ISSN:1124-318X    

DOI:10.1002/ett.4460030402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA new recursive technique for the synthesis of apth‐order inverse of a Volterra system is presented. In such a method, the condition that thepth‐order inverse be exactly of orderp, as proposed by Schetzen, is relaxed. The choice of the residuals, that is the operators of the inverse whose order is higher thanp, is done with the purpose of reducing the complexity of the synthesis scheme and of deriving a recursive procedure to build‐up such an inverse.A comparison between the complexity of Schetzen's synthesis schemes and those obtained with our recursive procedure shows that the structures that we obtain are much less complex and easier to derive, and the increment of complexity related to the increase in order is much slower than in Schetzen's case.As an example of application, we use the proposed method in order to linearize a digital radio link in which the high‐power amplifier is operated near sat

ISSN:1124-318X    

DOI:10.1002/ett.4460030403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractChain coding of hardwritten line drawings for digital transmission is considered in this paper. A line drawing is considered to be composed of unconstrained two‐dimensional open and closed thin curves. Each curve is quantized in line‐following fashion into a sequence of discrete links, i.e., the chain‐code representation. Chain quantization based on grid‐intersect quantization (GIQ) and object boundary quantization (OBQ) is considered. Their performance in terms of the quantization distortion is quantitatively analyzed. To reduce the amount of data required to represent a line drawing, differential chain coding (DCC) is used to convert the chain code of a line drawing into binary data. The performance of DCC in terms of the number of bits required per unit length of curve is analyzed. The tradeoff between quantization distortion and coding efficiency for DCC is det

ISSN:1124-318X    

DOI:10.1002/ett.4460030404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractDigital pulse position modulation (PPM) is a preferred modulation format for the ideal photon counting channel and optical intersateilite links. Here we examine its potential for the coherent optical fibre communications channel. We present a thorough performance and optimisation analysis. Comparisons, at a wavelength of 1.5 μm, are made with shot‐noise limited coherent PCM (homodyne and heterodyne ASK, FSK and PSK) over a range of fibre band‐widths and varying PPM word size. We conclude that for moderate to high fibre bandwidths homodyne digital PPM should achieve an improvement in sensitivity of typically 5 dB over homo‐dyne P

ISSN:1124-318X    

DOI:10.1002/ett.4460030405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe paper deals with the problem of the estimation of the scaling amplitudes and the arrival times of a multipath signal. An extensive study of two new spectral‐correlation based estimation methods is presented. These algorithms are applicable as long as the multipath signal is cyclostationary. They are inherently tolerant to both noise and interference, and can, in principle, provide arbitrarily accurate estimates when a sufficiently long collect time is available. The methods are compared in terms of temporal resolution, arrival time dynamics and estimate accuracy. Finally, the performance of both considered methods is compared with that of conventional techniques based on temporal correlatio

ISSN:1124-318X    

DOI:10.1002/ett.4460030406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe concept of transmission network availability is discussed and defined. On this basis, a method for measuring the transmission network availability is presented, along with its applications and usefulness to some networks.The presence of privileged customers into the network enable us to compare preemptive vs. non‐preemptive mechanisms of using network redundancies. The effects of the mechanisms on network availability are discussed and compare

ISSN:1124-318X    

DOI:10.1002/ett.4460030407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper deals with the development of a coding system for image data compression based on the Discrete Cosine Transform (DCT). The aim is to integrate several methods into a single approach in order to obtain an adaptive coder characterized by higher performances. In particular, a variable blocksize scheme is used, which is based on quadtree segmentation driven by edge information. To improve data compression, DCT coefficients are then coded by a vector quantizer.Experiments have shown that the values of compression factors can be notably increased, while maintaining a good reconstruction quality.

ISSN:1124-318X    

DOI:10.1002/ett.4460030408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractOne of the most serious problems when using IIR‐Filters is the behaviour of the settling which depends on the incoming signal and the values which are in the state vector or memory of the filter. The description of the state vector is given in the z‐domain for the second direct form and for the cascaded structure. If the incoming signal is monochromatic, and when magnitude, phase and frequency are given or can be calculated, it is possible to determine the state vector (memory) of the filter in order that the settling time of a response to a step change of the monochromatic signal is zero. Various results are shown for one case when the preinitialization is done exactly with no noise present and for other cases when the monochromatic signal is overlaid by white no

ISSN:1124-318X    

DOI:10.1002/ett.4460030409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractWe review the design of the state‐of‐the‐art of optical isolators intended for use in fiber optics communication systems. Special emphasis is given to the protection of narrow‐line, frequency stabilized lasers and of optical amplifiers. Finally, perspectives of future developments of OI's are di

ISSN:1124-318X    

DOI:10.1002/ett.4460030410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAt DLR (formerly DFVLR) in Oberpfaffenhofen, Germany, a coherent polarimetric C‐Band radar is in operation since about three years for applications in microwave propagation (satellite communications) and cloud physics research. Its functional aspects are briefly described. The radar permits the characterization of scatter volumes consisting of statistically distributed targets like weather targets by a time series of scattering matrices as well as by the Stokes matrix or the covariance matrix. Special consideration is given to the microphysical interpretation of polarimetric radar echoes using the fundamental second moments (covariances). Polarization signatures for backscattered power and correlation observables are derived applying polarization transformations to the covariance matrix. Finally, typical signal degradations on Earth‐satellite paths are derived from actually measured radar data and compared with beacon measureme

ISSN:1124-318X    

DOI:10.1002/ett.4460030411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY