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1. chinaXiv:201703.00311 [pdf]

Deep space communication channel characteristics under solar scintillation

Wu, Tong; Yan, Yi; Li, Yongcheng; Wang, Chunmei; Yao, Xiujuan; Li, Xue
Subjects: Geosciences >> Space Physics

Electromagnetic waves used for deep space communications are mainly affected by the charged particles ejected by the sun. These effects may result in degradation of communication quality or communication interruption. This paper discusses the effects of solar scintillation on electro-magnetic waves, including the scintillation index which is a measure of the intensity scintillation, the coherence bandwidth and the coherence time of deep space communication channel. The deep space communication channel under solar scintillation is modeled by using Rician fading channel according to the scintillation index. The coherence bandwidth will determine whether the channel is flat fading or frequency selective fading and the coherence time will determine whether the channel is slow fading or fast fading. The approach of choosing signal band width is determined by the coherence bandwidth and the coherence time with the change of the solar elongation angle. The simulation results show the bit error rate of the signal bandwidth chosen by the proposed approach is lower than a random choice.

submitted time 2017-03-10 Hits23408Downloads2255 Comment 0

2. chinaXiv:201703.00303 [pdf]

Single-layer reflectarray antennas with improved bandwidth by attaching phase-delay lines

Han, Chunhui; Zhang, Yunhua; Yang, Qingshan
Subjects: Geosciences >> Space Physics

A novel X-band unit cell structure with improved bandwidth performance for single-layer microstrip reflectarray antenna is proposed. The new element structure consists of two circular rings, each with a pair of gaps, and two phase-delay lines are attached to the outer ring to provide the required phase shift. A 9? center-fed reflectarray antenna operating at 10 GHz is designed to validate the broadband performance of the proposed unit cell. Simulated results show 20% 1-dB gain bandwidth and 38.5% 3-dB gain bandwidth. The maximum gain at 10 GHz is 20.1 dB, which is equivalent to 40 % efficiency.

submitted time 2017-03-10 Hits12870Downloads1305 Comment 0

3. chinaXiv:201703.00296 [pdf]

Single-layer broadband linearly polarized reflectarray antenna by using phase-delay lines

Han, Chunhui; Zhang, Yunhua; Yang, Qingshan
Subjects: Geosciences >> Space Physics

In this paper, a novel X-band broadband single-layer unit cell with attached phase-delay lines for reflectarray antennas is proposed to surmount the limitation of the reflectarray bandwidth. The unit cell is composed of three circular rings, each with a pair of gaps which are mutually placed orthogonally, and two identical circular phase-delay lines are attached to the outer ring to provide the required reflection phase. After the simulation for the unit cell carried out, a large reflecting phase range of about 600?and almost linear phase curve are achieved at the center frequency of 10 GHz. Parallel phase curves of different frequencies ranging from 9 GHz to 12 GHz are also obtained. To validate the broadband performance of the proposed unit cell, a 9 ?9 center-fed reflectarray antenna operating at X band is designed and simulated. Simulation results show that the designed antenna has 34% 1-dB gain bandwidth, which demonstrates that an obvious improvement on the bandwidth has been achieved compared to the previous works. Besides, the cross-polarization level is decreased to -40 dB by a mirror symmetric element arrangement.

submitted time 2017-03-10 Hits5786Downloads1312 Comment 0

4. chinaXiv:201703.00295 [pdf]

A broadband reflectarray using patch with slot ring on ground plane elements

Xue, Fei; Wang, Hongjian; Yi, Min; Dong, Xingchao
Subjects: Geosciences >> Space Physics

A broadband center-fed reflectarray antenna is presented in this paper. Patch with slot ring on ground plane elements are used for bandwidth improvement. It is shown that quasi-linear phase responses with broad frequency band can be achieved by such a phasing element. An 11?1 elements reflectarray is designed and simulated. The results show that the simulated gain is 23.92 dB at the center frequency of 13.58 GHz with 3-dB bandwidth of 52%, which demonstrate significant broadband operation compared with that of conventional reflectarray.

submitted time 2017-03-10 Hits2564Downloads1189 Comment 0

5. chinaXiv:201703.00250 [pdf]

A Novel Single-Layer Unit Structure for Broadband Reflectarray Antenna

Chunhui Han; Yunhua Zhang; Qingshan Yang
Subjects: Geosciences >> Space Physics

A novel X-band single-layer unit cell structure with enhanced bandwidth for linearly polarized microstrip reflectarray antenna is proposed. The unit-cell structure is composed of two circular rings, each with a pair of gaps which are orthogonally placed, and two identical phase-delay lines attached to the outer circular ring. With this novel structure, a linear phase response ranging about 550° is achieved by varying the length of the phase delay line. An offset-fed reflectarray antenna composed of 277 elements forming an octagon-shape aperture is designed, fabricated, and measured to verify the broadband characteristic of the proposed unit cell. Measurement results show that 20% 1-dB gain bandwidth is realized. Besides, the maximum gain at 10 GHz is about 26.38 dBi, which means about 51.3 % efficiency is achieved. At the same time, the side lobe level and cross polarization for E-plane are also measured which are below ?17.5 dB and ?26 dB, respectively.

submitted time 2017-03-10 Hits1091Downloads688 Comment 0

6. chinaXiv:201605.00220 [pdf]

A continuous cold atomic beam interferometer

Xue, Hongbo; Feng, Yanying; Chen, Shu; Wang, Xiaojia; Yan, Xueshu; Jiang, Zhikun; Zhou, Zhaoying
Subjects: Geosciences >> Space Physics

We demonstrate an atom interferometer that uses a laser-cooled continuous beam of Rb-87 atoms having velocities of 10-20 m/s. With spatially separated Raman beams to coherently manipulate the atomic wave packets, Mach-Zehnder interference fringes are observed at an interference distance of 2L - 19 mm. The apparatus operates within a small enclosed area of 0.07 mm(2) at a bandwidth of 190 Hz with a deduced sensitivity of 7.8 x 10(-5) rad/s/root Hz for rotations. Using a low-velocity continuous atomic source in an atom interferometer enables high sampling rates and bandwidths without sacrificing sensitivity and compactness, which are important for applications in real dynamic environments. (C) 2015 AIP Publishing LLC.

submitted time 2016-05-04 Hits1068Downloads597 Comment 0

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