placed on the spherical pillbox [15]. Miniaturization using virtual open circuit is at one end of the slot and the slot is folded by three, increasing electrical length, defects in ground plane is introduced by many researches [16]-[18]. In this paper high dielectric material is chosen to reduce the physical size of an antenna. In this paper Circular patch antenna with FR4 substrate is connected with hybrid coupler is designed and the parameters are examined. Finally size reduction is achieved by using high dielectric material; also the coupler is connected with microstrip antenna through ground plane to achieve perfect circular polarization. The patch antenna with single feed generally radiates linear polarization, therefore to produce circular polarization dual feed must be given. In this paper circularly polarized microstrip patch antenna is designed by connecting hybrid coupler with microstrip antenna. 3dB hybrid coupler is chosen to act as a splitter here and it consists of 50Ω characteristic impedance with two horizontal transmission lines of one eighth of guided wave length. Using hybrid coupler 90 degree phase is produced in the input signal without changing magnitude value which in turn provided that circular polarization to microstrip patch antenna. According to the impedance choice of the series and stub microstrip transmission lines, at first the hybrid coupler is designed for 2.4GHz with impedance (z 0 ) is 50Ω, dielectric constant ε r is 4.6 and thickness of dielectric material is 1.6mm. According to the design equations given by Pozar D.M. [5], 3dB hybrid coupler is designed with the width (w) is 2.958mm, ε e = and length is l = 16.81mm. 2. Hybrid Coupler Design for 2.4GHz with FR4 Material Microstrip antenna is regularly designed for single mode operation that radiates principally linear polarization. But nowadays communication equipment requires circular polarization. A microstrip patch is one among the foremost wide used radiators for circular polarization. A patch should support orthogonal fields of equal magnitude however in-phase quadrature for circular polarization radiation. This demand will be accomplished by single patch with correct excitations or by associating in array of patches with acceptable arrangement and phasing. A single patch antenna may be created to radiate circular polarization, if two orthogonal patch modes excited with equal amplitude and 90 degree out of phase. Two different techniques of feeding schemes will accomplish the task. Fig.2. Return loss for hybrid coupler with FR4 dielectric Fig.3. Axial ratio of hybrid coupler with FR4 dielectric at 2.4GHz Fig.1. Hybrid coupler design in ADS at 2.4GHz with FR4 By using the above mentioned values the hybrid coupler is drawn in ADS and is shown in Figure 1. Figure 2 and 3 shows the simulated results of hybrid coupler having return loss value dB at 2.400GHz and axial ratio is 0dB. Then the designed hybrid coupler is connected with the rectangular antenna to produce the circular polarization. This paper

3 presents circular patch antenna connected with the hybrid coupler which is fabricated and the parameters are measured with network analyzer and anechoic chamber. 3. Antenna Design 3.1 Development of circular patch with hybrid coupler with FR4 dielectric Circularly polarized antenna (CPA) has advantages over linearly polarized antennae because the electric field alignment between the transmitter and the receiver locations is not required. In this paper circularly polarized microstrip antenna is designed by connecting hybrid coupler with patch antenna. The circular patch is designed individually then it is connected with the 3dB hybrid coupler. The circular patch is designed as follows. For basic mode of operation the resonant frequency of the TM 11 mode is given by [19] reduction at the same operating frequency 2.4GHz. Here high dielectric constant material is taken as RT/Duroid 6010 with dielectric constant Then the new technique of connecting hybrid coupler is introduced here which is connected to patch antenna through ground. 3dB hybrid coupler consists of 50Ω characteristic impedance, the operating frequency is 2.4GHz, dielectric constant ε r is 10.2 and thickness of dielectric material is 0.8mm. The hybrid coupler designed length is 0.58mm and width is 1.138mm. It shows that nearly 50% of size reduction is achieved in this type of hybrid coupler when compared to the previously designed hybrid coupler with FR4 dielectric material. Where X nm = for the mode of operation X 11 f nm = resonant frequency. C = velocity of light in free space. = Effective dielectric constant. The resonating frequency is taken as 2.4GHz. According to the above equations the circular patch with radius 17mm is designed with the slot length of 1.4mm which is introduced in the middle of the patch. Then this patch is connected with previously designed 3dB hybrid coupler. This antenna is resonating at 2.4GHz. Figure 4 shows the hybrid coupler connected circular patch antenna with FR4 material. Fig.4. Hybrid coupler connected circular patch antenna with FR4 dielectric 3.2 Development of circular patch with hybrid coupler with RT/Duroid 6010 dielectric After the implementation of hybrid coupler connected microstrip antenna with FR4 dielectric, this paper is concentrated in reducing the antenna size. Though many techniques are available to attain this, the high dielectric material is chosen to achieve the size Fig.5. Top view of circular patch antenna with RT Duroid dielectric Fig.6. Bottom view of circular patch antenna with RT Duroid dielectric Figure 5 and 6 show the top view and bottom view of hybrid coupler connected circular patch antenna with RT/Duroid The calculated radius for the circular patch is 0.72mm. Then this 3dB hybrid coupler is connected to the patch through ground plane. This antenna is operating at 2.4GHz and presents very less return loss with good gain and far field characteristics. 4. Results and Discussions A detailed study of microstrip antenna for wireless applications is done. Here the simulation and measured results of microstrip antenna for FR4 and RT/Duroid dielectric material is discussed. Finally the fabrication of microstrip antenna is done, and the parameters are measured. In this paper, circular polarization is determined by using axial ratio graph. The ratio of

4 electrical field components is said to be axial ratio. For ideal circularly polarized microstrip antenna the axial ratio is 0dB but in practical it may be deviated up to 3dB that means + or 30 degree from the main beam. Figure 7 to 12 show the simulation and measured results of hybrid coupler circular patch antenna. The simulated return loss value of this antenna is dB at 2.396GHz and its measured value is dB at 2.59GHz. It is observed that the gain is 5.512dB and the directivity is 6.277dB and circular polarization is achieved and verified from the radian pattern and axial ratio graph. Worldwide Interoperability for Microwave Access (WiMAX) is covering long range system and it uses licensed and unlicensed spectrum to connect the devices in wireless network. This proposed circular patch antenna with FR4 dielectric material can be used for WiMAX applications. Fig.8. Measured result of return loss of circular patch antenna with hybrid coupler Fig.7. Simulated result of return loss of circular patch antenna with hybrid coupler Fig.9. Simulated result of 2D radiation pattern circular patch antenna with hybrid coupler at 2.4GHz Fig. 10. Measured result of radiation pattern of circular patch antenna with hybrid coupler at 2.4GHz Fig.11. Simulated result of axial ratio of circular patch antenna with hybrid coupler at 2.4GHz

5 Vol.2 (3): pp. 1-7 Figure 13 and 14 shows the simulated and measured return loss of hybrid coupler connected circular patch antenna. This antenna is having return loss of dB at 2.430GHz at simulation results and measured results of db at 2.42GHz. Fig.12. Simulated result of gain and directivity of circular patch antenna with hybrid coupler at 2.4GHz Fig.15. Simulated result of 2D radiation pattern of circular patch antenna with hybrid coupler with RTDuroid 6010 at 2.4GHz Fig.13. Simulated result of return loss of circular patch antenna with hybrid coupler with RT Duroid 6010 Size reduction is another important parameter for communication devices. Nowadays all communication equipments are portable. So in this research the next parameter considered in the proposed antenna is size reduction and also with high gain. By using high dielectric constant material, size reduction is accomplished. Therefore the hybrid coupled connected antenna is designed using rogers duroid material with the dielectric constant of Fig.16. Measured result of radiation pattern of circular patch antenna with hybrid coupler with RT Duroid 6010 at 2.4GHz Fig.17. Simulated result of axial ratio of circular patch antenna with hybrid coupler with RT Duroid 6010 at 2.4GHz Fig.14. Measured result of return loss of circular patch antenna with hybrid coupler with RTDuroid 6010

6 6. Conclusions and Future scope Fig.18. Simulated result of gain and directivity of circular patch antenna with hybrid coupler with RTDuroid 6010 at 2.4GHz Figure 15 and 16 show the simulated and measured results of the radiation pattern. This experimental results show that the proposed antenna is having circular polarization radiation behavior. Figure 17 shows the axial ratio of hybrid coupler connected microstrip antenna with RT/Duroid 6010and that is illustrating the axial ratio is less than 3dB at 2.4GHz. Therefore the circular polarization is achieved. Figure 18 shows that the gain of this antenna is 6.364dB and the directivity is 9.004dB. This antenna is very much useful in radio broadcasting antenna and in mobile devices. 5. Comparison between simulated and measured results Table 1 compares the simulated and measured return loss value of fabricated antenna. This shows the 3dB hybrid coupler connected through ground plane to the circular patch antenna having simulated return loss of dB and measured return loss value is dB at 2.42GHz. This proposed technique has the gain of 6.364dB and the directivity of 9.004dB. Table 1. Comparison between simulated and measured results Antenna structure Hybrid coupler connected Circular Patch (FR4) Hybrid coupler connected Circular Patch (RT/Duroid 6010) SIMULATED at 2.396GHz at 2.430GHz Return loss (db) MEASURED at 2.59GHz at 2.42GHz APPLICATON WiMAX applications Radio broadcasting antenna and mobile devices This paper discusses the effect of various structures of microstrip antenna with hybrid coupler in terms of return loss, gain and far field characteristics. The Method of Moments approach has been used for computation of the results. It has been established that with the appropriate choice of the substrate there has been a significant reduction in size of the antenna. The simulation is carried out by using advanced design software (ADS). The circular patch with hybrid coupler with different substrate is designed, fabricated and its different parameters are measured. Out of these, circular patch antenna with RT/Duroid 6010 material with hybrid coupler gives the results of dB return loss at 2.402GHz and 6.364dB the gain is and the directivity of 9.004dB. Since this proposed antenna is having 360 degrees of radiation pattern, it can be easily mounted upside down in wireless devices and also it can be used in radio broadcasting antenna and mobile devices. When compared with other designed antenna 50% of size reduction is achieved. A method for designing affordable, compact, 3dB hybrid coupler connected microstrip antenna is proposed in this paper. The future work will focus on increasing the bandwidth of antenna. The bandwidth can be varied by different methods such as increasing antenna's substrate thickness, meandered ground plane, slotted ground plane, embedding suitable slots in radiating patch, chipresistor loading and stacked shorted patches. References 1. Economou L. and Langley R.J. (1998), Circular microstrip patch antennas on glass for vechicle applications, IEE Proc. Microwave Antennas and Propagation, Vol.345, No.5,pp Laurent Desclos, Tomislav Drenski, and Mohammad Madihian, (1998), An Interdigitated Printed Antenna for PC Card Applications, Vol. 46, NO. 9, pp Kan H and Waterhouse R.B. (2000), Small circularly polarised printed antenna, IEE Electronics Letters, Vol.36, No.5, pp Mak C.L., Luk K.M and Lee K.F. (1999), Microstrip line-fed L-strip patch antenna, IEE Proc. Microwave Antennas and Propagation, Vol.146, No.4, pp Pozar D.M. (2005), Microwave Engineering, Third Edition, John Wiley & Sons. 6. Sahaya Anselin Nisha.A and Jayanthy.T.(2012), Design of Hybrid Coupled Rectangular Microstrip Antenna for Wireless Application, International Conference Future Communication

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