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Loss-Gain Equalized Reconfigurable Phaser for Dynamic Radio Analog Signal Processing (R-ASP)  [PDF]
Lianfeng Zou,Shulabh Gupta,Christophe Caloz
Physics , 2015,
Abstract: We present a loss-gain equalized reconfigurable phaser for dynamic radio analog signal processing (R-ASP). Such a phaser provides real-time tunable group delay response with all-pass transmission. We propose a lumped loss-gain implementation, where tuning and equalization are mostly easily achieved. A theoretical study derives the transfer function and the fundamental characteristics of the device. The phaser is finally experimentally demonstrated, first using a single loss-gain pair and finally a three cascaded loss-gain pair structure with full reconfigurability , where up-chirp and down-chirp group delays are shown for illustration. It is expected that this phaser will find wide applications in radio analog signal processing (R-ASP) systems requiring dynamic adaptability.
A Flexible Integrated Photonic True Time Delay Phaser for Phased Array Antennas
Amedeo Capozzoli;Claudio Curcio;Giuseppe D'Elia
PIER B , 2012, DOI: 10.2528/PIERB11111105
Abstract: An integrated photonic True Time Delay phaser for phased array, based on an innovative technology, is here presented. The module versatility is showed by presenting more driving strategies matching different antenna features. The phaser insertion loss, the fluctuations of the excitation coefficients corresponding to the various driving configurations and the statistical modeling of the realization defects are also discussed.
Planar Reflective Phaser and Synthesis for Radio Analog Signal Processing (R-ASP)  [PDF]
Lianfeng Zou,Qingfeng Zhang,Christophe Caloz
Physics , 2014,
Abstract: A planar reflective phaser based on an open-ended edge-coupled-line structure is proposed. This phaser is the first reported phaser that combines the benefits of high resolution, inherent to cross-coupled resonator reflective phasers, and of compactness, inherent to planar circuits. A 4-ns swing 4.9-5.5 GHz quadratic phase (linear group delay) 4th-order microstrip phaser is synthesized and experimentally demonstrated. Given its advantages, this phaser may find vast applications in Radio Analog Signal Processing (R-ASP) systems.
Bandwidth-Unlimited, Dispersion-Free Tunable Optical Delay Using a Prism Pair  [PDF]
C. Kim,B. S. Ham
Physics , 2009,
Abstract: We report a nearly perfect bandwidth-unlimited, dispersion-free tunable optical delay system using a prism pair. The observed delay-bandwidth product using a 25-femtosecond light pulse is ~7x104, where the delay time is independent of the signal bandwidth. The present technique breaks from the conventional methods constrained by delay-bandwidth product, nontunability, and delay time dependent optical loss.
A facile and efficient “one-step” synthesis of Auo with tunable size
Thathan Premkumar,Dongsik Kim,Kyungjae Lee,Kurt E Geckeler
Gold Bulletin , 2007, DOI: 10.1007/BF03215606
Abstract: We demonstrated for the first time that nonionic surfactants such as T-80 not only act as stabilizing or protecting agents, but also can act as reducing agents for a facile “one-pot” synthesis of gold nanoparticles in an aqueous medium with tunable size at ambient conditions.
Atomic Clouds as Spectrally-Selective and Tunable Delay Lines for Single Photons from Quantum Dots  [PDF]
Johannes S. Wildmann,Rinaldo Trotta,Javier Martín-Sánchez,Eugenio Zallo,Oliver G. Schmidt,Armando Rastelli
Physics , 2015,
Abstract: We demonstrate a compact, spectrally-selective, and tunable delay line for single photons emitted by quantum dots. This is achieved by fine-tuning the wavelength of the optical transitions of such "artificial atoms" into a spectral window in which a cloud of natural atoms behaves as slow-light medium. By employing the ground-state fine-structure-split exciton confined in an InGaAs/GaAs quantum dot as a source of single photons at different frequencies and the hyperfine-structure-split $D_1$ transition of Cs-vapors as a tunable delay-medium, we achieve a differential delay of up 2.4 ns on a 7.5 cm long path for photons that are only 60 \mu eV (14.5 GHz) apart. To quantitatively explain the experimental data we develop a theoretical model that accounts for both the inhomogeneously broadening of the quantum-dot emission lines and the Doppler-broadening of the atomic lines. The concept we proposed here may be used to implement time-reordering operations aimed at erasing the "which-path" information that deteriorates entangled-photon emission from excitons with finite fine-structure-splitting.
A High-Resolution Transmission-Type (TT) Phaser Based on Reflection-Type (RT) Units for Radio Analog Signal Processing (R-ASP)  [PDF]
Lianfeng Zou,Christophe Caloz
Physics , 2014,
Abstract: A high Radio Analog Signal Processing (R-ASP) resolution transmission-type (TT) phaser based on reflection-type (RT) phaser units is introduced, theoretically studied and experimentally demonstrated. It is first shown that RT phasers inherently exhibit higher R-ASP resolution than their TT counterparts because their group delay swing is proportional to the reflection coefficient associated with a resonator coupling mechanism (admittance inverter), easy to maximize towards unity, rather than to a coupled-line coupling coefficient, typically restricted to values will inferior to unity, as in the RT case. Moreover, a detailed sensitivity analysis reveals that the proposed phaser is simultaneously features high R-ASP resolution and low sensitivity to fabrication tolerance, which makes it an ideal solution for R-ASP. The proposed phaser exhibits a 5 ns group delay swing over a fractional bandwidth of about 50% around 4 GHz.
Postural tremor induced by paint sniffing  [cached]
Gautschi Oliver,Cadosch Dieter,Zellweger Rene
Neurology India , 2007,
Abstract: Volatile substance abuse is the intentional inhalation of volatile solvents, aerosols, gases or nitrates for the purpose of intoxication. This practice is more common among young people, due, in part, to the low cost and ready availability of these inhalants. In this report, we present the case of a 22-year-old male with a seven-year history of chronic paint sniffing. The patient presented with vigorous postural and kinetic tremor in both hands. A neurological examination revealed a bilateral, non-fatiguing geotropic positional nystagmus and a mild ataxia together with dysdiadochokinesis. He also had a mild chronic encephalopathy. Following treatment with clonazepam, the tremors subsided, but were not completely controlled.
Improved IIR Low-Pass Smoothers and Differentiators with Tunable Delay  [PDF]
Hugh L. Kennedy
Mathematics , 2015,
Abstract: Regression analysis using orthogonal polynomials in the time domain is used to derive closed-form expressions for causal and non-causal filters with an infinite impulse response (IIR) and a maximally-flat magnitude and delay response. The phase response of the resulting low-order smoothers and differentiators, with low-pass characteristics, may be tuned to yield the desired delay in the pass band or for zero gain at the Nyquist frequency. The filter response is improved when the shape of the exponential weighting function is modified and discrete associated Laguerre polynomials are used in the analysis. As an illustrative example, the derivative filters are used to generate an optical-flow field and to detect moving ground targets, in real video data collected from an airborne platform with an electro-optic sensor.
Electronically Tunable Wide Band Optical Delay Line Based on InGaAs Quantum Well Microresonators  [PDF]
Yan Zhang,Geoff W. Taylor
Advances in OptoElectronics , 2013, DOI: 10.1155/2013/930369
Abstract: A novel electronically tunable optical delay line based on InGaAs quantum well microresonators is proposed for high frequency RF transmission. The device utilizes the charge-controlled blue shift of the absorption edge in InGaAs quantum wells to change the effective refractive indices of the resonators and couplers, therefore, provides an efficient way to produce variable time delay. A theoretical model based on measurements is used to analyze the device performance. Simulation results for five 3 × 27?μm2 cascaded resonators with bias voltages <0.7?V show a continuous tuning range of 7~68?ps, a ripple delay <1.5?ps, and a useable bandwidth of 39.3?GHz. 1. Introduction Optical delay is a valuable concept for a multitude of microwave and millimeter wave applications. However to be useful, the value of this delay should be controlled electronically, and this has remained a challenging problem for the various implementations. This problem falls under the general classification of slow light which refers to the ability to decrease the group velocity of an optical medium in order to control the delay. Various approaches have been reported such as SOI ring resonators [1], SOI gratings [2], and LPCVD ring resonator [3]. But the most interest has centered on semiconductor waveguides because of the prospect of a high degree of device integration and room temperature operation as described recently [4]. The potential applications lie in the areas of information processing, communications, and the generalized RF area of Microwave Photonics (MWP). However, in all of these areas the intrinsic limitations of slow light have prevented its incorporation in high bit rate applications. All the proposed and reported tunable optical delay lines utilize the thermo-optic effect and, therefore, require high operating voltages and large footprints. For example, in the MWP area, silicon-on-insulator (SOI) microring resonators have been used to achieve full phase tuning over 40?GHz but the implementation employs temperature variations with microheaters to control the resonant frequency of the ring. The thermal response time in the ms range and the associated power dissipation are clearly limitations for the device applications. In this paper, we introduce a new concept for the microresonator which enables direct electrical control of slow light. This is implemented by the field effect control of charge in the input waveguide and the resonator separately, which shifts the absorption edge, resulting in index changes predicted by Kramers-Kronig relations, and provides coupling and
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