2018/3

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Analysis of Bistatic Ground Clutter
(Společnost pro radioelektronické inženýrství, 2018-09) Pidanic, Jan; Juryca, Karel; Kumar, Annt Mishra
This article presents analysis and parametrization of the bistatic ground clutter which is important from the point of view of the modelling/generating of bistatic clutter, and subsequent developing of the new suppression techniques. The analysis of the bistatic radar has been an active area of research for almost a decade now. The paper includes analysis of bistatic land clutter trials, run in the Czech Republic, specifically in Pardubice city. First, the theoretical part of bistatic radars and models of bistatic clutter is described. The bistatic clutter is measured by a passive radar system developed by the ERA a.s. company. The analysis of bistatic clutter starts with pre-processing techniques such as antenna virtual rotation and suppression of direct signal. The residuals of the signal are used for bistatic clutter analysis and consequently used for determination of bistatic clutter parameters. These parameters are replicas of individual channels, power of replicas, etc. The output is the development of universal analysis software for bistatic clutter that is used for bistatic clutter generation, mandatory for developing suppression techniques.
A New Target Radar Cross Section Based Passive Radar Surveillance Receiver Positioning Algorithm on Real Terrain Maps
(Společnost pro radioelektronické inženýrství, 2018-09) Tuysuz, Burak
Placing surveillance receivers on passive radar systems is a complex task because of the dependence on third party vendors. This paper presents an efficient and robust algorithm for positioning passive radar surveillance receivers for the intended coverage based on the available transmitters of opportunity in the area. First, by using the topology maps of the area of interest, depending on the expected targets and available transmitters, visibility maps of the terrain is generated with a line of sight algorithm. Then, in terms of the position and the orientation of the targets, the bistatic radar cross sections are determined. Finally, based on the bistatic radar cross sections of the targets, antenna characteristics, visibility analysis and received power levels, the optimum location for the surveillance receiver and the best transmitter of opportunity to be employed is decided. A practical scenario by using frequency modulation radio is realized in the manuscript for the rapid deployment of a mobile passive radar system. It is shown that on a terrain with multiple transmitters, depending on the characteristics of the transmitters and intended coverage, an optimum location for the surveillance receiver can be found for rapid deployment.
Improved Design and Implementation of Automatic Flight Control System (AFCS) for a Fixed Wing Small UAV
(Společnost pro radioelektronické inženýrství, 2018-09) Elbanna, Ahmed E. A.; Soliman, Tamer H. M.; Ouda, A. N.; Hamed, Essam M.
This paper presents an implementation of automatic flight control system (AFCS); analyzes and assures its performance during model in loop (MIL), software in loop (SIL), and processor in loop (PIL) stages. Based on both linear and analytic linear models with trimmed values of straight and leveling scenario, the proposed autopilot is applied to an Ultrastick-25e fixed wing unmanned aerial vehicle (UAV). The implementation of Ultrastick-25e AFCS is accomplished according to the resulted design parameters, and performing various flight scenarios. The choice of avionics and sensors of small UAV (SUAV) required for stability based on commercial off the Shelf (COTS) components. The proposed design uses low cost and light weight micro electro mechanical systems (MEMS) as new sensor technology. Since MEMS suffers from various types of noise, state estimation technique is introduced using both Kalman filter (KF) and complementary filter. Moreover, both results of KF and complementary filter are compared. Finally, PIL simulation is implemented to evaluate the autopilot as hardware components and software algorithms for management and PID control structure with its parameters proposed for implementing AFCS. The results show a good performance in disturbance rejection and robustness against sensors noise.
Digital Predistorter Design Using a Reduced Volterra Model to Linearize GaN RF Power Amplifiers
(Společnost pro radioelektronické inženýrství, 2018-09) Rezgui, Haithem; Rouissi, Fatma; Ghazel, Adel
In this paper, a novel method for reducing a Simplified Volterra Series (SVS) model size is proposed for GaN RF Power Amplifier (PA) Digital Predistorter (DPD) design. Using the SVS-modified model, the number of coefficients needed for the PA behavioral modeling and predistortion can be reduced by 60 % while maintaining acceptable performances. Simulation and implementation tests are performed for a Class AB GaN PA and Doherty GaN PA using a 20-MHz Long Term Evolution-Advanced (LTE-A) signal. The Adjacent Channel Power Ratio (ACPR) attains -40 dB and -41 dB for the Doherty and Class AB GaN PAs, respectively. The implementation complexity is also studied and the obtained results prove the capability of the proposed model to linearize PA using 3% of the Slice LUTs and 87% of the DSP48E1 available in the Xilinx Zynq-7000 FPGA.
RE-HARP: RF Energy Harvesting MAC Protocol to Prolong Life Time of CRSNs
(Společnost pro radioelektronické inženýrství, 2018-09) Wasif, Sardar; Ishtiaq, Ahmad; Waseem, Nazar
Energy drainage is a critical issue in sensor networks which is aggravated further by the incorporation of Cognitive Radio (CR). Radio Frequency Energy Harvesting (RF-EH) is a prominent method for mitigating energy constraints while providing potentially perpetual lifetime. However, its inclusion in Cognitive Radio Sensor Networks (CRSNs) instigates various Medium Access Control (MAC) layer challenges. Effective communication in a way to avoid collisions in the presence of multiple Primary Users (PUs) and CR nodes willing to access electromagnetic spectrum and EH are the significant challenges. In this paper, a MAC protocol for CRSNs which overcome challenges above is proposed. In our protocol, the CR nodes use Dedicated Common Control Channel (DCCC) for control information exchange among CR nodes and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol to access channel and avoid collisions. RF-EH technique is also incorporated to prolong the network lifetime. The proposed work is a state of the art MAC protocol in which CR nodes can communicate and harvest energy as well. Performance of the proposed protocol is evaluated in terms of throughput, harvested energy and lifetime of CRSNs by considering different parameters which include PU activities, number of CR nodes, number of flows and packet size. Simulations are performed on Network Simulator (NS-2).

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