STUDY THE MICROWAVE DIELECTRIC PROPERTIES OF B2O3 DOPED CERAMIC AND ITS APPLICATION ON PLANAR INVERTED L ANTENNA

STUDY THE MICROWAVE DIELECTRIC PROPERTIES OF B2O3 DOPED Nd(Mg0.4Zn0.1Sn0.5)O3 CERAMIC AND ITS APPLICATION ON PLANAR INVERTED L ANTENNA GVHD ：Dr YIH-CHIEN CHEN SVTH ：NGUYỄN HOÀNG MINH MSSV : 060507D LỚP : 06DD2D KHĨA : 10 SVTH : NGUYỄN HỒNG MINH MSSV :060507D LỚP :06DD2D CONTENTS 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 2.1 2.2 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 4.1 4.2 4.3 4.4 4.5 4.6 4.7 5.1 5.2 5.3 5.4 CHAPTER 1: PROPERTIES OF ELECTROMAGNETIC MAXWELL’EQUATION PLANE WAVE PROPERTIES DIFFRACTION FIELD RELATIONSHIPS POYNTING VECTOR PHASE VELOCITY POLARISATION STATES LOSSY MEDIA CHAPTER 2: PROPAGATION MECHANISMS 10 LOSSLESS MEDIA 10 ROUGH SURFACE SCATTERING 12 CHAPTER 3:ANTENNA FUNDAMENTALS 15 NECESSARY CONDITIONS FOR RADIATION 15 NEAR-FIELD AND FAR-FIELD REGIONS 16 FAR-FIELD RADIATION FROM WIRES 17 RADIATION PATTERN 18 RADIATION RESISTANCE AND EFFICIENCY 19 POWER GAIN 19 BANDWIDTH 21 DIRECTIVITY 22 CHAPTER 4: PRACTICAL ANTENNA .23 DIPOLE STRUCTURE 23 CURRENT DISTRIBUTION 24 REflECTOR ANTENNAS 24 HORN ANTENNAS 25 LOOP ANTENNAS 26 HELICAL ANTENNAS 27 PATCH ANTENNAS 27 CHAPTER 5: THE MICROSTRIP ANTENNA DESIGN 30 HISTORICAL DEVELOPMENT 30 BASIC MICROSTRIP LINE 30 MICROSTRIP FIELD RADIATION 31 SUBSTRATE MATERIALS 33 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14 5.15 5.16 MSSV :060507D LỚP :06DD2D BASIC MICROSTRIP ANTENNA 34 BASIC CONFIGURATION OF MICROSTRIP ANTENNA 35 RADIATED FIELDS OF MICROSTRIP ANTENNA 36 ADVANTAGES VS DISADVANTAGES OF MICROSTRIP ANTENNAS 37 APPLICATIONS 38 TYPES OF MICROSTRIP ANTENNAS 38 MICROSTRIP TRAVELING -WAVE ANTENNAS 39 MICROSTRIP SLOT ANTENNAS 41 EXCITATION TECHNIQUES 41 MICROSTRIP FEED 41 MICROSTRIP LINE FED ANTENNAS 42 COAXIAL FEED 43 CHAPTER : PRODUCTION PROCESS 43 6.1 PREPARE COMPOUND NMZS: 43 6.1.1 Atomic mass: 43 6.1.2 Calculated the balanced of chemical formula : 44 6.1.3 Powder weight reduced three fold: 44 6.1.4 Make up NMZS: 44 6.2 NMZS DOPE B2O3: 44 6.3 MEASUREMENT 46 6.4 ANTENNA 48 CHAPTER 7: STUDY THE MICROWAVE DIELECTRIC PROPERTIES OF B2O3 DOPED ND(MG0.4ZN0.1SN0.5)O3 CERAMIC AND ITS APPLICATION ON PLANAR INVERTED L ANTENNA .49 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 ABSTRACT: 49 INTRODUCTION 49 ANTENNA DESIGN STRUCTURE: 49 SIMULATIONS 50 EXPERIENCE DESIGN: 51 ANALYSIS RESULTS AND DISCUSSION: 51 CONCLUSIONS 58 MEASUREMENT RESULT: 59 RADIATION PATTERNS: 60 7.9.1 X.Y Plane (a) 60 7.9.2 X-Z Plane (b) 60 7.9.3 Y-Z Plane (c) 61 7.10 ACKNOWLEDGEMENT 61 7.11 REFERENCES 62 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D Figure 7-1: Geometry of the PILA antenna 50 7-2: Simulation Result 50 7-3 : 0.1 wt.% B2O3 doped NMZS 51 7-4 : 0.25 wt.% B2O3 doped NMZS 52 7-5: 0.5 wt.% B2O3 doped NMZS 52 7-6 : The X-ray diffraction patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens with different amounts of B2O3 additives sintered at 1450◦C for 4h 53 7-7: The X-ray diffraction patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens with different amounts of B2O3 additives sintered at 1400◦C for 4h .53 7-8 :The X-ray diffraction patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens with different amounts of B2O3 additives sintered at 1350◦C for 4h .54 7-9 : 0.1 wt% B2O3 doped NMZS 54 7-10 : 0.25 wt.% B2O3 doped NMZS 55 7-11 : 0.5 wt.% B2O3 doped NMZS 55 7-12:The apparent densities of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3 additives sintered in the range of 1300 to 1500◦C for 4h .56 7-13:shows the dielectric constants of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3 additive sintered at different temperatures for 4h 56 7-14 :The Q×f of of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3additives sintered in the range of 1300 to 1450◦C for 4h 57 7-15 :The τf of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3additive sintered at different temperatures for h 58 7-16: Measurement Result .59 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D Chapter 1: 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 µ0=4π x 10-7 Hm-1 µ=µrµ0 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 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 = LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 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: Principle The geometrical optics field described in Section 3.4 is a very useful description, 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 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 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 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 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= LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 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 In Figure 2.1 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 ypolarised 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 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, LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 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 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 as shown in Figure 2.2 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 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D Chapter 2: PROPAGATION MECHANISMS 2.1 Lossless Media : If Maxwell‟s equations are solved for this situation, the result is that two new waves are produced, each with the same frequency as the incident wave Both the waves have their Poynting vectors in the plane which contains both the incident propagation vector and the normal to the surface This is called the scattering plane The first wave propagates within medium but moves away from the boundary It makes an angle θr to the normal and is called the reflected wave The second wave travels into medium 2, making an angle θt to the surface normal This is the transmitted wave, which results from the mechanism of refraction.When analysing reflection and refraction, it is convenient to work in terms of rays; in a homogeneous medium rays are drawn parallel to the Poynting vector of the wave at the point of incidence They are always perpendicular to the wave fronts The angle of the reflected ray is related to the incidence angle as follows: θi=θr Equation is Snell‟s law of reflection, which may be used to find the point of reflection given by any pair of source (transmitter) and field (receiver) points as shown in the following figure This law is one consequence of a deeper truth, Fermat‟s principle, which states that every ray path represents an extremum (maximum or minimum) of the total electrical length kd of the ray, usually a minimum In Figure, the actual ray path is simply the path which minimises the distance (d1 + d2 ), because the wave number is the same for the whole ray Fermat‟s principle can also be used to find the path of the refracted ray In this case, the wave 10 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 6.4 Antenna: 48 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D CHAPTER 7: Study the Microwave Dielectric Properties of B2O3 doped Nd(Mg0.4Zn0.1Sn0.5)O3 ceramic and its Application on Planar Inverted L Antenna 7.1 Abstract: The design and analysis is presented of a low profile and dual-frequency inverted L-F antenna for WLAN and short range wireless communications, providing a compromise between size reduction and attainable bandwidth The optimum (minimized) volume of 30x30x8 of the proposed antenna gives 8% bandwidth at lower resonant mode of 2400 MHz, while at the higher resonant mode of 5500 MHz a bandwidth of 12.2% is obtained Both the simulated and measured characteristics of the proposed antenna are shown 7.2 Introduction: The applications of microwave ceramics in mobile communications, such as Resonators, Filters and Antennas, have been rapidly increasing in the last decade Many researches have been focused on developing good microwave dielectric materials to achieve device miniaturization and system stability Three dielectric properties must be considered for materials used in microwave devices: A high dielectric constant, A high quality factor, and A near-zero temperature coefficient of resonant frequency for the small size, low loss and high temperature stability Recently, many researches about Ln (Mg0.5Ti0.5)O3 (Ln=La, Sm, Nd, Da, Y) ceramics have been made for resonators, filters, and antennas in communication systems, such as radar and global positioning systems (GPS) operating at microwave frequencies Among them, Nd(Mg0.5Ti0.5)O3 ceramic is found to be suitable for microwave applications due to high dielectric constant and high quality factor Nd(Mg0.5Ti0.5)O3 has a dielectric constant 7.3 Antenna Design Structure: As shown in Fig the antenna structure consists of a PILA antenna, whose dimensions are designed to resonate at 3.5 GHz The Antenna 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 (NMZS (Nd(Mg0.4Zn0.1Sn0.5)O3) substrate of thickness mm and diameter is 11mm) 49 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7-1: Geometry of the PILA antenna 7.4 Simulations: The above structure was simulated using a commercial software Ansoft HFSS (High Frequency Structure Simulator) The PILA antenna has a resonant frequency at 3.5 GHz with –21 dB return loss The -10 dB bandwidth varies between 3.33 GHz and 3.77 GHz 7-2: Simulation Result 50 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7.5 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 7.6 Analysis results and discussion: 7-3 : 0.1 wt.% B2O3 doped NMZS 51 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7-4 : 0.25 wt.% B2O3 doped NMZS 7-5: 0.5 wt.% B2O3 doped NMZS The X-ray diffraction patterns of Nd(Mg0.4Zn0.1Sn0.5)O3 ceramics with 0.1;0.25; 0.5 wt% B2O3 additive after sintering from 13000C to 15000C for 4hours are shown in Fig 7.3 , 7.4 , 7.5 All the peaks were indexed based on the cubic perovskite unit cell As seen from Fig 3,4,5 series of extra peaks were observed corresponding to superlattice reflections According to Glazer, the superlattice reflections, with specific combinations of odd (o) and even (e) Miller indices point to definite types of deviation of the structure from the undistorted cubic one, such as octahedral in-phase tilting (ooe, oeo, eoo), anti-phase tilting (ooo, h+k+l>3), chemical ordering (ooo) and anti52 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D parallel displacement of A-cations (eeo, eoe, oee) The presence of (1/2 (2 0), 1/2 (3 0), 1/2 (3 0), 1/2 (4 0), ½ (4 1) and 1/2(4 2)) extra peaks indict that A-site cation displacement and ( 1/2 (3 1), 1/2 (3 1), and 1/2 (5 1) indict that anti-phase tilting The X-ray diffraction patterns of the Nd(Mg0.4Zn0.1Sn0.5)O3 ceramics have no significant difference at different sintering temperature with 0.1;0.25;0.5 wt% B2O3 additive 7-6 : The X-ray diffraction patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens with different amounts of B2O3 additives sintered at 1450◦C for 4h 7-7: The X-ray diffraction patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens with different amounts of B2O3 additives sintered at 1400◦C for 4h 53 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7-8 :The X-ray diffraction patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens with different amounts of B2O3 additives sintered at 1350◦C for 4h Figure 7.6, 7.7, 7.8 shows the XRD patterns of Nd(Mg0.40Zn0.10Sn0.5)O3 specimens sintered at 1450◦C,1400◦C,1350◦C for 4hwith B2O3additives from 0.1 to 0.5wt% More B2O3 additives seemed to enhance the formation of Nd2Sn2O7 in Nd(Mg0.40Zn0.10Sn0.5)O3 specimens slightly The formation of Nd2Sn2O7 might lower the dielectric constant and quality factor of the specimen 7-9 : 0.1 wt% B2O3 doped NMZS 54 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7-10 : 0.25 wt.% B2O3 doped NMZS 7-11 : 0.5 wt.% B2O3 doped NMZS The microstructures of B2O3 doped Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with 0.1;0.25;0.5 wt% B2O3 additive at different sintering temperatures for h are shown in Fig 7.9, 7.10, 7.11 Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with 0.1;0.25;0.5 wt% B2O3additive was not dense, and grains did not grow after it was sintered at 1400◦C It may affect the microwave dielectric properties of the ceramics The pores of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics was almost disappeared at 1500◦C Comparing the microstructures of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with with 0.1;0.25;0.5 wt% B2O3 additives sintered at different temperatures, the grain size increased with the increasing of sintering temperature 55 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D Density and dielectric properties : Bulk Density(g/cm3) 7.5 7.0 6.887 6.733 7.065 6.903 7.091 7.221 6.914 6.911 6.786 6.761 7.180 0.10 wt.% 6.772 0.25 wt.% 6.5 0.50 wt.% 6.0 1250 1300 1350 1400 Sintering Temperature (℃) 1450 1500 1550 7-12:The apparent densities of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3 additives sintered in the range of 1300 to 1500◦C for 4h The apparent density was found to increase to a maximum value at a sintering temperature of 1500, 1400, and 1350◦C as the amounts of B2O3additive is 0.1%, 0.25%, and 0.5 wt%, respec-tively This implies that B2O3 additives can effectively lower the sintering temperature of Nd(Mg0.40Zn0.10Sn0.5)O3 The maximum value of the bulk density decreased from 7.221 to 6.786 g/cm3as the amounts of B2O3 additive increased from 0.1% to 0.5 wt% A maximum apparent density of 7.221 g/cm3was obtained for Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with 0.1 wt% B2O3 additive sintered at 1450◦C for h 20.0 19.73 19.47 εr 19.5 18.98 19.0 18.5 18.54 19.65 19.50 19.05 19.31 19.26 18.72 18.79 18.72 1350 1400 1450 0.10 wt.% 0.25 wt.% 0.50 wt.% 18.0 1250 1300 Sintering Temperature (℃) 1500 1550 7-13:shows the dielectric constants of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3 additive sintered at different temperatures for 4h 56 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D The relationships between the dielectric constant and the sintering temperature revealed the same trend as that between the apparent density and the sintering temperature A maximum constant value of 19,73 was obtained for of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with 0.1 wt% B2O3 additive sintered at 1450◦C for h The decrease in dielectric constant was caused by the low densities of the ceramics Higher density leads to lower porosity.Thus, a higher dielectric constant can be achieved 0.10 wt.% 0.25 wt.% 0.50 wt.% 50000 40000 Q × f (GHz) 32500 30000 26867 22451 20000 10000 1250 16148 6274 4213 1300 9101 5877 1350 9807 9568 6464 6073 1400 1450 1500 1550 Sintering Temperature (℃) 7-14 :The Q×f of of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3additives sintered in the range of 1300 to 1450◦C for 4h The maximum value of the Q×f decreased from 32500 to 6464 GHz as the amounts of B2O3additive increased from 0.1 to 0.5 wt% A maximum Q×f of 32500 GHz was obtained for Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with 0.1 wt% B2O3 sintered at 1450◦C for h The relationship between the Q×f and the sintering temperature revealed the same trend as that between the apparent density and the sintering temperature This is caused by the microwave dielectric loss, which is affected by many factors that can be divided into the intrinsic and extrinsic loss The intrinsic loss is caused by the lattice vibrational modes The extrinsic loss is induced by the density, porosity, the second phases, the impurities, the oxygen vacancies, the grain size and the lattice defects Because the Q×f of Nd(Mg0.40Zn0.10Sn0.5)O3 was consistent with the variation of the apparent density, it is suggested that the Q×f of Nd(Mg0.40Zn0.10Sn0.5)O3 is mainly controlled by the apparent density 57 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D Sintering Temperature (℃) 1250 1300 1350 1400 -58.04 -58.13 -58.41 -58.34 -58.53 1450 1500 1550 τ f (ppm/℃) -45 -55 -65 -64.31 -63.37 -65.20 -58.12 -58.39 -65.25 -56.84 0.10 wt.% 0.25 wt.% 0.50 wt.% -75 7-15 :The τf of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with different amounts of B2O3additive sintered at different temperatures for h In general, τf is related to the composition, the amount of additive, and the second phases that existed in the ceramics Although second phase Nd2Sn2O7was found The amounts of second phase Nd2Sn2O7 was small to influence the τf of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics So the effect of second phase Nd2Sn2O7could be neglected No significant variation in τf was observed with a fixed amount of B2O3additive at different sintering temperature in the entire sintering temperature range Since there was no compositional variation in Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics with a fixed amount of B2O3additive with different sintering temperature, τf was measured as a function of the amounts of B2O3 additive in this experiment As the amount of B2O3 additive increased from 0.1 to 0.5 wt%, the average value of τf increased from−65.20 to−58.41 ppm/◦C for the Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics It is suggested that τf is influenced by the amount of B2O3additive in this study 7.7 Conclusions: The effect of amounts of B2O3 additive and sintering temperature on the microwave dielectric properties of Nd(Mg0.40Zn0.10Sn0.5)O3 were investigated The Xray diffraction patterns of the Nd(Mg0.40Zn0.10Sn0.5)O3 have no significant difference at different sintering temperature A density of 7.221 g/cm3, a dielectric constant of 19.73, and a Q×f of 32500 GHz were obtained for Nd(Mg0.40Zn0.10Sn0.5)O3ceramics with 0.1 wt% B2O3additive sintered at 1450◦Cfor4h The dielectric constant and Q×f of Nd(Mg0.40Zn0.10Sn0.5)O3 ceramics are strongly dependent on the density 58 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7.8 Measurement Result: Graph 3.27 GHz -10 dB -10 4.42 GHz -10 dB -20 3.55 GHz -24.73 dB DB(|S[1,1]|) 3.5GHz -30 Frequency (GHz) 6.5 7-16: Measurement Result The measured result of the network analyzer and the simulation result are not really different from each other 59 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7.9 Radiation Patterns: The Simulated Radiation Patterns In The X-Y, X-Z, Y-Z Planes at 3.5 GHz 7.9.1 X.Y Plane (a) 7.9.2 X-Z Plane (b) 60 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7.9.3 Y-Z Plane (c) At 3.5 GHz, the pattern in the x-y plane is with a peak gain magnitude of -22.13 dBi (Fig (a)), the pattern in the y-z plane is with a peak gain magnitude of -9.86 dBi (Fig (c)), while the pattern in the x-z plane is with a peak gain magnitude of -12.78 dBi (Fig (b)) 7.10 Acknowledgement: This work was sponsored by Lunghwa University laboratory The authors would like to thank all of the older student in the laboratory 61 LUẬN ÁN TỐT NGHIỆP SVTH : NGUYỄN HOÀNG MINH MSSV :060507D LỚP :06DD2D 7.11 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 [5] http://www.informaworld.com/smpp/title~content=t713617887 [6] http://www.informaworld.com/terms-and-conditions-of-access.pdf [7] http://ieeexplore.ieee.org 62 LUẬN ÁN TỐT NGHIỆP