PIER B | PIER Journals

2023-12-07

PIER B

Vol. 104, 51-68, 2024

download: 11

Advanced Analysis of Radar Cross-Section Measurements in Reverberation Environments

Corentin Charlo , Stéphane Méric , François Sarrazin , Elodie Richalot , Jérome Sol and Philippe Besnier

Reverberation chambers (RCs) were recently reported as a low-cost alternative to anechoic chambers (ACs) to perform radar cross-section (RCS) pattern measurements. The method consists i, using transmitting and receiving antennas pointing towards a target under test placed on a rotating mast. As a classical RCS characterization, the echo signal is analysed based on two measurements with and without the target in the RC. In the hypothesis of an ideal diffuse field generated in the RC, this signal difference appears as the echo signal hidden in a Gaussian noise. In case of a point-like backscattering target, observing this signal over a given frequency bandwidth allows the identification of the target response as a sinusoidal signal over this bandwidth whose period is related to the antenna-target distance measured from the measurement calibration plane positions. Therefore, the extraction of the magnitude of this sinusoidal signal requires a proper estimation of this distance. Furthermore, a sinusoidal regression processing relies on the approximation of a constant envelope over the selected frequency bandwidth, imposing some restrictions. In this paper, we introduce a two-step method that consists in identifying the most appropriate distance according to the target's orientation before estimating the magnitude of the sinusoidal signal. We highlight the improvement of RCS estimation on a point-like back-scattering target compared to the one-step procedure applied so far. In addition, it is shown that the analysis performed regarding the estimated distance provides a physical insight into the position of the equivalent backscattering point.

Advanced Analysis of Radar Cross-section Measurements in Reverberation Environments

2023-12-07

PIER B

Vol. 104, 35-50, 2024

doi:10.2528/PIERB23071501

download: 25

Effect of via-Array Side Walls on the Characteristics of SIW Resonator with Novel Design Equations

Samar M. Azab , Abdelhameed Abdelmoneim Shaalan , Khalid Fawzy Ahmed Hussein and Asmaa Elsayed Farahat

The present work proves by both simulation and experimental work that the most common empirical formulas available in the previous publications for the design of substrate-integrated waveguide (SIW) cavities are incorrect in most cases. Moreover, the present work provides correct and exact design equations that are examined by both simulation and experimental work. In planar circuit structures, rectangular waveguide and resonators are commonly integrated within a dielectric substrate to produce what is known as SIW structures. For ease of fabrication and embedding into the dielectric substrate, the closed (solid) side walls of the rectangular waveguides and resonators are replaced by metallic via arrays. The main concern of the present paper is to investigate the effects of such replacement on the performance of a SIW resonator through simulation as well as experimental work. The limiting constraints on the relative dimensions of such via arrays including the diameter of the vias and the spacing between them are numerically and experimentally investigated to ensure proper operation of the SIW resonator regarding the radiation loss due to leakage from the openings of the resonator side walls. The effects of the via array dimensions on the resonant frequency, radiation loss, and quality factor (Q-factor) of the resonator are evaluated. For this purpose, two models of the rectangular resonator embedded in the dielectric substrate are designed to operate at 10 GHz. The first model is an ideal box-shaped resonator of solid side walls whereas the other model is the conventional SIW resonator with via-array side walls. The two types of the substrate embedded resonators are fed through a microstrip line. The resonant frequency, losses, and Q-factor of the two resonator models are compared to each other taking the box-shaped resonator as a reference because of its ideal structure to evaluate the performance of a conventional SIW resonator. The two types of resonator are fabricated for comparison through experimental measurements. The empirical design equations that are commonly available in literature to calculate the effective dimensions of the SIW resonator are investigated by comparison with the exact simulation results and shown to be incorrect in most cases. More accurate and reliable design equations are proposed in the present work. The results of the proposed design equations are compared to the simulation results showing excellent accuracy and shown to be more reliable than those available in literature.

Effect of Via-array Side Walls on the Characteristics of SIW Resonator with Novel Design Equations

2023-11-29

PIER B

Vol. 104, 21-33, 2024

doi:10.2528/PIERB23091305

download: 36

The Influence of Contrast and Temporal Expansion on the Marching-on-in-Time Contrast Current Density Volume Integral Equation

Petrus Wilhelmus Nicolaas (Pieter) Van Diepen , Martijn Constant van Beurden and Roeland Johannes Dilz

The contrast current density volume integral equation, discretized with piecewise constant spatial basis and test functions and Dirac-delta temporal test functions and the piecewise polynomial temporal basis functions, results in a causal implicit marching-on-in-time scheme that we refer to as the marching-on-in-time contrast current density volume integral equation (MOT-JVIE). The companion matrix stability analysis of the MOT-JVIE solver shows that for a fixed spatial and temporal step size, the stability is independent of the scatterer's dielectric contrast for quadratic spline temporal basis functions. Whereas, Lagrange and cubic spline exhibit instabilities at higher contrast. We relate this stability performance to the expansion and testing procedure in time. We further illustrate the capabilities of the MOT-JVIE based on quadratic spline temporal basis functions by: comparing the MOT-JVIE solution to time-domain results from literature and frequency-domain results from a commercial combined field integral equation solver. Finally, we present a long time sequence for a high-contrast scatterer discretized with 24,000 spatial unknowns.

The Influence of Contrast and Temporal Expansion on the Marching-on-in-Time Contrast Current Density Volume Integral Equation

2023-11-24

PIER B

Vol. 104, 1-19, 2024

doi:10.2528/PIERB23060902

download: 94

BI-CMOS Design of a*exp (-j *φ0) Phase Shifter as Miniature Microwave Passive Circuit Using Bandpass NGD Resonant Circuit

Mathieu Guerin , Fayrouz Haddad , Wenceslas Rahajandraibe , Samuel Ngoho , Glauco Fontgalland , Fayu Wan and Blaise Ravelo

The purpose of this paper is to study the RF/microwave constant phase shift (CPS) designed as an integrated circuit (IC) in 130-nm Bi-CMOS technology. The CPS understudy is constituted by a bandpass (BP) negative group delay (NGD) passive cell combined in cascade with a positive group delay (PGD) circuit. The CPS real circuit is represented by a CLC-network associated in cascade with a BP-NGD passive cell. The CPS characterization is based on the S-parameter modelling. The CPS is analytically modeled by the frequency independent transmission phase modelling by the mathematical relation φ(f)=a*exp(-j*φ₀) = constant around working frequency [f_n-Δf/2, f_n+Δf/2] by denoting center frequency f_n and frequency band Δf. The analytical principle of the constant PS is explored by means of the RLC-network based NGD cell. The design formula of the NGD and CLC passive circuit parameters in function of desired operation frequency is established. The validity of the developed theory is verified with a proof-of-concept (POC). A CPS miniature IC having physical size 1.15 mm × 0.7 mm is designed and implemented as POC in 130-nm Bi-CMOS technology. The ADS® and layout versus schematic of Cadence® simulation results from 130-nm Bi-CMOS CPS POC confirms the theoretical investigation feasibility. The simulated results of the obtained CPS IC POC layout show φ₀=-67°+/-1° phase shift around f_n=0.85 GHz within the frequency band delimited by f₁=0.73 GHz to f₂=0.984 GHz or Δf=f₂-f₁=254 GHz. The CPS robustness designed in 130-nm Bi-CMOS IC technology is stated by Monte Carlo statistical analysis from 1000 trials with respect to the component geometrical parameters. It was reported that the phase shift and insertion loss flatness's of the CPS IC is guaranteed lower than 5% in Δf/f_n=30% relative frequency band around f_n.