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Duplex antenna system for MIMO application
Published in Yadwinder Kumar, Shrivishal Tripathi, Balwinder Raj, Multifunctional MIMO Antennas, 2022
D. Venkata Siva Prasad, Harsh Verdhan Singh, Punya P. Paltani, Shrivishal Tripathi
In recent years, millimeter-wave (mmWave) wireless communication has become a significant area in wireless communications beyond 5G. Compared to the existing LTE 2.5 GHz band, the atmospheric attenuation and free space path loss (FSPL) are considerably higher in mmWave wireless communication. For acceptable transmission distances, a high-gain antenna is required for the mmWave wireless communication system. Reflector antennas that are capable of giving high gains have been used in several mmWave and terahertz wireless communication systems for the past few years, and these high-gain reflector antennas can attain data rates up to tens of Gbps because the data rates are proportional to the gain of the antenna [33, 34]. The antenna system consists of a feed and a dual-reflector system based on an axially displaced ellipse (ADE) structure [35]. The feed is capable of generating both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) signals by using a stepped septum polarizer. The high gain in radiation is obtained by illuminating both the sub-reflector and the main reflector by stepped septum polarizer with ring focuses. An ADE reflector antenna is also designed to give a minimum back reflection to the feed maintaining the high gain of the antenna. Polarization-division multiplexing (PDM) is employed by using two circular polarized signals that are orthogonal to each other to simultaneously receive and transmit the signal to achieve full-duplex operation in mmWave wireless communication systems. High isolation and low axial ratio (AR) are achieved by properly designing and optimizing the antenna feed having a bandwidth range from 75 to 95 GHz.
Next Generation Transmission Systems Enabling Technologies, Architectures, and Performances
Published in Iannone Eugenio, Telecommunication Networks, 2017
This not only allows a high efficiency to be reached by the multilevel constellations, but also requires a certain degree of complexity at the transmitter and at the receiver. Polarization division multiplexing (PDM) is a way to exploit polarization with a smaller complexity: it consists in transmitting two channels at the same frequency but on orthogonal polarizations.
Depth-enhanced 2D/3D switchable integral imaging display by using n-layer focusing control units
Published in Liquid Crystals, 2022
Qiang Li, Fei-Yan Zhong, Huan Deng, Wei He
Many methods have been proposed to improve the 3D performance of 2D/3D switchable display. In terms of resolution, some methods have been proposed by using additional lens array [1] and different light-emitting diode arrays [2]. In terms of viewing angle, some methods have been proposed by using partial masking lens arrays [3], curved electroluminescent film [4], polarization selective scattering film [5], and aspherical liquid crystal lens array [6]. Kim et al. used electrically movable pinhole array to improve both the resolution and the viewing angle [7]. In addition, 2D/3D mixed or hybrid displays based on time-division multiplexing technology [8], space-division multiplexing technology [9], and polarization division multiplexing technology [10] were proposed. However, depth of field (DOF), one of the most direct 3D display features for the viewers to experience depth cues, has rarely been studied in 2D/3D switchable displays.
Two-dimensional multiplexing scheme both with ring radius and topological charge of perfect optical vortex beam
Published in Journal of Modern Optics, 2019
Le Wang, Xincheng Jiang, Li Zou, Shengmei Zhao
Nowadays, OAM multiplexing techniques have been extensively studied in free-space optical communication links (8-11), fibre communications systems (12, 13), and radio communications systems (14, 15). For example, Wang et al. proposed and demonstrated a new high-speed experiment based on 4-OAM multiplexing in 2012 (8). Furthermore, OAM multiplexing, together with other multiplexing techniques, such as polarization division multiplexing and wavelength multiplexing, had greatly increased the capacity and spectral efficiency. In 2014, Huang et al. demonstrated a multiplexing communication of 1008 channels using 12 OAM, 2 polarization modes and 42 wavelengths to achieve 100 Tbit/s transmission rate (16). In 2016, Shi et al. combined optical time division multiplexing (OTDM) with OAM multiplexing to increase transmission capacity and spectral efficiency (17). We have discussed the methods to eliminate the interference of atmosphere turbulence in OAM-multiplexed systems (18-20). However, only the topological charge is concerned in all the above OAM multiplexing techniques.
A hybrid multiplexer/de-multiplexer for wavelength-mode-division based on photonic crystals
Published in Journal of Modern Optics, 2018
Ke Ji, Heming Chen, Yuyang Zhuang, Wen Zhou
Optical communication systems are developing towards ultrahigh speeds and large capacities. In the past, wavelength-division multiplexing (WDM) (1,2), mode-division multiplexing (MDM) (3–7) and polarization-division multiplexing have been used to improve communication capacity. However, communication capacity expansion is limited with single multiplexing. Therefore, combinations of MDM and WDM have been developed (8–11). A hybrid multiplexer/de-multiplexer (HMUX/HDeMUX) for WDM-MDM is a key device for hybrid multiplexing. Notably, Yang et al. (9) reported a HMUX/HDeMUX for WDM-MDM based on SiN/SiO2 with low loss. However, the coupling length of the mode conversion was long, leading to a large device size. Jian Wang et al. (10) reported a HMUX based on three cascaded asymmetrical directional-couplers and four identical arrayed-waveguide gratings, but the excess loss and crosstalk were as large as −7 and −10 dB, respectively. Mulugeta and Rasras (11) reported a HMUX/HDeMUX for WDM-MDM based on a tapered directional coupler and multimode interference waveguide with relatively low crosstalk (<−18 dB) but large insertion loss (>1 dB).