Separated transmit and receive antennas are employed to improve transmit-receive isolation in conventional short-range radars, which greatly increases the antenna size and misaligns of the transmit/receive radiation p...Separated transmit and receive antennas are employed to improve transmit-receive isolation in conventional short-range radars, which greatly increases the antenna size and misaligns of the transmit/receive radiation patterns. In this paper,a dual circularly polarized(CP) monostatic simultaneous transmit and receive(MSTAR) antenna with enhanced isolation is proposed to alleviate the problem. The proposed antenna consists of one sequentially rotating array(SRA), two beamforming networks(BFN), and a combined decoupling structure. The SRA is shared by the transmit and receive to reduce the size of the antenna and to obtain a consistent transmit and receive pattern.The BFN achieve right-hand CP for transmit and left-hand CP for receive. By exploring the combined decoupling structure of uniplanar compact electromagnetic band gap(UC-EBG) and ringshaped defected ground structure(RS-DGS), good transmitreceive isolation is achieved. The proposed antenna prototype is fabricated and experimentally characterized. The simulated and measured results show good agreement. The demonstrate transmit/receive isolation is height than 33 dB, voltage standing wave ratio is lower than 2, axial ratio is lower than 3 dB, and consistent radiation for both transmit and receive is within4.25-4.35 GHz.展开更多
A millimeter-wave (mmW) broadband dual circularly polarized (dual-CP) antenna with high port isolation is proposed in this paper. The dual-CP performance is realized based on the symmetrical septum circular polarizer ...A millimeter-wave (mmW) broadband dual circularly polarized (dual-CP) antenna with high port isolation is proposed in this paper. The dual-CP performance is realized based on the symmetrical septum circular polarizer based on the gap waveguide (GWG) technology. Two sets of symmetrical septum circular polarizers are used for common aperture combination,achieving the broadband dual-CP characteristics. Taking advantage of GWG structure without good electrical contact, the antenna can also be fabricated and assembled easily in the mmW band. The principle analysis of the antenna is given, and the antenna is simulated and fabricated. The measured results show that the bandwidth for S11lower than-10.7 dB and the axial ratio (AR) lower than 2.90 dB in 75-110 GHz, with realative bandwidth of 38%. Over the frequency band, the gain is higher than 9.16 dBic, and the dual-CP port isolation is greater than32 dB. The proposed antenna with dual-CP and highly isolated in a wide bandwidth range has broad application prospects in the field of mmW communication.展开更多
圆偏振激光场中原子的非绝热强场电离为产生自旋极化电子提供了机会.我们应用这些解析电离速率公式[Ingo Barth and Olga Smirnova,Phys.Rev.A 88,013401(2013)]更系统地研究了通过Kr和Xe原子在右旋圆偏振激光脉冲中的强场电离产生自旋...圆偏振激光场中原子的非绝热强场电离为产生自旋极化电子提供了机会.我们应用这些解析电离速率公式[Ingo Barth and Olga Smirnova,Phys.Rev.A 88,013401(2013)]更系统地研究了通过Kr和Xe原子在右旋圆偏振激光脉冲中的强场电离产生自旋极化电子,并证实了不同自旋态的光电子能量分布有很大差异、电子的自旋极化敏感地依赖于光电子能量.另外,在光电子能谱的低能部分其自旋极化可以达到100%,并且通过调节激光强度和频率可以很好地控制能量积分的自旋极化.展开更多
从根分布的角度,对齐性二维球面分类结果给出比Bando和Ohnita(J Math Soc Japan,1987,39:477)更加明显的刻画,求出决定齐性二维球面的SU(2)轨道的李群多项式表示的显式表达式,证明复射影空间中SU(2)轨道的维数取决于一个对应的扩大复平...从根分布的角度,对齐性二维球面分类结果给出比Bando和Ohnita(J Math Soc Japan,1987,39:477)更加明显的刻画,求出决定齐性二维球面的SU(2)轨道的李群多项式表示的显式表达式,证明复射影空间中SU(2)轨道的维数取决于一个对应的扩大复平面系数上的一元n次方程的重根和负共轭倒数根对分布,把SU(2)轨道维数归结为黎曼球面上n个点是否重合或成为对径点的问题.也初步研究了SU(2)三维轨道性质与根分布的关系.展开更多
An improved algorithm for multi-polarization reconstruction from compact polarimetry （CP） is proposed. According to two fundamental assumptions in compact polarimetric reconstruction, two improvements are proposed. ...An improved algorithm for multi-polarization reconstruction from compact polarimetry （CP） is proposed. According to two fundamental assumptions in compact polarimetric reconstruction, two improvements are proposed. Firstly, the four-component model-based decomposition algorithm is modified with a new volume scattering model. The decomposed helix scattering component is then used to deal with the non-reflection symmetry condition in compact polarimetric measurements. Using the decomposed power and considering the scattering mechanism of each component, an average relationship between copolarized and crosspolarized channels is developed over the original polarization state extrapolation model. E-SAR polarimetric data acquired over the Oberpfaffenhofen area and JPL/AIRSAR polarimetric data acquired over San Francisco are used for verification, and good reconstruction results are obtained, demonstrating the effectiveness of the proposed algorithm.展开更多
基金supported by Guangdong Natural Science Foundation(2019A1515011622)Guangdong Provincial Laboratory of Southern Marine Science and Engineering (Zhuhai)(SML2021SP407)。
文摘Separated transmit and receive antennas are employed to improve transmit-receive isolation in conventional short-range radars, which greatly increases the antenna size and misaligns of the transmit/receive radiation patterns. In this paper,a dual circularly polarized(CP) monostatic simultaneous transmit and receive(MSTAR) antenna with enhanced isolation is proposed to alleviate the problem. The proposed antenna consists of one sequentially rotating array(SRA), two beamforming networks(BFN), and a combined decoupling structure. The SRA is shared by the transmit and receive to reduce the size of the antenna and to obtain a consistent transmit and receive pattern.The BFN achieve right-hand CP for transmit and left-hand CP for receive. By exploring the combined decoupling structure of uniplanar compact electromagnetic band gap(UC-EBG) and ringshaped defected ground structure(RS-DGS), good transmitreceive isolation is achieved. The proposed antenna prototype is fabricated and experimentally characterized. The simulated and measured results show good agreement. The demonstrate transmit/receive isolation is height than 33 dB, voltage standing wave ratio is lower than 2, axial ratio is lower than 3 dB, and consistent radiation for both transmit and receive is within4.25-4.35 GHz.
文摘A millimeter-wave (mmW) broadband dual circularly polarized (dual-CP) antenna with high port isolation is proposed in this paper. The dual-CP performance is realized based on the symmetrical septum circular polarizer based on the gap waveguide (GWG) technology. Two sets of symmetrical septum circular polarizers are used for common aperture combination,achieving the broadband dual-CP characteristics. Taking advantage of GWG structure without good electrical contact, the antenna can also be fabricated and assembled easily in the mmW band. The principle analysis of the antenna is given, and the antenna is simulated and fabricated. The measured results show that the bandwidth for S11lower than-10.7 dB and the axial ratio (AR) lower than 2.90 dB in 75-110 GHz, with realative bandwidth of 38%. Over the frequency band, the gain is higher than 9.16 dBic, and the dual-CP port isolation is greater than32 dB. The proposed antenna with dual-CP and highly isolated in a wide bandwidth range has broad application prospects in the field of mmW communication.
文摘圆偏振激光场中原子的非绝热强场电离为产生自旋极化电子提供了机会.我们应用这些解析电离速率公式[Ingo Barth and Olga Smirnova,Phys.Rev.A 88,013401(2013)]更系统地研究了通过Kr和Xe原子在右旋圆偏振激光脉冲中的强场电离产生自旋极化电子,并证实了不同自旋态的光电子能量分布有很大差异、电子的自旋极化敏感地依赖于光电子能量.另外,在光电子能谱的低能部分其自旋极化可以达到100%,并且通过调节激光强度和频率可以很好地控制能量积分的自旋极化.
文摘从根分布的角度,对齐性二维球面分类结果给出比Bando和Ohnita(J Math Soc Japan,1987,39:477)更加明显的刻画,求出决定齐性二维球面的SU(2)轨道的李群多项式表示的显式表达式,证明复射影空间中SU(2)轨道的维数取决于一个对应的扩大复平面系数上的一元n次方程的重根和负共轭倒数根对分布,把SU(2)轨道维数归结为黎曼球面上n个点是否重合或成为对径点的问题.也初步研究了SU(2)三维轨道性质与根分布的关系.
基金supported by the National Natural Science Foundation of China(41171317)the State Key Program of the Natural Science Foundation of China(61132008)the Research Foundation of Tsinghua University
文摘An improved algorithm for multi-polarization reconstruction from compact polarimetry （CP） is proposed. According to two fundamental assumptions in compact polarimetric reconstruction, two improvements are proposed. Firstly, the four-component model-based decomposition algorithm is modified with a new volume scattering model. The decomposed helix scattering component is then used to deal with the non-reflection symmetry condition in compact polarimetric measurements. Using the decomposed power and considering the scattering mechanism of each component, an average relationship between copolarized and crosspolarized channels is developed over the original polarization state extrapolation model. E-SAR polarimetric data acquired over the Oberpfaffenhofen area and JPL/AIRSAR polarimetric data acquired over San Francisco are used for verification, and good reconstruction results are obtained, demonstrating the effectiveness of the proposed algorithm.
