370 research outputs found

    Ultra-Wideband FSS-Based Antennas

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    As antennas are indispensable elements in wireless systems, it is necessary to provide UWB antennas suitable for UWB systems. The most proposed UWB antennas have omnidirectional radiation, which provides the wide coverage area that is highly demanded by many conventional UWB applications. However, directional radiation is more beneficial for other UWB applications and it may even be beneficial for the conventional UWB omnidirectional applications in some environments that contain many sources of interference and distorting objects, where the omnidirectional radiation leads to high interference and loss of power in undesirable directions. Consequently, an immense research has addressed the issue of realizing UWB planar antennas with unidirectional radiation characteristics. Basically, the main technique used to create unidirectional radiation patterns is employing cavity-baking reflectors to redirect the back radiation, hence increasing the gain of the radiators. In addition, these reflectors can decouple the mounted radiator from the surroundings that can damage its characteristics. Therefore, we suggest the employment of UWB reflectors to achieve UWB planar antennas with directional radiation. Our research for designing optimal UWB reflectors has led to the investigation in the field of frequency selective surfaces (FSSs), which are valuable structures and can be of great interest to a wide range of applications especially UWB applications. Subsequently, the main aim of this chapter is to give a review of the fundamental uses of FSSs in antenna engineering and the basic physical concepts that have been employed to serve the purpose of enhancing antennasโ€™ performances using FSSs with a variety of features and characteristics. Furthermore, it is geared toward the presentation of our proposed UWB FSS-based antennas. First, we use basic FSSs such as the capacitive and its complementary inductive FSSs to design UWB reflectors that can serve improving and stabilizing the gain of UWB antennas. Thereafter, a proposed UWB single-layer FSS is used to serve the same purpose. Then, the FSS is integrated and designed together with UWB radiator, which resulted in lower profile along with good performance

    Applications of circularly polarized crossed dipole antennas

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    ยฉ 2014 IEEE. Circularly polarized crossed dipole antennas are presented in this paper. A compact crossed dipole is realized with the use of a meander line and a barbed end in each dipole arm. A vacant-quarter printed ring is used as a 90ยฐ phase delay line to achieve circularly polarized radiation. For multi-band applications, each dipole arm is divided into multi-branches with different lengths to obtain multiple resonances. These radiators can be equipped with different reflectors, such as a finite planar metallic conductor, a cavity-backed metallic conductor, and a finite artificial magnetic conductor to obtain the desired antenna radiation characteristics. These antennas are quite practical for many wireless communication systems, such as satellite communications, global positioning systems, wireless local area networks, and radio-frequency identification devices

    ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ์›ํ˜• ํŽธํŒŒ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ์„ ์œ„ํ•œ ๋‹ค์ธต ์ ์žฌ๋œ ์‹ค์‹œ๊ฐ„ ์ง€์—ฐ ํšŒ๋กœ์™€ ์œ„์ƒ ์กฐ์ ˆ ๋ฐ˜์‚ฌํŒ ์„ค๊ณ„

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    ํ•™์œ„๋…ผ๋ฌธ(๋ฐ•์‚ฌ)--์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› :๊ณต๊ณผ๋Œ€ํ•™ ์ „๊ธฐยท์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€,2020. 2. ๋‚จ์ƒ์šฑ.๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ์„ ๊ตฌํ˜„ํ•˜๊ธฐ ์œ„ํ•ด ํ•„์š”ํ•œ ํ•ต์‹ฌ ๊ธฐ์ˆ  ๊ฐœ๋ฐœ์— ๊ด€ํ•ด ์—ฐ๊ตฌํ•˜์˜€๋‹ค. ๋ ˆ์ด๋”, ์ „์ž์ „, ๋ฌด์„  ํ†ต์‹ ๊ณผ ๊ฐ™์ด ๋งŽ์€ ๋ถ„์•ผ์—์„œ ํ™œ๋ฐœํžˆ ์‚ฌ์šฉ๋˜๋Š” ์žˆ๋Š” ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜๋Š” ์‚ฐ์—…์ด ๊ณ ๋„ํ™”๋˜๋ฉด์„œ ์š”๊ตฌํ•˜๋Š” ์‹œ์Šคํ…œ ์ŠคํŽ™์ด ๋”์šฑ ๊ณ ๊ธ‰ํ™”๋˜๊ณ  ์žˆ๋‹ค. ๊ทธ ์ค‘ ๋ฌด์ธ ๋น„ํ–‰์ฒด, ๋ฏธ์‚ฌ์ผ ๋“ฑ๊ณผ ๊ฐ™์€ ๊ณ ์† ์ด๋™์ฒด์˜ ๊ณก๋ฉด์— ๋ฐฐ์น˜ํ•  ์ˆ˜ ์žˆ๋„๋ก ํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ๋‚ฎ์€ ๋†’์ด์˜ ์•ˆํ…Œ๋‚˜ ์„ค๊ณ„๊ฐ€ ํ•„์š”ํ•œ๋ฐ, ํŠนํžˆ ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜๋Š” ๊ตฌ์กฐ์ ์œผ๋กœ ์„ค๊ณ„์— ํฐ ์–ด๋ ค์›€์ด ์žˆ๋‹ค. ์ด ๋…ผ๋ฌธ์—์„œ ๋ชฉํ‘œ๋กœ ์ •ํ•œ ์‘์šฉ ๋ถ„์•ผ๋Š” ์ „์ž์ „์—์„œ ๋น”ํฌ๋ฐ์„ ์ด์šฉํ•˜์—ฌ ์ ์˜ ์œ„์น˜๋ฅผ ํƒ์ƒ‰ํ•˜๊ณ  ํ•ด๋‹น ์œ„์น˜๋กœ ํŠน์ • ์ฃผํŒŒ์ˆ˜์˜ ํฐ ์ „๋ ฅ์˜ ์‹ ํ˜ธ๋ฅผ ์ „์†กํ•˜๋Š” ์ „ํŒŒ ๋ฐฉํ•ด๊ธฐ์ด๋‹ค. ์ „ํŒŒ ๋ฐฉํ•ด๊ธฐ๋Š” ๊ด‘๋Œ€์—ญ์˜ ์ฃผํŒŒ์ˆ˜ ๋Œ€์—ญ ๋‚ด์—์„œ ์„ ํƒ์ ์œผ๋กœ ์ฃผํŒŒ์ˆ˜๋ฅผ ์„ ํƒํ•˜์—ฌ ์‚ฌ์šฉํ•  ์ˆ˜ ์žˆ๋„๋ก ์„ค๊ณ„๋˜์–ด์•ผ ํ•˜๋ฏ€๋กœ ๊ด‘๋Œ€์—ญ์œผ๋กœ ๋™์ž‘ํ•˜๋Š” ์‹œ์Šคํ…œ ๊ตฌํ˜„์ด ํ•„์š”ํ•˜๋‹ค. ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ๋Š” ํฌ๊ฒŒ ๊ด‘๋Œ€์—ญ ๋น”์กฐํ–ฅ ๋„คํŠธ์›Œํฌ์™€ ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜๋กœ ๊ตฌ๋ถ„ํ•  ์ˆ˜ ์žˆ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ๊ฐ ๋ถ€๋ถ„์—์„œ์˜ ๋ฌธ์ œ๋ฅผ ๋ถ„์„ํ•˜๊ณ  ์ด๋ฅผ ํ•ด๊ฒฐํ•˜์—ฌ ์„ค๊ณ„ ๋ฐ ๊ตฌํ˜„ํ•˜๋Š” ๋ฐฉํ–ฅ์œผ๋กœ ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ์ˆ˜ํ–‰๋œ ์—ฐ๊ตฌ์˜ ๋‚ด์šฉ์€ ์•„๋ž˜์™€ ๊ฐ™๋‹ค. ์ฒซ ๋ฒˆ์งธ๋กœ, ๊ด‘๋Œ€์—ญ ๋น”์กฐํ–ฅ ๋„คํŠธ์›Œํฌ๋ฅผ ๊ตฌ์„ฑํ•˜๋Š” ๊ฐ€์žฅ ํ•ต์‹ฌ ์š”์†Œ์ธ ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ๋ฅผ ๊ตฌํ˜„ํ•  ๋•Œ ํ•„์š”ํ•œ ๊ธฐ์ˆ ์„ ๊ฐœ๋ฐœํ•˜์˜€๋‹ค. ๋จผ์ € ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ์˜ ์ค‘์š”ํ•œ ์„ฑ๋Šฅ ์ง€ํ‘œ์ธ ์ง€์—ฐ ์‹œ๊ฐ„ ํŠน์„ฑ์— ์˜ํ–ฅ์„ ์ค„ ์ˆ˜ ์žˆ๋Š” 3๊ฐ€์ง€ ์š”์†Œ๋“ค์— ๋Œ€ํ•ด ๋ถ„์„ํ•˜์˜€๋‹ค. ์ฒซ ๋ฒˆ์งธ ์š”์†Œ๋Š” off ์ƒํƒœ์—์„œ ๋ณด์ด๋Š” ์ปคํŽ˜์‹œํ„ฐ์— ์˜ํ•œ ๊ณต์ง„์ด๋‹ค. ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ์—์„œ ๊ณต์ง„์ด ๋ฐœ์ƒํ•˜๋ฉด ์ „์ฒด ์‹œ์Šคํ…œ ์„ฑ๋Šฅ์ด ์•…ํ™”๋  ์ˆ˜ ์žˆ๊ธฐ ๋•Œ๋ฌธ์— 30 dB ์ด์ƒ์˜ ๊ฒฉ๋ฆฌ ํŠน์„ฑ์„ ๊ฐ–๋Š” ์Šค์œ„์น˜๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ์•ผ ํ•œ๋‹ค. ๋‘ ๋ฒˆ์งธ๋กœ ๋ถ„์„ํ•œ ์š”์†Œ๋Š” ๋ถˆ์—ฐ์†์— ์˜ํ•ด ๋‚˜ํƒ€๋‚˜๋Š” ๋ฐ˜์‚ฌํŒŒ๋กœ ์ด๋Š” ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ์™€ ์ „์ฒด ์‹œ์Šคํ…œ์„ ๊ตฌ์„ฑํ•  ๋•Œ ๋งค์นญ์ด ํ•„์ˆ˜์ ์œผ๋กœ ์ˆ˜ํ–‰๋˜์–ด์•ผ ํ•˜๋Š” ์ด์œ ๊ฐ€ ๋œ๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ๋ถ„์„ํ•œ ์š”์†Œ๋Š” ์•ˆํ…Œ๋‚˜ ์ž„ํ”ผ๋˜์Šค์— ์˜ํ•œ ๋ฐ˜์‚ฌ ์†์‹ค์ด๋‹ค. ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜์˜ ์ž„ํ”ผ๋˜์Šค๋Š” ์ฃผํŒŒ์ˆ˜์— ๋”ฐ๋ผ ๋ณ€ํ•˜๊ฒŒ ๋˜๋Š”๋ฐ ์ด๋Š” ์•ˆํ…Œ๋‚˜์— ์ธ๊ฐ€๋˜๋Š” ์‹ ํ˜ธ์˜ ์œ„์ƒ์„ ๋ณ€ํ™”์‹œ์ผœ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ ์„ฑ๋Šฅ์— ์˜ํ–ฅ์„ ์ค„ ์ˆ˜ ์žˆ๋‹ค. ๋ชฌํ…Œ ์นด๋ฅผ๋กœ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•ด ์•ˆํ…Œ๋‚˜ ์ž„ํ”ผ๋˜์Šค ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์œ„์ƒ ์˜ค์ฐจ๊ฐ€ ๋น”์กฐํ–ฅ๊ฐ๊ณผ ์‚ฌ์ด๋“œ ๋กœ๋ธŒ ๋ ˆ๋ฒจ์— ์–ผ๋งˆ๋‚˜ ์˜ํ–ฅ์„ ์ฃผ๋Š”์ง€ ํ™•์ธํ•˜์˜€๋‹ค. ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜๋ฅผ ์„ค๊ณ„ํ•˜์—ฌ ํ•ด๋‹น ์•ˆํ…Œ๋‚˜์˜ ๋Šฅ๋™ ๋ฐ˜์‚ฌ ๊ณ„์ˆ˜๋ฅผ ํ†ตํ•ด ์ด๋ฅผ ๊ฒ€์ฆํ•˜์˜€๋‹ค. ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ์˜ ์„ค๊ณ„๋ฅผ ์ง„ํ–‰ํ•  ๋•Œ ์ถ”๊ฐ€์ ์ธ ์ด์Šˆ๋Š” ์†Œํ˜•ํ™”๊ฐ€ ์žˆ๋‹ค. ์•ž์—์„œ ๋ถ„์„ํ•œ 3๊ฐ€์ง€ ์š”์†Œ๋ฅผ ๊ณ ๋ คํ•˜์—ฌ 7-bit ์ ์ธต ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ๋ฅผ ์„ค๊ณ„ํ•˜์˜€๋‹ค. ์ œ์ž‘ ๋ฐ ์ธก์ •์„ ํ†ตํ•ด ์„ค๊ณ„ํ•œ ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ๊ฐ€ ์†์‹ค์— ๋”ฐ๋ฅธ ์ง€์—ฐ์‹œ๊ฐ„, ๋†’์€ bit ์ˆ˜, ์ €์ „๋ ฅ์˜ ์žฅ์ ์„ ๊ฐ€์ง€๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ์„ ๊ตฌ์„ฑํ•˜์—ฌ ์ œ์ž‘๋œ ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ๋ฅผ ๊ฒ€์ฆํ•˜์˜€๋‹ค. ์ธก์ •์„ ํ†ตํ•ด ์ œ์ž‘๋œ ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ์ด 3:1 ๋Œ€์—ญ์—์„œ ๋น” ์Šคํ€ธํŠธ ํ˜„์ƒ ์—†์ด ๋น”์กฐํ–ฅ์ด ๊ฐ€๋Šฅํ•จ์„ ํ™•์ธํ•˜์˜€๊ณ  ์†Œํ˜•ํ™”๋œ ์‹ค์‹œ๊ฐ„ ์ง€์—ฐํšŒ๋กœ๊ฐ€ ์ œ๋Œ€๋กœ ๋™์ž‘ํ•จ์„ ๊ฒ€์ฆํ•˜์˜€๋‹ค. ๋‘ ๋ฒˆ์งธ๋กœ, ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜๋ฅผ ๊ตฌํ˜„์— ํ•„์š”ํ•œ ๊ธฐ์ˆ ๋กœ ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜ ๊ฐ€๊นŒ์ด ๋ฐ˜์‚ฌํŒ์„ ๋ฐฐ์น˜ํ•˜์—ฌ ๋‹จ๋ฐฉํ–ฅ ๋น”์„ ํ˜•์„ฑํ•  ๋•Œ ๋ฐœ์ƒํ•˜๋Š” ๋ฌธ์ œ์ ์„ ๋ถ„์„ ๋ฐ ๊ทน๋ณตํ•˜์˜€๋‹ค. ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜์— ๊ฐ€์žฅ ์ ํ•ฉํ•œ ์•ˆํ…Œ๋‚˜๋Š” ๊ตฌํ˜„์ด ์‰ฝ๊ณ  ์†Œํ˜•ํ™”์— ์žฅ์ ์ด ์žˆ๋Š” ์ŠคํŒŒ์ด๋Ÿด ์•ˆํ…Œ๋‚˜์ด๋‹ค. ์–‘๋ฐฉํ–ฅ ํŒจํ„ด์„ ๊ฐ–๋Š” ์ŠคํŒŒ์ด๋Ÿด ์•ˆํ…Œ๋‚˜๋Š” ๋‹จ๋ฐฉํ–ฅ ํŒจํ……์„ ๋งŒ๋“ค์–ด ์ฃผ๊ธฐ ์œ„ํ•ด ๋ฐ˜์‚ฌํŒ์ด ํ•„์š”ํ•œ๋ฐ ํ•ด๋‹น ๋ฐ˜์‚ฌํŒ์œผ๋กœ ์ธํ•ด ๋งค์นญ๊ณผ ์ถ•๋น„์— ๋ฌธ์ œ๊ฐ€ ์ƒ๊ธฐ๋Š” ํฐ ๋‹จ์ ์ด ์žˆ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ๋จผ์ € ๋ฐ˜์‚ฌํŒ์ด ์ถ•๋น„๋ฅผ ์•…ํ™”์‹œํ‚ค๋Š” ์ด์œ ์— ๋Œ€ํ•ด ๋ถ„์„ํ•˜์˜€๋‹ค. ๋ถ„์„์„ ๊ธฐ๋ฐ˜์œผ๋กœ ์ถ•๋น„ ๊ฐœ์„ ์„ ์œ„ํ•ด varactor๋ฅผ ์‚ฌ์šฉํ•œ polarization-dependent ์œ„์ƒ ์กฐ์ ˆ ๋ฐ˜์‚ฌํŒ์„ ์ œ์•ˆํ•˜์˜€๋‹ค. polarization-dependent ์œ„์ƒ ์กฐ์ ˆ ๋ฐ˜์‚ฌํŒ์ด ํšจ๊ณผ์ ์œผ๋กœ ์ถ•๋น„๋ฅผ ๊ฐœ์„ ํ•˜๋Š”์ง€ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•ด ์ŠคํŒŒ์ด๋Ÿด ์•ˆํ…Œ๋‚˜์™€ ํ•จ๊ป˜ ๋ฐฐ์น˜ํ•˜์—ฌ ์„ค๊ณ„ํ•˜์˜€๋‹ค. ์ฃผ๊ธฐ ๊ตฌ์กฐ๋ฅผ ํ†ตํ•ด ๋ฌดํ•œ ๋ฐฐ์—ด ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ์ง„ํ–‰ํ•˜์—ฌ ์›ํ•˜๋Š” ์ฃผํŒŒ์ˆ˜ ๋Œ€์—ญ์—์„œ ์ถ•๋น„๊ฐ€ ํšจ๊ณผ์ ์œผ๋กœ ๊ฐœ์„ ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋ฅผ ๊ตฌํ˜„ํ•˜๊ธฐ ์œ„ํ•ด dummy๋ฅผ ์ถ”๊ฐ€ํ•œ 4 x 4 ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜๋ฅผ ์ตœ์ข… ์„ค๊ณ„ํ•˜์˜€๋‹ค. ์ฃผ๊ธฐ ๊ตฌ์กฐ ์‹œ๋ฎฌ๋ ˆ์ด์…˜๊ณผ ๋†’์€ ์ผ์น˜์„ฑ์„ ๋ณด์—ฌ ์ œ์ž‘ ๋ฐ ์ธก์ •์„ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ์ œ์ž‘๋œ ์•ˆํ…Œ๋‚˜์˜ ๋ฐ˜์‚ฌ ์†์‹ค์€ ์›ํ•˜๋Š” ๋Œ€์—ญ ๋ชจ๋‘์—์„œ -10 dB ์ดํ•˜์˜ ๊ฐ’์„ ๊ฐ€์กŒ๋‹ค. ์ถ•๋น„, ์ด๋“, ํŒจํ„ด ๋ชจ๋‘ ์‹œ๋ฎฌ๋ ˆ์ด์…˜๊ณผ ๊ฑฐ์˜ ์ผ์น˜ํ•œ ์ธก์ • ๊ฒฐ๊ณผ๋ฅผ ์–ป์„ ์ˆ˜ ์žˆ์—ˆ๋‹ค. ์ด๋ฅผ ํ†ตํ•ด polarization-dependent ์œ„์ƒ ์กฐ์ ˆ ๋ฐ˜์‚ฌํŒ์ด ํšจ๊ณผ์ ์œผ๋กœ ์ถ•๋น„๋ฅผ ๊ฐœ์„ ํ•˜๋Š” ๊ฒƒ์„ ๊ฒ€์ฆํ•˜์˜€๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ๋น”์กฐํ–ฅ ํŠน์„ฑ์„ ํ™•์ธํ•œ ๊ฒฐ๊ณผ polarization-dependent ์œ„์ƒ ์กฐ์ ˆ ๋ฐ˜์‚ฌํŒ์„ ์ ์šฉํ•˜๋ฉด์„œ ์†์‹ค์—†์ด ๋น”ํญ ๋‚ด์—์„œ 1.5 dB ์•„๋ž˜์˜ ์šฐ์ˆ˜ํ•œ ์ถ•๋น„ ๊ฐ’์„ ๊ฐ€์ง€๋ฉฐ -30๋„์—์„œ 30๋„๊นŒ์ง€ ๋น”์กฐํ–ฅ์ด ๊ฐ€๋Šฅํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๊ฒฐ๋ก ์ ์œผ๋กœ, ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ์•ˆํ…Œ๋‚˜ ์‹œ์Šคํ…œ์„ ๊ตฌํ˜„ํ•  ๋•Œ ๊ทน๋ณตํ•ด์•ผ ํ•˜๋Š” ๋‘๊ฐ€์ง€ ์ฃผ์ œ์— ๋Œ€ํ•ด ๋ถ„์„ ๋ฐ ํ•ด๊ฒฐํ•˜์˜€๋‹ค. ์ •ํ™•ํ•œ ๋ถ„์„ ๋ฐ ์ ์ ˆํ•œ ํ•ด๊ฒฐ ๋ฐฉ์•ˆ์„ ์ฐพ์„ ์ˆ˜ ์žˆ์—ˆ๊ณ  ์ด๋ฅผ ํ†ตํ•ด ๊ด‘๋Œ€์—ญ ๋น”์กฐํ–ฅ ๋„คํŠธ์›Œํฌ์™€ ๋‚ฎ์€ ๋†’์ด์˜ ๊ด‘๋Œ€์—ญ ๋ฐฐ์—ด ์•ˆํ…Œ๋‚˜์— ์ ์šฉํ•˜์—ฌ ์„ค๊ณ„ํ•˜์˜€๋‹ค. ์ตœ์ข…์ ์œผ๋กœ ์ธก์ • ๋ฐ ๊ฒ€์ฆ์„ ํ†ตํ•ด ์ „์ฒด ๊ณผ์ •์˜ ํƒ€๋‹น์„ฑ์„ ๊ฒ€์ฆํ•˜์˜€๋‹ค.In this thesis, two essential technologies to realize a low profile wideband phased array antenna system are described. Phased array antennas, which have been actively used in military and civil applications such as radar, electronic warfare (EW), and wireless communications, are becoming more advanced as the system specification demanded by the industry. Especially, low-profile wideband phased array antennas are actively studied. It has been a challenge to design wideband and low-profile antennas, which can be surface-mounted on airborne applications such as missile, aircraft, and unmanned aerial vehicle (UAV) to reduce air resistance. Target application in this thesis is jammer in electronic warfare which is to search the enemy's position and shoot a signal of a large power of a certain frequency to the position by beamforming, so it is designed to selectively choose a frequency in a wide band. The low-profile wideband array antenna system for the application consists of a wideband beamforming network and a low-profile wideband array antenna. In this thesis, we analyzed the issues and problems in each part and overcame them to design and implement the low-profile wideband antenna system. The contents of the study carried out are as follows. At first, design considerations and procedure of wideband beamforming network is presented. Three factors that can affect group delay variation are analyzed, which is the most important performance indicator of the true-time delay line (TTD). First factor that affects group delay characteristic is off-state capacitor resonance. To minimize degradation of TTD performance due to the resonances, switches with an off-state isolation of more than 30 dB are required. Second factor is reflected wave due to discontinuity, so that matching must be accomplished in design of TTDs and all system. The last factor is the phase error caused by the reflection coefficient due to the antenna impedance. Monte Carlo simulations were performed to investigate the effect of phase delay error on the beam steering angle and side lobe level due to antenna impedance. And the actual antenna is designed to verify the effect of the phase delay error on the antenna impedance. Considering these factors 7-bit multistacked TTD was designed and fabricated for miniaturization which is an additional issue when designing a TTD. Fabrication and measurement were performed and our approach shows an improved performance regarding a figure of merit defined as the relative delay divided by the insertion loss at the longest delay state, a large number of bits of resolution, and low power consumption. Finally, a wideband antenna system was constructed to verify the fabricated TTD. Beam steering is performed without beam squint within the 3 : 1 bandwidth, which verify that the miniaturized TTD is capable of wideband beam steering. Second, to solve performance degradation problems when forming a unidirectional beam by attaching a perfect electric conductor (PEC) reflector close to the wideband antenna is described for low-profile wideband phased array antenna systems. The most applicable type of antennas for low profile wideband antenna array is spiral antenna which has advantages of simple manufacture process and miniaturization for array. Spiral antenna has the disadvantage of requiring a reflector for unidirectional patterns due to its bidirectional circular polarized pattern. We analyzed the reason why the axial ratio (AR) could be deteriorated by the reflector first. Based on analysis, a polarization-dependent phase tunable reflector is proposed to implement the required reflection phase of x and y using varactors for improvement of AR. To verify that AR is effectively improved by the polarization-dependent phase tunable reflector, spiral array antenna backed by the polarization-dependent phase tunable reflector was designed and fabricated. Periodic boundary simulation for infinite array and simulation of 4 x 4 array with dummy were performed. A 4 x 4 array with dummy of the fabricated array with polarization-dependent phase tunable reflector for measurement. Fabricated array antenna has a reflection coefficient of less than โ€“10 dB in the entire target band. All measurement results and simulation results have high consistent. AR improvement was achieved through the measurement results by changing bias voltage applied to varactors on polarization-dependent phase tunable reflector. According to this measurement process and results we implemented a spiral array antenna capable of beam steering from -30หš to 30หš with excellent circular polarization (CP) characteristics with an AR value of less than 1.5 dB within the 3 dB beamwidth without loss by applying polarization-dependent phase tunable reflector. In conclusion, we investigated and analyzed two issues to overcome for implementation of a low-profile wideband antenna system. Through accurate analysis, appropriate solution could be found and applied to design of wideband beamforming network and low-profile wideband array antenna. Fabrications and measurements were conducted to prove the validity of the entire process.Chapter 1. Introduction 1 1.1. Motivation 1 1.2. Organization of the Dissertation 4 Chapter 2. Wideband Beamforming Network 5 2.1. Analysis of factors that affects group delay variation in TTD 6 2.1.1. Accurate group delay measurement technique in vector network analyzer 6 2.1.2. Off-switch capacitor resonance 10 2.1.3. Reflected wave due to discontinuity 13 2.1.4. Antenna impedance variation over frequency 16 2.2. Design of 7-bit multistacked true-time delay for miniaturization 26 2.2.1. Design considerations 27 2.2.2. TTD resolution and number of bits 30 2.2.3. Optimal design of signal vias 32 2.2.4. Fabrication and measurement results 36 2.2.5. Verification of TTD 40 2.3. Conclusion 53 Chapter 3. Low-profile Wideband Antenna 55 3.1. Analysis of AR deterioration backed by reflector 57 3.2. Improvement of AR with polarization-dependent phase tunable reflector 63 3.2.1. AR improvement through reflector with ideal reflection phase 63 3.2.2. Practical design issues of reflector with varactors 68 3.2.3. AR improvement through 1D phase tunable reflector 76 3.2.4. AR improvement through 2D phase tunable reflector 79 3.3. Design of spiral antenna array backed by polarizationdependent 1D phase tunable reflector 83 3.3.1. Periodic boundary simulation for infinite array 84 3.3.2. 4 x 4 array simulation with dummy 87 3.4. Fabrication and measurement results 90 3.5. Conclusion 107 Bibliography 110 Abstract in Korean 115Docto

    Wideband and UWB antennas for wireless applications. A comprehensive review

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    A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

    Printed Quasi-Yagi Antennas Using Double Dipoles and Stub-Loaded Technique for Multi-Band and Broadband Applications

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    ยฉ 2013 IEEE. Double dipoles on a single-layer substrate are utilized to construct a triple-mode printed quasi-Yagi antenna for the multi-band and broadband antenna applications. A stub-loaded dipole generating two resonant modes (i.e., lower dual-mode dipole) is allocated on the underside of a simple dipole (i.e., upper single-mode dipole) introducing the third resonant mode. Using these three resonant modes, three compact printed quasi-Yagi antennas, i.e., tri-band, dual-band, and broadband printed quasi-Yagi antennas, are designed with the same antenna prototype but different parameter values. Seen from the measured results, all of these three antennas have good unidirectional radiations, high radiation efficiencies, and low cross-polarization levels at the operating frequencies within the impedance bandwidths

    2009 Index IEEE Antennas and Wireless Propagation Letters Vol. 8

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    This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

    2008 Index IEEE Transactions on Control Systems Technology Vol. 16

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    This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

    Multi resonance patch antenna with multiple slits

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    In this paper, we have presented a new design of a multi resonance patch antenna with multiple slits. Slits are located on the three sides of the designed antenna. It is simulated in a planar 3D electromagnetic simulation program, called Sonnet Software, designed on the Aluminum (96%) substrate and operates at three frequencies with reflection coefficient (S11) values lower than -10 dB. Values for the operating frequencies are 4.14, 5.52, 9.24 GHz. Electric field theta polarized gains for these three frequencies are; 8.09, 8.35, and 8.39 dBs respectively. Cross polarization levels are well below -10 dB. A parametric study was conducted by changing the gap size and the dielectric thickness. As a result of the parametric study, it is seen that fabrication tolerances of the antenna are good enough

    Microwave System for the Early Stage Detection of Congestive Heart Failure

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    Fluid accumulation inside the lungs, known as cardiac pulmonary edema, is one of the main early symptoms of congestive heart failure (CHF). That accumulation causes significant changes in the electrical properties of the lung tissues, which in turn can be detected using microwave techniques. To that end, the design and implementation of an automated ultrahigh-frequency microwave-based system for CHF detection and monitoring is presented. The hardware of the system consists of a wideband folded antenna attached to a fully automated vertical scanning platform, compact microwave transceiver, and laptop. The system includes software in the form of operational control, signal processing, and visualizing algorithms. To detect CHF, the system is designed to vertically scan the rear side of the human torso in a monostatic radar approach. The collected data from the scanning is then visualized in the time domain using the inverse Fourier transform. These images show the intensity of the reflected signals from different parts of the torso. Using a differential based detection technique, a threshold is defined to differentiate between healthy and unhealthy cases. This paper includes details of developing the automated platform, designing the antenna with the required properties imposed by the system, developing a signal processing algorithm, and introducing differential detection technique besides investigating miscellaneous probable CHF cases
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