Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review

<table>Phase of the probe voltage <svg height="8.95535pt" id="M274" style="vertical-align:-0.1490297pt" version="1.1" viewbox="0 -8.80632 9.60567 8.95535" width="9.60567pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path d="M697 650H468L461 623L492 619C539 613 547 605 518 546C481 471 367 264 278 116H276C239 278 197 500 186 567C180 604 185 613 226 619L252 623L260 650H24L17 623C78 617 92 613 108 533L216 -11H247C365 200 515 462 560 529C616 612 624 615 689 623L697 650Z" id="g113-87"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="709" vert-adv-y="709"></glyph.data></g></svg> on the meridian at <svg height="13.3415pt" id="M275" style="vertical-align:-3.53603pt" version="1.1" viewbox="0 -9.80547 33.5635 13.3415" width="33.5635pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.0135,0,0,-0.0135,0,0)"><path d="M559 271C559 395 493 448 433 448C370 448 304 394 275 297C259 245 235 121 219 37C157 54 113 110 113 201C113 310 180 386 276 429L265 457C131 410 23 326 23 186C23 83 86 5 211 -10C180 -159 167 -220 158 -252L165 -261C198 -255 236 -246 251 -218L287 -5C421 9 559 119 559 271ZM484 273C484 144 400 40 293 33L352 331C364 389 382 406 405 406C431 406 484 370 484 273Z" id="g113-253"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="582" vert-adv-y="582"></glyph.data></g><g transform="matrix(.0135,0,0,-0.0135,11.671,0)"><path d="M535 323V373H52V323H535ZM535 138V188H52V138H535Z" id="g117-34"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="587" vert-adv-y="587"></glyph.data></g><g transform="matrix(.0135,0,0,-0.0135,23.409,0)"><path d="M241 635C89 635 35 457 35 312C35 153 89 -12 240 -12C390 -12 443 166 443 312C443 466 390 635 241 635ZM238 602C329 602 354 454 354 312C354 172 330 22 240 22C152 22 124 173 124 313S148 602 238 602Z" id="g113-49"></path><glyph.data ascent="3473" descent="-2876" horiz-adv-x="480" vert-adv-y="480"></glyph.data></g><g transform="matrix(.0095,0,0,-0.0095,29.912,-5.984)"><path d="M339 262C339 340 273 403 193 403S48 340 48 262S113 121 193 121S339 184 339 262ZM283 262C283 210 242 168 193 168S104 210 104 262S144 356 193 356S283 314 283 262Z" id="g54-73"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="385" vert-adv-y="385"></glyph.data></g></svg>. Solid line: exact. Crosses: interpolated.</table>

International Journal of Antennas and Propagation

fig9

Figure 9

Figure 9: Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review 