2020/3

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Design of OAM Beam Directional Modulation Signal in Communication and Guidance Integration
(Společnost pro radioelektronické inženýrství, 2020-09) Zhu, Changju; Song, Maozhong; Dang, Xiaoyu
An orbital angular momentum directional modulation (OAM-DM) signal is proposed for communication and guidance integration. This signal is transmitted by a uniform circular antenna array (UCA). We divide the array into odd and even antenna groups. Each group is excited by differential coded digital modulation waveform to send different signal constellations in different directions. In order to improve the performance of angle estimation, we have designed specific phase shift sequences to obtain the different OAM modes. Mode detection can eliminate multiple value ambiguity of elevation and azimuth angles. The single antenna receiver can demodulate the OAM-DM signal to communicate, detect OAM modes and estimate angles in different directions. Finally, we assess the effectiveness of the proposed approach via numerical simulation.
A Compact Circular Loop Inspired Frequency and Bandwidth Reconfigurable Antenna for 4G, 5G, and X- Band Applications
(Společnost pro radioelektronické inženýrství, 2020-09) Rasool, Maryam; Khan, Aabia; Bhatti, Farooq; Ijaz, Bilal; Iftikhar, Adnan
This paper presents a printed patch antenna design to achieve frequency and bandwidth reconfigurability. Two RF PIN diodes are simultaneously operated to achieve the multi-reconfigurability operation. The patch is inspired from a circular loop design. The basic structure of loop is altered, and PIN diodes are integrated into the patch. The antenna operates in dual band configuration at 3.42 and 8.02 GHz in the diodes ‘OFF’ state, whereas the antenna switches to triple band operation at 2.21, 4.85, and 10.19 GHz in the diodes ‘ON’ state. Moreover, the antenna also exhibits an increased bandwidth from 7.54 to 12 GHz in the diodes ‘ON’ state, as compared to a narrow bandwidth from 7.71 to 8.48 GHz in the diodes ‘OFF’ state. The proposed antenna structure is implemented and fabricated using FR4 epoxy substrate of relative permittivity 4.4, and thickness 1.6 mm. Implemented design exhibits measured gains of 3.06 dBi, 2.81 dBi, and 2.92 dBi at 2.21, 4.85, and 10.19 GHz in the PIN diodes ‘ON’ state, respectively, while in the PIN diodes ‘OFF’ state, at 3.42 GHz the gain is 3.03 dBi and at 8.02 GHz the gain is 3.37 dBi. Overall, simulation results agree well with the measured results.
Machine Intelligence Technique for Blockage Effects in Next-Generation Heterogeneous Networks
(Společnost pro radioelektronické inženýrství, 2020-09) Amalorpava Mary Rajee, Samuel; Merline, Arulraj
Millimeter wave (mmWave) links such as 28 GHz and 60 GHz propose high data rates and capacity needed in 5G Heterogeneous network (Hetnet) real-time system. The key factors in network planning of Hetnet are the locations and links of base stations, and their coverage, transmitted power, antenna angle, orientation etc. How-ever, large-scale blockages like static buildings, human etc. affect the performance of urban Hetnets especially at mmWave frequencies. A mathematical framework to model dynamic blockages is adapted and their impact on cellular network performance is analyzed. A machine learning approach based on Q-learning with Epsilon-Greedy algo¬rithm is proposed to solve the blockage problem in such complex networks. The proposed results are evident and show the positive effect of increasing the base station den¬sity linearly with the blockage density to maintain the net¬work connectivity. The performance of the proposed Epsi¬lon-Greedy algorithm is compared with Epsilon-Soft algo-rithm. The performances of above said mmWave links are compared in terms of their coverage probability and throughput. The results show that an Epsilon-Greedy algo¬rithm outperforms an Epsilon-Soft algorithm.
A Covert Communication System Using Non-Zero Mean Normal Distributions
(Společnost pro radioelektronické inženýrství, 2020-09) Xu, Zhijiang; Lu, Weidang; Gong, Yi; Hua, Jingyu; Jin, Wenbing
A covert communication system is proposed in this study, in which a~ non-zero mean Gaussian sequence is used as a~ random carrier and its mean is modulated by a~ covert binary bit. The aperiodic transmitted signal exhibits the same statistical characteristics as the ambient noise to confuse an~ eavesdropper. The received signal is multiplied with the pseudo-random sequence synchronized with the transmitter to recover these positive and negative mean Gaussian sequence. The sample mean estimator and hard decision are used to determine the covert message, and accordingly, theoretical bit error rate in additive white Gaussian noise channel is also derived. Simulation results are very consistent with the theoretical derivation. The proposed system works in the physical layer with the advantages of simple structure, strong concealment, good BER performance and very suitable for low-cost, resource-limited and low-rate transmission devices.
Dual HE11δ Mode CDRA for Polarization Diversity Applications in K Band Point-to-Point Communications
(Společnost pro radioelektronické inženýrství, 2020-09) Faiz, Alam M.; Shafique, M. Farhan; Gososh, Nayab; Khan, Shahid A.; Khan, Mahmood A.
A dual port Cylindrical Dielectric Resonator Antenna (CDRA) has been demonstrated for K band (22 GHz) applications in this work. The antenna offers polarization diversity which is introduced by degenerating HE11δ modes in a single CDRA. Orthogonal feed lines produce two modes which are perpendicular so they don’t interfere with each other and offer excellent linear polarization diversity in orthogonal planes. Since the CDRA size is compact, the feed lines have been modified to assure the generation of desired modes. A detailed investigation into the generation of resonant modes along with parametric analysis is presented. Measured results show fractional bandwidth of 9.5% and 18.18% for both port 1 and port 2 respectively. Isolation of better than 32 dB has been measured between the two ports through transmission coefficient. Difference of about 20 dB between co-polarization and cross polarization in both planes for broadside direction has been measured which endorses the polarization diversity performance of the antenna. Different MIMO performance parameters including envelope correlation coefficient, total active reflection coefficient, channel capacity loss and mean effective gain have been measured to assess the performance of the design.

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