Ben Witvliet

Ben Witvliet
University of Twente | UT · Faculty of EEMCS - Radio Systems group

PhD

About

36
Publications
79,493
Reads
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187
Citations
Introduction
** Robust telecommunications for remote-area infrastructure and disaster relief in developing countries ** Empirically verified models for Near Vertical Incidence Skywave (NVIS) propagation for humanitarian communications and innovations. Other research is on antenna measurement, propagation measurements, space weather, dynamic spectrum management and HF ambient electromagnetic noise.
Additional affiliations
April 2021 - April 2025
University of Twente
Position
  • PostDoc Position
Description
  • PITHIA-NRF research project, funded by Horizon2020 Research Infrastructure.
October 2017 - October 2019
University of Bath
Position
  • Project Manager
Description
  • Project management of scientific research projects, acquisition of research funding, PhD supervision. TREASURE-GNSS Bath Summer School.
January 2016 - April 2021
University of Twente
Position
  • PostDoc Position
Description
  • Research into radio noise, dynamic spectrum management for heterogenous wireless devices. Specialization: Near Vertical Incidence (NVIS) antennas and propagation for humanitarian organizations and for disaster relief.
Education
January 2011 - December 2015
University of Twente, Enschede, The Netherlands
Field of study
  • Near Vertical Incidence Skywave - Interaction of Antenna and Propagation Mechanism

Publications

Publications (36)
Conference Paper
Full-text available
High Frequency (HF) radio communications are used in humanitarian work in areas where local networks are non-existent, or destroyed by natural disaster or human conflict. Direct point-to-point communications are realized over long distances, independent of local networks, using the ionosphere as a natural high-altitude reflector. HF ionospheric rad...
Presentation
Full-text available
Presentation belonging to the paper with the same name
Article
Full-text available
In the E-region of the ionosphere, at heights between 90 and 130 km, thin patches of enhanced ionization occur intermittently. The electron density in these sporadic-E (Es) clouds can sometimes be so high that radio waves with frequencies up to 150 MHz are obliquely reflected. While this phenomenon is well known, the reflection mechanism itself is...
Poster
Full-text available
The LOFAR radio telescope is a low-frequency radio interferometer in the north of the Netherlands and across Europe. The location selection of the core area of LOFAR was based on its relatively large distance to urban areas, and to industrial and logistics infrastructures. Recently, to meet the demand for renewable energy in the Netherlands, new wi...
Article
Full-text available
Observation of the 3-dimensional (3-D) electron density of the ionosphere is useful to study large-scale physical processes in space weather events. Ionospheric data assimilation and ionospheric tomography are methods that can create an image of the 3-D electron density distribution. While multiple techniques have been developed over the past 30 ye...
Conference Paper
Full-text available
Sporadic-E (‘Es’) layers in the ionosphere allow communication at much higher frequencies than would be possible via the background ionosphere, especially at solar cycle minimum. Es is created by a different mechanism from the background ionosphere and the creation process and structure are not fully understood. Similarly, the way that radio waves...
Article
Full-text available
This article describes the design and validation of deployable low-power probes and sensors to investigate the influence of the ionosphere and the Earth's magnetic field on radio wave propagation below the plasma frequency of the ionosphere, known as Near Vertical Incidence Skywave (NVIS) propagation. The propagation of waves that are bent downward...
Article
Full-text available
The ionized upper portion of the atmosphere, the ionosphere, affects radio signals traveling between satellites and the ground. This degrades the performance of satellite navigation, surveillance, and communication systems. Techniques to measure and mitigate ionospheric effects and in particular to measure the total electron content (TEC) are there...
Article
Full-text available
The design, realization and measurement results of a high accuracy multiyear 3.5 GHz trans-horizon radio propagation measurement system are discussed, with both emphasis on the results and implemented technical measures to enhance the accuracy and overall reliability of the measurements. The propagation measurements have been performed on two diffe...
Article
Full-text available
Near Vertical Incidence Skywave (NVIS) propagation can be used for radio communication in a large area (200 km radius) without any intermediate man-made infrastructure. It is therefore especially suited for disaster relief communication, communication in developing regions and applications where independence of local infrastructure is desired, such...
Article
Full-text available
The articles in this special issue are dedicated to high-frequency (HF) radio systems and techniques. Up to the 1960s, most telecommunication between the continents was realized by large HF (3–30-MHz) radio systems built especially for that purpose. The ionosphere was used as a natural high altitude reflector to obtain the large operation distances...
Article
Full-text available
An experiment to investigate several characteristics of near vertical incidence skywave (NVIS) propagation (polarization, characteristic waves and their isolation, elevation angles, and radio noise) over a distance of 105 km and at 7 MHz was performed in The Netherlands. Daytime characteristic wave propagation with almost perfectly circular polariz...
Conference Paper
Full-text available
For empirical research on Near Vertical Incidence Skywave (NVIS) characteristic wave propagation, a beacon transmitter system is needed that can be programmed to emit precisely defined elliptically and circularly polarized waves at high elevation angles. This paper proposes a novel hybrid antenna-transmitter system, a combination of a synchronous d...
Article
Full-text available
Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.
Research
Full-text available
[Dissertation to obtain the degree of doctor at the University of Twente, The Netherlands.] In areas where no telecommunication infrastructure exists, or when that infrastructure is destroyed by a natural disaster, Near Vertical Incidence Skywave (NVIS) radio wave propagation may provide a lifeline to the outside world. In NVIS propagation, radio...
Conference Paper
Full-text available
In HF (3-30 MHz) communications the ambient electromagnetic background noise or 'radio noise' generally is the limiting factor in reception. Radio noise measurements are needed for spectrum pollution control and to provide reference levels for radio system design. This article discusses the influence of the measurement antenna on the measurement re...
Conference Paper
Full-text available
In HF (3-30 MHz) communications the ambient electromagnetic background noise or 'radio noise' generally is the limiting factor in reception. Radio noise measurements are needed for spectrum pollution control and to provide reference levels for radio system design. This article discusses the influence of the measurement antenna on the measurement re...
Article
Full-text available
Ionospheric radio wave propagation can be used to bridge hundreds of kilometers with a direct radio link. This makes ionospheric radio communication a practical solution for information transport in regions that have no telecommunication infrastructure, or for disaster relief operations in areas where the telecommunication infrastructure is destroy...
Conference Paper
Full-text available
In Near Vertical Incidence Skywave (NVIS) propagation, effective diversity reception can be realized using a dual channel receiver and a dual polarization antenna with polarization matched to the (left hand and right hand) circular polarization of the characteristic waves propagating in the ionosphere. This paper presents measurements on NVIS-signa...
Article
Full-text available
Near Vertical Incidence Skywave (NVIS) communication uses the ionosphere as a reflector to cover a continuous area with a radius of at least 150 km around the transmitter, on frequencies typically between 3 and 10 MHz. In developing countries – in areas lacking any other telecommunication infrastructure – it is used on a daily basis for voice and d...
Conference Paper
Full-text available
Near Vertical Incidence Skywave (NVIS) propagation can be used to realize radio communication without the need for an intermediate network. NVIS uses the ionosphere as a reflector to cover a large area (200 km radius) around the transmitter, on frequencies ranging from 3 to 10 MHz. NVIS is therefore used for telecommunication in areas that lack a t...
Conference Paper
Full-text available
Near Vertical Incidence Skywave (NVIS) propagation can be used to realize radio communication without the need for an intermediate network. NVIS uses the ionosphere as a reflector to cover a large area (200 km radius) around the transmitter, on frequencies ranging from 3 to 10 MHz. NVIS is therefore used for telecommunication in areas that lack a t...
Conference Paper
Full-text available
Near Vertical Incidence Skywave propagation can provide High Frequency (HF: 3-30 MHz) radio coverage in an area of 300 by 300 km without the need for any intermediate infrastructure. It is therefore very well suited for disaster relief communication. However, electromagnetic waves refracted in the ionosphere are prone to fading caused by multipath...
Conference Paper
Full-text available
Near Vertical Incidence Skywave propagation can provide High Frequency (HF: 3-30 MHz) radio coverage in an area of 300 by 300 km without the need for any intermediate infrastructure. It is therefore very well suited for disaster relief communication. However, electromagnetic waves refracted in the ionosphere are prone to fading caused by multipath...
Conference Paper
Full-text available
A novel antenna gain measurement method is described which uses power transfer values that are measured while varying the distance between two antennas (Distance Scan). It can be executed with simple means and is cost-effective. The Distance Scan method yields derived free space antenna gain values if a calibrated reference antenna is used and can...
Conference Paper
Full-text available
This paper presents a new approach for dynamic spectrum management for heterogeneous wireless devices. Local congestion degrades the reliability of wireless applications in the License Exempt bands. This leads to the research questions: (1) how to realize equal spectrum sharing between dissimilar systems, and (2) how to improve the collective spect...
Conference Paper
Full-text available
An extensive propagation measurement survey was performed between The Netherlands and the United Kingdom. Seven mixed land/sea paths were monitored simultaneously, with path lengths ranging from 55 to 370 km. Eight frequencies between 500 and 700 MHz were used. Over 21 million measurements were collected during 500 days. This paper describes the su...
Technical Report
Full-text available
This report describes a radio propagation measurement campaign that has been performed along paths between the Netherlands and the United Kingdom. The campaign focused on UHF propagation on mixed land/sea paths. Special attention was given to calibration accuracy and validation of the measurement data. The result is a highly accurate and very exten...
Conference Paper
Full-text available
This paper describes a method for airborne evaluation and verification of the antenna patterns of broadcasting stations. Although it is intended for governmental institutions and broadcasters it may be also of interest to anyone who wants to evaluate large radiating structures. An airborne measurement to investigate the properties of the structure...

Questions

Questions (14)
Question
From most Digisonde ionosondes I can download SAO-files containing all the measured and derived values.
I only need foF2, fxI, foE and foEs as function of time.
Does anyone have a MatLab script to get these fields from the SAO-file?
I have the SAO file description, but do not understand the structure. If I would know at what line and position I can find the time stamp, and the same for the other fields, I can write a MatLab script for it myself. And of course I will share it (e.g. via MatLab Central).
Question
Is there any software (e.g. ionospheric raytracing software) that produces the polarization of the downcoming waves in ionospheric radio wave propagation?
Question
I only know and use the PropLab Pro v3 as an ionospheric radio wave propagation ray-tracing program. Are there any other ionospheric ray-tracing programs that give realistic results for both the ordinary and extraordinary wave?
Question
How can I calculate the precise (elliptical) polarization of the downward characteristic (ordinary and extraordinary) waves in ionospheric (magneto-ionic) radio wave propagation?
Input parameters that I want to vary are the azimuth angle, the elevation angle and the orientation of the Earth magnetic field. Other parameters are kept constant. My main interest is in steep elevation angles, typically between 60 and 90 degrees (Near Vertical Incidence Skywave).
First situation I want to calculate is in the Netherlands, where the magnetic field has a dip angle of 67 degrees.
Question
I would like to know how to model an antenna above an underground metal plate in NEC4.2 or CST?
I need such a model to find out what is the influence of a metal plate of 21 x 21 meters that is buried 5 centimeters under lossy ground on a turnstile antenna of two inverted vee (thin) dipoles on the polarization, and the influence of position errors on the diagram and the polarization.
I have extensive experience with NEC4.2, but so far my experience is limited to wire antennas above ground. I have only modeled ground screens above ground, not just below it.
Question
Are there any researchers on antennas and propagation here that will also visit EuCAP 2015 in Lisbon?
Question
I would be interested in contact with other researchers who work in the domain of ionospheric radio communication (so the mix between pure scientific ionospheric research and application of that research in practical communication systems). Both long distance and short-haul (Near Vertical Incidence Skywave) researchers may react.

Network

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Projects

Projects (10)
Project
. . . . . . . . . . . . . . . . . . . . . . . . . https://pithia-nrf.eu/ . . . . . . . . . . . . . . . . . . . . . . . . . PITHIA-NRF aims at building a European distributed network that integrates observing facilities, data processing tools and prediction models dedicated to ionosphere, thermosphere and plasmasphere research. For the first time, PITHIA-NRF integrates on a European scale, and opens up, to all European researchers, key national and regional research infrastructures such as EISCAT, LOFAR, Ionosondes and Digisondes, GNSS receivers, Doppler sounding systems, riometers, and VLF receivers, ensuring optimal use and joint development. PITHIA-NRF is designed to provide organized access to experimental facilities, FAIR data, standardized data products, training and innovation services. Furthermore, PITHIA-NRF facilitates drastically research advances in the field of upper atmosphere and near-Earth space, through the integration of data collections from satellite missions (such as Cluster, DEMETER, Swarm and CHAMP) and results from key prediction models (such as IPIM-IRAP, MCM-SWAMI, SWIF and EUHFORIA) that can be accessed by scientific users for join exploitation with the data collected from the research infrastructures of the network. PITHIA-NRF paves the way for new observing technologies, and to standard-making processes for software and high-level data products that are tuned to meet the requirements of technologies concerned, linking best-in-class R&D facilities to provide seamless multi-technology services. € 5,300,000 – Horizon 2020 INFRAIA-02-2020 research infrastructure grant – consortium led by Anna Belehaki, NOA Greece.
Project
Warning and mitigation technologies for travelling ionospheric disturbances effects
Archived project
To acquire empirical data for the verification of propagation over typically Dutch terrain (wetlands) to assist frequency planning. Two long and two shorter path will be observed simultaneously to provide information on the correlation of propagation on two paths, as this information is critical for the assessment of cumulative interference.