Up gradation of Plasma Antenna by Using Fluorescent Tubes

Transcription

1 Up gradation of Plasma Antenna by Using Fluorescent Tubes Raviprakash Shriwas 1 and Sayali Gulhane 2 1 Raviprakash S. Shriwas Assist.Professor in EXTC Department Jawaharlal Darda Institute Of Engineering And Technology Yavatmal,India 2 Sayali Purushottam Gulhane Final Year (EXTC) Student Jahawarlal Darda Institute Of Engineering And Technology Yavatmal,India ABSTRACT Plasma antennas refer to a wide variety of antenna concepts that incorporate some use of an ionized medium. Plasma Antenna is a new captivating concept which could very well be the future of high-speed, high-frequency wireless communications. It is possible to transmit focused radio waves using Plasma antennas that would quickly dissipate using the conventional metal antennas. A plasma antenna is a type of radio antenna currently in development in which plasma is used, replacing the metal elements of a traditional antenna. Plasma antennas can be used for both transmission and reception. The advancement in plasma antenna is with the use of fluorescent tubes. The commercially fluorescent tubes consist of a glass tube filled with mixture mercury vapor and argon gas. The gas inside the fluorescent tube will ionize to plasma after getting sufficient voltage and formed plasma column. The plasma is highly conducting and it acts as a reflector. When all of the surrounding tubes are electrified, the radiation is trapped inside the antenna when the plasma frequency is greater than radio frequency. The developed antenna has potential in military application. Keywords :-Plasma antenna; 4.9 Ghz Frequency band; Transmitter and Receiver. 1. INTRODUCTION Transmission and reception of electromagnetic waves has become an integral part of the current day civilization. Antenna is a necessary device for this process. Antenna is an electrical transducer which transmits or receives electromagnetic waves. In other words, antenna is defined as an electrical conductor of a specific length that radiates radio-waves generated by a transmitter and collects these waves at the receiver. Antennas are used in systems such as wireless LAN (local area networks), mobile phones, radars, radio, television broadcasting, point-to-point Rf communication, and the communication using spacecraft. Antennas are generally used in air and space, although they can also be employed under the water or through soils and rocks.[1] The advancement of new technology in communication and radar application is giving improvement in radio frequency (RF) transmission. Besides the improvement in antenna structure, the material of the conducting element of the antenna is also an important aspect that influences the antennas performance. Plasma antenna is one of the antenna in which the material conducting element of metal is replaced by plasma.[5] Plasma antennas are radio frequency antennas that employ plasma as the guiding medium for electromagnetic radiation. Here, plasma discharge tubes are used as the antenna elements. The tubes become conductors when they are energized and can transmit and receive radio signals. And they revert to nonconducting elements when de-energized.[2] This plasma antenna uses plasma discharge tubes concept. When the tube is energized with electrical power, the gas inside the tube will be ionized into plasma state, where it becomes conductive and capable to transmit and receive radio signals and they revert to non-conducting elements when deenergized. In this state they not probing radio signals.[5] Plasma antenna can be "Steered" electronically. It can also be turned off rapidly reducing the effect of ringing on pulse on transmission.[2] It is an agile antenna which hides itself from hostile radar in switch or mode and brought to functioning or switch on mode immediately when it is needed.[7] In the last 10 years, there has been a tremendous growth in plasma based technologies including a number of spin off plasma based electronic devices such as plasma mirrors for plasma phase shifters, microwave reflection and plasma switches, plasma antennas, etc. In the communication area, the plasma element is considered as an effective radiator which releases the electromagnetic energy just as the metal element did. Many techniques for producing the plasma are also introduced and varied practicality.[3] A simple way to construct a plasma antenna is by using fluorescent tubes, since they are available commercially. Fluorescent tubes contain a mixture of gas argon and mercury vapor. When the Volume 3, Issue 1, January 2015 Page 9

2 gas inside the tubes is energized with RF signal, the vibration electrons will convert the gas into plasma state which is a strong conducting element that can act similarly to its metal counterpart, allowing radio frequency to be transmitted and received at certain frequency. In this state, the fluorescent tube behaves as an antenna. The advantage of this antenna is its low system and maintenance cost due to multi-functional capability which can eliminate the need of lightning protection mechanism used in conventional antenna. 2. LITERATURE REVIEW The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed dipole antennas at the focal point of parabolic reflectors for both transmitting and receiving. He published his work in Annalen der Physik und Chemie (vol. 36, 1889). Plasma antennas have become practical in recent years, the idea is not new; a patent for an antenna using the concept was granted to J Hettinger in The researchers of the plasma antenna laboratory of Canberra University in Australia find that the changing of variable parameters of plasma antenna will lead to the changing in its radiation pattern. Rayner finds that the length of plasma is directly proportional to the square root of excitation power, and the density of plasma along the antenna presents linear distribution. A rigorous representation has been obtained for the current distribution on an infinitely long plasma antenna. It is also found that the stability of resonant frequency increases with the increasing in frequency of the power supplied. From the related research works mentioned above, it can be says that the reconfigurable characteristics of the plasma antenna are the important advantage over the metallic antenna and the thorough and effective research work should be investigated.[8] Several works have reported the possibility using plasma antenna as conducting elements instead of metal. Kumar et. el. reported the possibility of using fluorescent tube as plasma antenna by applying AC voltage of 200 Hz or more, across the electrode of fluorescents tube.[4] Zheng et. al. reported that the average gain of plasma antenna is about 6 db lower than the metallic counterpart and the gain at lower frequency band is better than that at higher frequency band. Another research reported that lower frequency signals can be transmitted, receipted and reflected by plasma antenna while being transparent to higher frequency signals. In the particular work, a new kind of monopole plasma antenna have been design and analyzed, however the research does not have specific target frequency for the aim of antenna applications. Here fluorescent monopole Plasma antenna having operating frequency of 4.9GHz is designed. 3. PRINCIPLE OF PLASMA Plasma is ionized gas. Hence, they made up of positive and negative ions and electrons, as well as neutral species. The plasma is the state of matter which is often referred to as the fourth matter. The degree of ionization can vary from 100% (fully ionized gases) to very low values or partially ionized. The various techniques that can generate the plasma are applying electric and/or magnetic fields, laser excitation pre-ionization followed by high voltage breakdown to form the main conducting channel, RF heating, or by simply using commercial fluorescent tube. The power source that can be used to generate plasma can be RF, DC, and microwave. The process of Ionization occurs when a sufficiently high potential difference is applied between two electrodes placed in a gas; the latter will break down into positive ions and electrons. The gas breakdown mechanism can be explained as follows: The electrodes emits few electrons are emitted due to the omnipresent cosmic radiation. The electrons emitted from the cathode are not able to sustain the discharge without applying a potential difference. But when a potential difference is applied, the electric field in front of the cathode accelerates electrons and they collide with the gas atoms. Once plasma is formed, to maintain the energy and particle balance a sheath is formed automatically between the electrode and plasma. The Region outside the sheath where uniform plasma exists is called the positive column. Whose dimension and density are determined by the balance between ion diffusion to the surrounding wall of the tube and the ion generation mechanism.[3] Several types of plasma antennas can be constructed, including dipole, loop and reflector antennas. The emitting element in plasma antennas is the plasma with electric conductivity. The concept in the gas plasma antenna is to use plasma discharge tubes as the antenna elements. These get transformed into conductors, when the tubes are energized and can send and receive radio signals. When de-energized, these relapse into non-conducting components and do not reflect prying radio signals. In the absence of plasma in the discharge tube; such a device does not show electric conductivity. It laid back passive.[1] Volume 3, Issue 1, January 2015 Page 10

3 4. ANTENNA STRUCTURE AND DESIGN Figure 1 structure of plasma Figure 2 Antenna Structure Figure 3 Cross section view Figure 4 Top view The structure of the antenna is shown in figure 2,3 and 4. The antenna structure consists of 12 tubes of commercial fluorescent lamps that containing the mixture of mercury vapor and argon gas. The ground is circular aluminum with monopole antenna at the centre of ground. The antenna is fed by a standard SMA connector that is located at the middle of the ground. The probe feed (coaxial feed) is a technique that used in this project for feeding micro strip patch Volume 3, Issue 1, January 2015 Page 11

4 antennas and fed by a SMA connector. SMA connector design is according to specification in using Teflon with dielectric constant = The impedance of feeding coaxial transmission line is 50 Ω..The tube wall has a thickness, t = 0.1mm with radius 10mm. The default antenna dimension is presented in Table I. Table 1 Antenna dimensions Parameter s Description Dimensions(mm) R_gnd Radius ground T Thickness ground Dd Diameter dipole Ld Length dipole Dg Diameter glass Lg Length glass The behavior of the plasma is given by drude dispersion model in CST software. The drude dispersion model describes simple characteristic of an electrically conducting collective carriers, where thermic movement of electrons is neglected. The dielectric constant of the drude dispersion model is given by equation 1 (1) Where ɛ is the relative dielectric constant at infinite frequency, generally ɛ =1 and ω is EM wave frequency. The plasma frequency ωp and the collision frequency νc are called drude parameters. Plasma frequency is a natural frequency of the plasma and is a measure of amount ofionization in plasma νc=n e K(T e ) (2) Where νc is collision frequency, n e is electron density in 1/cm 3, K is boltzman s constant and T e is electron temperature of plasma elements. The difference between the plasma frequency and operating frequency of the plasma elements is the plasma frequency is a measure of amount of ionization in plasma and the operating frequency of the plasma elements is the same as the operating frequency of a metal antenna. The ratio gas between argon and mercury vapor is 0.9:0.1 for fluorescent tubes used. For simulation of antenna, Drude dispersion material is designed as following Table 2: Table 2 Drude dispersion material Parameter Value Epsilon infinity, 1 Plasma frequency, 5.634e11 Collision frequency, 10e9 Relative magnetic permeability, 1 5. RESULT AND DISCUSSION OF SIMULATION In this section, simulation outcome were explained. The simulation is performed by using the commercially available simulation software CST Microwave Studio software. 5.1 The return loss effect of monopole Antenna with Plasma and without Plasma The monopole antenna is fed by a standard SMA connector that is located at the centre of dipole. The line impedance generated for the antenna is 50Ω. Fluorescent tubes were added surrounding at the dipole. Figure V. shows the S11 parameter at operating frequency 4.9 GHz. Referring to the Figure V, the red line represent for dipole antenna without plasma with the S 11 equal to dB while blue line represent monopole antenna with plasma and the S11 is dB. Volume 3, Issue 1, January 2015 Page 12

5 Figure 5 The return loss effect on monopole antenna with and without fluorescent tubes 5.2 Gain of Monopole Antenna with Plasma and without Plasma Figure 6 Gain measured during simulation result Figure 6 shows the gain result from simulation. The blue line represent the monopole with fluorescent tubes While red line for monopole antenna without fluorescent tubes. Referring to figure 3 the gain measured at operating frequency at frequency (4.9GHz) for monopole antenna with fluorescent tubes is 7.061dB while monopole antenna without fluorescent tubes is 1.351dB only. From the graph, the percentage of efficiency 13% increment is noticed for monopole antenna with fluorescent tubes compared to without fluorescent tubes. Therefore the use of fluorescent tubes is can be considered effective in enhancing the gain and efficiency. 5.3 Voltage Standing Wave Ratio (VSWR) between Monopole antenna with fluorescent tubes and monopole antenna without fluorescent tubes Figure 7 Voltage Standing Wave Ratio (VSWR) between Monopole antenna with fluorescent tubes and monopole antenna without fluorescent tubes. Volume 3, Issue 1, January 2015 Page 13

6 VSWR is a measurement of how well matched an antenna is to the line impedance. A perfectly matched antenna would have a VSWR of 1:1. This indicates how much power is reflected back or transferred into a cable. Fig. 7 shows the VSWR between monopole antenna with and without fluorescent tubes. Both result show a satisfy outcome since the ratio is VSWR<2.At its most optimum frequency of 4.9Ghz, VSWR for both monopole antenna without fluorescent tubes and monopole antenna with fluorescent tubes is 1.19 and 1.06 respectively Effect Due To Number of Fluorescent Tubes Figure 8 Relationship between gain and number of fluorescent tubes Table 3 Relationship between gain and number of fluorescent tubes No. of fluorescent tubes Gain(dB) Figure 8 and table 3 show the gain in db of the changes done to number of fluorescent tubes. From the graph, as the number of fluorescent tubes is increased the gain decreases. This is because the plasma elements inside the fluorescent tubes trapped the radiation inside hence reduces the gain. 5.5.Effect Due To Various Height of Monopole Antenna, Ld Figure 9 Gain against various height of monopole antenna Volume 3, Issue 1, January 2015 Page 14

7 Table 4 Various Dimensions of Height Monopole Antenna, Ld Height, Ld(mm) Gain(dB) From figure 9 and table 4 the higher gain at height, Ld equal to mm which is 7.061dB. 6. TRADITIONAL ANTENNA VS PLASMA ANTENNA It is an important advantage that plasma antennas are much lighter than conventional antennas. By using the conventional arrays high frequency radio waves will dissipate quickly if they are beamed, but they can be focused by using plasma antennas. The plasma antenna under special circumstances has less thermal noise than a metal antenna. [1] Unlike simple antenna, plasma antenna selects a beam avoiding the need for mechanical or manual alignment and realignment of fixed point to point communication links. Because of lower Ohmic losses higher power can be achieved in the plasma antenna than in the corresponding metal antenna. The range of power capability is much wider in plasma antenna than metals. By controlling plasma density the greater bandwidth of the plasma antenna can be achieved than the corresponding metal antenna of the same geometry. Plasma antenna selectable beam antennas provide similar advantages to phased array antennas but at a fraction of a cost together with much wider bandwidth of operation. [2] 7. ADVANTAGES AND DISADVANTAGES 7.1. Advantages As soon as the plasma generator is switched off, the plasma becomes non conducting and therefore becomes effectively invisible to radar. They can be dynamically tuned and reconfigured, so replacing the need for multiple antennas. They exhibit much less thermal noise and are capable of faster data rates. [2] Plasma antennas are maintenance-free because they do not contain mechanical parts. They are ideally suited for a wide range of wireless communications and sensing applications. Plasma antennas have a number of potential reconfigurable advantages for antenna design. When one plasma antenna is de-energized, the antenna goes back to being a dielectric tube. A second antenna can transmit through it. This allows the use of several massive antennas stacked over each other instead of several small antennas placed next to each other. This results in higher directivity and sensitivity.. The signal is prevented by degradation and results in good quality transmission. Nearby elements does not get affected by radiation when a particular plasma element is not energized. Solid-state plasma antennas gives bandwidth in gigabit and high frequency plasma antenna could hold the key for economically viable superfast wireless networking. Plasma antennas have developed an innovative range of selectable multi-beam antennas that meet the demands in today s defense, wireless communication and security markets.[1] 7.2Disadvantages The current antenna hardware uses a wider range of frequencies so it s impractically massive to be used for mobile environments. Plasma antennas are quite expensive and hard to manufacture. Antennas operating at higher frequencies mean that high-frequency signals couldn t penetrate walls like standard Wi-Fi, so signals ought to be reflected throughout the buildings. Volume 3, Issue 1, January 2015 Page 15

8 8. APPLICATIONS The plasma antenna has military applications for its stealth, weight and easily reconfiguration. Among other applications are: Unmanned air vehicle sensor antennas. In high speed digital communication and radar system IFF ("identification friend or foe") land-based vehicle antennas Stealth aircraft antenna replacements Broad band jamming equipment including for spread-spectrum emitters ECM (electronic counter-measure) antennas. Phased array element replacements. Detection and tracking of ballistic missiles Side and back lobe reduction The commercial applications comprise: Telemetry Broad-band communications Ground penetrating radar Navigation Weather radar Wind shear detection and collision avoidance Used for transmission and modulation techniques (PM, AM, FM). Defense, Space and Homeland Security. 9. CONCLUSION Thus it can be seen that that a simple fluorescent tube, used for household applications can be used to work as a plasma antenna. From the simulated performances of monopole antenna with fluorescent tubes, utilization of plasma elements inside the commercial fluorescent tube contributes in gain and efficiency enhancement and proven to overcome the problem occurred in monopole antenna that suffers from low gain. The design and construction of monopole antenna with fluorescent tubes shows the advantageous advancement in antenna s technology. With plasma antenna technology, there are problems to smooth out, but researchers and engineers. REFERANCES [1] Aboli Moroney & Monal Mehta ( Nov 2013) Plasma Antennas IJGET, Vol. 2, Issue 5. [2] Ritika Nahar, Garima Tiwari, Shaifali Tiwari (Feb 2013) Plasma Antenna IJETMR,Vol 1 Issue 1 [3] Hajar Ja afar1*, M. T. Ali1, Ahmad Nazri Dagang2, Hanisah Mohd Zali1, Nur Aina Halili (2013) Performance Analysis Of A Monopole Antenna With Fluorescent Tubes At 4.9ghz Application IEEE Vol.4, No.10 [4] H.M.Zali, M.T.Ali, I.Pasya, N.Ya acob, N.A.Halili, H.Ja afar, A.A.Azlan A Monopole Fluorescent Tube Antenna With Wi-Fi Router (2014) 21st International Conference On Telecommunications (Ict) [5] Hanisah Mohd Zali*, Mohd Tarmizi Ali, Nur Aina Halili, Hajar Ja afar, Idnin Pasya study of monopole plasma antenna using fluorescent tube in wireless transmission Experiments 2012 IEEE [6] M. Khadir and K. Forooraghi Plasma Monopole Antenna Simulations and Measurement ICEEM [7] V. Kumar1, *, M. Mishra1, And N. K. Joshi Study Of A Fluorescent Tube As Plasma Antenna Vol. 24, 17{26, 2011 Volume 3, Issue 1, January 2015 Page 16