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Many scientists and engineers contributed – more or less successfully – to the development of radio and wireless. This historical survey describes briefly the projects realized more than a century ago by some of them, at the early beginnings of wireless. It is hoped, in this manner, to draw attention to the unknown or forgotten researchers who built up the considerable body of knowledge that led to Marconi's remarkable achievements.

This paper describes some key points in the history and development of the European Microwave Conference, the European Microwave Week, and the European Microwave Association, starting from 1969. It captures the way in which the conference since the earliest days has sought to create a successful blend of scientific and industry interests and has adapted itself to and indeed shaped the many existing technical changes that have characterized and continue to be at the core of the field of microwave engineering.

A novel and efficient method to determine Green's functions in photonic crystals (PCs), i.e., the phased-array method (PAM), is presented. The PAM is a combination of the plane-wave method and the array-scanning method, which is both more flexible and computationally faster than the eigenmodes expansion method. A complete derivation of the electric- and magnetic-field Green's functions associated, respectively, with an infinite electric and magnetic current line exciting a two-dimensional PC is given. Although the developments are presented only for a line source, the PAM can be extended to a dipole source. Thus, the PAM represents a promising method for the analysis of printed-circuit elements or antennas on PC materials. Numerical results for the Green's functions are shown for different positions of the source and a discussion about radiation patterns, asymptotic behaviors, and convergence characteristics is proposed.

A modal series representation of spatial-domain electric field Green's functions for arbitrarily oriented electric current sources embedded in shielded multilayer media is presented. The Green's func- tions associated with planar excitations are briefly recalled, and the method to compute them is generalized to vertical current sources, yielding new components of the Green's function necessary for the anal- ysis of vertical metallizations embedded in waveguides or cavities. Universidad Politécnica Federal de Lausanne (EPFL)

Reference LEMA-ARTICLE-1991-001View record in Web of Science Record created on 2006-11-30, modified on 2016-08-08

Thirteen respondents describe the mechanics and reflect on the environment of teaching electromagnetics in their respective countries. A brief description of the survey by F.J. Rosenbaum is followed by the 13 individual presentations, whose titles are: undergraduate EM teaching at the University of New South Wales; teaching electromagnetism to undergraduates in Belgium: teaching electromagnetics to undergraduates in Brazilian universities; electromagnetism to undergraduates in China; teaching electromagnetics in Egypt and Saudi Arabia; a view of teaching electromagnetism to undergraduates in Karlsruhe, FRG; teaching of electromagnetism at III, Bombay, India; electromagnetic engineering education in Israel; teaching undergraduate electromagnetics in the Soviet Union; and teaching antennas and propagation to undergraduates-a UK view. >

The reflection from an array of narrow series slots on the broad face of a rectangular waveguide is used in order to determine the dielectric properties of the medium into which the slots radiate. The relationship linking the reflection coefficient to the complex permittivity is obtained, from the theoretical study of the electromagnetic field in the vicinity of the slots. A system of integral equations is established for an arbitrary set of slots, taking into account both internal and external mutual coupling. The numerical solution is discussed and an optimization procedure for the array is presented, providing a simple relationship over a specified permittivity range. Computed results are compared to experimental values.

In the close vicinity of an electronic device or of an antenna, the electric and magnetic fields often exhibit a complex behavior, and a good knowledge of the resulting field pattern would be a most valuable asset for many practical applications. But when one inserts a probe antenna connected to a receiver, close to the the device, one modifies the filed, because metal locally short-circuits the tangential electric field components. The modulated scatterer technique provides an indirect approach to determine field components, by introducing a small “scatterer” that does not perturb as much as a receiving probe would. The signal returned by the scatterer is very small, and to detect it one “modulates” the scatterer and then uses coherent detection. The amplitude and the phase of the field components are then determined. Keywords: near fields; perturbation; scattering; diagnostic antennas

A magnetic field Green's function expressed as an eigenmodes expansion and based on the plane wave method is formulated first for an infinite magnetic current line embedded in an unbounded 2D photonic crystal (PC) and then for a magnetic dipole embedded in a 2D PC truncated by two metallic plates. The underlying idea of analyzing a slot antenna printed on a 2D PC with a standard method of moment through the principle of equivalence is shown to motivate the present investigation. A complete solution for the line problem is derived, whereas the inadequacy of the method in nits present form for the dipole problem is demonstrated rigorously. Numerical results of the Green's function for the first problem are shown for different positions of the source, and a discussion about radiation patterns, asymptotic behaviors and convergence problems of the Green's function is proposed.

Thes Words pronounced forty years ago by Maurice Gay- Balmaz, opened the lecture series at the unveiling of the commemorative plaque installed on September 26, 2008, by the ITU (International Telecommunications Union). The words describe prosaically Gay-Balmaz's first encounter with Guglielmo, Marconi, who carried out major experiments in wireless telegraphy in Salvan during the summer of 1895. Exactly five years after the inauguration on the same spot of an IEEE Milestone [1], the ITU recognized the site of Salvan for its invaluable contribution in "Telecommunication Heritage" (Figure 1). (The announcement of this recognition by the ITU created some turmoil in Italian newspapers, as the Lady Mayor of the little town of Sasso Marconi felt that, instead of Salvan, the ITU should have recognized the Villa Griffone in Pontecchio, where Marconi carried out his very first attic experiments. We were very pleased to have nice Italian Figure 1. The ITU Commemorative plaque installed reporters covering the event in Salvan.)

This paper presents an efficient technique for the optimization of cavity backed printed antennas which could be used in broadband communication applications. The method is applied to several antenna cases and the results obtained are validated with measured data. Results show that the technique is efficient and can be used to systematically optimize the antennas treated for maximum frequency bandwidth.

When analyzing large printed antenna arrays with irregularly located radiating elements, the method of moments yields a very large system of equations, which cannot be solved by matrix inversion. An iterative scheme was therefore developed, in which each element is first analyzed independently, to determine the surface current flowing on it. The coupling between elements is then introduced as a perturbation, yielding an iterative process based on the Jacobi decomposition of a matrix linear equation. However the convergence of the process is not guaranteed, but can be "restored" by coupling the iterative scheme with a convergence accelerator algorithm. The interest of the proposed technique is illustrated by the analysis of a slot-fed array of printed patches.

On September 26, 2008, for the first time in its history, the International Telecommunications Union (ITU/UIT) will recognize a particular site for its invaluable contribution in the "Telecommunication Heritage." This honor will be granted to the township of Salvan, in Valais, Switzerland, where, in 1895, Guglielmo Marconli carried some of his first experiments in wireless telegraphy.

Reflection measurement techniques require a way to correlate measured reflection factors with the permittivity of the materials. This relationship is derived for the open-ended coaxial line propagating the TEM mode.

An instrument was developed to simultaneously measure both the resonant frequency and the bandwidth (which is related to the loaded quality factor) of a resonant microwave cavity under continuous operating conditions. Voltages proportional to both parameters monitored are obtained at the output. The principle of operation, the main causes of error and the accuracy obtained for actual measurements are presented. This instrument could easily be connected to a digital data-acquisition system; it could also be adapted to study resonance phenomena at frequencies other than microwaves.

Reference LEMA-ARTICLE-1985-010View record in Web of Science Record created on 2006-11-30, modified on 2016-08-08

A computer-controlled system for the measurement of the field distribution in microwave cavities is described. Examples of field measurements at various resonant frequencies are given for a cavity with a complex geometry.

Cet article vise a fournir un apercu general du domaine des circuits en microruban, decrivant l’allure generate des circuits imprimes pour hyperfrequences, leurs particularites au point de vue electromagnetisme et mesures, les techniques utilisees pour les fabriquer et les connecter, les materiaux le plus couramment utilises pour lew fabrication et, finalement, les logiciels d’ordinateur disponibles pour analyser, synthetiser, optimiser, puis preparer et decouper les masques destines a la realisation de circuits. Les relations approchees les plus precises actuellement disponibles pour caracteriser les lignes sont presentees, et les principals techniques mises au point pour analyser les discontinuites sont brievement decrites.

Considerations for the effects of second-harmonic reactive terminations on the performances of a UHF class-C transistor power amplifier are presented. An experimental amplifier circuit design using coupled-TEM-bar transmission lines is described. This circuit can vary the fundamental and the second-harmonic impedance terminations of the amplifier independently. With this amplifier circuit, significant improvement in the performance characteristics of a class-C power amplifier were achieved by presenting proper values of second-harmonic reactive terminations, both at the input and the output of the transistor.

Reference LEMA-ARTICLE-1977-012View record in Web of Science Record created on 2006-11-30, modified on 2016-08-08

Les auteurs presentent une theorie rigoureuse permettant le calcul du rayonnement des antennes microruban a partir des courants electriques de surface qui circulent dans le conducteur superieur de l’antenne (plaque). Le modele adopte est celui d’un milieu stratifie ou substrat et plan de masse ont des dimensions transverses infinies. Des expressions asymptotiques pour les champs rayonnes d’un doublet de Hertz place en surface du substrat, sont obtenues en faisant usage des techniques d’integration complexes dans le plan spectral. On trouve que les champs rayonnes resultent de la superposition d’une onde spatiale spherique et une onde de surface cylindrique. L’importance relative de chacune et leur dependance avec les parametres du substrat et avec la frequence sont discutees en detail. Finalement, la theorie des antennes en reseaux a ete utilisee pour calculer le rayonnement d’une antenne microruban de forme arbitraire.

The reflection from an array of narrow series slots on the broad face of a rectangular waveguide is used to determine the permittivity of lossy materials. The theoretical study of the electromagnetic field in the vicinity of the slots yields a system of integral equations which takes into account the internal and external coupling between slots. The numerical solution is discussed and an optimization procedure for the array is presented, which provides a simple relationship linking the reflection coefficient to the complex permittivity over a specified range. Computed results are compared to experimental values for air and a lossy dielectric at 10 GHz, showing good agreement. Interpolation from computed data is provided by a polynomial expansion: this allows one to determine the complex permittivity once the reflection factor has been measured.

A method has been developed to optimize the geometry of the structure and the permittivity of the dielectric material used in E-plane isolators, for an arbitrary ferrite material. The structure is first computer analyzed, using an exact analytical approach. The minimum isolation and the maximum forward attenuation per unit length are calculated within a specified frequency band. The objective function, defined as the ratio minimum isolation per maximum forward losses, is then maximized. Several optimization procedures are compared and tested; the optimum gradient method was found to be well suited to this problem. Various optimized results are presented.

E-plane ferrite resonance isolators are commonly used in most medium-power waveguide systems, allowing to effectively decouple successive stages. The study of propagation in this type of structure leads to a set of transcendental equations, for which exact theoretical results have not been available so far. The design of these devices has been done experimentally, which is time consuming and does not allow for achievement of optimal performance due to the large number of parameters involved. The present study considers the TE/sub m0/, modes in an isolator structure. A matrix formalism is used to derive the dispersion relation, which is then solved with the help of a computer program. Experimental results for a simple structure show good agreement with the computed values. The influence of ferrite parameters on the isolation and forward losses is presented. Higher order modes in the structure and the methods to avoid them are discussed. Finally, the field distribution in the device is determined, showing a large concentration of the fields within the loading material.

The influence of 2nd harmonic on the performances of an UHF class-C transistor power amplifier was determined. A matching circuit was designed, in which the reactive impedance termination presented at the second harmonic can be varied without affecting the impedance presented at the fundamental frequency. The main performance characteristics of the transistor power amplifier (output power, efficiency, intermodulation) were then determined, using two such matching circuits at the input and the output ports of the transistor. A graphical presentation of the results facilitates the choice of the 2nd harmonic terminations which significantly improve the performances of the amplifier.

The present work is devoted to the characterization and measurement of the phase instabilities produced by microwave amplifiers. We describe a special receiver designed for phase noise measurements at low Fourier frequencies. i.e. very close to the carrier in the spectral domain. Phase noise measurements of a microwave amplifier are presented and the noise floor of the receiver is shown and discussed.

The accurate determination of surface currents in microstrip planar antennas requires the solution of a two-dimensional singular integral equation. The first problem encountered when solving this equation numerically, is the obtention of a fast and accurate algorithm for evaluating its kernel, which cannot be calculated by standard computer integration methods. A second problem is the implementation of an efficient moment method. This task is very delicate because the kernel is singular. In particular, the diagonal or self terms in the moment matrix must be carefully evaluated. This paper discusses both problems and presents some new techniques for their resolution.

Publisher Summary This chapter deals with the models currently used to improve the quasistatic approximation of microstrip structures. The chapter presents a brief review of the microstrip fundamentals; a comprehensive account of these dynamical models. A particular model based on the calculation of the electric surface currents in the structure is introduced in the chapter. The Green's functions involved are constructed and numerically evaluated using the exact formulation for dipole potentials in a stratified medium. New evaluation techniques developed for Sommerfeld integrals permit a very accurate computation of Green's functions. Their properties are then extensively discussed; the validity of the quasistatic approximations is checked and the importance of the surface wave is pointed out in detail. Finally, the integral equations for the currents are set up and solved by numerical methods in that also give several practical applications. The chapter concludes the model is that the surface currents on the antenna are directly determined and the near field can then be determined easily, that becomes most important when microstrip structures are utilized as radiators or biological applicators.

In this paper we give a description of the different noise sources occurring in the receiving electronics of an active hydrogen maser and their influence on overall stability. It is shown that the most significant noise sources in the PLL locking a VCXO to an atomic oscillator are the preamplifier and the frequency multiplier. A measuring method yielding the noise behavior of the entire receiver is presented and compared to the calculated result obtained by taking into account the different relevant singular noise sources in the loop.

The measurement of reflection from an open-ended waveguide is a simple and nondestructive technique for determining the dielectric properties of materials. A flange-mounted waveguide is considered, the flange being pressed on an unknown material which may be of finite or infinite thickness. The relationship linking the reflection coefficient to the dielectric properties is obtained from a theoretical analysis of the electromagnetic field in the vicinity of the aperture. The theory includes the effects of both cross polarization and higher order modes. An integral equation is obtained, the kernel of which is the dyadic Green function in each medium. The method of characteristic modes is used for the numerical computation. The theoretical results are in good agreement with experimental measurements. Futhermore, a simple and handy technique for data inversion is provided.

Reference LEMA-ARTICLE-2000-003doi:10.1002/(SICI)1098-2760(20000305)24:5 3.0.CO;2-RView record in Web of Science Record created on 2006-11-30, modified on 2016-08-08

A compact and light-weight cavity with empty core and uniform field distribution is described contrary to dielectric loaded cavities. Only metallic losses are present. Thus the quality factor is reasonably high. An efficient and rigorous method yielding the resonant frequencies is described and theoretical results are compared with experimental measurements.

Reference LEMA-ARTICLE-2000-014doi:10.1002/1098-2760(20001205)27:5 3.0.CO;2-KView record in Web of Science Record created on 2006-11-30, modified on 2016-08-08

A simple nondestructive method is presented for the measurement of the complex permittivity ?r of materials. The reflection coefficient ? of a flanged open-ended rectangular waveguide placed, next to a flat large sample is computed by a variational method as a function of the dielectric constant. Computer-generated charts and an optimization computer program are elaborated. ?r can then be easily determined from the measured amplitude and phase angle of the reflected wave in the waveguide. The method is best suited for materials having high dielectric constants and large losses.

Nowadays, electromagnetic wave propagation and scattering are studied directly in the time-domain, whereas previously one consldered sine-wave excitations and Fourier transformations into the frequencydomain. Time-domain approaches are certainly much closer to the physical reality, but how do they deal with propagation within (or with scattering from) material media, since material properties are dispersive (frequency-dependant), at least over parts of the frequency spectrum? It is not obvious that timedomain approaches can determine the resulting distortion of the signal.