RF MODULE

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Creating the Geometry in MATLAB To create the geometry, start COMSOL Multiphysics with MATLAB or initiate a MATLAB connection from the File menu. Open a new 3D model by selecting 3D from the Space dimension list in the Model Navigator and clicking OK. After running the script below from the command line, choose File>Import>Geometry Objects. In the dialog box that appears, enter the geometry object g7. lx = 1.827/2; ly = 3.015/2; e1 = ellip2(lx,ly); y0 = 1.142999999817202; x0 = sqrt((1-y0^2/ly^2)*lx^2); p1 = point2(x0, y0); p2 = scale(p1,1,-1); p3 = rotate(p1,pi); p4 = scale(p3,1,-1); g1 = solid2(geomcsg({e1},{},{p1},{p2},{p3},{p4})); lx2 = 1.016; ly2 = 2.286; r1 = solid2(geomcsg({rect2(lx2,ly2,'Base','center')},... {point2(0,-2.286/2)},{point2(1.016/2,0)},... {point2(0,2.286/2)},{point2(-1.016/2,0)})); z0 = 3.0; z1 = 11.0; wrk0 = geomgetwrkpln('quick',{'xy',z0}); wrk1 = geomgetwrkpln('quick',{'xy',z1}); t = cell(1,8); t{1} = 3; t{2} = 2; t{3} = 4; t{4} = 5; t{5} = 6; t{6} = 7; t{7} = 8; t{8} = 1; g2 = loft({r1 g1},'LoftEdge',t,... 'wrkpln',{wrk0 wrk1},'loftmethod','linear'); g3 = extrude(r1,'distance',3); g4 = extrude (g1,'distance',3,'wrkpln',wrk1); g5 = geomcomp({g2,g3,g4}); g6 = geomdel(g5); g7 = scale(g5,0.01,0.01,0.01); geomplot(g7); 128 | CHAPTER 3: <strong>RF</strong> AND MICROWAVE MODELS
Microwave Cancer Therapy Introduction Electromagnetic heating appears in a wide range of engineering problems and is ideally suited for modeling in COMSOL Multiphysics because of its multiphysics capabilities. This example comes from the area of hyperthermic oncology and it models the electromagnetic field coupled to the bioheat equation. The modeling issues and techniques are generally applicable to any problem involving electromagnetic heating. In hyperthermic oncology, cancer is treated by applying localized heating to the tumor tissue, often in combination with chemotherapy or radiotherapy. Some of the challenges associated with the selective heating of deep-seated tumors without damaging surrounding tissue are: Control of heating power and spatial distribution Design and placement of temperature sensors Among possible heating techniques, <strong>RF</strong> and microwave heating have attracted much attention from clinical researchers. Microwave coagulation therapy is one such technique where a thin microwave antenna is inserted into the tumor. The microwaves heat up the tumor, producing a coagulated region where the cancer cells are killed. This model computes the temperature field, the radiation field, and the specific absorption rate (SAR)—defined as the ratio of absorbed heat power and tissue density—in liver tissue when using a thin coaxial slot antenna for microwave coagulation therapy. It closely follows the analysis found in Ref. 1. It computes the temperature distribution in the tissue using the bioheat equation. Model Definition Figure 3-20 shows the antenna geometry. It consists of a thin coaxial cable with a ring-shaped slot measuring 1 mm cut on the outer conductor 5 mm from the short-circuited tip. For hygienic purposes, the antenna is enclosed in a sleeve (catheter) made of PTFE (polytetrafluoroethylene). The following tables give the relevant MICROWAVE CANCER THERAPY | 129
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COMSOL Multiphysics RF MODULE V ERS
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CONTENTS Chapter 1: Introduction Mo
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Results and Discussion. . . . . . .
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Chapter 4: Optics and Photonics Mod
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1 Introduction The RF Module Model
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highlights. The categories here inc
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TABLE 1-1: RF MODULE MODEL LIBRARY
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2 Tutorial Models This chapter cont
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Results and Discussion Figure 2-1 s
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4 Draw a square with corners at (
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COMPUTING THE SOLUTION Click the So
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Results and Discussion The dipole a
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PHYSICS SETTINGS Variables 1 Choose
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5 Click OK to close the dialog box
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Model Library path: RF_Module/Tutor
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4 From the Solve menu, open the Sol
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them from the eigenvalues. The appl
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5 On the Port page, set the values
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5 On the Port page, enter 36.4 in t
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Waveguide Optimization Introduction
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Results and Discussion Figure 2-3 s
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Modeling Using the Graphical User I
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3 Select Boundary 7 and set the Con
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POSTPROCESSING AND VISUALIZATION Fo
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The solution takes a few minutes to
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Night side Earth surface Ionosphere
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Results and Discussion The model pr
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4 Select both spheres and click the
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RF and Microwave Models In this cha
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measure of the transmittance and re
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y 1 cm is at about 7.5 GHz. At the
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By feeding the circulator at a diff
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Importing the Geometry from a Binar
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MESH GENERATION This model uses the
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It is more instructive to look at t
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Note: When displaying S-Parameter v
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Monoconical RF Antenna Introduction
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50 Ω, to obtain maximum transmiss
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Figure 3-7 shows the antenna radiat
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2 Select the RF Module>Electromagne
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13 Zoom in around (0, 0) using the
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4 In the Contour levels area, click
Page 85 and 86: 2 Clear the Keep current plot check
Page 87 and 88: 6 Click the Solve button on the Mai
Page 89 and 90: Results and Discussion The figure b
Page 91 and 92: PHYSICS SETTINGS Point Settings Def
Page 93 and 94: 2 In the x-axis area, select the Ex
Page 95 and 96: Because the impedance is inversely
Page 97 and 98: 4 From the Space dimension list, se
Page 99 and 100: 2 Select Boundaries 1, 2, 4, and 6.
Page 101 and 102: 4 On the Pointwise Constraints page
Page 103 and 104: 12 Click the Solve button on the Ma
Page 105 and 106: Module. The electromagnetic cavity
Page 107 and 108: EIGENFREQUENCY VS. TEMPERATURE By r
Page 109 and 110: GEOMETRY MODELING 1 Go to the Draw
Page 111 and 112: 3 Set dx, dy, and dz to u, v, and w
Page 113 and 114: 20 Select the Solve using solver se
Page 115 and 116: Computing the Solution Using a Para
Page 117 and 118: 8 Click Solve. 9 When the parametri
Page 119 and 120: H-Bend Waveguide with S-parameters
Page 121 and 122: Model Library path: RF_Module/RF_an
Page 123 and 124: 1 From the Postprocessing menu, cho
Page 125 and 126: The rectangular port is excited by
Page 127 and 128: Figure 3-16 shows a single-mode wav
Page 129 and 130: Figure 3-18: The S 21 parameter (in
Page 131 and 132: PHYSICS SETTINGS First set up the b
Page 133 and 134: FREEZING THE BOUNDARY MODE ANALYSIS
Page 135: 12 Click the Solve button on the Ma
Page 139 and 140: The model takes advantage of the pr
Page 141 and 142: DOMAIN AND BOUNDARY EQUATIONS—HEA
Page 143 and 144: Figure 3-23: The computed microwave
Page 145 and 146: solutions for both the electromagne
Page 147 and 148: 4 Select Subdomain 1, then enter th
Page 149 and 150: 1 Click the Plot Parameters button
Page 151 and 152: sar_in_human_head_interp.txt. That
Page 153 and 154: The bioheat equation produces a sim
Page 155 and 156: 3 Click OK. 4 From the Options menu
Page 157 and 158: 17 In the Work-Plane Settings dialo
Page 159 and 160: SETTINGS SUBDOMAIN 19 epsilonr_brai
Page 161 and 162: 4 Click the Init tab and type 0 in
Page 163 and 164: POSTPROCESSING AND VISUALIZATION 1
Page 165 and 166: The walls of the oven and the waveg
Page 167 and 168: Figure 3-29: Temperature in the cen
Page 169 and 170: 3 Click the block symbol again and
Page 171 and 172: 2 At the waveguide end, Boundary 23
Page 173 and 174: 4 Click OK to generate the plot bel
Page 175 and 176: 3 Click OK to generate the plot bel
Page 177 and 178: Because the filter cutoff should be
Page 179 and 180: the force is applied. Figure 3-32 d
Page 181 and 182: 6 Then the ECAD Import Options dial
Page 183 and 184: PHYSICS SETTINGS Subdomain Settings
Page 185 and 186: solver takes more steps than it sto
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3 Select Subdomain 1 and clear the
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13 Click the Solve button on the Ma
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Balanced Patch Antenna for 6 GHz In
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k0 = ω ε0 µ 0 All metallic objec
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divided by the input power. In Figu
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Reference 1. E. Recht and S. Shiran
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10 Select the objects SQ2, CO1, and
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43 Specify two spheres with the fol
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inputs are feeding the antenna, lik
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the width of the PML is equal to λ
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a toggle button that shifts between
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5 Select Coarse solver from the tre
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maxE = max(EdB); minE = min(EdB); E
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exterior of the PML that shows a ve
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13 Choose Extrude from the Draw men
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2 Click the Settings button. 3 In t
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Sea Bed Logging Introduction The Se
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Figure 3-39: Electric field magnitu
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PHYSICS SETTINGS Scalar Variables 1
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4 Click OK to generate the plot bel
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5 Click the General tab. From the P
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Optics and Photonics Models In this
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Model Definition The model is built
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Model Library path: RF_Module/Optic
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PHYSICS SETTINGS Scalar Variables S
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POSTPROCESSING AND VISUALIZATION By
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Model Definition The geometry is a
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2 In the list of application modes,
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Because the refractive index of GaA
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5 Click OK twice to see the followi
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Bandgap Analysis of a Photonic Crys
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a 2 a 3 × b1 = 2π----------------
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The five lowest bands for the (1, 1
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Modeling Using the Graphical User I
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Subdomain Settings 1 Open the Subdo
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3 Click the Parametric tab. Select
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3 Click OK to see the following plo
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fem.appl{1}.prop.analysis = 'harmon
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Model Definition The mode analysis
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2 Select the RF Module>Perpendicula
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4 On the Contour page, give Magneti
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includes only two independent param
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OPTIONS AND SETTINGS 1 Open the Con
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The problem becomes well-posed by a
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POSTPROCESSING AND VISUALIZATION Th
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7 Click OK. 8 From the Postprocessi
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the computed propagation constants
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3 The default eigenmode is the one
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Compare these ideal values of the p
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Stress-Optical Effects with General
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The PDE solved is Navier’s equati
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and εx ∂u = ∂x εy ∂v = ∂y
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Model Library path: RF_Module/Optic
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NAME EXPRESSION DESCRIPTION B2 0.65
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2 In the Subdomain Expressions dial
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4 Initialize the mesh in this geome
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Note: This model includes an extens
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3 Enter 1.46 in the text field Sear
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In these expressions, w 0 is the mi
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After 90 fs the pulse has reached t
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4 Select the RF Module>In-Plane Wav
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Boundary Conditions 1 From the Phys
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6 Click the Remesh button; when the
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2 On the General page, make sure th
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Propagation of a 3D Gaussian Beam L
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Figure 4-15: After 20 fs the pulse
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7 Click the Delete Interior Boundar
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Boundary Conditions 1 From the Phys
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5 From the Options menu, select Sup
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INDEX 3D electromagnetic waves mode
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efractive index 222, 254 resistance
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RF MODULE

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