Dye laser pumped Pr3+-doped fiber lasers: basicparameter investigation, CW operation, and Q-switched operation

An investigation of a Pr³⁺-doped Al₂O₃ -SiO₂ glass fiber is described. The basic material parameters like fluorescence lifetime and stimulated emission cross section, measured around 1048 nm, where the fiber has a strong emission band, are discussed. The pump source was a Rh6G dye laser at 590 nm. Continuous wave (CW,) operation with a slope efficiency of 26% and a pump threshold of 1.2 mW was obtained. The Q-switched operation, yielding a repetition rate up to 10 kHz with a maximum peak power of 30 W and a minimum pulsewidth of 25 ns, is described     

A floating-gate analog memory device for neural networks

A floating-gate MOSFET device that can be used as a precision analog memory for neural network LSIs is described. This device has two floating gates. One is a charge-injection gate with a Fowler-Nordheim tunnel junction, and the other is a charge-storage gate that operates as a MOSFET floating gate. The gates are connected by high resistance, and the charge-injection gate is small so that its capacitance is much less than that of the charge-storage gate. By applying control pulses to the charge-injection gate, it is possible to charge and discharge the MOSFET floating gate in order to modify the MOSFET current with high resolution over 10 b. The charge injection can be carried out without disturbing the MOSFET output current with high voltage control pulses. This device is useful for on-chip learning in analog neural network LSIs     

On the application of the Wiener-Hopf technique to electrostaticfield problems in interdigital transducers

The Wiener-Hopf technique is used to compute the electrostatic field distribution in an interdigital transducer at the plane interface between two dielectric media sandwiched between two grounded metallic plates, with two grounded semi-infinite neighboring plates at the interface on each side of the transducer. To this end, the associated Green's function, which already satisfies the boundary conditions at all the grounded plates, is computed. The Green's function is used to derive the elements of the charge-potential-interrelation matrix for various basis and testing functions for a method-of-moments application. Examples demonstrate that the method has considerable advantages with respect to accuracy and computer-memory requirements     

A simple scheme for slot reuse without latency for a dual busconfiguration

A simple scheme for slot reuse without latency for the dual bus configuration is studied. The scheme relies on information read in the previous slot and will be referred to as previous slot information (PSI) slot reuse. The scheme requires a minimal addition to the station hardware and its reliability is high. The efficiency of PSI is checked over a wide range of parameters and is found to be almost as good as destination release. The scheme can be implemented with or without the addition of erasure nodes     

252 km repeaterless 10 Gb/s transmission demonstration

Using a practical erbium-doped fiber postamplifier, a dual-stage optical preamplifier, a lithium niobate Mach-Zehnder external modulator and a dispersion-shifted line fiber, IM/DD repeaterless transmission over 252 km at 10 Gb/s with a wavelength-independent receiver sensitivity in the 1530-1565-nm range is achieved     

Bi-2223/Ag-sheathed tape processing studies

The production of high critical current density J_c Bi-2223/Ag sheathed conductors is a complex process involving interactions among many different parameters. The effects of three factors: 1) powder production path, 2) the first sinter temperature, and 3) the subsequent sinter temperatures were investigated. Statistical methods were used to design the experiment and interpret the results. Transport J_c was the main response for the analysis, but microstructural results were also used to assess the physical basis for the differences in performance. The powder variable had the largest main effect with only very weak main effects for the other factors.     

Performance analysis of linear MIMO equalizers for multitone DS/SS systems in multipath channels

In [11] the combination of multitone modulation with direct sequence spectrum spreading has been introduced. The performance of a correlation receiver has been evaluated for a multipath channel. In [12] the analysis has been extended to the presence of a multiple access interference. In the present paper we analyze the equalization problem of such a system for a single user scenario. In order to understand the potential of the system we first investigate the steady-state behavior of the MIMO equalizer for an MMSE design. The investigation is carried out for an equalizer following a receiver made of a bank of filters matched to both the symbol shape and the channel, which is a two-path channel. Assuming BPSK symbols an exact expression of the bit error probability before and after equalization is obtained in the form of an integral by means of the characteristic function method. Next adaptive LMS and RLS structures are proposed. The performance of the RLS algorithm is demonstrated.Part of this work has been presented at ICC '95, Seattle, June 1995.This author would like to thank the Belgian NSF for its financial support.This author is a Research assistant of FRIA.     

Design of efficient M-band coders with linear-phase andperfect-reconstruction properties

This paper presents a new design technique for obtaining M-band orthogonal coders where M=2ⁱ. The structures obtained using the proposed technique have the perfect reconstruction property. Furthermore, all filters that constitute the subband coder are linear-phase FIR-type filters. In contrast with conventional design techniques that attempt to find a unitary alias-component matrix in the frequency domain, we carry out the design in the time domain, based on time-domain orthonormality constraints that the filters must satisfy. The M-band design problem is reduced to the problem of finding a suitable lowpass filter h₀(n). Once a suitable lowpass filter is found, the remaining (M-1) filters of the coder are obtained through the use of shuffling operators on the lowpass filter. This approach leads to a set of filters that use the same numerical coefficient values in different shift positions, allowing very efficient numerical implementation of the subband coder. In addition, by imposing further constraints on the lowpass branch impulse response h₀(n), we are able to construct continuous bases of M-channel wavelets with good regularity properties. Design examples are presented for four-, eight-, and 16-band coders, along with examples of continuous wavelet bases that they generate     

M-ary PSK burst mode transmission in multipath channels

A novel and efficient burst mode transmission method is presented. M-ary PSK bursts were transmitted through an underwater acoustic channel exhibiting long time spread multipath behaviour, and a DPSK detector was used at the receiver. The phase constellation plots obtained show that up to eight phases can be resolved without evidence of errors in the received data     

A low cost and low power silicon npn bipolar process with NMOS transistors (ADRF) for RF and microwave applications

A silicon bipolar process for RF and microwave applications, which features 25-GHz double-polysilicon self-aligned npn bipolar transistors with 5.5-V BV/sub CEO/, optional 0.7-/spl mu/m (L/sub eff/) NMOS transistors with p/sup +/ polysilicon gates for switch applications, lateral pnp transistors, high and low valued resistors, p/sup +/ polysilicon-to-n/sup +/ plug capacitors, and inductors is described. The npn transistors utilize nitride-oxide composite spacers formed using sacrificial TEOS spacers, a process which is simpler than the previously reported composite spacer processes. Use of the composite spacer structure virtually eliminates problems relating to the extrinsic-intrinsic base link-up and reduces plasma induced damage associated with the conventional spacer process. Microwave and RF capabilities of the process up to several GHz are demonstrated by fabricating and characterizing RF amplifiers, low noise amplifiers, and RF switches.<>