Propagation of Short Radio Waves

This thesis treats the development of a deterministic model for the electromagnetic (EM) field-strength prediction in built-up areas. The model uses Geometrical Opties (GO) together wi th various diffraction contributions based on the Uniform Theory of Diffraction (UTD) to determine the interaction of the EM wave with the environmental objects. Two applications of the model are discussed in this dissertation. The first one concerns the determination of the effeetiveness of placing an obstacle on the propagation path of an interfering signal in order to raise the signa.l-to-interference ratio of an earth-space link. Results of this intentional signal obstruction are presented for various obstacle types and positions of the observation point. Attention is also paid to the case where a receiving antenna is vcry close to the obstacle. In that case, a separate far-field treatment of obstacle and antenna diffraction is no longer allowed and a combined analysis should be carried out. This near-field analysis is performed for two types of parabolic reflector antennas, and results for the shielding effectiveness of obstacles are presented and compared. Also the validity of applying spatial far-field antenna weighting functions in field-strength prediction models based on ray methods is discussed. The second application of the model described in this thesis is the prediction of the EM field strength of a Land Mobile Satellite (LMS) signal in an urban environment. Due to its deterministic character the model developed is capable of analysing effects such as specular refiection and st rong shadowing. The lat ter are not taken into account in conventional statistical LMS field-strength prediction modeIs. Because the GO j UTD model accepts a detailed description of the urban environment, it can be used to analyse an arbitrary environment, whereas conventiona.l statistical models a.re suited for one specific geometry only. To demonstrate the capability of the model, it was used for the determination of the field strength along two trajectories at the campus of Eindhoven University of Technology. Not only the field strength, but also the Doppier spectrum, the time-delay profile and the delay-Doppler spectrogram were derived. The deterministic model is expeded to be a. valuable complement to existing statistical LMS field-strength prediction modeIs, especially if detailed digital databases of towns and cities are available.

A deterministic approach to the modelling of electromagnetic wave propagation in urban environments

two listed  are 1) the reference  model is a  nonlinear, time-varying system, and 2) the adjustable  system also contains  nonlinearities. These situations may lead to violations of the basic hypothesis in the parameter identification and adaptive observer problems, but not in the adaptive control problem.  Another  consequence is that here seems to be a serious omission of one assumption required in the control problem but not in the other two. That is that Ahe sign of the leading coefficient in the plant’s numerator polynomial b , in equation (6.4-35), must be known. Solutions which do not require this assumption have been discussed by various people, but are not very satisfactory because the algorithms invariably involve pogntial division by zero. The requirement for knowledge of the sign of bm in the control case. is obscured in the general discussion of Section 4.2 of Chapter Iv. Chapters 7 and 8 give a good development of the model reference adaptive  approach to the parameter  identification  problem and the simultaneous adaptive state observation and parameter identification problem, respectively. Chapter 7 contains the development for both continuous time and discrete time identification algorithms, and considers the importance of variable (time decreasing) adaption g a i n s in the presence of measurement noise. The advantages and disadvantages of parallel identifiers (output error method) and series-parallel identifiers (equation error method) are discussed. Two case studies are included, one using the continuous time algorithm and one the discrete time algorithm. Chapter 8 deals only with discrete time algorithms in a deterministic context. The last statement in Chapter 7 is, “ M U S identifiers can be used for implementing adaptive control schemes.” Some discussion concerning the potential  stability  problems associated with this approach would have been helpful. The author should be commended for even attempting a book in this extremely active area of research where many concepts have not yet completely solidified. He has achieved to a considerable degree his stated goals of making the book interesting to practicing engineers, useful as a textbook for graduate students, and a starting point for further investigation by researchers.

Principles of digital communication and coding

The representation of acoustic and electromagnetic fields the special theory of relativity radiation resonators the theory of waveguides refraction surface waves scattering by smooth objects diffraction by edges transient waves. Appendices: Bessel functions Legendre functions Mathieu functions parabolic cylinder functions spheroidal functions tensor calculus asymptotic evaluation of integrals.

Acoustic and electromagnetic waves

In this paper the Uniform Theory of Diffraction (UTD) is used to calculate the electric field strength near perfectly conducting obstacles. In case suppression of an interfering radio wave is wanted, a parameter of interest is the site shielding factor, which expresses the attenuation of an electromagnetic wave that propagates around an obstacle. Site shielding results are presented for a thin screen and a block-type obstacle, and good agreement between theory and experiment is found for both cases. Another application of the site shielding concept is the prediction of the field strength in an urban environment. For this application the use of a versatile block-type obstacle seems more appropriate. To demonstrate the capability of the models presented, the field strength near a cluster of obstacles is calculated. It is explained how communication parameters such as the Doppler and the delay-Doppler spectrum can be derived from the wave analysis. The model proposed can be of use for the planning and analys...

A deterministic approach for the modeling of wave propagation around buildings

5 List of abbreviations 7 List of major symbols 8 1. Introduetion 11 1.1. Background 11 1.2. Terminology 14 1.3. Organizations and responsibilities 15 1.4. Scope of the thesis and survey of the contents 19 1.5. References 21 2. Radio-inteiference problems and mutual coordination 23 2.1. Introduetion 23 2.2. Review of practical interference problems 23 2.2.1. General remarks 23 2.2.2. Interference between terrestrial stations 24 2.2.3. lnterference between satellite-earth links 26 2.2.4. Interference between terrestrial stations and earth stations 28 2.2.5. System studies 30 2.3. Interference from digital radio-relay stations into satellite TV receivers 32 2.4. Coordination areas 34 2.5. Relerences 40 3. Transhorizon propagation mechanisms -a review 43 3.1. General introduetion 43 3.2. Introduetion to transhorizon-propagation research 43 3.2.1. Time variability 43 3.2.2. General concepts and terminology 44 3.2.3. Presentation of results 50 3.3. Review of transhorizon-propagation mechanisms 50 3.3.1. General remarks 50 3.3.2. Permanent clear-air mechanisms 52 3.3.3. Occasional clear-air mechanisms 55 3.3.4. Permanent scatter mechanisms 58 3.3.5. Occasional scatter mechanisms 58 3.4. Relative importance of the mechanisms 61 3.5. References 61 4. Clear-air transhorizon propagation 65 4.1. Introduetion 65 4.2. Review of clear-air interference-predietion models 65 4.2.1. General remarks 65 4.2.2. CCIR interference-prediction model 66 4.2.3. Other clear-air interference--prt:>diction models 68 4.3. Transhorizon-propagation experiments 70 4.3.1. Measurement programme and equipment 70 4.3.2. Experimental results obtained at EUT 72 4.3.3. Discussion of the experimental results 73

Peter Maria Joseph Scheeren

Papers

Reduction of transhorizon radio interference in satellite earth stations