Peter Knott - Academia.edu (original) (raw)

Papers by Peter Knott

IEEE Aerospace and Electronic Systems Magazine

ith 175 scientific presentations, international experts put the newest radar technologies, system... more ith 175 scientific presentations, international experts put the newest radar technologies, systems, and applications-whether increasingly compact or cognitive sensors, e.g., for autonomous driving, or resource-efficient and passive for surveillance tasks-up for discussion at the International Radar Symposiums IRS 2018 in Bonn, Germany. The symposium, organized by the German Institute of Navigation (DGON) and the Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR, is co-sponsored by the IEEE Aerospace & Electronic Systems Society and celebrated the event's 20 th anniversary. Chairman Prof. Dr. P. Knott and the Conference Organization Team welcomed over 300 attendees from 38 countries, which highlights the great interest shown and the growing importance of radar and radar research for an ever increasing range of applications. The series of successful IRS symposia will continue in Ulm, Germany, from 26-28 June 2019.

2006 IEEE Aerospace Conference, 2000

The present paper 1,2 gives an overview over a radar demonstrator currently under development and... more The present paper 1,2 gives an overview over a radar demonstrator currently under development and the design of the system's conformal antenna array front-end. Important system parameters and overall performance of the planned system are described and experimental results for reflection coefficients, mutual coupling and embedded antenna element far field patterns will be included as well as simulated pattern synthesis results for different operational modes. In addition, a circularly polarized antenna sub-array suitable for integration in double curved apertures has been developed. The structure combines multiple cavity-backed patch antennas on a circular substrate and is connected to the feed network via a single coaxial line. A conformal antenna array of spherical shape based on this technology is currently being built for beam forming experiments.

2016 10th European Conference on Antennas and Propagation (EuCAP), 2016

Conformal antenna arrays fitted to the surface of a non-planar part of modern aircrafts, vehicles... more Conformal antenna arrays fitted to the surface of a non-planar part of modern aircrafts, vehicles or ships are considered an attractive alternative for certain applications where planar arrays or reflector antennas have definite drawbacks. Some of the potential advantages are improved aerodynamics, increased payload, large field of view (LFOV) and low observability. The occurrence of static and dynamic deformations can have a severe impact on the performance of conformal antennas on aircrafts and other vehicles. Therefore it is essential to study the different deformation and vibration mechanisms and their influence on the antenna system. The present paper gives an overview over different tools for the electromagnetic modelling and design of conformal array antennas. A method for the passive compensation of static deformations and vibrations based on the estimation of the elements' position and the deformed array shape will be presented. Examples of the numerical analysis of con...

The present paper describes the development of a sub-array element and a conformal array antenna ... more The present paper describes the development of a sub-array element and a conformal array antenna front-end suited for radar applications. The aperture was built in a piecewise planar (faceted) and a novel smoothly curved way. Experimental results for both cases are shown and compared. Investigations on the radiation performance and mutual coupling are conducted for the case of a single curved antenna array of elliptical shape.

A V-shaped printed dipole antenna element has been designed for application in the GAMMA passive ... more A V-shaped printed dipole antenna element has been designed for application in the GAMMA passive radar demonstrator system. Preliminary measurement results show good agreement with electromagnetic simulations. The fabrication of the full scale antenna array is currently in progress. For calibration of the array, the embedded radiation patterns of the antenna element have yet to be measured. Future work will include evaluation of the antenna performance in operation. Performance and radiation pattern measurements with the full scale antenna array are currently in progress.

2015 German Microwave Conference, 2015

2007 2nd International ITG Conference on Antennas, 2007

Conformal antenna arrays fitted to non-planar surfaces on parts of modern aircrafts, vehicles or ... more Conformal antenna arrays fitted to non-planar surfaces on parts of modern aircrafts, vehicles or ships are considered an attractive alternative for many applications whereas planar arrays or reflector antennas have definite drawbacks. Some of the potential advantages are improved aerodynamics, increased payload, large field of view (LFOV) and low observability (LO). However, the usage of conformal array technology in commercial applications is still comparably rare. Recent examples of antenna arrays on curved apertures are typically of cylindrical shape but only exhibit a weak degree of curvature. The present paper describes the development of a spherical antenna array with 95x3 antenna elements, a diameter of 300 mm and an opening angle of 112deg . Since the number of antenna elements on a planar or curved antenna aperture required for high directivity and two-dimensional beam steering can easily become very large, especially if an element spacing around half the free space wave length is required, the antenna elements are arranged in sub-arrays, each carrying 3 circularly polarized patch antennas at a centre frequency of f = 9.5 GHz and a phase corrected feed network on a common substrate. The sub-array is suited for easy integration into antenna arrays with double curved aperture and can be seen as a trade-off between antenna gain vs. beam granularity. Experimental results on antenna matching and radiated far field patterns as well as measured beam forming results will be presented.

2006 First European Conference on Antennas and Propagation, 2006

The number of antenna elements on a planar or curved antenna aperture required for high directivi... more The number of antenna elements on a planar or curved antenna aperture required for high directivity and two-dimensional beam steering can easily become very large, especially if an element spacing around half the free space wave length is required. The present paper describes the design of an antenna sub-array carrying 3 circularly polarized patch antennas at a centre frequency of f = 9.5 GHz and a phase corrected feed network on a common substrate. The sub-array is suited for easy integration into antenna arrays with double curved aperture and can be seen as a trade-off between antenna gain vs. beam granularity. The application of the triple patch antenna to the development of a spherical antenna array with 95 sub-arrays, a diameter of 300 mm and an opening angle of 112° is also shown. Experimental results on antenna matching and radiated far field patterns as well as numerical beam forming results are presented.

2008 IEEE Radar Conference, 2008

ABSTRACT Planar electromagnetic lenses like the Rotman lens are attractive candidates for beambea... more ABSTRACT Planar electromagnetic lenses like the Rotman lens are attractive candidates for beambeam forming networks forming networks because of their high bandwidth of operation and their capability to form multiple beams at lower cost as comparable electronic phase shifting networks. The principles of Rotman lenses have been studied for several decades and examples have been successfully built using different technologies, including parallel plate cavities fed by rectangular waveguides or microstrip lines on dielectric substrate. Due to the true time delay nature of Rotman lenses they theoretically exhibit extremely large bandwidth. However, lenses with rectangular waveguides as ports suffer from propagation of higher order modes inside the waveguide which limits the bandwidth to less than one octave in practical applications. Higher order waveguides, e.g. single or double ridged waveguides, allow for the propagation of a transversal electromagnetic (EM) mode and thus incorporate a larger bandwidth. But the symmetric nature of the TEM mode and the presence of the ridge complicate integration in the lens. The proposed paper outlines the design of a novel feed network based on higher order waveguides suited for multi- octave operation in Radar or Electronic Support Measures (ESM) applications. Each port includes coaxial feeding, a step transformer and a tapered section leading into the parallel plate section of the lens. An overview over the system will be given and numerical as well as experimental results on matching, insertion loss, mutual coupling and expected bandwidth obtained for a laboratory sample will be shown.

IEEE Antennas and Propagation Magazine, 2014

Frequenz, 2003

ABSTRACT Gegenstand der vorliegenden Arbeiten sind die theoretischen Grundlagen für die Antennenm... more ABSTRACT Gegenstand der vorliegenden Arbeiten sind die theoretischen Grundlagen für die Antennenmodellierung und Diagrammsynthese bei Gruppenantennen auf beliebig geformten Oberflächen, sowie numerische und experimentelle Ergebnisse für ausgewählte Beispielgeometrien. Ein neuartiges Antennenmodell für Gruppenantennen wurde entwickelt, das auf dem Einsatz von Antennenelementen beruht, die verschiedene sphärische Moden niedriger polarer Ordnung abstrahlen. Es wird ein voll polarimetrisches, mehrmodiges Antennenelement nachgebildet, das die Berechnung der Wechselwirkung zwischen den einzelnen Elementen der Gruppe und somit die Vorhersage wichtiger HF-physikalischer Parameter wie Gruppendiagramm, Richtfaktor und Verkopplungskoeffizienten zur effizienten Systemanalyse erlaubt. Darauf aufbauend wurden polarimetrische Diagrammsyntheseverfahren für konforme Gruppenantennen durch Anregung mit Sektor-Wellenmoden entwickelt. Die hergeleiteten Sätze von physikalischen Modenfunktionen sowohl im zylindrischen, als auch im sphärischen Koordinatensystem eignen sich zur Bildung gewünschter Referenzdiagramme für verschiedene einfach und zweifach gekrümmte Geometrien, wahlweise mit Einschränkung des Geltungsbereiches der Funktionen auf einen Teilbereich/Sektor. Im Rahmen der Arbeit wurde ein Programmsystem auf Basis der beschriebenen Verfahren zur Antennenmodellierung und Diagrammsynthese erstellt, mit dessen Hilfe sich Systemparameter wie erzielbarer Gewinn, Schwenkbereich oder Bandbreite einer Antennengruppe ermitteln lassen. Die Verfahren wurden auf eine Reihe typischer ein- und zweifach gekrümmter Antennengeometrien angewandt. Zur Validierung der Arbeiten wurden die Daten mit Messergebnissen ausgewählter Geometrien von Antennengruppen verglichen. In einem weiteren Teil der Arbeit wurde die spezielle Fragestellung des kohärenten Empfangs mehrerer Signale gleicher Frequenz aus unterschiedlichen Richtungen untersucht. Neben Beispielen aus der Literatur wurden Ansätze zu Hochauflösung und digitaler Diagrammbildung für mehrkanalfähige Antennensysteme vorgestellt und mit den im Rahmen der Arbeit entwickelten Verfahren untersucht. Die Ergebnisse wurden hinsichtlich der erzielbaren Anzahl und Trennung der Kanäle ausgewertet. The present work deals with theoretical principles of antenna modelling and pattern synthesis methods for antenna arrays on arbitrarily shaped surfaces including numerical and experimental results for selected exemplary geometries. A novel antenna modelling method is presented which is based on antenna elements radiating spherical wave modes of low order. The application of this fully polarimetric multimode antenna element allows for the calculation of mutual coupling interferences between different elements and prediction of important high-frequency parameters such as array far field, directivity and coupling coefficients for system performance prediction. Additionally, a polarimetric pattern synthesis method for conformal antenna arrays based on excitation by sector wave modes has been developed. Physical wave functions in the cylindrical and spherical coordinate system are derived for the composition of desired reference far fields for single or double curved geometries. The domain of these functions may optionally be limited to a sector subarea. The methods presented in the scope of this thesis have been applied to several typical single and double curved antenna geometries. System parameters such as directivity, scanning range, bandwidth etc. have been calculated. For validation of the work data have been compared to measured results of selected antenna array geometries. Furthermore, the special problem of coherent reception of multiple signals with different angles of incidence and identical frequency has been investigated. In addition to literature examples, basic approaches for superresolution and digital beam forming for multi-channel antenna systems have been presented and examined using the presented methods. From these results the realized number of channels and signal-to-interference ratio have been evaluated.

ABSTRACT Passive Coherent Localisation (PCL), also known as Passive Radar, making use of RF sourc... more ABSTRACT Passive Coherent Localisation (PCL), also known as Passive Radar, making use of RF sources of opportunity such as Radio or TV Broadcasting Stations, Cellular Phone Network Base Stations, etc. is an advancing technology for covert operation because no active radar transmitter is required. It is also an attractive addition to existing active radar stations because it has the potential to discover low-flying and low-observable targets. The CORA (Covert Radar) experimental passive radar system currently developed at Fraunhofer-FHR features a multi-channel digital radar receiver and a circular antenna array with separate elements for the VHF- and the UHF-range and is used to exploit alternatively Digital Audio (DAB) or Video Broadcasting (DVB-T) signals. For an extension of the system, a wideband antenna array is being designed for which a new discone antenna element has been developed covering the full DVB-T frequency range. The present paper describes the outline of the system and the numerical modelling and optimisation methods applied to solve the complex task of antenna array design: Electromagnetic full wave analysis is required for the parametric design of the antenna elements while combinatorial optimization methods are applied to find the best array positions and excitation coefficients for a regular omni-directional antenna performance. The different steps are combined in an iterative loop until the optimum array layout is found. Simulation and experimental results for the current system will be shown.

ABSTRACT A Digital Video Broadcast Terrestrial (DVB-T) based passive radar requires the developme... more ABSTRACT A Digital Video Broadcast Terrestrial (DVB-T) based passive radar requires the development of a dedicated antenna array that performs satisfactorily over the entire DVB-T band. The array should require no mechanical adjustments to interelement spacing to correspond to the DVB-T carrier frequency used for any particular measurement. This paper describes the challenges involved in designing an antenna array with a bandwidth of 450 MHz. The design procedure is discussed and a number of simulated array configurations are demonstrated. The final configuration of the array will be shown as well as simulations of the expected performance over the desired frequency span.

2007 IEEE Aerospace Conference, 2007

Array antennas which are integrated onto structures of aircraft and unmanned aerial vehicles (UAV... more Array antennas which are integrated onto structures of aircraft and unmanned aerial vehicles (UAVs) are subject to unsteady aerodynamic loads. Mechanical forces and these aerodynamic loads will cause deformation of the antenna supporting structure. As a consequence, the positions and orientations of the elements of the phased array antenna change. The relative phases of the respective signals feeding the antennas

Josefsson/Conformal Array Antenna Theory and Design, 2006