This paper presents the design, fabrication, and measurement of two ultra-wideband doubleridge open-ended waveguide antennas (OEWAs) for emerging high-resolution millimeter-wave (mm-wave) medical imaging applications. The proposed antennas can collectively provide a 95-GHz synthetic imaging bandwidth in the mm-wave regime. The antennas feature the smallest aperture sizes while providing the widest bandwidths amongst all OEWAs reported in the literature. The proposed antennas consist of coaxial to double-ridge waveguide (DRW) transitions and free-space matching sections. Two DRWs with 8:1 single-mode bandwidth in the mm-wave regime are designed. In the transition structures, coaxial flange launchers are connected to the DRWs through customized $50-\Omega$ coaxial lines. To improve the impedance matching while meeting the fabrication requirements, an effective tuning technique is applied to adjust the input impedance of the transitions. Finally, to achieve a smooth transition and a well-matched impedance to the free space while maintaining small aperture sizes, piecewise tapered-ridge matching sections with the same aperture size as that of the designed DRWs are employed. The antennas are fabricated using the computer numerical control (CNC) milling process. Each antenna demonstrates $\left|\mathrm{S}_{11}\right|\lt -10 \mathrm{~dB}$ and stable and symmetric radiation patterns across $15-40 \mathrm{GHz}$ and $40-110 \mathrm{GHz}$ with aperture sizes of $9.47 \times 5.79 \mathrm{~mm}^{2}$ and $3.78 \times 2.27 \mathrm{~mm}^{2}$ , respectively, reporting state-of-the-art results.

中文翻译：

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适用于超宽带医学成像应用的15–40 GHz和40–110 GHz双脊开放式波导天线

本文介绍了用于新兴的高分辨率毫米波（mm-wave）医学成像应用的两个超宽带双脊开放式波导天线（OEWA）的设计，制造和测量。所提出的天线可以在毫米波范围内共同提供95 GHz的合成成像带宽。这些天线具有最小的孔径尺寸，同时在文献中报道的所有OEWA中提供了最宽的带宽。拟议的天线由同轴到双脊波导（DRW）过渡和自由空间匹配部分组成。设计了两个毫米波状态下具有8：1单模带宽的DRW。在过渡结构中，同轴法兰发射器通过定制连接到DRW $ 50- \ Omega $ 同轴线。为了在满足制造要求的同时改善阻抗匹配，应用了有效的调谐技术来调整过渡的输入阻抗。最后，为了在保持较小的孔径尺寸的同时实现到自由空间的平滑过渡和良好匹配的阻抗，采用了与设计的DRW具有相同孔径尺寸的分段锥形脊匹配部分。天线是使用计算机数控（CNC）铣削工艺制造的。每个天线演示 $ \ left | \ mathrm {S} _ {11} \ right | \ lt -10 \ mathrm {〜dB} $ 稳定且对称的辐射方向图 $ 15-40 \ mathrm {GHz} $ 和 $ 40-110 \ mathrm {GHz} $ 孔径为 $ 9.47 \ times 5.79 \ mathrm {〜mm} ^ {2} $ 和 $ 3.78 \ times 2.27 \ mathrm {〜mm} ^ {2} $ 分别报告最新的结果。