High Gain Modified Dual-Band and Dual-Circularly Polarized Array Antenna

Wireless Personal Communications - A novel design of double-layer dual-band circularly polarized array antennas (DDCPAAs) is presented in this paper. First, a DDCP single antenna is introduced as...     

Security anomaly detection in software‐defined networking based on a prediction technique

Nowadays, software‐defined networking (SDN) is regarded as the best solution for the centralized handling and monitoring of large networks. However, it should be noted that SDN architecture suffers from the same security issues, which are the case with common networks. As a case in point, one of the shortcomings of SDNs is related to its high vulnerability to distributed denial of service (DDoS) attacks and other similar ones. Indeed, anomaly detection systems have been considered to deal with these attacks. The challenges are related to designing these systems including gathering data, extracting effective features, and selecting the best model for anomaly detection. In this paper, a novel combined approach is proposed; this method uses NetFlow protocol for gathering information and generating dataset, information gain ratio (IGR), in order to select the effective and relevant features and ensemble learning scheme (Stacking) for developing a structure with desirable performance and efficiency for detecting anomaly in SDN environment. The results obtained from the experiments revealed that the proposed method performs better than other methods in terms of enhancing accuracy (AC) and detection rate (DR) and reducing classification error (CE) and false alarm rate (FAR). The AC, DR, CE, and FAR of the proposed model were measured as 99.92%, 99.83%, 0.08%, and 0.03%, respectively. Furthermore, the proposed method prevents the occurrence of excessive overload on the controller and OpenFlow.     

On the implementation of adaptive sliding mode robust controller in the stabilization of electrically actuated micro-tunable capacitor

Microsystem Technologies - Parallel-plates based micro-tunable capacitors are known to have low travel ranges, which deteriorate as going even lower in terms of their initials gap sizes. Such...     

A fully on-chip LDO voltage regulator with 37 dB PSRR at 1 MHz for remotely powered biomedical implants

This article presents a fully on-chip low-power LDO voltage regulator dedicated to remotely powered wireless cortical implants. This regulator is stable over the full range of alternating load current and provides fast load regulation achieved by applying a time-domain design methodology. Moreover, a new compensation technique is proposed and implemented to improve PSRR beyond the performance levels which can be obtained using the standard cascode compensation technique. Measurement results show that the regulator has a load regulation of 0.175 V/A, a line regulation of 0.024%, and a PSRR of 37 dB at 1 MHz power carrier frequency. The output of the regulator settles within 10-bit accuracy of the nominal voltage (1.8 V) within 1.6 μs, at full load transition. The total ground current including the bandgap reference circuit is 28 μA and the active chip area measures 290 μm × 360 μm in a 0.18 μm CMOS technology.     

A reconfigurable frequency-selective surface for dual-mode multi-band filtering applications

A reconfigurable single-layer frequency-selective surface (FSS) with dual-mode multi-band modes of operation is presented. The proposed structure is printed on a compact 10 × 10 mm² FR4 substrate with the thickness of 1.6 mm. A simple square loop is printed on the front side while another one along with two defected vertical arms is deployed on the backside. To realise the reconfiguration, two pin diodes are embedded on the backside square loop. Suitable insertion of conductive elements along with pin diodes yields in dual-mode multi-band rejection of applicable in service frequency ranges. The first operating mode due to diodes’ ‘ON’ state provides rejection of 2.4 GHz WLAN in 2–3 GHz, 5.2/5.8 GHz WLAN and X band in 5–12 GHz, and a part of Ku band in 13.9–16 GHz. In diodes ‘OFF’ state, the FSS blocks WLAN in 4–7.3 GHz, X band in 8–12.7 GHz as well as part of Ku band in 13.7–16.7 GHz. As well, high attenuation of incident waves is observed by a high shielding effectiveness (SE) in the blocked frequency bands. Also, a stable behaviour against different polarisations and angles of incidence is obtained. Comprehensive studies are conducted on a fabricated prototype to assess its performance from which encouraging results are obtained.