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This article reports a novel 3-D imaging approach for remote, nondestructive material inspection at depth. The approach is based on a frequency-modulated continuous-wave (FMCW) radar system operating in the 75–110-GHz frequency band. Time-domain spectroscopy (TDS) measurements demonstrate that such a frequency band has manage-able attenuation levels in centimeter-long materials, thereby offering an advantageous resolution-versus-measurement-depth tradeoff compared with higher frequencies. The proposed setup includes a long delay on the reference signal in order to cancel redundant signals that would otherwise degrade the measurement. Furthermore, specific signal-processing techniques used to improve the performance of the system, which requires stringent component performances in terms of radio-frequency nonlinearity and return loss, are presented. Radio-frequency nonlinearity correction is based on a reference measurement, and the impact of deleterious reflections is reduced by averaging measurements conducted on a target at different longitudinal positions. As a result, an improvement of the signal-to-noise (S/N) ratio up to 20 dB is demonstrated. Tomography experiments were conducted on building materials showing 3-D imaging with theoretically limited longitudinal and transverse resolutions of 5 and 20 mm, respectively, thus opening the door to civil infrastructure monitoring applications.

We report the first THz emission at 280 GHz excited by a Continuous-Wave Dual-Frequency Vertical-External-Cavity Semiconductor Laser emitting at 1064 nm and using a long carrier-lifetime plasmonic-based photomixer. These encouraging results pave the way toward coherent, tunable, compact, powerful, and low-cost terahertz sources working at room temperature.

International audience; We investigate the use of an InP-based double-heterojunction bipolar transistor as a detector for wireless communications around 300~GHz. The sensitivity of the detector, along with its complex output impedance are characterized for a transistor (un)coupled to a log-spiral antenna, at different biases. A real-time uncompressed high-definition video signal is successfully transmitted at 1.5 Gbps in a heterodyne configuration.

International audience; Increasing the data rates of wireless communicationsrequires to increase the carrier frequency to hundred’s of GHz,thus emitters and detectors that can operate at high data ratesare required. We review a possible source and receiver that canbeen used for THz communications. We present a photonic-basedemitter that provides a coherent THz signal in the 50–700+ GHz,based on the excitation of a uni-travelling carrier photodiodeby a two-frequency semiconductor laser that operates on twotransverse modes. The performance of THz detectors basedon GaAs field-effect transistors are also presented, along withcommunications using direct amplitude modulation at 8.3 Gbpsand an heterodyne communication at 1.5 Gbps.

This paper presents the design of an imaging FMCW (Frequency-Modulated Continuous-Wave) radar system operating in the frequency band 75–110 GHz. The 35-GHz bandwidth offers a theoretical longitudinal resolution of 4.2 mm to detect inner defects. The study concerns defects such as holes and cracks. True 3D imaging is obtained by scanning transversally the material under test, the transverse resolution being limited by the beam waist.

Compact and fast detectors, for imaging and wireless communication applications, require efficient rectification of electromagnetic radiation with frequencies approaching 1 THz and modulation bandwidth up to a few tens of GHz. This can be obtained only by using a mature technology allowing monolithic integration of detectors with low-noise amplifiers. One of the best candidates is indium phosphide bipolar transistor (InP HBT) technology. In this work, we report on room temperature high sensitivity terahertz detection by InP double-heterojunction bipolar transistors (DHBTs) operating in a large frequency range (0.25–3.1 THz). The performances of the DHBTs as terahertz sensors for communications were evaluated showing the modulation bandwidth of investigated DHBTs close to 10 GHz.

In this work we investigate the back-lobe reduction of a sectoral antenna. The antenna is fed by a coaxial cable and presents a good impedance matching in the 2.4–2.48 GHz WI-FI band. It has 9 dBi of gain in the main lobe direction and most importantly, presents a very high front to back ratio (over 40 dB). The antenna is composed of a printed folded dipole coupled with a metallic plate placed behind the driven element at a distance of tenth the wavelength. The system is low cost and easy to manufacture.

This paper presents a technique to determine the refractive index of materials based on the Frequency-Modulated Continuous-Wave (FMCW) radar operating at the frequency band 75–110 GHz. The refractive index of a material is one of its physical constants that can characterize it, which makes its determination is of great interest. The 35-GHz bandwidth offers a theoretical resolution of 0.133 for a measurement support depth of 3.2 mm. The proposed study concerns solid and liquid materials state. A better resolution obtained by using a signal processing. This resolution is limited by the bandwidth. The results of materials refractive index experimental measurements demonstrate the performance of the proposed setup and the potential application for fast materials characterization.

Design, manufacturing and measurements results for silicon plasma wave transistors based wireless communication wideband receivers operating at 300 GHz carrier frequency are presented. We show the possibility of Si-CMOS based integrated circuits, in which by: (i) specific physics based plasma wave transistor design allowing impedance matching to the antenna and the amplifier, (ii) engineering the shape of the patch antenna through a stacked resonator approach and (iii) applying bandwidth enhancement strategies to the design of integrated broadband amplifier, we achieve an integrated circuit of the 300 GHz carrier frequency receiver for wireless wideband operation up to/over 10 GHz. This is, to the best of our knowledge, the first demonstration of low cost 130 nm Si-CMOS technology, plasma wave transistors based fast/wideband integrated receiver operating at 300 GHz atmospheric window. These results pave the way towards future large scale (cost effective) silicon technology based terahertz wireless communication receivers.

International audience; The extraction of the equivalent circuit parameters for bipolar transistors is undertaken via high-frequency S-parameter and low-frequency noise measurements. The extraction is exhaustively detailed here for a double purpose. First, it highlights the not-so-justified approximations so often made for the extraction of the extrinsic base-collector capacitance. Second, it emphasizes the similarity of the values obtained for series resistances in both the low-frequency and high-frequency ranges

A fully integrated 0.3 THz antenna-coupled plasma-wave detector with 10 GHz (measured) bandwidth is presented. Fabricated in 130nm CMOS technology, the chip is formed of an E-shaped patch antenna, plasmonic based Field Effect Transistor (FET) detector and a wide bandwidth amplifier employing inductive shunt peaking. The open drain mode of operation of the detector achieves an absolute responsivity of 10 V/W with a minimum signal to noise ratio (SNR) of 40 dB over the entire bandwidth. With a drain current of 0.24 mA, the responsivity increases by 10X with a decrease in bandwidth to 3 GHz. The detector is also characterized without the on chip amplifier for imaging applications and shows a measured absolute responsivity of 150 V/W for a drain current of 5 μA at 0.3 THz.

A fully integrated THz detection system consisting of an on chip dipole antenna, a plasmonic detector, and a wide band amplifier in 130 nm AlGaAs/InGaAs pHEMT technology is reported. The fabricated chip achieves an absolute responsivity of 3 V/W, while maintaining a 50 dB signal to noise ratio (SNR) over a modulation bandwidth of 8.5 GHz at ∼ 0.3 THz.

We report on terahertz wireless communication experiments at 0.3 THz using 250-nm gate-length GaAs/AlGaAs field-effect transistor (FET) as a detector and unitraveling-carrier photodiode as a source. The physical mechanism of the detection process is terahertz wave rectification on nonlinearities related to overdamped plasma oscillations in the transistor channel. We present an experimental study of rectification bandwidth and show for the first time that room-temperature direct detection with modulation bandwidth of up to 8 GHz can be achieved, thus showing that nanometer-sized FETs can be used as valuable detectors in all-solid-state terahertz wireless communication systems.

The detection of high data-rate wireless communication using a terahertz- frequency carrier, and a GaAs transistor as a detector, is reported. Communications are investigated around 0.2 and 0.3087 THz. For the first time, an error-free transmission at data rates up to 8.2 Gbit/s is demonstrated, using a carrier frequency of 0.3087 THz.

We report on the first error-free terahertz (THz) wireless communication at 0.310 THz for data rates up to 8.2 Gbps using a 18-GHz-bandwidth GaAs/AlGaAs field-effect transistor as a detector. This result demonstrates that low-cost commercially-available plasma-wave transistors whose cut-off frequency is far below THz frequencies can be employed in THz communication. Wireless communication over 50 cm is presented at 1.4 Gbps using a uni-travelling-carrier photodiode as a source. Transistor integration is detailed, as it is essential to avoid any deleterious signals that would prevent successful communication. We observed an improvement of the bit error rate with increasing input THz power, followed by a degradation at high input power. Such a degradation appears at lower powers if the photodiode bias is smaller. Higher-datarate communication is demonstrated using a frequency-multiplied source thanks to higher output power. Bit-error-rate-measurements at data rates up to 10 Gbps are performed for different input THz powers. As expected, bit error rates degrade as data rate increases. However, degraded communication is observed at some specific data rates. This effect is probably due to deleterious cavity effects and/or impedance mismatches. Using such a system, real-time uncompressed high-definition video signal is successfully and robustly transmitted.

The issue of this paper concerns 0.35 μm Bi-CMOS double polysilicon bipolar transistors and 0.5 μm Bi-CMOS simple polysilicon bipolar transistors. Low-frequency noise measurements are performed. Noise spectral densities are analysed versus bias and geometry. From these noise measurements, base and emitter series resistances are extracted. A comparison of both technologies is done. Though double polysilicon transistors have a more complex structure than the simple polysilicon ones, they exhibit similar or even better performances. Indeed, DC characteristics and noise levels are equivalent for both technologies. Double polysilicon transistors exhibit a reduction of the base resistance and a significant improvement of the transition frequency f T is obtained.

Transistors are possible THz detectors using rectification in the channel that can be applied for detection of high data-rate wireless communications, based on THz-frequency carrier. For the first time, we present the transmission of pseudo-random bit sequence at 0.2 THz using a commercial GaAs transistor and demonstrate open eye patterns up to 0.250 Gbps.

The possibility to develop a novel technique that might provide a direct measurement of the impedance field using an electromagnetic near-field equipment is investigated. Preliminary experiments have been performed on silicon substrate using a coaxial near-field probe. The first results show a signal transmission via an air coupling and not a propagation inside the device. Some critical problems have been identified to improve the test-bench.

We present experimental study of terahertz detection by asymmetric dual-grating gate HEMT structures. The separate contributions of the gate leakage current and the loading effect to the rectification signal in the sub-threshold region was investigated versus temperature and frequency range.

International audience; We report on terahertz wireless communication experiments at 0.2 THz, using a commercial GaAs field-effect-transistor as detector. For the first time, we will present the transmission of pseudo-random bit sequence at 0.2 THz using this commercial transistor and demonstrate open eye-patterns up to 1.5 Gbps. This transistor is integrated into a machined horn, so that its sensitivity is improved to 1 V/W, and has a 10 GHz cut-off frequency. We will discuss signal-to-noise ratio in the terahertz wireless data transmission.

In this paper, we report on the detection of terahertz heterodyne mixing in GaAs ultra-low noise Pseudomorphic High Electron Mobility Transistors (pHEMT) at room temperature. For this purpose, we used two 0.300 THz sources in order to generate mixing up to 45 GHz.

We report on Terahertz wireless communications and fast imaging experiments at 300 GHz, using nanometer-sized transistors as detectors. The physical mechanism of the detection is related to the overdamped plasma waves in the transistor channel.

International audience; A versatile cw measurement setup for terahertz near-field reflectometry is proposed. Propagation, coupling, and focusing of wire guided modes are used to achieve a λ/33 resolution while imaging a metal corner deposited on glass. The setup is source and detector independent owing to wave coupling and decoupling with differential phase plates.

Abstruct- We investigate in this work the perlbrmance of two conligurations of room temperature bolometers dedicated to THz applications. Fabrication processes, noise level, sensitivity and resolution characterizations ùre presented. Results emphasize the cllicicncy of the proposed approach.

By means of a numerical hydrodynamic model, we investigate the influence of collective plasma modes in a field-effect transistor channel under different excitation and biasing conditions. Firstly, we study the case of a device externally-excited by a harmonic optical beating or an electronic excitation and current-driven operation at the drain. The harmonic and continuous responses of the drain-source bias show sharp resonances related to the first odd plasma modes, whose frequencies and amplitudes can be modified by playing on the drain bias. Secondly, we calculate the spectral density of drain voltage fluctuations in the absence of external excitations by using the generalized impedance-field method. Also the noise spectrum exhibits peaks corresponding to the excitation by the background noise of odd plasma modes.

International audience; We describe a near-field experiment using a Y splitter supporting cw THz Sommerfeld wire modes coupled and de-coupled with differential phase plates. Owing to a taper up to similar to 50 mu m of one of the Y ends, a near-field imaging resolution of similar to 90 mu m is demonstrated in agreement with calculations.

We propose a method for the heterodyne detection of terahertz (THz) signals. The nonlinear element is constituted by the channel of an High Electron Mobility Transistor (HEMT), while the optical beating of two laser beams exciting plasma waves in the transistor channel plays the role of the THz local oscillator. We numerically show, through an hydrodynamic modelling, the efficiency of such a mixer.

International audience; We present a theoretical model of metallic absorbers for electromagnetic waves. This model allows the design of any kind of structured absorber metallic films and dielectrics. The absorption theory of metallic structures was studied with aim of a room temperature bolometer design. To validate the theoretical concept, grids of size much larger than the wavelength were built and measured. Transmission, reflection and absorption results obtained at 0.3 THz are in good agreement with the model. Grids of size smaller than the wavelength were built and measured at RF frequencies. Results show the tremendous influence of grid size over wavelength in term of equivalent resistivity and absorption.

International audience; This paper addresses a passive system capable of converting a linearly polarized THz beam into a radially polarized one. This is obtained by extending to THz frequencies and waveguides an already proven concept based on mode selection in optical fibers. The approach is validated at 0.1 THz owing to the realization of a prototype involving a circular waveguide and two tapers that exhibits a radially polarized beam at its output. By a simple homothetic size reduction, the system can be easily adapted to higher THz frequencies.

International audience; We propose here a nondestructive electromagnetic (EM) near-field test bench for both EM compatibility and susceptibility of circuits. This setup permits both the collection of the near field and injection without contact of a disturbing EM field, all through a probe. Exhaustive characterizations of probes are undertaken via simulations and experiments. According to their design, they are supposedly linked more to the electric or the magnetic field. Simulations of their EM behavior are undergone to fix their optimal geometries, leading to the best measurement performances. It is shown by both the simulations and the S-parameter measurements that their presence does not interfere with the electric behavior of the device under test. Then, logic circuits are characterized from the EM point of view, with the help of this test bench. Circuits are placed on three different printed boards: one double-sided low-frequency board without a ground plane and two single-sided boards with a ground plane and a design that is more or less optimized. EM near-field mappings highlight the strong field areas of the circuits. The need for a ground plane is highlighted. Field patterns on the traces are linked with those observed on microstrip lines. Then, an EM aggression is injected over a supposed sensitive zone of the circuit. Whichever printed board is considered, a parasitic signal superimposes itself on the output signal of the gates. Deepened studies are undergone to exhaustively explain the phenomena observed

International audience; A new THz radial polarizer suitable to convert the usual linearly polarized signal from a millimeter or sub-millimeter source is described. It is based on mode-filtering within a cylindrical waveguide combined with two tapers and a discontinuous phase element. An experimental demonstration is given at ap 100 GHz and transposition to higher THz frequencies by scaling is straightforward.

The low-frequency noise characteristics of double self-aligned InP/InGaAs and two types of Si/SiGe heterojunction bipolar transistors (HBTs) were investigated. Spectral analysis shows no striking differences; the spectra are composed of a 1/f component and the white noise is always reached at low biases. A general trend for all the transistors was the presence of Lorentzian component(s) for the smallest devices. The voltage coherence function was always unity for SiGe transistors; and for the first time, it was found to be close to zero for InP devices. Concerning the 1/f noise level, both types of transistors have approximately a quadratic dependence on base current bias and an inverse dependence on the emitter area. Thus, a comparison of the 1/f noise level has been made using the K/sub b/ parameter, and values around 10/sup -9/ /spl mu/m/sup 2/ for SiGe HBTs and around 10/sup -8/ /spl mu/m/sup 2/ for InP HBTs were found. These results are of the same order of magnitude as the best published ones. The low-frequency noise results suggest that excess noise sources are mainly located at the intrinsic emitter-base junction for the two types of SiGe devices, and, for the InP HBTs, a correlated noise source is located at the emitter periphery. To compare different devices and technologies, f/sub c//f/sub T/ was studied as a function of collector current density and for some HBT technologies f/sub c//f/sub T//spl prop/J/sub c/ (f/sub c/ is corner frequency at which the white noise and 1/f noise are equal and f/sub T/ is the unity current gain frequency). The effects of different processing conditions, designs and temperature were also investigated and discussed.

International audience; The 1/f noise of double InP/InGaAs heterojunction bipolar transistors is measured and analyzed. Standard mesa transistors, transistors with an air-bridge-connected base and hexagonal shaped transistors conceived for digital circuits are studied. These differences in the technology will have an influence on the origin of the noise sources. Regarding noise analysis, the base and collector internal current noise sources ib and ic are assumed to be correlated for all devices. This is highlighted by the voltage noise correlation function between the input and the output of the devices presenting an unusual behavior versus bias and geometry. The collector current noise source is divided into a correlated and uncorrelated part with base current. These parts give rise to spectral densities Sc and Snc. They are shown to have distinct origins for the different types of transistor geometry.

Low-frequency noise results obtained for III-V pseudomorphic high electron mobility transistors (PHEMTs) and heterojunction bipolar transistors (HBTs) are reviewed. The experimental noise set-up is presented and the equivalent circuits of devices including noise sources are established. Excess low-frequency noise comprises 1/f and Lorentzian-type components. An overview of gate and drain low-frequency noise of heterostructure field-effect transistors is provided in the paper. Different activation energy values attributed to traps are also reported. The authors concentrate on the 1/f noise of GaAs-based PHEMTs. The results are analysed with the help of an equivalent circuit deduced from a study of the conduction. The fundamental 1/f noise sources are analysed and modelled according to the different bias range. With regard to HBTs, results for AlGaAs/GaAs, GaInP/GaAs and InP/InGaAs are used for comparison. The effect of the DX centre on the different materials is investigated. The analysis against the bias of the 1/f noise level of the current spectral density referred to the input Si/sub n/ gives information on the origin of the noise. The experimental bias dependencies of Si/sub n/ are compared to those available in the literature and are discussed. The importance of electrical passivation for the improvement of noise is investigated. An analysis of noise against emitter area and emitter perimeter is undertaken for an accurate location of noise sources.

International audience; Low-frequency noise measurements are performed in order to characterize quasi-self-aligned polysilicon bipolar transistors. After a theoretical analysis we present a study of the influence of the base source resistance on the correlation between the input and the output noise sources of the transistors. We observe that a partial correlation between the input and the output voltage noise sources appears and varies with the source resistance, the bias and the emitter size of the transistors. As a consequence we demonstrate the influence of the fluctuations of the collector current. Taking into account these results, we propose different extraction methods for the emitter and base series resistances. To confirm and extend these measurements, high-frequency results are also presented.

In this paper, we have studied the 1/f low frequency noise of self-aligned and non self-aligned InP/InGaAs heterojunction bipolar transistors (HBTs). The total noise of transistor is modeled by two current noise sources. The evolution with geometry, technological process and bias, of the current spectral densities referred to the input and output of the devices, permit us to locate the noise sources. Noise is mainly generated in the intrinsic transistor, and an extra noise perimetric source has been identified for the self-aligned transistors at the emitter periphery.

International audience; A passive probe antenna for cw near-field microscopy at millimeter and submillimeter wavelengths is defined. It is based on the coupling between a free-space linearly polarized propagating beam to a wire mode. This is obtained efficiently owing to a discontinuous phase plate. This passive “optical” structure allows either the generation of a subwavelength confinement of the longitudinal electric field (polarized along the wire antenna) or, due to reciprocity, the collection of the longitudinal component of the electric field (along the wire antenna) with subwavelength resolution. The emission and collection properties of the proposed antenna have been demonstrated experimentally using a preliminary realization designed to work at 0.1 THz. Experimental results are well supported by calculations

Robusta est un satellite de norme cubesat entierement concu et realise par les etudiants issus de formations diverses de l'Universite Montpellier 2 : IUT , ecole d'ingenieur, licence et master EEA. C'est un projet en partenariat avec le CNES et soutenu par d'autres grands industriels du secteur electronique. Le satellite a pour mission scientifique de mesurer la degradation sous l'effet de rayonnements ionisants de composants electroniques bases sur des transistors bipolaires. Ces degradations seront par la suite comparees a celles obtenues par des methodes de test au sol. Ce projet est une experience de nature industrielle qui reste de par sa duree, son cout et sa technicite a l'echelle des etudiants. Robusta, en tant que systeme, permet aux etudiants de niveau bac + 2 a bac + 8 de developper des prototypes techniques pointus et d'ameliorer leur sens de la communication tout en decouvrant le monde du spatial.