A review is presented of models for the depolarization, caused by scattering from raindrops and ice crystals, that limits the performance of dual-polarized satellite communication systems at frequencies above 10 GHz. The physical mechanisms of depolarization as well as theoretical formulations and empirical data are examined. Three theoretical models, the transmission, attenuation-derived, and scaling models, are described and their relative merits are considered.

A review of depolarization modeling for earth-space radio paths at frequencies above 10 GHz

Continuous-wave (CW) performance of modern 1.3-μm InAsP/InGaAsP multi-quantum-well (MQW) tunnel-junction vertical-cavity surface-emitting diode lasers (TJ-VCSELs) is investigated using our comprehensive self-consistent simulation model to suggest their optimal design for room and elevated temperatures. For increasing ambient temperatures, an increase in the VCSEL threshold current has happened to be mostly associated with the Auger recombination. Nevertheless, the InAsP/InGaAsP VCSELs have been found to exhibit encouraging thermal behaviour with the quite high value of maximal operating temperature of 350 K. It has been found that 5-μm devices seem to be the most optimal ones because they demonstrate both the room temperature (RT) threshold current equal to only 0.55 mA and maximum operating temperature equal to as much as 345 K. For these devices, the characteristic temperature T0 is equal to 92 K for 290–305 K, 51 K for 310–325 K and 29 K for 330–345 K. Therefore, the InAsP/InGaAsP VCSELs have been found to offer very promising performance both at room and elevated temperatures as sources of the carrier 1.3-μm wave in the fibre optical communication using silica fibres.

Investigation of temperature characteristics of modern InAsP/InGaAsP multi-quantum-well TJ-VCSELs for optical fibre communication

Fixed-interval Bayesian smoothing in state---space systems has been addressed for a long time. However, as far as the measurement noise is concerned, only two cases have been addressed so far : the regular case, i.e., with positive definite covariance matrix; and the perfect measurement case, i.e., with zero measurement noise. In this paper we address the smoothing problem in the intermediate case where the measurement noise covariance is positive semi definite with arbitrary rank. We exploit the singularity of the model in order to transform the original state---space system into a pairwise Markov model with reduced state dimension. Finally, the a posteriori Markovianity of the reduced state enables us to propose a family of fixed-interval smoothing algorithms.

Fixed-Interval Kalman Smoothing Algorithms in Singular State---Space Systems

In this review some of the factors which are important in ion implantation doping of III–V compound semiconductors will be discussed Emphasis will be placed on the results so far obtained in GaAs A discussion of the results in other III–V materials will be included as well as some comments on the application of ion implantation to the fabrication of devices in semiconducting III–V compounds

Ion Implantation In III–V Compounds

User programmable hardware structures for the realization of one- or two-dimensional recursive digital filters are presented. These structures do not require the use of look-up tables or multipliers. They require a modest amount of hardware in comparison to most other IIR filter implementations.

Programmable non-multiplier architectures for one- and two-dimensional IIR filters

A sequential fixed-lag smoothing algorithm is derived here for linear systems, when it is assumed that the measurements contain the sum of signals with known time delays and are corrupted by coloured noise. The innovations approach is used to derive the algorithm that is suitable for online computations.

V. Shukla

Papers

Estimation in linear time-delay system with coloured observation noise