Nano-Watt silicon-on-sapphire ADC using 2C-1C capacitor chain

An analogue-to-digital converter (ADC) in a 0.5 /spl mu/m silicon-on-sapphire CMOS technology is reported. This innovative ADC uses a 2C-1C capacitor chain and a switched capacitor comparator. The ADC is capable of sampling at 409 kS/s, consuming 900 nW at 1.1 V power supply and 1.35 /spl mu/W at 1.5 V. It uses an active area of 300/spl times/700 /spl mu/m/sup 2/ and 640/spl times/1070 /spl mu/m/sup 2/ with pads.     

Noise limit in heterodyne Interferometer demodulator for FBG-based sensors

This paper reports the results of a recent investigation on the noise-limited performance in heterodyne interferometric demodulation systems for fiber Bragg grating strain sensors. Theoretical and simulation results are presented and compared with experimental results.     

A new PWM controller with one-cycle response

This paper proposes a new nonlinear control technique that has one-cycle response, does not need a resetable integrator in the control path, and has nearly constant switching frequency. It obtains one-cycle response by forcing the error between the switched variable and the control reference to zero each cycle, while the on and off pulses of the controller are adjusted each cycle to ensure near constant switching frequency. The small switching frequency variation due to changes in the reference signal and supply voltage and delays in the circuit are quantified. Using double-edge modulation, the switching frequency variation is further reduced, thus, the associated signal distortion is minimized. An experimental 0-20 kHz bandwidth 95 W RMS power audio amplifier using the control method demonstrates the applicability of this control technique for high-fidelity audio applications. The amplifier has a power supply ripple rejection (PSRR) of 63 dB at 120 Hz. Additionally, the total harmonic distortion plus noise (THD+N) is less than 0.07% measured with a power supply ripple of 15%     

Temperature dependence of lasing characteristics forlong-wavelength (1.3-μm) GaAs-based quantum-dot lasers

Data are presented on the temperature dependence of 1.3-μm wavelength quantum-dot (QD) lasers. A low-threshold current density of 90 A/cm² is achieved at room temperature using high reflectivity coatings. Despite the low-threshold current density, lasing at the higher temperatures is limited by nonradiative recombination with a rapid increase in threshold current occurring above ~225 K. Our results suggest that very low threshold current density (⩽20 A/cm ²) can be achieved at room temperature from 1.3-μm QD lasers, once nonradiative recombination is eliminated     

A comparison of the temperature dependences of photoeffect quantum efficiencies in GaAs p-n structures and Schottky diodes

A comparison is made of how the quantum efficiencies for photoelectric conversion in p-n-and m-s-structures based on GaAs depend on temperature. For photon energies less than or the same order as the width of the band gap, the temperature dependences of the p-n-and m-s-structures are similar. In the range of photon energies larger than the width of the band gap, the quantum efficiency of p-n-structures is temperature independent, whereas the quantum efficiency of m-s-structures exhibits a strong temperature dependence. A qualitative explanation of this phenomenon is given. Fiz. Tekh. Poluprovodn. 33, 876–879 (July 1999)     

Optically active layers of silicon doped with erbium during sublimation molecular-beam epitaxy

A study is made of the electrical, optical, and structural properties of Si:Er layers produced by sublimation molecular-beam epitaxy. The Er and O contents in the layers, grown at 400–600°C, were as high as 5×10¹⁸ and 4×10¹⁹ cm⁻³, respectively. The electron concentration at 300 K was ∼10% of the total erbium concentration and the electron mobility was as high as 550 cm²/(V·s). Intense photoluminescence at 1.537 μm was observed from all the structures up to 100–140 K. The structure of the optically active centers associated with Er depended on the conditions under which the layers were grown. Fiz. Tekh. Poluprovodn. 33, 156–160 (February 1999)     

Metrics and Criteria for Quality Assessment of Testable Hw/Sw Systems Architectures

The purpose of this paper is to present a novel methodology for assessing the quality of architecture solutions of hw/sw systems, with particular emphasis on testability. Criteria and metrics for quality assessment are proposed and used to assist the design team in selecting a best-fitted architecture that satisfies not only functional requirements, but also test requirements. The methodology makes use of object-oriented modeling techniques. Near-optimum clustering of methods and attributes into objects is carried out, in such a way that objects with moderate complexity, low coupling and high functional autonomy, result. The main features of the methodology are ascertained through a case study.     

Tunable wavelength conversion in a semiconductor-fiber ring laser

A tunable wavelength converter is demonstrated using highly nondegenerate four-wave mixing in a semiconductor-fiber ring cavity with no external pump light and low input signal power requirements. This device allows continuous tuning of both pump and converted wavelengths over the semiconductor optical amplifier gain bandwidth. Results for 11.8-nm down- and 6.9-nm up-wavelength conversion with input signal power as low as -10 dBm have been obtained at 1 Gb/s with less than 1.6-dB power penalty     

Incremental learning approach based on vector neural network for emitter identification

To deal with the problem of emitter identification (EID) caused by the measurement uncertainty of emitter feature parameters and to realise the automatic updating of the emitter database, which is usually used as emitter templates in identification processing, a vector neural network based incremental learning (VNNIL) approach for EID is proposed. This method combines the vector neural networks (VNNs) and the ensemble-based incremental learning (Learn++) algorithm. The VNN is adopted to construct a weak classifier and the Learn++ is used to generate ensembles of the weak classifiers. Considering that the VNN can realise the non-linear mapping between the interval-value input data and the interval-value output emitter types, and that the Learn++ can update the emitter database automatically, the VNNIL treats the two mentioned problems above as a single one and realises EID and parameters updating at the same time. A number of simulations are presented to demonstrate the identification and updating capability of the VNNIL algorithm. As shown in the simulation results, the VNNIL algorithm not only possesses a better learning and identification capability, but also achieves a better noise adaptability.