This article describes a method for filtering speckle noise from synthetic aperture radar images using wavelet transforms and nonlocal means. The proposed method utilizes a spatial-frequency representation of the image and analyzes the similarity of local wavelet coefficient structures in subbands. Experimental results demonstrate that the developed method outperforms some known methods in terms of metrics such as mean square error, peak signal-to-noise ratio, and structural similarity index, as well as subjective visual assessment. The method effectively filters speckle while preserving fine details, contrasting edges, and correctly restoring background brightness without introducing noticeable artifacts.

Keywords: radar image, synthetic aperture radar, speckle noise, image filtering, wavelet transform, thresholding, non-local means

Local Multipoint Distribution Service (LMDS) is a broadband microwave communications technology offering a low-cost and multifunctional solution for terminal access applications. This paper develops a rectangular waveguide-based duplexer with a square-ridge T-junction for LMDS. The design of a rectangular waveguide-based metal diaphragm filter in the E-plane is described. The metal diaphragm of this filter can be processed using methods such as etching, ensuring high precision and low cost. The characteristics of a rectangular waveguide-based T-junction in the H-plane used in the duplexer are analyzed.

Keywords: microwave duplexer, E-plane metal diaphragm, microwave filter, ribbed T-junction, local multi-drop distribution service

A low-profile wideband circularly polarized antenna is proposed for use in navigation satellite systems. The VSWR ≤2 bandwidth is 75%. The 3-dB axial ratio (circular polarization) bandwidth is 54%. The designed radiating element was fabricated and measured as part of the antenna array.

Keywords: circular polarization, wideband antenna,, antenna array, axial ratio

This article analyzes the problem of determining the location of an object based on the method of passive positioning of single-station systems with a long baseline. The method proposed in the article implies that the antenna array is integrated into a single-station system with a long baseline using three antennas. The mentioned method is able to determine the actual location of the radiation object and the parameters of the object's position by estimating the phase difference and the actual direction of the radiation object. The simulation results confirm the validity of the proposed method.

Keywords: antenna array, passive positioning system, phase difference, bearing, azimuth, error