Home > All Issues > PIER B
ISSN: 1937-6472

Vol. 94

Latest Volume
All Volumes
All Issues

2021-10-20 PIER B Vol. 94, 53-74, 2021. doi:10.2528/PIERB21082004

Enhancing Detection Performances of Nonhomogeneous Weibull Clutter by Knowledge Based Systems Exploitation

Abdellatif Rouabah, M'hamed Hamadouche, Djamal Teguig, and Hamza Zeraoula

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 (Pfa) 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.

2021-10-17 PIER B Vol. 94, 37-52, 2021. doi:10.2528/PIERB21082106

Electromagnetic Boundary Conditions Defined by Reflection Properties of Eigen Plane Waves

Ismo Veikko Lindell and Ari Sihvola

In a previous study [1] it was shown that the generalized soft-and-hard/DB (GSHDB) boundary has the unique property that the two eigen plane waves are reflected as from the PEC or PMC boundary, i.e., with reflection coefficients -1 or +1, for any angle of incidence. The present paper discusses a more general class of boundaries by requiring that the reflection coefficients R+ and R-, corresponding to the two eigen plane waves, have opposite values, R±R with R independent of the angle of incidence. It turns out that there are two possibilities, R=1 for the class of GSHDB boundaries, and R=j, defining an extension of the class of perfect electromagnetic conductor (PEMC) boundaries. Matched waves at, and plane-waves reflected from, boundaries of the latter class are studied in the paper.

2021-10-10 PIER B Vol. 94, 19-36, 2021. doi:10.2528/PIERB21071305

Inversion of Electrical and Geometrical Parameters of a Stratified Medium from Data Derived from the Small Perturbation Method and the Small Slope Approximation

Nada Djedouani, Saddek Afifi, and Richard Dusséaux

The goal of the present paper is on retrieving the electrical and geometrical parameters of a stratified medium with two rough interfaces. The inversion problem is formulated as a cost function optimization problem, and it is solved using the simulated annealing algorithm. The cost function consists in the integrated squared deviation between the co-polarized incoherent intensities obtained from the Small Slope Approximation and those obtained from the Small Perturbation Method. The inversion scheme is applied to the electrical and geometrical parameters involved into the analytical expressions of the incoherent intensities given by the SPM. We study the influence of the shape of the autocorrelation function and the isotropy factor upon the estimation of parameters. We test the sensitivity of the inversion scheme to noisy synthetic data. The study is applied to snow-covered soils in L-band. For the configurations under study, we show that the inverse method is efficient for eight-parameter or ten-parameter predicting problems.

2021-09-14 PIER B Vol. 94, 1-18, 2021. doi:10.2528/PIERB21071209

Negative Group Delay Prototype Filter Based on Cascaded Second Order Stages Implemented with Sallen-Key Topology

Miodrag Kandic and Greg E. Bridges

A Negative Group Delay (NGD) filter prototype design based on cascaded identical 2nd-order baseband stages is presented. The prototype design achieves an NGD-bandwidth product that in the upper asymptotic limit for a distributed design is a function of out-of-band gain in decibels raised to the power 3/4. This is an improvement of previous cascaded first-order designs that have an NGD-bandwidth functional dependency of out-of-band gain in decibels to the power of 1/2. The bandwidth is taken as the 3 dB amplitude response bandwidth. The corresponding NGD design upshifted to a non-zero center frequency, i.e. a Band-Stop Filter (BSF) design, is shown to be possible to implement with Sallen-Key topology, and an example is presented for a 500 MHz center frequency and a 100 MHz (20%) 3 dB bandwidth. The filter shows a 4.05 ns negative group delay with a 1.28 ns in-band variation and a 3-dB amplitude response over the bandwidth of 100 MHz, achieving an NGD-bandwidth product of 0.405. An in-band distortion metric is presented, which can be evaluated for any specified time-domain input waveform. It is shown that the bandwidth, order of filter and desired distortion for a particular input waveform are interrelated. Therefore, the proposed in-band distortion metric constitutes another trade-off quantity to be checked for any type of NGD design.