Title Page
Abstract
Contents
Chapter 1. Introduction 28
1.1. Concept of tightly coupled array 28
1.2. Development of tightly coupled array and our contributions 32
1.3. Dissertation overview 35
Chapter 2. EQUIVALENT CIRCUIT MODEL OF UNBALANCED FED ARRAY 36
2.1. Equivalent circuit of even-excited unit cell 36
2.1.1. Monopole array 36
2.1.2. Tightly coupled dipole array 39
2.2. Equivalent circuit of unbalanced fed unit cell 42
2.3. Conclusion 44
Chapter 3. COMPACT AND WIDEBAND ANTENNA WITH ARTIFICIAL BOUNDARY WALL 46
3.1. Compact single antenna with electric wall 46
3.1.1. Antenna design and analysis 46
3.1.2. Simulated and experimental results for the proposed single antenna 53
3.1.3. Conclusion 57
3.2. Low mutually coupled linear array antenna with resistive wall 57
3.2.1. Introduction 57
3.2.2. Design of antenna structure and operation 58
3.2.3. Simulated and experimental results for the proposed full array antenna 61
3.2.4. Conclusion 65
3.3. Wideband linear array antenna with polarization-selective wall 66
3.3.1. Introduction 66
3.3.2. Theory of 2-D and 1-D TCDA 67
3.3.3. Design of the proposed array antenna 72
3.3.4. Simulated and experimental results for the proposed full array antenna 77
3.3.5. Conclusion 83
Chapter 4. WIDEBAND OPERATING ARRAY ANTENNA WITH POLARIZATION CONVERTOR 84
4.1. Polarization convertor 84
4.2. Extremely low-profile array antenna 84
4.2.1. Design of antenna structure and operation 84
4.2.2. Simulated and experimental results for the proposed 6 x 6 array antenna 87
4.2.3. Conclusion 91
4.3. 20:1 Ultra-wideband array antenna 91
4.3.1. Development and description of the proposed unit cell antenna 91
4.3.2. Simulated and experimental results for the 4 x 4 finite array antenna 97
4.3.3. Conclusion 104
Chapter 5. PASSIVE TIGHTLY COUPLED DIPOLE ARRAY 105
5.1. Reflection type ultra-wideband polarization convertor 105
5.1.1. Introduction 105
5.1.2. Design and operation principles of the TCDA-based PC 106
5.1.3. Results and discussion 113
5.1.4. Experimental verification 118
5.1.5. Conclusion 123
5.2. Transmission type ultra-wideband polarization convertor 124
5.2.1. Proposed unit cell structure and operating principle 124
5.2.2. Simulated and experimental results 128
5.2.3. Conclusion 133
5.3. Ultra-wideband absorber 133
5.3.1. Introduction 133
5.3.2. Design of the proposed TCDA-under-TCDA based absorber 135
5.3.3. Simulated and experimental results for the proposed 1-D absorber 149
5.3.4. Conclusion 153
Chapter 6. LOW-PROFILE AND HIGH GAIN SUBARRAY ANTENNA 155
6.1. Introduction 155
6.2. Design of dipole antenna unit cell and 4 x 4 array 158
6.3. Design of CM excited 2 x 2 subarrays 160
6.4. Design of UCM excited 2 x 2 subarrays 166
6.5. Simulated and experimental verification of the performance of three types of 2 x 2 subarrays 172
6.6. Discussion about application 177
6.7. Conclusion 179
Chapter 7. WIDEBAND 5G MMWAVE ARRAY ANTENNA OPERATING IN FULL FR2 180
7.1. 2x2 Broadside radiated planar array antenna 180
7.1.1. Introduction 180
7.1.2. Proposed 2 x 2 array antenna and connector calibration for measurement 181
7.1.3. Performance of the proposed array antenna and comparison with state-of-the-art works 189
7.1.4. Conclusion 192
7.2. End-fired tightly coupled monopole 1x4 linear array 192
7.2.1. Vertical-polarized array antenna 192
7.2.2. Dual-polarized array antenna with TCDA 210
Chapter 8. CONCLUSIONS 227
Bibliography 229
초록 247
Table 2.1. Dimensions of the proposed unit cell. 39
Table 2.2. Values of circuit parameters. 40
Table 3.1. Comparison with compact and wideband antennas. 56
Table 3.2. Comparison of performances of wideband, low-profile and wide scanning 1-D TCDA antennas. 81
Table 4.1. Performance comparison of proposed and previous antennas. 90
Table 4.2. Comparison with ultra-wideband array antennas. 103
Table 5.1. Comparison of unit cell simulation results using reflection-type polarization convertors. 117
Table 5.2. Unit cell simulation results of various transmissive PCs. 132
Table 5.3. Values of the parameters of equivalent circuit. β₀ and z₀ are the propagation and characteristic impedance in free space, respectively. 139
Table 5.4. Comparison of simulated results of wideband and low-profile absorbers. 152
Table 6.1. Active input impedance (Ω), characteristic impedance (Ω) of the transformers for dominant CM. 167
Table 6.2. Active input impedance (Ω), electrical length (°), and characteristic impedance (Ω) of the transformers for UCM. 171
Table 7.1. Performance comparison of millimeter-wave array antennas. 191
Table 7.2. Performance Comparison of End-fire and Vertically Polarized Millimeter-wave Linear Array Antennas 207
Table 7.3. Dimensions of the Proposed Unit Cell Structure 215
Table 7.4. Performance Comparison of End-fire and Dual-polarized Millimeter-wave Linear Array Antennas 225
Figure 1.1. (a) Progressively phased current sheet array radiating plane waves up- and downwards and (b) its equivalent circuit. 29
Figure 1.2. (a) Unit cell of tightly coupled dipole array and (b) its equivalent circuit. (c) Reflection coefficient at the discrete port with... 30
Figure 1.3. (a) Current sheet array on the ground plane and (b) equivalent circuit of the unit cell. 31
Figure 1.4. Relative pros and cons: Vivaldi antenna versus tightly coupled dipole array. 32
Figure 1.5. Development of the tightly coupled array as of 2023. 33
Figure 2.1. (a) Infinite 2-D periodic twin monopoles antenna with unit cell size d. (b) Equivalent circuit of the twin monopoles antenna.... 37
Figure 2.2. Comparison with the full wave simulation result and formula. 39
Figure 2.3. Even mode excited TCDA unit cell with shorting vias radius b. (a) Front and (b) top view of the unit cell. (c) Equivalent... 41
Figure 2.4. (a) Even and odd modes decomposition of the unbalanced fed TCDA. (b) Proposed unbalanced fed TCDA unit cell.... 43
Figure 2.5. Reflection coefficients, and the imaginary part of the antenna input impedance of even mode excited TCDA (Figure... 44
Figure 3.1. (a) The conventional 2-D TCDA structure (top view); (b) an infinite array and (c) the equivalent circuit of the unit cell. 48
Figure 3.2. (a) Front (left) and back (right) side of the dipole PCB; (b) the configuration of the antenna with a finite height of the... 49
Figure 3.3. (a) The structure of the proposed PEC/OPEN boundary antenna; (b) the comparison of the antennas using the proposed... 51
Figure 3.4. The y-component electric field intensity of Figure 3.1(b) and Figure 3.3(a) on the dashed line (a - b). 52
Figure 3.5. Directivity to broadside direction of Figure 3.2(b) and Figure 3.3(a). 52
Figure 3.6. The prototype of the proposed antenna. 54
Figure 3.7. The VSWR and the peak gain of the proposed antenna. 54
Figure 3.8. The normalized gain pattern of the proposed antenna on the E-plane (left) and the H-plane (right) at (a) 1GHz, (b) 2GHz,... 55
Figure 3.9. The simulated cross polarization pattern of Figure 3.2(b) (α = 0.3) with and without PMC walls. 56
Figure 3.10. The radiation efficiency of the proposed antenna. 56
Figure 3.11. Configuration of proposed unit cell antenna. 59
Figure 3.12. The dimensions of the full array structure (17 elements) are 30 x 230 x 11 mm (Wgro = 30 mm and Wₜₒₜ = 230mm).[이미지참조] 59
Figure 3.13. Dimension of (a) PCB of front side, (b) back side and (c) side wall laminated with resistive films. 59
Figure 3.14. The effect of electric side walls without resistive films on the dipole antenna characteristic. 60
Figure 3.15. Distribution of current density on the side wall before laminating resistive films on the wall at 12 GHz. 61
Figure 3.16. Parametric studies on the effect of the length of resistive films (s₁ = 1.5 mm) on (a) mutual coupling and (b)... 62
Figure 3.17. Prototype of the full array structure (a) without (side view) and (b) with superstrates (top view). 62
Figure 3.18. Simulated and measured results of (a) the impedance matching property and (b) the mutual coupling characteristic. 63
Figure 3.19. Simulated and measured radiation efficiency. 64
Figure 3.20. Simulated and measured broadside gain. 64
Figure 3.21. Simulated and measured normalized active element gain pattern on yz-plane (left column) and xz-plane (right column)... 65
Figure 3.22. (a) Ideal boundary condition of the unit cell of a TCDA when scanning to θ = θ₀. (b) The equivalent circuit of the unit cell. 68
Figure 3.23. (a) Dimensions of the proposed unit cell antenna without superstrates. (b) Description of the front side. (c)... 71
Figure 3.24. Dimension of PCB (a) front side of HP, (b) back side of HP, (c) front side of VP and (d) back side of VP. 73
Figure 3.25. (a) Configuration of the conventional side wall. (b) Power loss density on the ferrite sheet. (c) Configuration of the... 73
Figure 3.26. The radiation efficiency of the (a) conventional and (b) proposed array antenna for both polarizations. 74
Figure 3.27. yz-plane from Figure 3.23(b). Only VP dipoles are excited at 0.8GHz and the TM mode is dominant. (a) Electric field... 75
Figure 3.28. (a) Electric field at 1.5 GHz is shown when TM plane wave is propagating toward the VMS region from the bottom. (b)... 76
Figure 3.29. Simulated VSWR of the antenna (a) without VMSs and (b) with VMSs. 77
Figure 3.30. Configuration of the proposed array antenna (a) without and (b) with superstrates. (c) Measurement setting, only... 78
Figure 3.31. Simulated and measured normalized gain pattern of the proposed array antenna for both polarizations on the xz plane and when scanning the beam to θ₀ = 0°, 25°, and 50° on the yz plane. 80
Figure 3.32. Simulated and measured HPBW of proposed array antenna (a) for VP and (b) HP. 82
Figure 3.33. Simulated and measured CoPol/XPol gains of the proposed array antenna for (a) VP and (b) HP. 82
Figure 4.1. Concept of polarization convertor. 85
Figure 4.2. (a) The proposed unit element. (b) Exploded view of the unit element. (c) Top and bottom of layer α. (d) Top of layer... 86
Figure 4.3. Simulated VSWR of the unit cell with and without the PC, and Γyx of the PC unit cell.[이미지참조] 88
Figure 4.4. Configuration of the 6 x 6 proposed array antenna. (a) Simulated configuration of the prototype array antenna. (b) Photo of... 88
Figure 4.5. Active VSWR at the center element (3, 3). 88
Figure 4.6. (a) Simulation and measurement results of realized array gain and XPol/CoPol ratio. (b) Normalized CoPol and XPol... 89
Figure 4.7. (a) The unit cell of TCDA which is periodic with dE along x-axis and dH along y-axis and (b) the equivalent circuit...[이미지참조] 92
Figure 4.8. The PC unit cell at the height hpc is on the x-y plane with the proper periodic conditions. (a) The unit cell of PC, (b) The... 94
Figure 4.9. Proposed unit cell. (a) Structure of the proposed unit cell antenna. (b) Equivalent circuit of the proposed antenna at... 94
Figure 4.10. Comparison with circuit simulations with and without the GP. (a) VSWR and (b) antenna input impedance. 95
Figure 4.11. The proposed antenna combined with the feeding line. (a) The structure of the proposed antenna with feeding line. (b)... 96
Figure 4.12. (a) The unit cell of TCDA and the superstrate with a thickness of hsup. (b) The equivalent circuit of the unit cell with the superstrate.[이미지참조] 96
Figure 4.13. The proposed 4 x 4 finite array antenna. 98
Figure 4.14. Photos of fabricated antenna. (a) Front and (b) top view. 98
Figure 4.15. Simulated and measured active VSWRs of the proposed 4 x 4 finite array antenna on the E-plane (ϕ = 0°), D-plane (ϕ =... 99
Figure 4.16. Simulated and measured array gain of the proposed 4 x 4 finite array antenna with scanning the beam up to 30° on the... 100
Figure 4.17. Simulated radiation efficiency and VSWR of the proposed 4 x 4 finite array antenna with different materials of PCB. 102
Figure 4.18. Simulated and measured gain pattern of the proposed 4 x 4 finite array antenna at 400 MHz and 1400 MHz on the E-plane... 102
Figure 5.1. (a) Schematic diagram of the structure. (b) Bottom-side metallic pattern of the superstrate with unit cell size a x a... 107
Figure 5.2. Proposed unit cell structure of the dual-polarized PC. (a) Overall view of the structure. (b) Bottom-side of the superstrate. 108
Figure 5.3. Schematic representation of the operating principle of the proposed PC. (a) Operating concept (the superstrate is hidden)... 109
Figure 5.4. Schematic of the incident and scattered fields wherein the superstrate is hidden. 111
Figure 5.5. Equivalent circuits for the single-polarized TCDA antenna (top) and dual-polarized PC (bottom). Here, the... 111
Figure 5.6. Real and imaginary components of the reflection coefficient at the DP of the Figure 5.1(a) structure as the beam is... 113
Figure 5.7. (a) Reflection coefficients at the DP of the single-polarized TCDA antenna (Figure 5.1(a)) with or without the VMS.... 114
Figure 5.8. Unit cell simulation results for rxy and ryy of the proposed PC (a) without and (b) with the VMS. (c) Phase of rxy.[이미지참조] 116
Figure 5.9. (a) Varying the incidence angle, rxy with a = 9 mm. (b) Varying the unit cell size, rxy when the incidence angle θ is 5°....[이미지참조] 119
Figure 5.10. Fabricated 40 x 40 PC array structures. (a) Bottom of the superstrate. (b) Overview of the PC. The superstrate is fixed... 120
Figure 5.11. Setup for measurements using the fabricated PC array. 121
Figure 5.12. Simulated and measured PCRs of the unit cell and fabricated 40 x 40 array structure. 123
Figure 5.13. (a) Configuration of the dual-polarized TCDA antenna unit cell and (b) the proposed TCDA-based PC unit cell in unit cell... 125
Figure 5.14. (a) x-direction polarized plane wave illuminates the PC array and (b) y-direction polarized plane wave illuminates the... 127
Figure 5.15. Parametric study results. (a) Height with FSSg = 0.2 mm and (b) gap of the FSS with FSSh = 4 mm. SVH is the...[이미지참조] 129
Figure 5.16. Response of the polarization conversion under a steered plane wave illumination angle. (a) Balanced line and (b)... 129
Figure 5.17. (a) Prototype of the proposed 20 x 20 PC array and (b) measurement environment. (c) Simulated (solid line) and... 131
Figure 5.18. Design of the proposed TCDA-under-TCDA absorber. (a) TCDA-under-TCDA absorber. The equivalent structures of... 136
Figure 5.19. Equivalent circuit of the proposed absorber shown in Figure 5.18 (a) for whole band, (b) band1, and (c) band2. (d)... 137
Figure 5.20. The structure in periodic boundary and the comparison of the reflection coefficients (E₀¯/E₀⁺): (a) FSS1 (b) two-layer... 141
Figure 5.21. (a) TCDA1 without FSS1: Geometry of an infinite dipole array in free-space excited by a plane wave. (b) │S₁₁│. 143
Figure 5.22. (a) Γupper and Γlower are shown in a Smith chart where the results are normalized to free space impedance. (b) │S₃₃│.[이미지참조] 143
Figure 5.23. (a) The proposed unit cell of the absorber based on the structure in Figure 5.18(a) with added VMS and MS. Crossed... 145
Figure 5.24. Effects of VMS and MS on │S₃₃│. 146
Figure 5.25. Geometries of the proposed square unit cell. (a) Front and (b) back side of the TCDA-under-TCDA. (c) Unit cell of the 4... 148
Figure 5.26. │S₃₃│ for normal incident wave with various polarization angles. 148
Figure 5.27. (a) Front and (b) back of the unit cell PCB. (c) Prototype of 1 x 14 sample of the proposed absorber. 150
Figure 5.28. (a) Simulation, measurement setup using a TEM cell. (b) Simulated and measured │S₁₁│ of the three cases with the... 151
Figure 6.1. Current distributions associated with UCM, UIPM, and dominant CM on the 4 x 4 dipole antenna array. 156
Figure 6.2. (a) Infinitely periodic unit cell structure and its layers. The drawn yellow parts are printed coppers. (b) The reflection... 159
Figure 6.3. (a) Finite 4 x 4 dipole antenna array composed of unit cell structures where Aw = 32 mm, and (b) ARCs at all ports are...[이미지참조] 159
Figure 6.4. MS associated with three lowest eigenvalues of Figure 6.3(a) structure. Mode 1 (k = 1) is the dominant CM operating over wideband. 163
Figure 6.5. Calculated ARCs at all ports when the dominant CM is excited at the center frequency of (a) 21.1 GHz, (b) 24.1 GHz, and... 163
Figure 6.6. Design process of the proposed power divider for CM by circuit simulator. (a) 4 x 4 array network of Figure 6.3(a)... 164
Figure 6.7. Circuit-simulated ARCs at all ports of Figure 6.6 corresponding to (a) Step 1 (port impedance = Rₙ), (b) Step 2... 167
Figure 6.8. Calculated ARCs at all ports are shown when UCM is excited at the center frequency at (a) 21.1 GHz, (b) 24.1 GHz, and... 169
Figure 6.9. Design process of the proposed power divider for UCM. (a) Step 1: ports 1-4 (blue circles) in Figure 6.6(a) are... 170
Figure 6.10. Circuit-simulated ARCs at all ports of Figure 6.9 corresponding to (a) Step 1 (port impedance = Rₙ), (b) Step 2... 171
Figure 6.11. Implementation of the 2 x 2 subarray dividers for three cases by full-wave simulator. 173
Figure 6.12. Current distributions associated with three cases of the proposed 2 x 2 subarrays at the resonant frequency. 173
Figure 6.13. (a) Front and back sides of the fabricated subarrays associated with three cases. (b) Measurement setup for the... 174
Figure 6.14. Full-wave simulated and measured (a) TARC and (b) broadside gain for the three cases. 176
Figure 6.15. Beam scanning performance is shown by full-wave-simulated (a) TARC and (b) gain for the three cases. 176
Figure 6.16. Absolute surface current density associated with three cases on the proposed 2 x 2 subarrays when scanning to θₛ = 30°. 176
Figure 6.17. Full-wave-simulated (solid) and measured (dashed) gain patterns at the resonant frequencies in xz- and yz-plane for... 178
Figure 7.1. Proposed 2 x 2 array antenna structure. (a) Perspective view of the array. (b) Top view (TCFSS) of the... 182
Figure 7.2. (a) Impedance matching of the antenna (left antenna in Figure 7.1(d)) presented by Smith chart. (b) Parametric study with... 184
Figure 7.3. (a) Effect of H-wall and TCFSS and (b) height of TCFSS on impedance matching. 184
Figure 7.4. Parametric study with variance of dipole length e and gap of TCFSS a when (a) a = 0.04 mm and (b) e = 1.12 mm. 185
Figure 7.5. Parametric study with variance of extended side arm B. (a) TARC and (b) broadside gain. 186
Figure 7.6. (a) N-port network of the array structure. (b) Symmetric connector and line sample (top) and open-terminated... 186
Figure 7.7. Simulation results without and with calibration process, and measurement results with calibration process. 188
Figure 7.8. Simulated and measured (a) realized array gain, radiation efficiency, (b) reflection characteristics, and (c) CDF of... 188
Figure 7.9. Simulated and measured gain patterns in E-, D- and H-plane scanning for θ=0°, 30° at 24 GHz and 40 GHz. 189
Figure 7.10. Simulated and measured EIRP scan patterns at 24 GHz, 30 GHz, 37 GHz, and 40 GHz when each channel is excited at 9 dBm. 190
Figure 7.11. Proposed unit cell of feeding structure in an infinitely periodic boundary along the y-direction. (a) Perspective view of... 195
Figure 7.12. Current and electric field distributions on the unit cell structure with BC 1 at 32 GHz are shown at (a) t = 0 and (b) t =... 197
Figure 7.13. Reflection coefficient of the unit cell at the discrete port is shown, depending on the boundary condition. BC 1: infinitely 197
Figure 7.14. (a) Unit cell structure of the MS with a spatial period of p = 1.96 mm. (b) Normalized dispersion diagram is shown as the... 198
Figure 7.15. Bloch impedance of the MS. (a) Real and (b) imaginary parts. 200
Figure 7.16. Electric field distributions of the TCMPA fed MS are shown at various frequencies, and time instants t = 0 and t = T/4. 200
Figure 7.17. Parametric study on the proposed unit cell structure with the MS, varying (a) the diameter of the capacitor, Rₚ, (b) the... 202
Figure 7.18. (a) Proposed finite array structure composed of 1 x 4 unit elements. (b) 3 dB beam width on the zx-plane is shown. 204
Figure 7.19. Simulated and measured (a) TARC and (b) realized array gain as scanning the beam from ϕₛ = 0° to ϕₛ = 45°. 205
Figure 7.20. Simulated gain patterns at various frequencies as scanning the beam from ϕₛ = 0° to ϕₛ = 45° where the H-plane is... 206
Figure 7.21. Simulated EIRP scan patterns with 4-bits beam scanning states at various frequencies when excited power per a... 209
Figure 7.22. Simulated CDF of the EIRP scan patterns at various frequencies. 209
Figure 7.23. Proposed unit cell structure. (a) Perspective view. (b) Exploded view. (c) Side view without the side vias. (d) H-layer,... 213
Figure 7.24. Surface current distribution on the inner structure at 32 GHz is shown at two different instances when V- and H- ports... 216
Figure 7.25. At 32 GHz, electric field distribution viewed from the side without the side vias is shown at two different instances when... 217
Figure 7.26. Reflection coefficients of the unit cell (a) when the V-port is excited with and without the horn, and (b) the H-port is... 218
Figure 7.27. Parametric study on the GND position, (a) V and (b) H, when the positions of the TCDA and TCMA are fixed. Left and right... 219
Figure 7.28. Parametric study on the slit horn. Left and right columns are V- and H-ports, respectively. 220
Figure 7.29. Proposed 1 x 4 finite array configuration considering arrangement of the mini SMPMs and the horn. (a) Perspective view.... 222
Figure 7.30. Parametric study on the extended side arm, E, of the finite array. (a) TARCs at the H-port and (b) broadside array gains... 222
Figure 7.31. Simulated (a) TARCs and (b) realized array gains as scanning the beam from ϕₛ = 0° to ϕₛ = 45°. Left and right... 223
Figure 7.32. Simulated V-pol (left) and H-pol (right) gain patterns at various frequencies as scanning the beam from ϕₛ = 0° (red) to... 224