Showing 3 results for Mitigation
M. R. Mosavi, Z. Shokhmzan,
Volume 11, Issue 3 (9-2015)
Abstract
The Global Positioning System (GPS) signals are very weak signal over wireless channels, so they are vulnerable to in-band interferences. Therefore, even a low-power interference can easily spoof GPS receivers. Among the variety of GPS signal interference, spoofing is considered as the most dangerous intentional interference. The spoofing effects can mitigate with an appropriate strategy in the receiver. In this paper, we use methods of adaptive filter based on Least Mean Squares (LMS) and Normalized Least Mean Squares (NLMS) algorithms in-order to defense against spoofing. The proposed techniques are applied in the acquisition stage of the receiver. The proposed methods have been implemented on real dataset. The results explain that the suggested algorithms significantly decrease spoofing. Also, they improve Position Dilution of Precision (PDOP) parameter. Based on the results, NLMS algorithm has better performance than LMS algorithm.
Z. Shokhmzan, M. R. Mosavi, M. Moazedi,
Volume 13, Issue 4 (12-2017)
Abstract
The vulnerability of civil GPS receiver to interference may be intentional or unintentional. Among all types of interference, replay attack intended as the most dangerous intentional one. The signal structure of replay attack is almost the same with the satellite signal. The interference effects can be reduce with the design of an appropriate filter in the receiver. This paper presents two methods based on Finite Impulse Response (FIR) filter in frequency and time domain to mitigate the interference effect on GPS signals. Designed FIR filter protects GPS against the replay attack. The suggested filter is applied in the acquisition of the receiver. The proposed method has been implemented on collected dataset. The results show that the proposed algorithms significantly reduce interference. Also, they improve Position Dilution of Precision (PDOP) parameter. Based on the results, the FIR filter technique in time domain has better performance than the frequency domain.
S. R. Mousavi-Aghdam, N. Elahi Kachaei,
Volume 17, Issue 2 (6-2021)
Abstract
This paper presents a new single to three phase converter using rotating magnetic field transformer. Conventional transformers have been used in many converters aiming at supplementary improvements and they usually have no critical effect on the conversion technique. In this paper, the conversion technique is based on a special rotating magnetic field transformer in which there are two windings in the primary and six windings on the secondary side. In the proposed converter, first a single-phase voltage source is applied on the primary windings via a switching technique using thyristors to create a rotating magnetic field. Next, the created field induces three phase voltages on the secondary three phase windings. Nevertheless, the created field in the primary side suffers from low frequency harmonics and can be transmitted to the secondary three phase voltages. Hence, design of the secondary windings is modified to mitigate these harmonics. The paper discusses how the harmonics can be mitigated using two sets of three phase windings with appropriate shift. Finally, the proposed converter is modeled using state equations and the simulation results exhibit the effectiveness of the proposed converter.
