This paper presents the development and characterization of a wideband noise source, involving Commercial Off-The-Shelf components. The noise source relies on avalanche noise generation by driving the base-emitter junction of a packaged Si–Ge Heterojunction Bipolar Transistor into reverse breakdown. The paper discusses the noise source operation principle and its extensive characterization in both mm-Wave K band, as well as in C and X bands. Two prototypes were implemented without including output impedance matching, such as to preserve the wideband capabilities of the noise source. Performances were validated in terms of output Excess Noise Ratio (ENR), values reaching 10.8 dB were obtained for the K band at 6.71 mA breakdown current, in a 24–32 GHz bandwidth and $21-102^{\circ}\mathrm{C}$ device temperature excursion. A calibration model is also provided, which fits ENR fluctuations with an average error under 0.05 dB, when considering the maximum current and temperature excursions, as compared with 0.8 dB ENR drift reported for the non-calibrated source. The C and X band validation in 4–6 and 10–12 GHz frequency ranges highlights ENR reaching 25.6 and 22.6 dB, respectively, at 6.9 mA bias current.

Antenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feedhorns and QCL devices for future space-borne ultra-high-frequency Earth-observing heterodyne radiometers.

The design of a high-stability radiometer is presented in this paper. It is used to characterize the stability of a microwave active cold load at L-band. The two-load radiometer takes advantage of a noise injection technique to improve its sensitivity. A temperature-stabilized enclosure is used to minimize gain and noise temperature fluctuations of the receiver. The radiometer sensitivity is 0.031 K and the gain fluctuations are less than 0.005 dB during 1 day. The total gain and the receiver noise temperature of the radiometer exhibit very small variations (<0.03 dB and 1 K, respectively) on the long term.

La directive européenne 2006/25/CE, relative à l’exposition des travailleurs auxrayonnements optiques, prévoit l’évaluation des risques au poste de travail par la mesureet/ou le calcul. L’objectif de cette étude était de permettre à des organismes de contrôlede mettre en œuvre la directive en mettant à leur disposition une méthodologie simpled’évaluation des risques in situ, compatible avec leurs moyens. Cette étude a doncconsisté à faire un état du marché, acquérir quelques appareils de mesure de coûtraisonnable (radiomètres et spectroradiomètres) et ensuite évaluer leurs performances. Lesrésultats des mesures effectuées sur 5 lampes de spectres divers, à l’aide de cesappareils, ont été comparés à ceux donnés par un spectroradiomètre de laboratoire priscomme référence. De cette étude il est ressorti qu’aucun d’eux ne permet de mesurer avecune précision acceptable le rayonnement émis par des sources de différentes natures surl’ensemble du domaine spectral compris entre 180 et 3 000 nm. Les radiomètres ne sont pasadaptés à la mesure de sources émettant sur un domaine spectral étroit. Lesspectroradiomètres à simple monochromateur ou à barrettes CCD linéaires présentent quant àeux des erreurs importantes attribuables à la lumière parasite (stray light). Cependant,l’approche d’une méthode de correction de cette lumière parasite a montré qu’il étaitpossible d’améliorer la précision de ces appareils.