Entwurf nichtrekursiver Digitalfilter mit beliebigen Betrags- und Phasengängen

This paper presents an efficient multiple exchange algorithm for the frequency domain design of digital FIR filters with arbitrary magnitude and phase responses. The designed filters minimize theL ₂ norm of the weighted complex frequency domain error function subject to constraints on the resulting magnitude and phase errors. This general design criterion allows for an arbitrary trade-off between complexL ₂ approximation and Chebyshev approximation of given magnitude and phase responses. The optimization can be carried out by iteratively solving small quadratic programs. These linearly constrained subproblems can be solved using robust standard software.     

Magnetoresistive Sensoren

Depending on the angle between magnetization and current density in a thin permalloy film, the anisotropic magnetoresistive effect is utilized for high performance sensors. Both the parameters of the sputtering process and the sensor layout have to be optimized. Aiming a magnetic field resolution of some nT in a frequencey range from 0–1 kHz, the results of Wheatston-bridge circuits are discussed.     

A Combined Interleaving Technique for Trellis Coded MPSK Systems in Rayleigh Fading Channels

Freedom of mobility is the latesttrend in the evolution of digital communicationsystems. In these systems bandwidth and powerconstraints limit the mobility of the users. TCM(trellis coded modulation) is a combined coding andmodulation scheme which increases the productivity ofa digital communication system without increasing thetransmitted power or the required bandwidth. A mobilecommunication channel is affected from noise andfading because of the multipath propagation. On aRayleigh fading channel, coding should be used withtechniques which uncorrelate the received energy ofeach consecutive coded symbol. Interleaving is one ofthese techniques and used to make burst errors intorandom errors which can be corrected by errorcorrecting codes. In this paper, the trellis codingsystem which combines a regular convolutional encoder,bit interleaver, coordinate interleaver, and anappropriate decoder is considered. The analytical biterror probability upper bounds are derived for the8-PSK TCM system whose diversity is increased by usinga regular 2/3 rate convolutional code followed bythree bit interleavers and a 8-PSK signal mapperfollowed by two coordinate interleavers. Theanalytical and simulation results show that toincrease the diversity of the trellis coded M-PSKsystems in Rayleigh fading channels is the primary keyfor reliable transmission of high quality voice anddigital data.     

Norm constraint regard for stable H2 controllers

For stable output controllers, the standard H₂ problem is modified by additionally including the H₂ controller norm.      

Konvergenz der Kommunikationsnetze zu Multiservice-Netzen

The rapid progress in the convergence of communication networks (fixed and mobile networks with data networks) to multi service networks has an impact on the principles of the traditional switching technologies. Future requirements will also have to be fulfilled through service-convergence (bundling of individual services to new services) regardless of organizational or technical boundaries. Requirements in the information- and communication-business all the way to technical network aspects are to be faced. Based on developments in microelectronics, two converging evolutions by packet-oriented technologies (within the network and at the edge of the network) are now taking place. Starting with the principles of circuit-switching and packet-switching the change in today’s telecommunications world will be discussed. Apart from that emphasis will be put on the distribution of the switching functions within the network, the change of the network’s topology, as well as the influence on the signalling protocols (extensions and new approaches).     

Codierte Modulation in modernen Übertragungssystemen

Modern communication systems offer high speed and reliable data transmission services. The quality of these services is achieved by combining coded multi-level modulation techniques and modern digital signal processing (Viterbi-decoding) in the receiver. In this paper we first present an introduction to Trellis Coded Modulation (TCM) and then some new results on unversal techniques adapted for the AWGN-channel as well as for the fading channel. It is shown that TCM is well suited for communication channels with time variant characteristics (e.g. mobile communication channels), especially when our new codes are applied.