ABSTRACT: This article presents a hybrid computational method to address the datalink characteristics of an Unmanned Aerial Vehicle (UAV) relay. It uses the 3D far-field gain data from the antennas (UAV and ground station), separately computed or based on available measurements as inputs, and then applies the 2-Ray propagation model, taking into consideration the ground permittivity and the respective antenna heights. By doing so, different numerical approaches cover the two different physical scales. Since the installed antennas (i.e. antennas considered placed on the UAV fuselage) performances are considered, a higher reliability can be achieved with the covered procedure, at lower costs when compared to field measurements. Results for different example scenarios are presented and discussed.

Abstract: This article presents a set of measurements and simulations that evaluate the technical feasibility of a Compact Open Area Test Site (COATS), for the frequency range of 200 MHz to 2 GHz. Its main goal is to provide shielding effectiveness measurements. The described test setup is used for the tests in both semi anechoic chamber and COATS. These experimental and computational results offer orientations and guidelines about the best method to measure radiated emission in a COATS. These measurements results can be quantified through the Feature Selective Validation technique.

This article covers the design of an electromagnetic noise generator which uses an automotive coil as the main component. A short theoretical analysis covers the generation of high voltage pulsed current from the available DC source originated from the battery. An electronic dimmer, a circuit used to control the brightness of a light, by controlling the effective voltage that is delivered to the load, is used here to provide more degrees of freedom to the generated power as well as to insert higher order harmonics into the emitted electromagnetic spectrum. A prototype was built and its time domain current waveform is measured and shown, altogether with the measured radiated spectra, covering the frequency range from 20Hz to 1GHz. A broadband emission characteristics is verified, turning the use of common AM/FM radios impossible when close to the noise generator. A visible strong plasma is also seen due to the high generated voltages (around 60kV).

ABSTRACT The design, prototyping, and free-space measurement of a 6-GHz Frequency Selective Surface filter is presented. The prototyping resolution of a large (A4 sheet size) Frequency Selective Surface with small loops as elements is checked, as well as the correlation with measurements performed with a 3-D full-wave solver. The test also involved the effect of cascading two different Frequency Selective Surfaces with a viewpoint towards a narrower frequency range, which provided good results.

Estruturas de onda lenta possuem aplicações em vários setores tais como aceleradores lineares, usados em aplicações médicas e em física nuclear; em válvulas eletrônicas e em filtros de micro-ondas. Uma compreensão adequada deste tópico requer conceitos de engenharia de micro-ondas, física e instrumentação, que são dificilmente cobertos em sua plenitude durante cursos de graduação. O artigo explora o tópico utilizando uma analogia com circuitos elétricos e também com o uso de um simulador tridimensional de campos eletromagnéticos. Um experimento em laboratório é sugerido de maneira a proporcionar uma atividade prática. A montagem de laboratório requer instrumentação comum em laboratórios de eletrônica e possui construção simples.

Slow wave structures have uses in several areas, as linear accelerators used for atomic studies and in medical applications, vacuum tubes and as microwave filters. An adequate understanding of this topic requires knowledge on microwave engineering, physics and instrumentation, which is hardly possible to be covered during normal physics or engineering undergraduate courses. This article aims to explore this topic using a circuit analogy and also a 3D electromagnetic field solver. A laboratory experiment is proposed to have a hands-on experience as well. The laboratory test requires common electronic instrumentation and it is easily constructed.

Abstract: The remote detection of a vehicle requires that some kinds of its emissions are tracked and detected. Usually, electromagnetic emissions are used in the form of radar (electromagnetic waves in the range of radiofrequency and microwaves). Different types of antennas are used as sensors, tailored to the signal frequency band and its polarization, as well as to the target distance (higher gain antennas used for low amplitude signals). For the specific case of radars, the use of computational methods to address the electromagnetic signature (spatial pattern of the scattered energy from the object) has become widespread, given the high costs and complex equipment associated with these respective measurements. Therefore, the use of computer simulation is ideally suited for creating a realistic database of targets and its respective signatures. The same computer-created signatures database can also be used for the thermal range, enabling a complete technology solution for the signature and design of stealth vehicles, with reduced emissions.