A lattice realization for 2-D separable-denominator digital filters

New properties useful in connection with 1-D and 2-D lattice realizations are developed. These properties enable one to represent given, complicated 2-D separable-denominator digital filters in terms of simpler, more elemental building blocks which consist of two 1-D lattice realizations having dynamics in different directions and connected in a cascade form. The matrix-relationship between a 2-D discrete Schwarz form and a controller-observer canonical form is also derived. A notable property of the proposed 2-D lattice realization is that the impulse response energy of a 2-D separable-denominator digital filter can be readily obtained from the reflection coefficients and input/output tapped coefficients of the realization.This work was supported by the National Science Council of the Republic of China under Grant NSC79-0402-E0006-02, the US Army Research Office under Grant DAAL-03-91-G0106, and the NASA-Johnson Space Center under Grant NAG-9-380.     

Photoconductivity effects in CuInS2, CuInSe2 and CuInTe2 thin films

Photoconductivity response spectra for CuInS₂, CuInSe₂ and CuInTe₂ thin films are reported. The temperature dependences of the spectra are utilized to determine the bandgap energies as functions of temperature. Photoconductive response times are measured for these I–III–VI₂ ternary semiconductors and are discussed in terms of deposition parameters and post-deposition treatments. The photoconductive decay times are in the range 10^-3 – 10¹ ms.     

An algebraic method for steady-state responses of linear state equations with periodic input

An algebraic method is presented to evaluate periodic conditions for the steady-state responses of state equations with a continuous or piecewise-continuous periodic input. As a result, the analytical and experimental steady-state responses to periodic excitation may be directly obtained.     

Passive coupling of InGaAsP/InP laser array and singlemode fibres using silicon waferboard

Passive alignment of semiconductor lasers and singlemode fibres has been achieved for the first time using a micro-machined silicon substrate. Mechanical alignment features fabricated on the substrate surface were used to align the active regions of an InGaAsP/InP laser array to four singlemode fibres held in V grooves. Optical coupling efficiencies have been achieved that are comparable to values obtained using the conventional technique of active fibre manipulation. The approach, called silicon waferboard, offers the potential for low-cost optoelectronic device packaging as well as a means for dense hybrid integration of optoelectronic, electronic and optical components required for multifibre, multichip systems.<>     

A polarization-independent and contrast-ratio-enhancing module for all-optical wavelength shifting using SOA's

We demonstrate a polarization-independent and contrast-ratio-enhancing all-optical wavelength shifting module using polarization-dependent SOA's. When comparing our robust module to a single polarization-dependent SOA wavelength shifter, we reduce the polarization dependence from 3.5-0.5 dB and the contrast-ratio-induced power penalty from 5-1.5 dB when upshifting over 19 nm at 1 Gb/s.     

Transfer function fitting from experimental frequency-response data

A simple method is proposed that will fit the coefficients of a transfer function from the real and imaginary parts of experimental frequency-response data. An approximate logarithmic amplitude-frequency plot is used to formulate an irrational transfer function which then estimates the interpolation data and the degree of the final transfer function. The present method is applicable to either minimum or non-minimum phase system identification.