Abstract-In this letter, we report on the design, simulation and implementation of an active negative group delay circuit that operates at 1 GHz with a group delay and a gain, respectively, around 2 ns and 2 dB. Analytical formulas are proposed to demonstrate that the adopted topology is able to simultaneously achieve negative group delay (NGD) and gain while fulfilling active device constraints. The theoretical and simulated results are both validated by frequency measurements of a two-stage active microwave circuit.Index Terms-Active devices, negative group delay (NGD).
Optical imaging, including infrared imaging, generally has many important applications, both civilian and military. In recent years, technological advances have made multi- and hyperspectral imaging a viable technology in many demanding military application areas. The aim of the CEPA JP 8.10 program has been to evaluate the potential benefit of spectral imaging techniques in tactical military applications. This unclassified executive summary describes the activities in the program and outlines some of the results. More specific results are given in classified reports and presentations. The JP 8.10 program started in March 2002 and ended in February 2005. The participating nations were France, Germany, Italy, Netherlands, Norway, Sweden and United-Kingdom, each with a contribution of 2 man-years per year. Essential objectives of the program were to: 1) analyze the available spectral information in the optronic landscape from visible to infrared; 2) analyze the operational utility of multi- and hyperspectral imaging for detection, recognition and identification of targets, including low-signature targets; 3) identify applications where spectral imaging can provide a strong gain in performance; 4) propose technical recommendations of future spectral imaging systems and critical components. Finally, a stated objective of the JP 8.10 program is to "ensure the proper link with the image processing community". The presentation is organized as follows. In a first step, the two trials (Pirrene and Kvarn) are presented including a summary of the acquired optical properties of the different landscape materials and of the spectral images. Then, a phenomenology study is conducted analyzing the spectral behavior of the optical properties, understanding the signal at the sensor and, by processing spectroradiometric measurements evaluating the potential to discriminate spectral signatures. Cameo-Sim simulation software is presented including first validation results and the generation of spectral synthetic images. Results obtained on measured and synthetic images are shown and discussed with reference to two main classes of image processing tasks: anomaly detection and signature based target detection. Furthermore, preliminary works on band selection are also presented which aim to optimize the spectral configuration of an image sensor. Finally, the main conclusions of the WEAG program CEPA JP8.10 are give
We analyze a self-assembled quantum-dot laser where lasing levels are pumped purely through Auger carrier capture. Analysis shows that Auger carrier capture and Auger transport of carriers between quantum dots can provide effective laser pumping and fast modulation at least up to 10 GHz. Auger carrier transport decreases spectral hole burning, which together with dot-barrier hole burning can damp relaxation oscillations.
Physically based rendering needs numerical models from real measurements, or analytical models from material definitions, of the Bidirectional Reflectance Distribution Function (BRDF
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