K.O. Joseph
Registrar/ Professor Department of Electronics and Communication Engineering IEEE Member, GKM College of Engineering and Technology
G.K.M Nagar, New perungalathur -600 063, Chennai, Tamilnadu, India E-mail: josephkandath49@gmail.com
D. Balasubramaniam
Associate Professor Department of Electronics and Communication Engineering IEEE Member, GKM College of Engineering and Technology, G.K.M Nagar
New perungalathur -600 063, Chennai, Tamilnadu, India E-mail: drdbmaniam@gmail.com
N. Archana
Assistant Professor Department of Electronics and Communication Engineering IEEE Member, GKM College of Engineering and Technology
G.K.M Nagar, New perungalathur -600 063, Chennai, Tamilnadu, India E-mail: archanaarul@yahoo.com
S. Rengaraj
P.G. Student (Communication Systems) SM ASDF GKM College of Engineering and Technology
G.K.M Nagar, New perungalathur -600 063, Chennai, Tamilnadu, India E-mail: srenga84@gmail.com
Abstract
Wireless Communication is boon to our generation. It depends on the factors like system capacity, data rate and coverage. To improve the wireless application significantly the enhancement in those factors are required. The project uses the Butler matrix beam forming network for Multi Beam Antenna for design. The structure is implemented using substrate integrated waveguide (SIW) technology. SIW is a transition between microstrip and dielectric-filled waveguide (DFW). Dielectric filled waveguide is converted to substrate integrated waveguide (SIW) by the help of side walls of the waveguide. SIW cruciform couplers are used as fundamental building blocks for their wide range of coupling factors. The Antenna is optimised for the ku-band at 12 to 14 GHZ,. The Antenna thus implemented is compact size and has low loss, lightweight, high density integration with other microwave and millimeter wave planner integrated circuits. HFSS software is used for simulation of Antenna radiation pattern. The ability to get a main beam from an Antenna array in to one of eight possible directions, the eight radiating elements Array Antenna enables us to study the impact of the beam pointing angles over wide band frequency.
Keywords: Beam forming network (BFN), Butler matrix, Couplers, Phase shifter, Substrate Integrated waveguide (SIW), Multiple beam forming network (M-BFN)
I. Introduction
A. Multibeam Antenna
Recently, Multiband Antennas (MBA) [1] have a key element in Mobile Communication systems where increased channel capacity, improved transmission quality with minimum interference and multipath phenomena are strict design constraints. One way to implement a MBA is to use an Antenna collection fed by a multiple beam forming network (beam former) (M-BFN). Such Antennas are widely used in Wireless applications and Satellite Communication systems.
A waveguide-based structure has been used for a narrow-band Butler matrix. Although a compact area layout was proposed, the use of classical waveguides gives rise to a bulky structure.
Good performances have also been obtained using a multilayered design with suspended strip line technology. However, the circuit suffers from a linear phase variation with frequency besides its fabrication complexity. Butler matrix [2] is proposed in SIW technology offering wideband performances for both transmission magnitudes and phases with good isolation and input reflection characteristics. The use of SIW technology combines the advantages of classical rectangular waveguides while being compatible with standard low-cost printed circuit board technology. A Knowledge about Integrated waveguides, Couplers, Phase shifters and various design Parameters for 3-db couplers, microstrip technology and simulation software like CST, ADS, HFSS is a basic requirement for working with SIW.
B. Substrate Integrated Waveguide (SIW)
In high frequency applications, microstrip devices are not efficient, and because wavelength at high frequencies are small, microstrip device manufacturing requires very tight tolerances. At high frequencies waveguide devices are preferred; however their manufacturing process is difficult.
Therefore a new concept emerged: substrate integrated waveguide (SIW). SIW is a transition between microstrip and dielectric-filled waveguide (DFW). Dielectric filled waveguide is converted to substrate integrated waveguide (SIW) by the help of the side walls in the waveguide. The Butler matrix has received particular attention in literature as it is theoretically lossless and employs the minimum number of components. Another method for single-layer realizations is to employ extra 0 dB couplers by means of back-to-back pairs of 3 dB couplers to produce the crossover transfer function. This leads to increased number of components with increased losses especially for larger matrices. In a planar design with wideband performances is reported. However, the complete structure is rather adapted to microstrip technology as it requires wire bonding.
The Antenna has active elements and each output of the butler matrix feed one element.
Consequently, the butler matrix must comprise eight outputs. The butler matrix be made up of eight inputs, it is ideal to implement hybrid in the structure. The function of the butler matrix could have been achieved by 3-dB couplers and phase shifters. Hence, eight inputs give the ability to attain eight different beams pointing at eight directions. The Antenna is optimised for the ku-band [1] at 12 to 14 GHZ, which belongs to the Wireless, Mobile Communication band.
C. Directional Couplers
Directional couplers are passive devices used in the field of radio & telecommunication. They couple a defined amount of the electromagnetic power in a transmission line to a port enabling the signal to be used in another circuit. An essential feature of directional coupler is that they only transfer power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the forward port.
close enough together such that energy passing through one is coupled to the other. However, lumped component devices are also possible at lower frequencies. Also at microwave frequencies, particularly the higher bands, waveguide designs can be used. Many of these waveguide couplers [4] correspond to one of the conducting transmission line designs, but there are also types that are unique to waveguide.
Figure 1: Directional coupler
II.
Design of Matrices
In this design of matrices, the two sets of row and column structures of array matrices, are organized at intersect position or end node by a directional coupler. The Fig.1.shows the layout of a 4x4 matrix is using 3-dB coupler and 90o phase shifter hybrid coupler. The SIW [2] directional coupler is design and utilized to single SIWs with a common conductor wall to coupling between single SIW which is working with H-plane modes. The SIW is made of substrate with a permittivity ofr=2.33 and width 0.5 mm (Rogers RT/Duroid 5870) is used.
III. Parameter Specfication for SIW Coupler
The parameter such as Idis=16.366 mm, Hdis=15.604 mm, dy1=0.781 mm, dia=0.762 mm. where dy1 is distance between the two integrated posts and dia is the diameter of the integrated posts. The specification of the SIW coupler dimensions are given in the table I.
Table I: Parameters of SIW Couplers
dx1 0.781 mm
dy1 0.781 mm
Dis 1.32 mm
Dia 0.762 mm
d1 0.8 mm
d2 0.4 mm
Idis 16.366 mm
Hdis 15.604 mm
Figure 2: SIW 3-dB Coupler
We studied the parameters and equivalent rectangular waveguide model design the coupler. As shown in Fig.2. Port 1 is the input port, port 2 is the coupling port, port 3 is the direct port, port 4 is the isolated port. Hdis is the corresponding rectangular waveguide model width, assigned over the desired frequency range. The posts are included in the crossing area to get desired coupling. The coupling variation is a function the diameter and the position along the axis of the SIW waveguide.
The simulation results for SIW waveguide couplers are as below. Since the coupling range between S11 and S41 is important in -3dB couplers application, simulated results are shown in Fig3.
The -3dB coupler has magnitude of S21 with a solution frequency at 13 GHZ.The S-parameter of S21and S31 value is -12.041dB and -14.498dB from 11.4 to 14 GHZ and isolation below -17dB over the same bandwidth.
Figure 3: Simulation results for the -3dB coupler S21 and S31.
IV.
Conclusion
A Novel matrix based on SIW technology has been designed in our paper. The matrix is optimized using the HFSS software to operate from KU band frequency of 12 to 14 GHZ. The proposed SIW technology design has the advantage of minimum cost, high integration density and easy fabrication.
The Experimental and simulation results have been measured. The proposed directionals are totally arranged by single substrate and hence achieving the compact size. It has immense potential for designing microwave and wave planar circuits.
Reference
[1] ―Design and Implementation of Two-Layer Compact Wideband Butler Matrices in SIW Technology for Ku-Band Applications‖ Ahmed Ali Mohamed Ali, Nelson J. G. Fonseca, Senior Member, IEEE, Fabio Coccetti, Member, IEEE, and Hervé Aubert, Senior Member, IEEE Transaction on Antennas and propagation. vol., 59. N0.2. FEBRUARY 2011.
[2] ―Design of Fully Integrated 4x4 and 8x8 Butler Matrices in Microstrip/Slot Technology for Ultra Wideband Smart Antennas Marek E. Bialkowski 1, Feng-Chi E. Tsai 2, Yu-Chuan Su, 2 Kai-Hong Cheng 2 1 School of ITEE, University of Queensland St Lucia, Brisbane, QLD 4072, Australia, meb@itee.uq.edu.au 2 Antenna Design Department, Wistron NeWeb Corporation No. 10-1, Li-Hsin Road 1, Hsinchu Science Park, Hsinchu 300, Taiwan R.O.C.,{ eddie_tsai, vincent_su, kh_cheng}@wneweb.com.tw
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[8] Substrate-Integrated –Waveguide Beam forming Networks and Multi beam Antenna Arrays for Low-Cost Sate llite and Mobile Systems Yu Jian Cheng1, Peng Chen2, Wei Hong2, Tarek DjerafP, and Ke Wu3 IEEE Antennas and Propagation Magazine, Vol. 5 3, No. 6, December 2011.
ISSN 1450-216X / 1450-202X Vol. 98 No 1 March, 2013, pp.118-122 http://www.europeanjournalofscientificresearch.com