This work presents a low-profile, compact quad-port MIMO antenna structure optimized for sub-6 GHz and X-band wireless communication. The antenna employs a tapered and stepped monopole radiator in conjunction with defected substrate and ground plane modifications to enhance isolation, improve diversity performance, and support dual-band operation. A single monopole element, designed on an FR-4 substrate (ε_r = 4.3, tan δ = 0.002), has been extended into a quadport configuration with orthogonally oriented ports to achieve polarization diversity and minimize mutual coupling. Although the spacing is less than λ_max/2 (0.14 λ₀), a reduced inter-element gap of 11.25 mm is adopted to achieve compact integration. The antenna measures 44 × 44 × 1.6 mm³ and operates across two frequency bands: 2.75–4.4 GHz and 10.33–13 GHz (S_xx < -10 dB) with S_xy values below –17.5 dB and –25 dB in the respective bands, ensuring robust MIMO performance. With its compact design and efficient radiation characteristics, the proposed antenna is well-suited for 5G-NR systems, IoT devices, V2X communication, and satellite-based applications.

Speckle noise, a granular noise, occurs in synthetic aperture radar (SAR) data due to the interference of reflected signals with several scatterers in a resolution cell. One of the simplest techniques to suppress speckle noise from polarimetric SAR data is to use local statistics. The Lee filter employs sample mean and variance of pixels of data degraded by speckle noise, which can be multiplicative, additive, or a mixture of both, in a searching window. The refined Lee method utilizes directional windows with local minimum mean square error (LMMSE), which ensures superior maintenance of spatial resolution and features. The Lee-Sigma filter is constructed on the basis of the two-sigma probability, which effectively suppresses the speckle noise. However, insufficiencies were observed in the generation of a biased evaluation, blurring of edges, and suppression of point targets. To eliminate these insufficiencies, the improved Lee-Sigma filter was developed, which employs the minimum mean square error estimate as a priori mean. Thus, an excellent maintenance of point targets and subtle details is displayed. In this study, the Lee, refined Lee, Lee-Sigma, and improved Lee-Sigma filters were evaluated using full polarimetric data. The evaluated results indicated that the improved Lee-Sigma filter performed better than other local statistics filters.

This study proposes a modified 11-sided polygonal wideband MIMO antenna on a 1.6 mm FR4 substrate for next-generation wireless IoT applications. The antenna features a polygonal patch with a hook-shaped slot and a partial ground plane to achieve a wide impedance bandwidth of 3.725–7.525 GHz. Enhanced isolation is ensured through a partial ground structure with a decoupling element, maintaining S ₁₂ < –20 dB across resonant frequencies. It demonstrates excellent diversity performance with ECC < 0.4, DG of 10 dB, TARC < 0 dB, and CCL < 0.1 bits s ⁻¹ Hz ⁻¹ , along with a peak gain of 5.6 dB and 97% efficiency. The design supports applications including 5G sub-6 GHz (N79), V2X communication, WLAN, Wi-Fi, and Wi-Fi 6E. Additionally, all Specific Absorption Rate (SAR) values are below the safe limit of 1.6 W kg ⁻¹ , confirming its suitability for practical deployment.