Current Issue : April - June Volume : 2017 Issue Number : 2 Articles : 6 Articles
A novel dual-band, single element multiple input multiple output (MIMO) dielectric resonator antenna (DRA) with a\nmodest frequency tuning ability is presented in this communication. The proposed antenna operates at GPS L1/Bluetooth/Wi-\nFi/LTE2500/WLAN2400 frequency bands.A single dielectric resonator element is fed by two coaxial probes to excite the orthogonal\nmodes. A couple of slots are introduced on the ground plane to improve the isolation between antenna ports.The slots also serve the\npurpose of reconfiguration in the lower band on placement of switches at optimized locations.The measured impedance bandwidth\nis 5.16% (1.41ââ?¬â??1.49GHz) in the lower band and 26% (2.2ââ?¬â??2.85GHz) in the higher band. The lower band reconfigures with an\nimpedance bandwidth of 6.5% (1.55ââ?¬â??1.65GHz) when PIN diodes are switched ON. The gain, efficiency, correlation coefficient,\nand diversity gain of the MIMO DRA are presented with a close agreement between simulated and measured results....
We consider device-to-device (D2D) communications in millimeter-wave (mmWave) for the future fifth generation (5G) cellular\nnetworks. While the mm Wave systems can support multiple D2D pairs simultaneously through beamforming with highly\ndirectional antenna arrays, the mmWave channel is significantly more susceptible to blockage compared to microwave; mmWave\nchannel studies indicate that if line-of-sight (LoS) paths are blocked, reliable mm Wave communications may not be achieved for\nhigh data-rate applications. Therefore, assuming that an outage occurs in the absence of the LoS path between two wireless devices\nby obstructions, we focus on connectivity of the mmWave D2D networks.We consider two types of D2D communications: direct\nand indirect schemes. The connectivity performances of the two schemes are investigated in terms of (i) the probability to achieve\na fully connected network ...
This paper presents a novel calibration method that equalizes the impulse responses of all the Radio Frequency (RF) modules\nof an antenna array system operating in Long-Term Evolution (LTE) evolved NodeB (eNB). The proposed technique utilizes the\nZadoff-Chu (Z-C) sequence of the Primary Synchronization Signal (PSS) and Sounding Reference Signal (SRS) that are available\nin every LTE data frame for downlink and uplink, respectively, for estimating and compensating the differences in the impulse\nresponses among the RF modules. The proposed calibration method is suitable for wide bandwidth signal environments of LTE\nbecause it equalizes the impulse response of each RF module, which is ultimately equivalent to compensate the phase and amplitude\ndifferences among RF modules for the entire frequency band. In addition, the proposed method is applicable while the target eNB is\ntransmitting or receiving a data stream. From various experimental tests obtained from a test-bed implemented with 2 RF modules,\nit has been verified that the proposed method provides a reliable calibration for Release 10 Time Division Duplex (TDD) LTE signals.\nPhase errors after the calibration in our test-bed have been found to be about 2.418âË?Ë? and 2.983âË?Ë? for downlink and uplink, respectively....
In this research, the novel concept of a resonance-based reflector (RBR) was proposed,\nand a ring-shaped RBR was utilized to design a unidirectional antenna with low-profile and\nbroadband characteristics. Research found the ring operates as two half-wavelength (Ã?»/2) resonators.\nThen, the resonance effect transforms the reflection phase of the ring RBR, and achieves a reflection\nphase of 0ââ??¦ < Ãâ?¢ < 180ââ??¦ in a wide frequency range above the resonance. Then, the in-phase reflection\ncharacteristic (âË?â??90ââ??¦ < Ãâ?¢ < 90ââ??¦) can be obtained in the wide frequency band by placing an antenna\nabove the RBR with a distance smaller than Ã?»/4. Two unidirectional antennas, named Case 1 and\nCase 2, were designed with the ring-shaped RBRs and bowtie antennas (RBR-BAs). The impedance\nbandwidths of Case 1 and the Case 2 are 2.04ââ?¬â??5.12 GHz (86.3%) and 1.97ââ?¬â??5.01 GHz (87.1%),\nrespectively. The front-to-back ratio (FBR, an important parameter to measure the unidirectional\nradiation) of Case 1 ranges from 5ââ?¬â??9.9 dB for frequencies 2.04ââ?¬â??2.42 GHz, and the FBR of Case 2 ranges\nfrom 5ââ?¬â??16 dB for frequencies 2.16ââ?¬â??3.15 GHz. The proposed concept of RBR is desirable in wideband\nunidirectional antenna design, and the designing antennas can be used at the front end of wireless\nsystemsââ?¬â?such as indoors communication, remote sensing, and wireless sensor systemsââ?¬â?for signal\nreceiving or transmitting....
This work investigates a novel numerical procedure for the solution of an exact formulation for the Geometrical Optics synthesis\nof a single reflector antenna by simultaneously imposing Snell�s Law and Conservation of Energy in a tube of rays, yielding a\nsecond-order nonlinear partial differential equation of Monge-Ampere type, which can be solved as a boundary value problem.\nThe investigation explores the interpolating properties of confocal quadrics to locally represent the shaped reflector surface. It\nallows the partial derivatives involved in the formulation to be analytically expressed. To illustrate the method, two examples of\noffset single reflectors shaped to radiate a Gaussian power density within a super elliptical contoured beam are presented.The results\nare validated by Physical Optics analysis with equivalent edge currents....
A two-stage design approach is proposed to address the sparse antenna array design for multiple-input multiple-output radar. In\nthe first stage, the cyclic algorithm (CA) is used to establish a covariance matrix that satisfies the beam pattern approximation\nfor a full array. In the second stage, a sparse antenna array with a beam pattern is designed to approximate the desired beam\npattern. This paper focuses on the second stage. The optimization problem for the sparse antenna array design aimed at beam\npattern synthesis is formulated, where the peak side lobe (PSL) is weakly constrained by the mean squared error. To solve this\noptimization problem, the differential evolution (DE) algorithm with multi strategy is introduced and PSL suppression is treated\nas an inequality constraint. However, in doing so, a new multiobjective optimization problem is created. To address this new\nproblem, a multiobjective differential evolution algorithm based on Pareto technique is proposed.Numerical examples are provided\nto demonstrate the advantages of the proposed approach over state-of-the-art methods, including DE and genetic algorithm....
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