This work describes the implementation of an FPGA-based teaching and research platform for university education of electric engineers. The aim is to provide students with practical experience in design and implementation of control systems, particularly with regard to electromagnetic compatibility (EMC). The platform enables students to implement different control strategies and investigate their effects. The importance of FPGAs for real-time applications is explained and initial measurement results are presented. As a result, this platform offers an effective opportunity to experience and deepen the interaction between the various engineering disciplines.

This work is using a new method allowing to identify reflecting objects in the surrounding area of Doppler VHF Omnidirectional Radio-range (DVOR) transmitters. It is based on a bi-static, partially cooperative Radar application. Here, this method is applied – using received signal power measurements – to derive a quantitative value of an equivalent radar cross section (RCS) of wind turbines. The analysis is focussed on wind turbines in a distance of 5 to 12 km around a DVOR transmitter in Hehlingen, Germany.

Doppler VOR (D-VOR) transmitters are used as navigation aids in aviation. They transmit an omnidirectional phase reference in an amplitude-modulated (AM) sideband and directional phase information on a frequency-modulated (FM) subcarrier. In an airborne D-VOR navigation receiver, a directional information (azimuth angle) related to the position of the aircraft and the location of the transmitter can be derived from the difference of these two phase signals. In this work, the accuracy of AM and FM phase signals is firstly investigated analytically and afterwards verified by measurements. It will be shown that in established procedures, phase inaccuracy is dominated by the AM signal, since the FM signal is about 21 dB less noisy. Subsequently, a novel method is presented that improves the accuracy of the azimuth angle by orders of magnitude in case of D-VOR transmitters. This new method inherently reduces noise of the AM phase and thus yields a significant increase in accuracy. As a result, the remaining FM phase uncertainty becomes dominant for the total uncertainty of the bearing indication. Finally, the application of the new method to real measured signals confirms the theoretical expectations.

This dataset provides digital IQ baseband data, IMU and GPS time stamps for an orbital flight around Bremen Doppler VOR. The data was recorded on July, 13th 2020.

A Doppler VHF Omnidirectional Radio range (DVOR) radiates an omnidirectional signal that is used to generate a ground clutter map of reflective objects in this Passive Bistatic Radar (PBR) application. The derivation of the clutter map and its RCS values are discussed in this paper. The data are finally used as preload parameters to forecast the degradation of the VOR angular bearing when used for aircraft navigation. A small aircraft carrying a VHF sensor performs an orbit flight around the transmitter. Two signal properties are analyzed: Doppler shifts from the direct to the scattered signal deliver the difference of incident angles for all scatterers. Secondly, the DVOR inherently transmits a signal that has a directional-sensitive frequency modulation component which means that the PBR transmitter is partially cooperative. A Matched Filter is used to derive that directional information from the same scatterers, which then allows their localization by means of a cross bearing. Since the system is strictly linear, specific RCS values can be assigned to reflective objects on ground.

An experimental DC-DC buck converter architecture is presented that allows on-line optimisation of conducted emissions. It is based on a micro-controller allowing a very flexible implementation of the voltage controller itself and simultaneously to run an embedded optimisation algorithm in order to find best parameter sets for spread spectrum pulse width modulation methods. In addition to minimising EMI noise, further quality targets, e.g. load or line regulation can also be optimised. The embedded design makes it attractive for modern Artificial Intelligence (AI) strategies which need a huge number of parameter evaluations.

The one-antenna method is adopted to the practical antenna validation needs in EMC laboratories. The proposed setup allows verification of important characteristics like antenna gain and antenna factor on a regular basis. The experiments show very good agreement with manufacturer calibration data. For frequency bands above 1 GHz the metallic wall of a typical shielded room can be used to calibrate e.g. wide band horn antennas. Considerations about potential sources of measurement errors are investigated, while the application of equi-ripple FIR filters - applied during the time domain gating - allows to minimize the uncertainty.

The radar echo of a large wind turbine (WT) is investigated in the C band: An unmanned aerial system (UAS) is used to perform a reflectivity measurement across the flight altitude using a passive bistatic radar (PBR) constellation of a non-cooperative precipitation radar transmitter in horizontal polarization. This is done at various distances to check if far field conditions apply to derive a radar cross section (RCS). As a fully independent method, a monostatic FMCW radar is installed on ground at certain distances to the WT. The results of both methods are compared against each other regarding the applicability of the RCS.

During recent years, automation and optimized production processes within a variety of different agriculture sectors allowed farmers to achieve higher harvesting rates and therefore to maximize the outcome of their efforts. Besides harvesting, storing the crop is the next challenging step in improving agricultural practices. Monitoring and adjusting the environmental conditions in storage are important tasks to achieve an optimal and efficient storability. This paper focuses on the communication part of such a monitoring system. Modern warehouses are usually organized as box storage, which means that the crop to be stored is filled into boxes and then piled up in large warehouses. Selective ventilation and air conditioning ensure a maximum storage period. This paper examines which radio frequencies are suitable for transmitting sensor data from stored boxes to a sink. The obtained sensor data could be used, for example, to control the air conditioning of the warehouse more precisely. The investigations are carried out on potatoes as an example, for which first a simulation and then a prototypical sensor node is created.

The interference of Doppler echoes caused by rotating wind turbines is a major concern for meteorological institutes in the proper operation of weather radar stations. While research is ongoing to characterise this interference by means of simulation or measured data of pulsed radar system, this paper addresses measurements with FMCW signals. Most weather radar stations are operated in the C-Band (5.6 GHz). For the characterisation of wind turbines, a portable, flexible and economic design of an bi-static FMCW radar is presented. Initial measurements show adequate spatial resolution and sensitivity. The architecture is using IQ-mixing allowing complex signal processing of the baseband signal.

During the increasing dissemination of renewable energy sources the potential and actual interference effects of wind turbine plants became obvious. Turbines reflect the signals of weather radar and other radar systems. In addition to the static radar echoes, in particular the Doppler echoes are to be mentioned as an undesirable impairment Keränen (2014). As a result, building permit is refused for numerous new wind turbines, as the potential interference can not be reliably predicted. As a contribution to the improvement of this predictability, measurements are planned which aim at the high-frequency characterisation of wind energy installations. In this paper, a cost-effective FMCW radar is presented, which is operated in the same frequency band (C-band) as the weather radars of the German weather service. Here, the focus is on the description of the hardware design including the considerations used for its dimensioning.

For many modern communication and measurement systems, continuous signals of wide bandwidth are required. Maximum length sequences generated in linear feedback shift registers are a proven way to generate signals meeting these criteria. We present a number of discrete implementations that allow signal generation in both laboratory and production environments with higher flexibility and lower initial cost than integrated solutions and analyze their jitter performance.

Employing a continuous-wave radar system, with the stepped-frequency radar being one type of this class, all reflections from the environment are present continuously and simultaneously at the receiver. Utilizing such a radar system for Ground Penetrating Radar purposes, antenna cross-talk and ground bounce reflection form an overall dominant signal contribution while reflections from objects buried in the ground are of quite weak amplitude due to attenuation in the ground. This requires a large dynamic range of the receiver which in turn requires high sensitivity of the radar system.In this paper we analyze the sensitivity of our vector network analyzer utilized as stepped-frequency radar system for GPR pipe detection. We furthermore investigate the performance of increasing the sensitivity of the radar by means of appropriate averaging and low-noise pre-amplification of the received signal. It turns out that the improvement in sensitivity actually achievable may differ significantly from theoretical expectations.In addition, we give a descriptive explanation why our appropriate experiments demonstrate that the sensitivity of the receiver is independent of the distance between the target object and the source of dominant signal contribution. Finally, our investigations presented in this paper lead to a preferred setting of operation for our vector network analyzer in order to achieve best detection capability for weak reflection amplitudes, hence making the radar system applicable for Ground Penetrating Radar purposes. (C) 2014 Elsevier B.V. All rights reserved.