DUAL FREQUENCY 24 GHZ TSHAPED AND 52 GHZ INVERTED LSHAPED MONOPOLE ANTENNA FOR WLAN APPLICATIONS

DUAL FREQUENCY 2.4 GHZ T-SHAPED AND 5.2 GHZ INVERTED L-SHAPED MONOPOLE ANTENNA FOR WLAN APPLICATIONS Adviser Dr YIH-CHIEN CHEN NGUYEN XUAN KIM CUONG Student ID Student : 060534D Class : 06DD2D SV:Nguyễn Xuân Kim Cương MSSV:060534D Contents Chapter1: PROPERTIES OF ELECTROMAGNETIC 1.1 Maxwell’ Equation 1.2 Plane Wave Properties 1.3 Diffraction 1.4 Field Relationships 1.5 Poynting Vector 1.6 Phase Velocity .7 1.7 Polarisation States 1.8 Lossy Media Chapter 2: PROPAGATION MECHANISMS 10 2.1 Lossless Media 10 2.2 Rough Surface Scattering 13 Chapter 3:ANTENNA FUNDAMENTALS .15 3.1 Necessary Conditions for Radiation .15 3.2 Near-Field and Far-Field Regions 16 3.3 Far-Field Radiation from Wires 17 3.4 Radiation Pattern 18 3.5 Radiation Resistance and Efficiency 19 3.6 Power Gain 20 3.7 Bandwidth 21 3.8 Directivity 23 Chapter 4: PRACTICAL ANTENNA 24 4.1 Dipole Structure 24 Page SV:Nguyễn Xuân Kim Cương MSSV:060534D 4.2 Current Distribution 25 4.3 Reflector Antennas 25 4.4 Horn Antennas 26 4.5 Loop Antennas 27 4.6 Helical Antennas 28 4.7 Patch Antennas .28 Chapter 5: THE MICROSTRIP ANTENNA DESIGN 31 5.1 Historical Development 31 5.2 Basic Microstrip Line .31 5.3 Microstrip Field Radiation 32 5.4 Substrate Materials 33 5.5 Basic Microstrip Antenna 35 5.6 Basic configuration of Microstrip Antenna 36 5.7 Advantages vs Disadvantages of Microstrip Antennas 38 5.8 Applications 39 5.9 Types of Microstrip Antennas .39 5.10 Microstrip Traveling-Wave Antennas 40 5.11 Microstrip Slot Antennas 42 Chapter 6: PRODUCTION PROCESS .45 6.1 Production Overview 45 6.2 Production Details 45 6.3 Improving Antenna 49 6.4 Measurement .49 6.5 Antenna 50 Page SV:Nguyễn Xuân Kim Cương MSSV:060534D CHAPTER 7: THE FINAL REPORT .51 7.1 Introduction 51 7.2 Antenna Design Structure: 51 7.3 Simulations 52 7.4 Experience Design .53 7.5 Measurement Result: 53 7.6 Radiation Patterns: 53 7.6.1 The Simulated Radiation Patterns In The X-Y, X-Z, Y-Z Planes at 2.4 GHz 53 7.6.2 The Simulated Radiation Patterns In The X-Y, X-Z, Y-Z Planes at 5.2 GHz 55 7.7 Conclusion: 57 Page SV:Nguyễn Xuân Kim Cương MSSV:060534D Chapter1: PROPERTIES OF ELECTROMAGNETIC 1.1 Maxwell’ Equation The existence of propagating electromagnetic waves can be predicted as a direct consequence of Maxwell’s equations [Maxwell, 1865] These equations specify the relationships between the variations of the vector electric field E and the vector magnetic field H in time and space within a medium The E field strength is measured in volts per metre and is generated by either a time-varying magnetic field or a free charge The H field is measured in amperes per metre and is generated by either a time-varying electric field or a current Maxwell’s four equations can be summarised in words as An electric field is produced by a time-varying magnetic field A magnetic field is produced by a time-varying electric field or by a current Electric field lines may either start and end on charges; or are continuous Magnetic field lines are continuous The first two equations, Maxwell’s curl equations, constain constants of proportionality which dictate the strengths of the fields These are the permeability of the medium µ in the henrys per metre and permittivity of the medium Ɛ in the farads per metre They are normally expressed relative to the value of free space: Ɛ=ƐrƐ0 µ=µrµ0 µ0=4π x 10-7 Hm-1 Ɛ0=8.854 x 10-12 Fm-1 Ɛr, µr =1 in the free space Free space strictly indicates a vacuum, but the same value can be used as good approximations in dry air at typical temperatures and pressures Page SV:Nguyễn Xuân Kim Cương MSSV:060534D 1.2 Plane Wave Properties Many solutions to Maxwell’s equations exist and all of these solutions represent fields which could actually be produced in practice However, they can all be represented as a sum of plane waves, which represent the simplest possible time varying solution Figure shows a plane wave, propagating parallel to the z-axis at time t = The electric and magnetic fields are perpendicular to each other and to the direction of propagation of the wave; the direction of propagation is along the z axis; the vector in this direction is the propagation vector or Poynting vector The two fields are in phase at any point in time or in space Their magnitude is constant in the xy plane, and a surface of constant phase (a wavefront) forms a plane parallel to the xy plane, hence the term plane wave The oscillating electric field produces a magnetic field, which itself oscillates to recreate an electric field and so on, in accordance with Maxwell’s curl equations This interplay between the two fields stores energy and hence carries power along the Poynting vector Variation, or modulation, of the properties of the wave (amplitude, frequency or phase) then allows information to be carried in the wave between its source and destination, which is the central aim of a wireless commu- nication system 1.3 Diffraction The geometrical optics field, accurate for many problems where the path from transmitter to receiver is not blocked However, such a description leads to entirely incorrect predictions when considering fields in the shadow region behind an Page SV:Nguyễn Xuân Kim Cương MSSV:060534D obstruction, since it predicts that no field whatsoever exists in the shadow region as shown in Figure 3.11 This suggests that there is an infinitely sharp transition from the shadow region to the illuminated region outside In practice, however, shadows are never completely sharp, and some energy does propagate into the shadow region This effect is diffraction and can most easily be understood by using Huygen’s principle Each element of a wave front at a point in time may be regarded as the centre of a secondary disturbance, which gives rise to spherical wavelets The position of the wave front at any later time is the envelope of all such wavelets 1.4 Field Relationships The electric field can be written as E=E0cos(ωt-kz)x^ where E0 is the field amplitude [V m -1], ω=2πf is the angular frequency in radians for a frequency f [Hz], t is the elapsed time [s], k is the wave number [m - 1], z is distance along the z-axis (m) and ^x is a unit vector in the positive x direction The wave number represents the rate of change of the phase of the field with distance; that is, the phase of the wave changes by kr radians over a distance of r metres The distance over which the phase of the wave changes by π radians is the wavelength λ Thus k=2π/λ Similarly, the magnetic field vector H can be written as H=H0Cos(ωt-kz)y^ where H0 is the magnetic field amplitude and ^y is a unit vector in the positive y direction The medium in which the wave travels is lossless, so the wave amplitude stays constant with distance Notice that the wave varies sinusoidally in both time and distance 1.5 Poynting Vector The Poynting vector S, measured in watts per square metre, describes the magnitude and direction of the power flow carried by the wave per square metre of area parallel to the xy plane, i.e the power density of the wave Its instantaneous Page SV:Nguyễn Xuân Kim Cương MSSV:060534D value is given by S = E x H* Usually, only the time average of the power flow over one period is of concern Sav= E0H0z^ The direction vector in Eq emphasises that E, H and Sav form a right-hand set, i.e Sav is in the direction of movement of a right-handed corkscrew, turned from the E direction to the H direction 1.6 Phase Velocity The velocity of a point of constant phase on the wave, the phase velocity v at which wave fronts advance in the S direction, is given by V= Hence the wavelength λ is given by λ= 1.7 Polarisation States The alignment of the electric field vector of a plane wave relative to the direction of propagation defines the polarisation of the wave The electric field is parallel to the x axis, so this wave is x polarised This wave could be generated by a straight wire antenna parallel to the x axis An entirely distinct y-polarised plane wave could be generated with the same direction of propagation and recovered independently of the other wave using pairs of transmit and receive antennas with perpendicular polarisation This principle is sometimes used in satellite communications to provide two independent communication channels on the same earth satellite link If the wave is generated by a vertical wire antenna (H field horizontal), then the wave is said to be vertically polarised; a wire antenna parallel to the ground (E field horizontal) primarily generates waves that are horizontally polarised The waves described so far have been linearly polarised, since the electric Page SV:Nguyễn Xuân Kim Cương MSSV:060534D field vector has a single direction along the whole of the propagation axis If two plane waves of equal amplitude and orthogonal polarisation are combined with a 90 phase difference, the resulting wave will be circularly polarised (CP), in that the motion of the electric field vector will describe a circle centred on the propagation vector The field vector will rotate by 360 for every wavelength travelled Circularly polarised waves are most commonly used in satellite communications, since they can be generated and received using antennas which are oriented in any direction around their axis without loss of power They may be generated as either right-hand circularly polarised (RHCP) or left-hand circularly polarised (LHCP); RHCP describes a wave with the electric field vector rotating clockwise when looking in the direction of propagation In the most general case, the component waves could be of unequal amplitudes or at a phase angle other than 90 The result is an elliptically polarised wave, where the electric field vector still rotates at the same rate but varies in amplitude with time, thereby describing an ellipse In this case, the wave is characterised by the ratio between the maximum and minimum values of the instantaneous electric field, known as the axial ratio, AR, AR = Wave Impedance Maxwell’s equations, provided the ratio of the field amplitudes is a constant for a given medium, where Z is called the wave impedance and has units of ohms In free space, µ0, µr=1 and 1.8 Lossy Media So far only lossless media have been considered When the medium has Page SV:Nguyễn Xuân Kim Cương MSSV:060534D significant con- ductivity, the amplitude of the wave diminishes with distance travelled through the medium as energy is removed from the wave and converted to heat And The constant a is known as the attenuation constant, with units of per metre [m - 1], which depends on the permeability and permittivity of the medium, the frequency of the wave and the conductivity of the medium, measured in siemens per metre or per- ohm-metre [ Ω m] -1 Together Ɛ,µ and are known as the constitutive parameters of the medium In consequence, the field strength (both electric and magnetic) diminishes exponentially as the wave travels through the medium The distance through which the wave travels before its field strength reduces to e- = 0.368 = 36.8% of its initial value is its skin depth , which is given by Page SV:Nguyễn Xuân Kim Cương MSSV:060534D Coaxial Feed Shown above are the various coaxial feed excitations The coaxial connector is attached to the backside of the printed circuit board and the coaxial centre conductor is attached to the antenna conductor The position of the connector is found empirically for the given mode as that which produces the best match The coaxial feed is also easy to fabricate and match, and it has low spurious radiation However, it also has narrow bandwidth and is more difficult to model, especially for thick substrates Page 44 SV:Nguyễn Xuân Kim Cương MSSV:060534D Chapter 6: PRODUCTION PROCESS 6.1 Production Overview Tracing paper Exposure + 60 second Etching Add Add reagent Develop Ferric chloride Alcohol wipe Finish 6.2 Production Details Page 45 SV:Nguyễn Xuân Kim Cương MSSV:060534D Print the antenna sharp on the substrate Add reagent Clean the blue painting on the substrate Page 46 SV:Nguyễn Xuân Kim Cương Etching MSSV:060534D Add Develop Ferric chloride Put the printed FR4 substrate into the Fe2O3 liquid Alcohol wipe Page 47 SV:Nguyễn Xuân Kim Cương MSSV:060534D Finish Welding SMA into the FR4 substrate \ Page 48 SV:Nguyễn Xuân Kim Cương MSSV:060534D 6.3 Improving Antenna Use the copper tape to figure out the best performance 6.4 Measurement Page 49 SV:Nguyễn Xuân Kim Cương MSSV:060534D 6.5 Antenna Page 50 SV:Nguyễn Xuân Kim Cương MSSV:060534D CHAPTER 7: THE FINAL REPORT Dual Frequency 2.4 Ghz T-Shaped And 5.2 Ghz Inverted L-Shaped Monopole Antenna For Wlan Applications Abstact: a printed dual-band T-shaped and inverted L-shaped monopole antenna is proposed The two monopoles in the structure generate two separate resonant frequencies for the desired 2.4/5.2 GHz dual-band operation in WLAN applications The proposed antenna was designed to meet the 2.4/5.2 GHz band requirements occupying small volume and good omnidirectional radiation 7.1 Introduction In recent year, wide development and deployment of a variety of Wireless Local Area Network (WLAN) protocols has generate the need of developing antennas for use at base station and peripheral devices Today, the most widespread WLAN protocols are IEEE 802.1l b/g, which uses the 2.4 GHz ISM frequency band, and IEEE 802.1l a, which employs the 5.2 GHz UNII frequency band As a result such availability, many WLAN providers are interested in offering access to the two frequency bands of 2.4 GHz and 5.2 GHz To meet this requirement, a WLAN access point antenna has to feature a dual-band, 2.4 GHz and 5.2 GHz operations To meet the requirements for the 2.4/5.2 GHz applications, different design structures are given WLAN access point antennas can play an important role in improving the overall performance of the WLAN system We only adjust in the physical layer, which could enhance the quality of the communication link, are the radiation properties of the antenna These include parameters such as gain, directivity, bandwidth, radiation efficiency 7.2 Antenna Design Structure: As shown in Fig the antenna structure consists of a T-shaped monopole, whose dimensions are designed to resonate at 2.4 GHz, and an inverted L-shaped monopole designed to resonate at 5.2 GHz The two monopoles are fed from the same input 50 Ohm feed line The monopoles and the microstrip feed line are printed on the same side of the dielectric substrate (FR4 substrate of thickness 1.6mm and max relative permittivity 4.8) The T-shaped monopole is on the top and controls the first or lower operating band (2.4 GHz band) An inverted L-shaped monopole was chosen for the 5.2 GHz operation because it reduces the overall size of the antenna structure a rectangular odd part on the top generate another lower frequency than 2.4Ghz frequency (1.19GHz) Page 51 SV:Nguyễn Xuân Kim Cương MSSV:060534D Fig 1: Geometry of the T-shaped and inverted L-shaped antenna 7.3 Simulations The above structure was simulated using a commercial software Ansoft HFSS (High Frequency Structure Simulator) The T-shaped monopole has a resonant frequency at 2.43 GHz with a bandwidth of 495 MHz and – 18.78 dB return loss The -10 dB bandwidth varies between 2.175 GHz and 2.67 GHz The inverted L-shaped monopole has a resonant frequency at 5.2 GHz with a bandwidth of 5.07 GHz The -10 dB bandwidth extends from 4.47 GHz to 9.84 GHz Both monopoles cover the required IEEE 802.11(b) 2.4 GHz and 802.11(a) 5.2 GHz bands Fig 2: Simulation Result Page 52 SV:Nguyễn Xuân Kim Cương MSSV:060534D 7.4 Experience Design By changing the height and width of resonant monopole, the frequency can be changed If It’s smaller, the frequency will move up If it’s bigger, the frequency will move down We realized the simulation result and measurement result are very different The lower frequency did not appear on the network analyzer screen in some first designs By adding a rectangular odd part, the antenna had a better measurement result (making the bandwith of 5.2GHz frequency better and making the return loss of the 2.4 GHz frequency smaller) 7.5 Measurement Result: The measured result of the network analyzer and the simulation result are not really different from each other 7.6 Radiation Patterns: 7.6.1 The Simulated Radiation Patterns In The X-Y, X-Z, YZ Planes at 2.4 GHz a)X.Y Plane Page 53 SV:Nguyễn Xuân Kim Cương MSSV:060534D b)X-Z Plane Page 54 SV:Nguyễn Xuân Kim Cương MSSV:060534D c) Y-Z Plane At 2.4 GHz, the pattern in the x-y plane is with a peak gain magnitude of 7.6 dBi (Fig (a)), the pattern in the y-z plane is with a peak gain magnitude of 4.81 dBi (Fig (c)), while the pattern in the x-z plane is with a peak gain magnitude of 2.89 dBi (Fig (b)) 7.6.2 The Simulated Radiation Patterns In The X-Y, X-Z, YZ Planes at 5.2 GHz a) X-Y Plane Page 55 SV:Nguyễn Xuân Kim Cương MSSV:060534D b) X-Z Plane c) Y-Z Plane Page 56 SV:Nguyễn Xuân Kim Cương MSSV:060534D At 5.2 GHz, the pattern in the x-y plane is with a peak gain magnitude of 1.55 dBi (Fig (a)), the pattern in the y-z plane is with a peak gain magnitude of -3.66 dBi (Fig (c)), while the pattern in the x-z plane is with a peak gain magnitude of 3.73 dBi (Fig (b)) 7.7 Conclusion: The designed antenna is suitable for WLAN operations in the 2.4 but it not really good in 5.2 GHz because of the antenna gain It has only the good performances of the operating frequencies for the 2.4 GHz Large effects of varying monopole parameters and ground-plane sizes on the antenna’s resonant frequencies and impedance bandwidths have also been seen Acknowledgement This work was sponsored by Lunghwa University laboratory The authors would like to thank all of the older student in the laboratory References [1] Ultra-compact CPW-fed Monopole Antenna with Double Inverted-L Strips for Dual-band WLAN Applications , H S Choi, S H Kim, K H Oh, and J H Jang [2] Printed Double-T Monopole Antenna for 2.4/5.2 GHz Dual-Band WLAN Operations, Yen-Liang Kuo and Kin-Lu Wong, Senior Member, IEEE [3] A Compact T-Shaped Antenna For Dual-Band WLAN Communications, Mustapha Hannouzi and Mohamed Ben Ahmed [4] Antennas and Propagation for Wireless Communication Systems_ 2nd Ed, Simon R Saunders Page 57 ��������������������������������������������������������������������������� ��������������������������������������������������������������������������������� ����������������������������������������������������� ... fields in the air and in the dielectric substrate Page 29 SV:Nguyễn Xuân Kim Cương MSSV:060534D Page 30 SV:Nguyễn Xuân Kim Cương MSSV:060534D Chapter 5: THE MICROSTRIP ANTENNA DESIGN 5.1 Historical... Details Page 45 SV:Nguyễn Xuân Kim Cương MSSV:060534D Print the antenna sharp on the substrate Add reagent Clean the blue painting on the substrate Page 46 SV:Nguyễn Xuân Kim Cương Etching MSSV:060534D... the Fe2O3 liquid Alcohol wipe Page 47 SV:Nguyễn Xuân Kim Cương MSSV:060534D Finish Welding SMA into the FR4 substrate Page 48 SV:Nguyễn Xuân Kim Cương MSSV:060534D 6.3 Improving Antenna Use the