An Active Retro-Directive Array with Different Transmit and Receive Frequencies

Mandal, Joydeb; Mandal, Mrinal Kanti; Kahar, Manisha; Chakrabarty, S. B.; Jyoti, Rajeev

doi:10.1109/imarc45935.2019.9118712

Cited by 2 publications

(2 citation statements)

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“…有关 [25,26] ,其本质上体现了朗道能级不稳定性。两者的差异性在于：(1)方程( 23)是一个包含能级数 ν 的、复杂的求和公式，并且 ν max 取值非常小，通常情况下 0≤ν max ≤3 [26][27][28] ；费米面附近的电子主要集中在基态 ν=0 和第一激发态 ν=1，有意思的是，在给定电子费米能和物质密度时，体积束缚能等参量密切相关 [30][31][32][33][34][35] ；超强磁场可能会增加核物质的非对称性，提高质子的丰度，因此，核物质的平均电子数密度也相应地增加。当然，这些理论上的可能性有待于实验上的验证。 4.2 超强磁场下费米子自旋极化现象最近，不少作者 [35][36][37][38][39] 对中子星内部零温(T=0)和强磁场下费米子系统自旋极化现象进行研究。本节考虑自然单位制。费米子数密度 [36] 由下列方程给出 [39] ，磁星内部可能包括化石起源的原始磁场和顺磁磁化产生的感应磁场 [38] 。后者为磁星提供制动力矩, 影响磁星辐射特性和内部热演化。电子磁化由两种成分构成：一是电子内禀磁矩在外磁场中的顺向分布引起的泡利顺磁部分；二是在外场中电子轨道运动量子化引起的朗道抗磁部分。高志福等人 [40] 采用霍尔斯坦-普里马可夫变换等方法，对外磁场中的铁磁体、反铁磁及亚铁磁体的自旋波谱进行讨论，计算了临界磁场。由电动力学可知, 磁化强 M = χB 及相对磁导率 µ r =1/(1-µ 0 χ)，µ 0 为真空磁导率，当 µ 0 χ→1 时，磁场变得越强，出现临界磁化现象。强磁场中相对论电子的磁化系数为 [41] ：…”

Section: 前人的相关工作根据文献[25-27]，通过引入与本文相同的电子自旋简并度unclassified

Modified pressure of relativistic electrons in a superhigh magnetic field

Dong¹,

Gao²,

Yang³

et al. 2023

Acta Phys. Sin.

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Magnetars are a kind of pulsars powered by magnetic field energy. The study of magnetars is an important hotspot in the field of pulsars. In this paper, based on the work of Zhu Cui et al. (2016), we reinvestigate the Landau-level stability of electrons in a superhigh magnetic field (SMF), B>> Bcr (Bcr =4.414×1013G is the quantum critical magnetic field) and their influences on the pressure of electrons in magnetars. Firstly, we briefly review the pressure of electrons in neutron stars (NSs) with a weak-magnetic field limit (B<< Bcr). By introducing the electron Landau level stability coefficient gn and the Dirac -δ function, then we deduce a modified formula for pressure of degenerate and relativistic electrons in a SMF with an application range of ρ ≥107g cm-3and Bcr<<B<1017G. By modifying the phase space of relativistic electrons, a SMF can enhance the electron number density ne, and decrease the maximum of electron Landau level number νmax, which results in a redistribution of electrons. As B increases, more and more electrons will occupy higher Landau levels, the electron Landau level stability coefficient gν will decrease with the increase in Landau energy-level number ν. By modifying the phase space of relativistic electrons, the electron number density ne increases with the MF strength, leading to an increase in the electron pressure Pe. Utilizing this modified expression of electron pressure, we discuss the phenomenon of Fermion spin polarization and electron magnetization in SMFs, and the modification of the equation of state by the SMFs. We calculate the baryon number density, magnetization pressure, and pressure differences parallel to and perpendicular to the magnetic field under the relativistic mean field model and find that the pressure anisotropy due to the strong magnetic field is very small and can be ignored under the present model. We have compared our results with other similar works, and found that there are similarities and differences between our work and other similar work. The similarities include: (1) the abnormal magnetic moment of electrons and the interaction between them are ignored; (2) The electron pressure is related to magnetic field intensity B, electron number density ne and electron Fermi energy EF(e) and the latter two are complex functions containing B. (3) Given ne and EF(e), Pe increases with B; (4) As B increases, the pressure-density curve fitted by other similar work will have irregular protrusions or fluctuations, which is caused by the transformation of electron energy state from partial filling to complete filling at the ν -level or the transition of electrons from the ν to the (ν+1)-level. This phenomenon is believed to be related to the behavior of electrons near the Fermi surface in a strong magnetic field, which essentially reflects the Landau level instability. Finally, we look forward to the prospects of the future research. The results provide a reference for future studies on the equation of state and emission mechanism of high-B pulsars, magnetars and strongly magnetized white dwarfs.

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Section: 前人的相关工作根据文献[25-27]，通过引入与本文相同的电子自旋简并度unclassified

Modified pressure of relativistic electrons in a superhigh magnetic field

Dong¹,

Gao²,

Yang³

et al. 2023

Acta Phys. Sin.

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“…Retro-directive array antennas (RDAs) have captured the attention of researchers during past decades because of their advantages upon smart antennas in terms of simplicity and functionality. These arrays can perform smart antennas functionalities (beam-tracking and beam-forming in most of the cases), needless of using phase shifters and other bulky and complex steering systems behind the array [1][2][3][4][5][6][7][8][9][10][11][12]. They can automatically reflect the incoming signal toward its source direction without any prior knowledge about signal direction of arrival (DOA).…”

Section: Introductionmentioning

confidence: 99%

Passive 2-D Retro Directive Array Antenna with Adjustable Reflection Angle

Fallah¹,

Bahar²,

Sedighy³

2022

PIER Letters

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In this paper, a planar passive array antenna is proposed with capability of reradiating the incoming incident wave to predetermined θ and φ reflection angles (2-D). This purpose is achieved by differentiating array elements' phases with the help of inter-connecting transmission lines. Incident and reradiated signal paths are isolated through two orthogonal polarizations used in the array structure. The idea is realized with a 2 × 2, microstrip, dual linearly polarized antenna array in 2 GHz operating frequency on the Ro5880 substrate with 1.2 mm height. Nonlinear nature of the theory behind this idea leads to some limitations in choosing the angles of incident and reflected signals which is thoroughly investigated.

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An Active Retro-Directive Array with Different Transmit and Receive Frequencies

Cited by 2 publications

References 15 publications

Modified pressure of relativistic electrons in a superhigh magnetic field

Modified pressure of relativistic electrons in a superhigh magnetic field

Passive 2-D Retro Directive Array Antenna with Adjustable Reflection Angle

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