Volume 114 No. 7 2017, 447-457 ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version) url: http://www.ijpam.eu ijpam.eu Design of a UHF Pyramidal Horn Antenna Using CST Biswa Ranjan Barik and A.Kalirasu Department of EEEM, AMET University, Chennai, India barikbiswa65@gmail.com and akalirasu@yahoo.co.in Abstract This technical paper highlights about design of pyramidal horn antenna and simulation of its parameters using computer simulation technology. Horn antennas are extensively used in the fields of T.V. broadcasting, microwave devices and satellite communication. Since horn antennas do not have any resonant elements they operate at wide range of frequencies and have a wide bandwidth. They are also used as high gain devices in phased arrays and as a feeder for reflector and lens antennas in satellite communication. The material used in the design of antenna is Perfect Electric Conductor (PEC). The designed Pyramidal horn antenna is functional for each UHFband applications and here it is having gain of 5dB operating at 2.8GHz frequency. The performance parameters like Directivity, impedance, Efficiency, s-parameters are evaluated using CST Key Words:- Horn Antenna, resonant element, Phased arrays, Feeder, PEC,CST 1. Introduction The horn antenna is most widely used simplest form of microwave antenna, which comes from the aperture antenna family. The first horn antenna was constructed by an Indian radio researcher and one of the father of radio science Jagadish Chandra Bose (1858-1937), in the year 1897. The horn makes a transition of EM waves propagating in a waveguide, and launches it into free space. The flaring of the metal helps in the gradual 447
matching of the impedance of the waveguide, usually 50 Ω, to that of the free space i.e., 377 Ω. The advantages of a horn are its wide bandwidth, low VSWR and simplicity of construction and adjustment. They are designed in variety of shapes and sizes to fulfill many practical applications, such as communication systems, electromagnetic sensing, directive antenna applications, microwave applications, biomedical applications and as a reference source for testing of other antennas. These horns can be used as feeds for other antennas such as reflectors, compound and lens antennas. Due to such a vast area of application and advantages, the horn antenna can be preferred over other aperture antennas. Basically the horn antennas are classified as rectangular horn antennas and circular horn antennas. The rectangular horns are further divided into sectoral horn and pyramidal horn. The sectoral horn is divided into two types based on the direction of flaring in accordance of the field vectors. The E plane sectoral horn is obtained when the flaring is done in the direction of the electric field vector. The H plane sectoral horn is obtained when the flaring is done in the direction of the magnetic field vector. When the flaring of the walls of the waveguide is done along the direction of both E and H field vectors, it gives rise to a horn called Pyramidal Horn The pyramidal horn antennas are the most extensively used antennas since they have the combined characteristics of both E plane and H plane sectoral horns. 2. Antenna Parameters The characteristics of an antenna can be understood by the antenna parameters. The various parameters such as radiation pattern, beam width, directivity, radiation intensity help us for the analysis of an antenna. 2.1 Antenna Radiation Pattern It is the graphical representation of electric and magnetic fields at all points equi-distance from the antenna. It gives radiation properties of an antenna as a function of space coordinates. If it is measured in terms of volts/m then it is called Field Radiation Pattern. If it is measured in terms of power per unit solid angle, then it is called Power Radiation Pattern. The relative measure of magnitude of the antenna s ability to direct or concentrate the electromagnetic energy in a particular direction or pattern is called Gain. It is measured in decibels. The expression to calculate the Gain is D P(, ) max...(1) P (, ) average The Directivity of an antenna is its capability to direct or concentrate the radiated power in a particular direction and attenuate in undesirable directions. 448
D 4 4 4...(2) P (, ) n d A Radiation intensity is the measure of the power radiated from an antenna per unit solid angle in a given direction. It is a far-field parameter. Total power radiated is given by 2 P Ud U sin dd...(3) rad 0 0 3. Design Equations of Horn Antenna The electromagnetic horn produces uniform phase front with larger aperture as compared to wavelength. Because the horn aperture, at higher frequencies, is electrically larger when compared to wavelength. Due to this the directivity increases. Assuming that there is a line source which radiates cylindrical waves, and the dimensions of the imaginary apex of the horn as shown in the figure. Where, δ is the difference in the path of travel, θ is the flare angle, h is the height of aperture, ρ is length of aperture. Fig:1 Section view of Horn Antenna Then from geometry[4] 449
COS...(4) Also h tan 2 h...(5) 2 Hence we get COS h tan...(6) 2 1 1 The angle θ represented in equation is called the optimum aperture angle. The directivity of maximum value can be obtained at the largest flare angle for which the path difference does not exceed typical values of 0.32 λ for conical horn, 0.25 λ for plane horn and 0.40 λ for H plane sectoral horn antenna. Because of more than one flare angle the pyramidal and conical horn antenna has the highest directivity compared to any other horns. For optimum flare horn, the half power beam width can be approximated as H 67...(7) a H And E 56...(8) a E Directivity in terms of effective aperture of the horn as D 4 A e 4 ap A 2 2 p...(9) Where Ae is effective aperture, in m 2, Ap is physical aperture, in m 2,ε ap = Ae /Ap is Aperture efficiency 450
4. Pyramidal Horn Antenna using CST The pyramidal antenna is generally excited using a waveguide which is fed with a coaxial cable. The antenna here is constructed using a simulation software called Computer Simulation Technology (CST) and it is assumed that antenna is made up of PEC; the plates of finite thickness are modeled as infinitesimally thin plates resulting in surface currents that represent the sum of interior and exterior antenna currents. This software has the maximum of 30,000 cells.the geometry of a horn antenna with spatial coordinates is as x min = -25; x max = 25 and y min = -14; y max = 14 and z min = 0 and z max = 70 modeled as shown in Figure. Pyramidal flare of horn antenna is the most significant part in the antenna design, which varies the impedance of waveguide from 50Ω at the feeding point to 377Ω at the aperture of the antenna. The symmetry feature in both electric and magnetic planes can be used, so as only half or quarter of given antenna can be modeled. The gain obtained is 5.50 db approximately, near field is observed and analysis characteristics for different models of antenna at various frequencies are observed. Fig. 2 Pyramidal Horn Antenna using CST 5. Simulation and Experimental Results 451
Fig. 3. S- Parameter Fig. 4 VSWR Fig. 5. Power Excitation Signals Fig. 6. Input Excitation Signal 452
Fig. 7. 3D Plot of gain for 3GHz Fig. 8. Polar Plot of gain for 3GHz Fig. 9. Polar Plot of gain for 6GHz Fig. 10. 3D Plot of gain for 6GHz 453
Figure-1 Shows the analysis of the design with S(1,1) parameters. S- parameters are called complex scattering parameters because both the magnitude and phase of the input signal are altered by the network. Due to impedance mismatch some energy is reflected back in the system which is called as return loss (db). It is a numerical measure of dissimilarity between impedances of loads and metallic transmission lines. It is important in applications that use simultaneous bidirectional transmission. Larger values of it indicate less reflection. The value of -15 to-20 db and higher are considered acceptable. Figure-2 shows VSWR graph. Voltage standing wave ratio gives the value that how our antenna is matched with transmission line impedance or with load resistance. The simulated value for voltage standing wave ratio is less than 2 and hence can be fair for signal transmission when low attenuation is present. It also concludes that the designed antenna is matched to the operating frequency. Both VSWR and Return loss play an important role in the study of transmission from antenna and reception of signal. Figure-3 shows the power excitation of the designed antenna. The amount of power accepted, radiated, Power outgoing of all port and power stimulated Figure-4 shows the default excitation signal which is used to activate the antenna. Figure-5 shows the 3D and polar plot of gain which shows the magnitude of main lobe for the designed Pyramidal horn antenna. The value is found to be 5.49 dbi. 6. Conclusion The successful implementation and simulation of pyramidal horn antenna is done by using CST. As a result of experimental studies, it is evident that signal integrity be intercepted or transmitted depend on the design considerations of the pyramidal horn antenna. These antennas can be enhanced using dielectric lens, good conductive materials and ridges. They are used significantly where directivity of signal is of main concern. CST is a useful tool for better 2D and 3D analysis and design of antenna structure within small time. By using CST simulation results, we have designed our antenna of gain 5dB with a resonant frequency of 2.8GHz, VSWR is 2 and normalized impedance of 50Ώ. References 454
[1] Ayodele S.Oluwole,viranjan M.Srivastava, Design of smart antenna using waveguide-fed pyramidal horn antenna for wireless communication systems, IEEE(INDCON),2015. [2]. N.Smitha,Vipula Singh,S.N.Sridhara, Pyramidal horn antenna for ground penetrating radar application, IEEE(INDICON), 2016. [3] Katsushige Harima, Makato Sakasai, Katsumi Fujji, Determination of gain for pyramidal horn antenna on basis of phase center location, IEEE (ISEC), 2008. [4]. Deqinsyang, Sihaolio, Bao Sun, Jin Pan, Research on Pyramidal Horn Antenna using integrating optical E field probe, IEEE (APMC), Vol.3, 2015. [5] Chintin A. Patel, Shobhit K. Patel, Pyramidal Horn antenna design loaded by meta material for performance enhancement, IEEE (MEMO), 2015. [6]. Aniket Bhumkar, Design and Implementation of Pyramidal Horn Antenna, IJRASET, Vol. 3 Issue V, May 2015. [7] Arvind Roy, Design and Analysis of X band Pyramidal Horn Antenna Using HFSS, IJARECE, Vol. 4 Issue 3, March 2015. [8] Daniyan O.L., Horn Antenna Design: The Concepts and Considerations, IJETAE, Vol. 4 Issue 5, May 2014. [9]Priyanka Bhagwat, High gain Conical Horn Antenna for short range communications, IJERA, Vol 3 Issue 6, Nov-Dec 2013. [10]. Arvind Roy, Isha Puri, Design and Analysis of X band Pyramidal Horn Antenna Using HFSS, IJARECE, Volume 4, Issue 3, March 2015. [11]. G.Abhignya, B.Yogita, C.Abhinay, B.Balaji, MBR Murthy, Design, fabrication and testing of pyramidal horn antenna, IJEAS ISSN: 2394-3661, Volume-2, Issue-4, April 2015 455
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