Universal behaviour of a wave chaos based electromagnetic reverberation chamber

In this article, we present a numerical investigation of three-dimensional electromagnetic Sinai-like cavities. We computed around 600 eigenmodes for two different geometries: a parallelepipedic cavity with one half- sphere on one wall and a parallelepipedic cavity with one half-sphere and two spherical caps on three adjacent walls. We show that the statistical requirements of a well operating reverberation chamber are better satisfied in the more complex geometry without a mechanical mode-stirrer/tuner. This is to the fact that our proposed cavities exhibit spatial and spectral statistical behaviours very close to those predicted by random matrix theory. More specifically, we show that in the range of frequency corresponding to the first few hundred modes, the suppression of non-generic modes (regarding their spatial statistics) can be achieved by reducing drastically the amount of parallel walls. Finally, we compare the influence of losses on the statistical complex response of the field inside a parallelepipedic and a chaotic cavity. We demonstrate that, in a chaotic cavity without any stirring process, the low frequency limit of a well operating reverberation chamber can be significantly reduced under the usual values obtained in mode-stirred reverberation chambers

Study of a reverberation chamber shape inspired from chaotic cavities

International audienceUsing the knowledge gained from the wave chaos theory, we present a simple modification of the shape of a reverberation chamber (RC) consisting in inserting a metallic hemisphere on a cavity wall. The presented simulation results show a significant improvement of the field statistical properties, and this without resorting to a mode stirrer

Universal intensity statistics in a chaotic reverberation chamber to refine the criterion of statistical field uniformity

International audienceThis article presents a study of the intensity statistics of the electromagnetic response in a chaotic reverberation chamber (RC) in the presence of losses. Through an experimental investigation, intensity statistics of the response in a conventional mode-stirred RC are compared with those in a chaotic RC in the neighborhood of the Lowest Useable Frequency. The present work illustrates how the universal statistical properties of the field in an actual chaotic RC can ensure the validity of the standard criterion proposed to evaluate the uniformity of the field distribution. In particular, through a theoretical approach based on the random matrix theory applied to open chaotic systems, we find that the modal overlap seems to be the only relevant parameter of the corresponding intensity distribution

Statistiques de la réponse électromagnétique d'une chambre réverbérante chaotique

Cet article présente une étude de la réponse électromagnétique d'une chambre réverbérante (CR) chaotique en présence de pertes. Au moyen de simulations et d'expériences, sont comparées les fluctuations des maxima du champ obtenus dans une CR à brassage de modes conventionnelle et dans une CR chaotique au voisinage de la fréquence minimum d'utilisation. Ce travail illustre que les propriétés statistiques spectrales et spatiales universelles des CR chaotiques permettent de mieux répondre aux critères exigés par la norme pour réaliser des tests d'immunité ou de compatibilité électromagnétique

Comparison of reverberation chamber shapes inspired from chaotic cavities

International audienceUsing the knowledge gained from the wave chaos theory, we present simple shapes of resonant cavities obtained by inserting metallic hemispheres or caps on the walls of a parallelepiped-shaped cavity. The presented simulation results show a significant improvement of the field statistical properties when the number of hemispheres or caps increases, and the comparison with a classical reverberation chamber geometry shows an improved homogeneity and isotropy can be attained using these new proposed shapes

Study of lateral scaling impact on the frequency performance of SiGe Heterojunction Bipolar Phototransistor

The influence of the lateral scaling such as emitter width and length on the frequency behavior of SiGe bipolar transistor is experimentally studied. Electrical transistors of different emitter sizes are designed and fabricated by using a commercial bipolar transistor technology. The effect of peripheral current and collector current spreading on electrical bipolar transistor performances are analyzed in regards to the state of the art. Furthermore, the lateral scaling effect on SiGe phototransistor electrical and opto-microwave frequency behavior is studied. The impact of the lateral flow of photo-generated carriers toward the optical opening in phototransistor structure is investigated. Moreover, the 2-D carrier flow effect on the opto-microwave frequency behavior of the phototransistor is characterized through optomicrowave scanning near-field optical microscopy measurements, in the course of which the intrinsic parameters, such as transit time and junction capacitances are extracted over the surface of the phototransistor. An intrinsic optical transition frequency of 6.5 GHz is measured for 10 × 10 μm2

Improving the opto-microwave performance of SiGe/Si phototransistor through edge-illuminated structure

This paper demonstrates the experimental study of edge and top illuminated SiGe phototransistors (HPT) implemented using the existing industrial SiGe2RF Telefunken GmbH BiCMOS technology for opto-microwave (OM) applications using 850nm Multi-Mode Fibers (MMF). Its technology and structure are described. Two different optical window size HPTs with top illumination (5x5µm 2 , 10x10µm 2) and an edge illuminated HPTs having 5µm x5µm size are presented and compared. A two-step post fabrication process was used to create an optical access on the edge of the HPT for lateral illumination with a lensed MMF through simple polishing and dicing techniques. We perform Opto-microwave Scanning Near-field Optical Microscopy (OM-SNOM) analysis on edge and top illuminated HPTs in order to observe the fastest and the highest sensitive regions of the HPTs. This analysis also allows understanding the parasitic effect from the substrate, and thus draws a conclusion on the design aspect of SiGe/Si HPT. A low frequency OM responsivity of 0.45A/W and a cutoff frequency, f-3dB , of 890MHz were measured for edge illuminated HPT. Compared to the top illuminated HPT of the same size, the edge illuminated HPT improves the f-3dB by a factor of more than two and also improves the low frequency responsivity by a factor of more than four. These results demonstrate that a simple etched HPT is still enough to achieve performance improvements compared to the top illuminated HPT without requiring a complex coupling structure. Indeed, it also proves the potential of edge coupled SiGe HPT in the ultra-low-cost silicon based optoelectronics circuits with a new approach of the optical packaging and system integration to 850nm MMF

Low loss Goubau Line on high-resitivity silicon in the 57–64 GHz band

Planar Goubau Line (PGL) structures on high resistivity silicon are simulated and measured in the 57-64GHz frequency band. It is shown that the increase of the substrate thickness permits to adapt this line, used at THz frequencies, to this frequency band. Very low losses are attained with a measured average attenuation of 0.064dB/mm on the whole band. Another advantage of the PGL consists in its very simple technological process, as just one level of metallization is necessary. A transition between the PGL and a coplanar waveguide is designed in order to perform on-wafer measurements, and very good agreement is obtained with simulation results for the attenuation of PGL

60 GHz stepped impedance filter using Planar Goubau line technology

This paper presents a fifth order stepped impedance low-pass filter using low loss Planar Goubau Line (PGL) technology on high resistivity Silicon substrate at millimeter-wave frequencies. The filter is simulated and optimized using 3D full-wave electromagnetic field simulations performed on HFSS (High Frequency Simulator Structure). On-wafer measurements in the 50-65 GHz band are in good agreement with simulation results. At 60 GHz, the measured insertion loss is 3.6dB which includes the two coplanar waveguide-to-GPL transitions

60 GHz square open-loop resonator (SOLR) based on planar Goubau line (PGL) technology

This study presents the design, fabrication, and measurement of a square open-loop resonator (SOLR) on high resistivity silicon substrate feed with a planar Goubau line (PGL), which is a very low-loss transmission line around 60 GHz fabricated through a very simple and low-cost process. Electromagnetic simulations using ANSYS high frequency structure simulator are performed for the PGL structure, in order to determine the PGL characteristics (impedance, losses and quality factor) versus the line width. The geometrical parameters of the SOLR structure are studied to observe their impact on reflection and transmission properties. An equivalent lumped element circuit is extracted from the distributed planar design to study and optimise the resonating structure using Advanced Design System. This electrical circuit response is successfully compared to the planar electromagnetic structure one, and a parametric study permits to better understand the role of the different circuit elements. Field displays lead to a better understanding of the SOLR behaviour. For measurement purpose of the fabricated structure, a coplanar waveguide-PGL transition is optimised with 0.9 dB losses. Simulation and measurement results show good performances for filter applications with 1 dB losses and small size at 60 GHz for 10% bandwidth