This article aims to study the behavior of Constant False Alarm Rate (CFAR) detectors for a heterogeneous Weibull clutter and its derivatives. CFAR architectures based on exploitation of the Combined Environmental Knowledge Base (CEKB) have been proposed, called Knowledge Based Systems-Maximum Likelihood-CFAR (KBS-ML-CFAR) and KBS-Log-t-CFAR for nonhomogeneous Weibull clutter at general parameters. A CFAR architecture that uses Geographic Information System (GIS) as a Knowledge Base (KB), called KBS-Forward Automatic Order Selection Ordered Statistics-CFAR (KBS-FAOSOS-CFAR) has been proposed for special Weibull parameters. The performances of the proposed detectors have been studied and analyzed by conducting MATLAB simulations. The simulation results show that the KBS-CFAR based on CEKB outperforms the ML and Log-t-CFAR in terms of clutter edge detection capability in nonhomogeneous Weibull clutter case. Compared with other KB, this KBS-CFAR based on CEKB performs well to preserve the probability of false alarm (P_fa) at a desired constant value. For special Weibull parameters, the proposed KBS-FAOSOS-CFAR based on GIS performs better than KBS-Dynamic-CFAR and KBS-Adaptive Linear Combined-CFAR (KBS-ALC-CFAR) in severe interference case. CFAR techniques have been implemented on the ADSP (Advanced Digital Signal Processor) processing board, and the results have been evaluated and discussed.....

A novel 4-element UWB MIMO (multiple-input multiple-output) slot antenna with triple band-notched characteristics is designed and fabricated. It is composed of four rectangular slot antennas with two C-slots and a T-slot. To improve the isolation, cross-shaped branches are added. The measured results demonstrate that the antenna can operate ranging 2.51-11.07 GHz with the impedance bandwidth (S₁₁ < -10 dB) of 856 MHz except three rejected bands, including 3.02-4.07 GHz, 4.54-5.83 GHz and 7.88-9.38 GHz, and the inter-element isolation of antenna in the range of UWB band is higher than 21 dB. The presented antenna can filter the interference of WiMAX (3.3-3.7 GHz), WLAN (5.15-5.825 GHz) and X-band (7.9-8.4 GHz). What's more, the parameters of diversity performance like envelope correlation coefficient (ECC), diversity gain (DG), efficiency, gain, channel capacity loss (CCL), mean effective gain (MEG) and total active reflection coefficient (TARC) have been analyzed. Based on the analysis on simulated and measured results, the proposed MIMO antenna is competent for UWB applications with notched bands for WiMAX, WLAN and X-band.....

A wideband circular patch antenna with broadside and conical radiation patterns is proposed. In addition to realizing a wide shared impedance bandwidth of ~48% for both the modes of operation, the unparalleled advantage of the proposed antenna is its reduced sidelobes in the E-plane broadside radiation patterns. The achieved sidelobe-free bandwidth is in the order of 39%, which is much wider than the pertinent art works on wideband pattern diversity antennas using a single radiating patch. The antenna characteristics are validated by fabricating and testing the designed prototype. The proposed antenna is also numerically investigated in front of a parabolic reflector antenna for monopulse radar applications.....

A 3-dB compact hybrid coupler is presented in this paper in an ultra-wideband frequency range from 1.5 GHz to 3.2 GHz with 90˚ phase deference between the two output ports. The proposed coupler is formed by two notched elliptically shaped microstrip lines and four phase shifters, which are broadside coupled through an elliptically shaped slot. A combination of impedance matching technique and structural modification then has been employed to increase coupler efficiency. The design is demonstrated assuming a 0.51-mm-thick Rogers RO4350B substrate. Results of simulation and measurements show that the designed device exhibits a coupling of 3±1 dB across the aimed bandwidth. This ultra-wideband coupling is accompanied by smooth isolation in the order of better than 25 dB and return loss in the order of better than 17 dB. The manufactured device including microstrip ports and phase shifters occupy an area of 35 mm × 30 mm × 1.1 mm (0.27λ × 0.23λ × 0.009λ) which makes it a compact suitable device for UHF applications and measurements, specifically measuring and determining isolation in in-band full duplex transceivers, because of its smooth isolation versus frequency and ultra-wideband bandwidth.....