REV Journal on Electronics and Communications
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A Novel Chebyshev Series Fed Linear Array with High Gain and Low Sidelobe Level for WLAN Outdoor Systems
Get PDFThis paper proposes a novel high gain and low sidelobe level (SLL) linear microstrip array antenna for outdoor WLAN applications. The antenna consists of two main parts, which are a linear array and a reflector. The linear array comprises of 10 elements; those have been designed on Rogers RT/Duroid 5870tm with the dimensions of 422×100×10.15 mm3. To gain low SLLs, a series fed network was designed to have the output signals being proportional to the Chebyshev distributions (with preset SLL of -30 dB). Furthermore, Yagi antenna theory has been applied by adding directors above every single element to increase the directivity of the single element. The reflector has been constructed at the back of the proposed structure. Simulation results show that the array can provide high gain of 17.5 dBi and a low SLL of -26 dB. A prototype has been fabricated and measured. Good agreements between simulation and measurement data have been obtained
FPGA Implementation of Channel Mismatch Calibration in TIADCs for Signals in Any Nyquist Bands
Get PDFThis paper presents a fully digital background calibration technique of the gain and timing mismatches in undersampling Time-Interleaved Analog-to-Digital Converters for the wideband bandlimited input signal at any Nyquist bands. The proposed technique does not require an additional reference channel nor a pilot input. The channel mismatch parameters are estimated based on the mismatch frequency band. The experimental results shows the efficiency of the proposed mitigation technique with the SNDR improvement of 16dB for 4-channel 60dB SNR TIADC clocked at 2.7GHz given a multi-tone input occupied at the third Nyquist band. The hardware architecture of the proposed technique is designed and validated on Altera FPGA DE4 board. The synthesized design utilizes a very little amount of the hardware resource in the FPGA chip and works correctly on a Hardware-In-the-Loop emulation framework
Hybrid OFDM RoF-Based WDM-PON/MMW Backhaul Architecture For Heterogeneous Wireless Networks
Get PDFIn this paper, a hybrid backhaul architecture, which is based on wavelength-division multiplexing passive optical networks (WDM-PON) and millimeter-wave (MMW) communications, is proposed to deliver orthogonal frequency-division multiplexing (OFDM) signals in heterogeneous wireless networks. MMW radio-over-fiber (RoF) technique, which combines the advantages of the both optical fiber and wireless communications, is used to simplify the base stations and provide flexibility long reach and high capacity connections. The feasibility of the proposed hybrid backhaul architecture is investigated via the bit-error rate (BER) performance of a downlink under the impacts of fiber nonlinear, wireless fading and noise components including clipping noise, amplifier noise and photodetector noise. The numerical results obtained from this study help to determine the optimum system parameters such as the optical launched power, modulation index, and amplifier gain so as to minimize the link’s BER
BAT Algorithm Based Beamformer for Interference Suppression by Controlling the Complex Weight
Get PDFIn this study, an adaptive beamformer for pattern nulling of Uniformly Spaced Linear Array (ULA) antennas, which utilized BAT algorithm (BA) to suppress interferences, has been proposed. This pattern nulling has been obtained by controlling the complex weight (both the phase and the amplitude) of each array element. So as to verify the proposal, a number of scenarios of ULA pattern imposed the pre-set nulls have been carried out and compared with those of accelerated particle swarm optimization (APSO). The proposed beamformer has demonstrated the capability to place with precise single, multiple, and broad nulls at arbitrary interference directions, suppress side lobes, and maintain a predefined beamwidth. Moreover, the beamformer shows faster convergence and higher efficiency regarding null steering and side lobe suppression in pattern synthesis, as compared with an APSO based beamformer
Performance Analysis of IEEE 802.15.4 MAC Protocol Under Light Traffic Condition in IoT Environment
Get PDFIn this paper, we propose analytic models for throughput and latency performance of the IEEE 802.15.4 MAC protocol operating under very low duty cycles In the Internet of Things applications. Our analytic models are intended for IEEE 802.15.4 MAC protocol in beacon-enabled star topology with light traffic conditions. Accuracy of the analytic models are verified through extensive simulations using the network simulator ns-2. A strong agreement between simulation results and our theoretical analysis is observed. In addition, we compare throughput and latency performance of two different CSMA/CA protocols in IEEE 802.15.4 and IEEE 802.11. This is motivated by a significant discrepancy of the CSMA/CA mechanism: IEEE 802.15.4 and IEEE 802.11. We observe a remarkable difference in throughput between two protocols. The simulation results also demonstrate an interesting fact that increasing the packet size will degrade the throughput of IEEE 802.15.4 due to the nature of the CSMA/CA mechanism, while a throughput improvement is usually expected
A Survey on Reconfigurable System-on-Chips
Get PDFThe requirements for high performance and low power consumption are becoming more and more inevitable when designing modern embedded systems, especially for the next generation multi-mode multimedia or communication standards. Ultra large-scale integration reconfigurable System-on-Chips (SoCs) have been proposed to achieve not only better performance and lower energy consumption but also higher flexibility and versatility in comparison with the conventional architectures. The unique characteristic of such systems is integration of many types of heterogeneous reconfigurable processing fabrics based on a Network-on-Chip. This paper analyzes and emphasizes the key research trends of the reconfigurable System-on-Chips (SoCs). Firstly, the emerging hardware architecture of SoCs is highlighted. Afterwards, the key issues of designing the reconfigurable SoCs are discussed, with the focus on the challenges when designing reconfigurable hardware fabrics and reconfigurable Network-on-Chips. Finally, some state-of-the-art reconfigurable SoCs are briefly discussed
Efficient Detectors based on Group Detection for Massive MIMO systems
Get PDFIn Multiple Input Multiple Output (MIMO) systems, the complexities of detectors depend on the size of the channel matrix. In Massive MIMO systems, detection complexity becomes remarkably higher because the dimensions of the channel matrix get much larger. In order to recover the signals in the up-link of a Massive MIMO system at reduced complexities, we first divide the system into two sub-systems. After that, we apply the Minimum Mean Square Error (MMSE) and Bell Laboratory Layer Space Time (BLAST) detectors to each subsystem, resulting in the so-called MMSE-GD and BLAST-GD detectors, respectively. To further enhance the BER performance of Massive MIMO systems under the high-load conditions, we propose two additional detectors, called MMSE-IGD and BLAST-IGD by respectively applying the conventional MMSE and BLAST on the sub-systems in an iterative manner. It is shown via computer simulation and analytical results that the proposed detectors enable the system to achieve not only higher BER performance but also low detection complexities as compared to the conventional linear detectors. Moreover, the MMSE-IGD and BLAST-IGD can significantly improve BER performance of Massive MIMO systems
A Very Wideband Circularly Polarized Crossed Straight Dipole Antenna with Cavity Reflector and Single Parasitic Element
Get PDFA very wideband circularly polarized (CP) crossed dipole antenna is presented in this paper. The primary radiating element of the antenna consists of two straight dipoles arranged orthogonally through double printed rings. To further enhance the axial ratio bandwidth, a cavity with proper size and single parasitic element are employed to generate two additional bands. The use of cavity reflector is investigated thoroughly, providing a solid framework for designing this type of antennas. The final design with an overall size of 0.92λo × 0.92λo × 0.32λo at the center CP frequency yields a measured –10 dB-impedance bandwidth of 75.2% and 3 dB-axial ratio bandwidth of 67.7%. The proposed antenna exhibits right-handed circular polarization and an average broadside gain of about 8.3 dBi over the CP operating bandwidth