Search

Summary: In this paper, we propose an efficient method for generating two types of novel optimized long binary spreading sequences (OLBSS) with improved autocorrelation function (ACF) properties. The first type is constructed from concatenated short binary subsequences belonging to the same code family, such as Walsh Hadamard and Gold subsequences, provided that their cross‐correlation functions (CCFs) have good properties. The second category uses the same subsequences but which are rather interlaced. Here, the number and size of the subsequences are related to the chosen length of the final constructed long sequence and the desired performances. The realization of the OLBSSs is achieved using two different optimization techniques, namely, the genetic algorithms (GAs) and particle swarm optimization (PSO) method. The simulation results, based on MATLAB tool, have shown that the proposed long sequences, composed of Walsh–Hadamard subsequences and optimized by the GA, have better ACF properties compared to the original Gold, Weil, and random sequences of the same length. [ABSTRACT FROM AUTHOR]

Summary: In this paper, we propose an efficient method for eliminating ambiguity in the acquisition and tracking processes of binary offset carrier (BOC)‐modulated signals. Our contribution is realized in two stages. The first one is based on the use, at the receiver end, of optimized locally generated subcarrier sequences to get a completely unambiguous composite correlation function (CF). This first stage is used to initialize and control the second stage of the proposed method designed on the basis of a maximum likelihood algorithm (MLA) to mitigate, specifically, multipath (MP) effect. In fact, the idea is to combine, in this second stage, the received signal (affected by noise and MP) with a set of locally generated ideal BOC(m,n)‐modulated signals, which are delayed and weighted by the MLA‐estimated parameters of delays, amplitudes, and phases of all the MP signals, to obtain an unambiguous CF with better performance. The simulation results, based on MATLAB tool, have demonstrated that the proposed method effectively eliminates the ambiguity problem. Besides, a comparative study with several methods has shown that the proposed method grants better performance than the most popular techniques. [ABSTRACT FROM AUTHOR]

In this study, the authors propose a simple structure of a new broadband planar slot antenna using a wide single-layer frequency selective surface (FSS) stopband. The proposed design is realised in two stages. First, the performances of the FSS unit cells are investigated using the finite element method of high-frequency structure simulator. Besides, the FSS structure considered as a stop-band filter in the bandwidth (3 - 7 GHz), is also validated by computer simulation technology microwave studio. Second, this FSS reflector is combined with a miniaturised wideband planar slot antenna (29 × 24 × 1.57 mm³). The final proposed combination is also designed, optimised, fabricated and validated by measurements. The obtained results show an operating impedance bandwidth of 86.38% (2.92 - 7.36 GHz) including the Worldwide interoperability for Microwave Access band, the C band for satellite applications, and the Wireless Local Area Network band. Furthermore, the antenna provides an 8.87 dBi measured maximum gain. Compared to the same antenna without FSS, a maximum gain enhancement of 5.53 dBi is achieved by the proposed structure. In addition, the back lobes are reduced in the proposed structure by > 15 dBi, compared to a simple antenna. The total size of the proposed antenna, integrating the FSS, is 0.63λ0 × 0.63λ0 × 0.12λ0. [ABSTRACT FROM AUTHOR]

In this study, the authors propose reliable sequences of binary coded symbol (BCS) modulation, and their characteristics and performances for Global Navigation Satellite System (GNSS) application are described. A BCS sequence vector is formed by eight variable length sub‐chips of alternated + 1 and −1 (or −1 and + 1) values. A judicious choice of the sub‐chips lengths of the BCS sequence permitted to propose several BCS sequences that provide high performances in terms of multipath mitigation, resistance to the noise and interferences rejection. An overview of the essential characteristics and the resulting autocorrelation functions (ACFs) and power spectral densities of the proposed BCS sequences were introduced. The latter ACFs have a sharp main peak due to the increase in the number of transitions of the BCS sequences within a chip interval, which corresponds to a larger slope of the discrimination function, and consequently a reduced range of search in the delay locked loop with a minimum calculation load. The theoretical and simulation results indicate that the proposed BCS sequences are more consistent compared to the conventional signals adopted by the GNSS navigation systems. [ABSTRACT FROM AUTHOR]