Volume 73 (2022): Edizione 6 (December 2022)

In view of the bad operation environment of large motor, which often suffers from various strong noise interference, the partial discharge ultrasonic signal is often annihilated, which makes it difficult to detect and analyse. A de-noising method based on generalized minimax concavity (GMC) and wavelet for partial discharge (PD) ultrasonic signal is proposed. GMC is used to enhance the sparsity of PD ultrasonic signal and eliminate the high-frequency noise signal at the same time. Then the residual high-frequency sparse noise and low-frequency noise of the former are de-noised again combined with wavelet. Finally, the signal is reconstructed to achieve the purpose of de-noising the original PD ultrasonic signal with noise. Compared with ℓ₁ -norm method, GMC method, wavelet method and ℓ₁ -norm-wavelet method, the simulation results show that based on time domain analysis, the de-noising effect of the proposed method is obviously better than the other four methods. The SNR and MSE of the former are better than those of the latter. In addition, the insulation bar discharge model of large motor is constructed to obtain the actual PD ultrasonic signal, which further verifies its effectiveness, and its de-noising effect is also better than the four methods. This method can not only enhance the sparsity of the target signal and improve the estimation accuracy, but also achieve the de-noising effect, while retaining the effective information of PD ultrasonic signal characteristics. This method can provide new ideas for other types of PD signal de-noising, and lay the foundation for later feature analysis.

We propose a single channel blind source separation algorithm for convolutively mixed linear frequency modulation (LFM) signals based on smoothed Wigner-Ville distribution (SWVD) time-frequency analysis, Canny edge detection, and Hough transform detection. First, the SWVD time-frequency analysis diagram is obtained as an image based on the LFM time-frequency characteristics. Second, Canny edge detection is performed on the image. Then, Hough transform is used to detect the characteristic parameters of the linear signal. Finally, the source signal is recovered. The simulation results show that the algorithm is effective for single channel detection and extraction of convolutively mixed LFM signals.

This paper presents an instruction mapping technique for generating a low-level assembly code for digital signal processing algorithms. This technique helps developers to implement retargetable kernel functions with the performance benefits of the low-level assembly languages. The approach is aimed at exceptionally long instruction word (VLIW) architectures, which benefits the most from the proposed method. Mapped algorithms are described by the signal-flow graphs, which are used to find possible parallel operations. The algorithm is converted into low-level code and mapped to the target architecture. This process also introduces the optimization of instruction mapping priority, which leads to the more effective code. The technique was verified on selected kernels, compared to the common programming methods, and proved that it is suitable for VLIW architectures and for portability to other systems.

This article begins with an explanation of a frequency selective surface, also known as an FSS, which is used to increase gain across a wide frequency range. The proposed unit design is a modified combination of circular and square elements with two cross dipoles and a T-type structure at the inner side. In the second step of the process, a single wideband antenna that covers the same range as FSS is designed and then analyzed in terms of its gain and radiation patterns. After that, an antenna array was built using the same solo structure in order to take advantage of the benefits that come with using an array system. The array is made up of elements that are CPW fed. A ground-backed T-shaped power divider network with additional shorting pins is used to supply power to the entire array. In the fourth step, an array of the FSS unit cell has been positioned beneath the UWB solo antenna and its array in order to investigate the possibility of improved gain and radiation pattern. The FSS equivalent lumped circuit model is presented here for validation purposes. It has been determined that the results of the experiment and the simulation are consistent with one another. In contrast to the structures that have been reported in the past, the newly developed model possesses a greater bandwidth, a higher gain, and a lower profile.

Four types of magnets were used in this study: neodymium NdFeB (grade N35 and N52), ferrite (Y10), and samarium-cobalt SmCo (XG30 2:17). They were chosen to represent a wide range of volumes from 0.035 to 19 cm³ (540 times), radius R from 1.5 to 12.5 mm (8 ×), length L from 0.5 to 40 mm (80 ×), aspect ratio L/R from 0.051 to 17 (330 ×), and contact forces from 0.2 to 250 N (over 1000 ×). The study shows that previously reported closed-form equations are valid only at large distances (small forces). At short distances (large forces) the calculated force diverges to infinity or the accuracy depends on the aspect ratio, and some equations fail more than others. A new equation is proposed as a small modification of a previously known function, which provides reasonable behaviour over the whole studied range. However, the accuracy is unknown in a general practical case, because theoretical calculations do not take into account imperfections of real magnets, so there is no single absolute reference.

The coupling between closely spaced split-ring resonators, when employed as sub-components of electromagnetic structures, is an important feature often leveraged upon to provide bulk material properties. In its contribution, this paper employs characteristic-mode analysis (CMA) to examine modal interactions intrinsic to the coupling between a pair of split-ring resonators. The analysis reveals the influence of feed impedance and rotational orientation of a pair of coupled SRRs on the excited resonant modes, which, in turn, determine the power transfer levels between both SRRs and the frequencies at which these occur. The insights provided suggest the aptness of rotational orientation and feed impedance as critical design parameters for the realization of SRR-based magneto-inductive waveguides and wireless power transfer setups.

This communication suggests an orthogonal interleaver set for interleave division multiple access (IDMA) based non orthogonal multiple access (NOMA) schemes from beyond 5G viewpoint to support enormous increase in user count. The method generates an orthogonal interleaver set by providing two mother interleavers as seed to generate other users’ interleaving patterns progressively. The key feature of the proposed scheme is that it reduces implementation complexity and memory requirement at the base station, while implementing iterative multiuser detection (MUD), which most of the interlaever designs suggested in literature do not consider. It provides additional security to the user data due to progressively changing mother interleavers’ pattern along with the conventional purpose of providing unique identity for individual users in the system. The proposed orthogonal interleaver set is tested through simulations under multiple IDMA system configurations. It has been observed that it preserves the bit error rate (BER) performance of the IDMA scheme along with the optimal implementation complexity and minimal information exchange requirement between base station and mobile station to share the interleaver design.

In the present study, a new methodology in computational electromagnetics is developed for two-dimensional arbitrarily-shaped objects with impedance boundary conditions. The proposed approach investigates the E-polarized electromagnetic diffraction by a two-dimensional object with the Leontovich boundary condition. The scattered electric and magnetic fields are expressed as the convolution integral of the corresponding Green’s function and the current induced on the obstacle surface. After obtaining integral equations by applying the boundary condition, the integral equations are solved as in the case of the method of auxiliary sources (MAS) which is a well-known method in computational electrodynamics. The results are compared with first, different methods such as the method of moments (MoM), orthogonal polynomials (OP), and second, different boundary conditions such as Dirichlet, Neumann, and fractional boundary conditions. Some results are also obtained for the different shape scatterers at some values of the surface impedance.

This paper presents the construction of RLL-ECCs (run length limited error control codes) from three selected ECCs specified by Consultative Committee for Space Data Systems (CCSDS) for optical communications. The RLL-ECCs obtained present a practical alternative to CCSDS codes with pseudo-randomizers. Their advantage is that the maximal run lengths of equal symbols in their codeword sequences are guaranteed, which is not the case if the common approach with pseudo-randomizers is used. The other advantages are that no additional redundancy is introduced into encoded codewords and that the encoding and decoding procedures of the original error control CCSDS codes do not have to be modified in the following cases: Firstly, if hard decoding is used and the transmission channel can be modeled as a BSC (binary symmetric channel) and secondly, if soft decoding and coherent BPSK (binary phase shift keying) modulation is used and the appropriate transmission channel model is an AWGN (additive white Gaussian noise) channel.

The paper deals with a new application of the key term separation principle in identification of nonlinear dynamic systems. A multiplicative form of this operator decomposition technique is proposed and applied to the Wiener model. The resulting mathematical model is linear in both the linear and the nonlinear block parameters. Illustrative examples are included.