【摘要】：毫米波成像技術(shù)廣泛應(yīng)用于安檢、醫(yī)療中,但目前,毫米波成像系統(tǒng)中聚焦部分無(wú)論是采用反射面天線或者透鏡,體積龐大、笨重。設(shè)計(jì)一種結(jié)構(gòu)緊湊、易于集成、體積足夠小的聚焦方式對(duì)于加快毫米波成像技術(shù)向便攜化發(fā)展具有重要意義。利用超表面進(jìn)行波束調(diào)控為我們提供了新的思路。本課題主要研究35 GHz垂直入射情況下透射波束的偏轉(zhuǎn)與聚焦。首先,我們?cè)O(shè)計(jì)了一種工作在35 GHz、主極化傳播模式下,透射系數(shù)模值較大,透射相位隨尺寸變化可以實(shí)現(xiàn) π~+π相位覆蓋的三層圓環(huán)單元結(jié)構(gòu)用以構(gòu)造偏轉(zhuǎn)與聚焦表面。通過(guò)對(duì)不同尺寸內(nèi)徑單元進(jìn)行大角度入射情況下S參數(shù)穩(wěn)定性仿真分析,我們發(fā)現(xiàn),在0~60°入射時(shí),該圓環(huán)結(jié)構(gòu)透射系數(shù)模值與相位基本保持不變,保證了偏轉(zhuǎn)和聚焦表面邊緣電磁波束的有效工作。根據(jù)推廣的斯涅耳定律,我們進(jìn)行了波束偏轉(zhuǎn)表面的設(shè)計(jì)與仿真。我們分別設(shè)計(jì)了垂直入射條件下透射波束小角度21°與大角度72°偏轉(zhuǎn)。CST仿真結(jié)果顯示,透射波束有效偏轉(zhuǎn),與理論設(shè)計(jì)擬合良好,透射效率分別為86%與83%,能量得到有效傳輸。最后,我們進(jìn)行了聚焦表面的設(shè)計(jì)。根據(jù)準(zhǔn)光路定理,我們?cè)O(shè)計(jì)了聚焦于3λ0,5λ0和10λ0的聚焦表面。通過(guò)仿真結(jié)果的對(duì)比,我們發(fā)現(xiàn)在保持聚焦平面尺寸不變的情況下,焦距越短,焦斑越小,焦深越小,聚焦效果越明顯。為方便測(cè)試,我們選擇加工聚焦于5λ0的表面進(jìn)行實(shí)物測(cè)試。仿真結(jié)果顯示,此時(shí),焦點(diǎn)附近電場(chǎng)由51.34 d BV/m增加到61.98 d BV/m,增加了10.64 d B。焦斑大小為8.4 mm,小于λ0。我們將焦點(diǎn)處場(chǎng)強(qiáng)與35 GHz時(shí)焦點(diǎn)處場(chǎng)強(qiáng)相差3 d B,且焦斑寬度小于λ0的頻率范圍,定義為聚焦表面的工作帶寬。仿真結(jié)果顯示該聚焦表面工作帶寬為33~37 GHz,絕對(duì)帶寬為4 GHz,相對(duì)帶寬11.43%。實(shí)測(cè)結(jié)果與仿真結(jié)果良好擬合,該結(jié)構(gòu)具有很好的聚焦功能。
[Abstract]:Millimeter wave imaging technology is widely used in security inspection and medical treatment, but at present, the focusing part of millimeter wave imaging system is bulky and bulky, whether it is a reflector antenna or a lens. It is of great significance to design a compact, easy to integrate and small enough focusing mode for speeding up the development of millimeter wave imaging technology towards portability. The use of the supersurface for beam control provides us with a new way of thinking. In this paper, the deflection and focusing of transmission beam at 35 GHz vertical incidence are studied. First of all, we design a three-layer ring element structure which works at 35 GHz, the transmission coefficient mode is large, and the transmission phase can cover the 蟺 ~ 蟺 phase with the change of the size to construct the deflecting and focusing surfaces. Based on the simulation analysis of the S-parameter stability of different size inner diameter elements under the condition of large angle incidence, we find that the transmission coefficient modulus and phase of the ring structure remain basically unchanged at 0 ~ 60 擄incidence. The effective operation of the electromagnetic beam at the edge of the deflection and focusing surface is ensured. According to the generalized Sneel's law, we design and simulate the beam deflection surface. The simulation results show that the effective deflection of the transmission beam is well fitted to the theoretical design. The transmission efficiency is 86% and 83%, respectively, and the energy is transmitted effectively. Finally, we design the focused surface. According to the quasi-optical path theorem, we design the focusing surfaces focused on 3 位 0 5 位 0 and 10 位 0. By comparing the simulation results, we find that the shorter the focal length, the smaller the focal spot, the smaller the focal depth, and the more obvious the focus effect is. In order to facilitate the test, we choose to process the surface focused on 5 位 0 for physical testing. The simulation results show that the electric field near the focal point increases from 51.34 d BV/m to 61.98 dBV / m, with an increase of 10.64 dB / m. The focal spot size is 8.4 mm, less than 位 0. The frequency range of focal spot width less than 位 0 is defined as the working bandwidth of the focusing surface, which is 3 dB different from that at 35 GHz and the focal spot width is less than 位 0. The simulation results show that the working bandwidth of the focused surface is 3337 GHz, the absolute bandwidth is 4 GHz, and the relative bandwidth is 11.43 GHz. The measured results fit well with the simulation results, and the structure has a good focusing function.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN015;TN820

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本文編號(hào)：2168940