Zhurbenko V.,Technical University of Denmark |
Rubaek T.,Chalmers University of Technology |
Krozer V.,Goethe University Frankfurt |
IET Microwaves, Antennas and Propagation | Year: 2010
An active microwave-imaging system for non-invasive detection of breast cancer based on dedicated hardware is described. Thirty-two transceiving channels are used to measure the amplitude and phase of the scattered fields in the three-dimensional (3D) imaging domain using electronic scanning. The 3D inverse electromagnetic scattering problem is then solved in order to reconstruct the distribution of the complex permittivity in the imaging domain. The dedicated hardware is based on an array architecture allowing for a short acquisition time while maintaining a high sensitivity, which is important for measurement accuracy and reproducibility as well as for patient comfort. The dedicated hardware achieves a receiver noise figure of 2.3 dB at a gain of 97 dB. The operating frequency range is from 0.3 to 3 GHz. The image acquisition time at one frequency is approximately 50 s and an image is created within 2 h using the single-frequency reconstruction algorithm. The performance of the system is illustrated by an analysis of the standard deviations in amplitude and phase of a series of measurements as well as by a simple image reconstruction example. © 2010 The Institution of Engineering and Technology.
Christiansen P.L.,Technical University of Denmark |
Albertsen Chr. N.,TICRA |
Breinbjerg O.,Technical University of Denmark
IEEE Antennas and Propagation Magazine | Year: 2013
In the introduction, Danish contributions to J. B. Keller's Geometrical Theory of Diffraction are surveyed. The edge diffraction coefficient in the case of scattering by a half-plane with an impedance surface is then analyzed. In short-wavelength scattering theory, the amplitudes of the incident and the reflected rays are of the same order of magnitude. The consequence of this point of view for the structure of the diffraction coefficient is investigated. © 2013 IEEE.
Hansen T.B.,Seknion Inc. |
Radio Science | Year: 2015
A multilevel computation scheme for time-harmonic fields in three dimensions will be formulated with a new Gaussian translation operator that decays exponentially outside a circular cone centered on the line connecting the source and observation groups. This Gaussian translation operator is directional and diagonal with its sharpness determined by a beam parameter. When the beam parameter is set to zero, the Gaussian translation operator reduces to the standard fast multipole method translation operator. The directionality of the Gaussian translation operator makes it possible to reduce the number of plane waves required to achieve a given accuracy. The sampling rate can be determined straightforwardly to achieve any desired accuracy. The use of the computation scheme will be illustrated through a near-field scanning problem where the far-field pattern of a source is determined from near-field measurements with a known probe. Here the Gaussian translation operator improves the condition number of the matrix equation that determines the far-field pattern. The Gaussian translation operator can also be used when the probe pattern is known only in one hemisphere, as is common in practice. Also, the Gaussian translation operator will be used to solve the scattering problem of the perfectly conducting sphere. ©2015. American Geophysical Union. All Rights Reserved.
IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) | Year: 2013
A fast and accurate approach to designing horns and reflectors is implemented in the CHAMP code. The paper presents examples of designs, including shaped reflectors and a horn with a dielectric lens. © 2013 IEEE.
Skokic S.,University of Zagreb |
Casaletti M.,University of Siena |
Maci S.,University of Siena |
IEEE Transactions on Antennas and Propagation | Year: 2011
A method is presented for computing aperture radiated fields by means of new conical beams with azimuth phase variation. These beams are generated in a natural way starting from the spectral-domain radiation integral, by expanding the electric field spectrum in the aperture plane in a Fourier series, and by approximating the obtained Fourier series coefficients by a sum of complex exponentials using the generalized pencil-of-function method. This transforms the radiation integral to a simpler form which can be evaluated analytically. Two types of wave objects are derived, both of them arising from the same spectral GPOF process, that possess different properties. Aperture fields obtained via the new approach are successfully compared to those calculated via direct near field integration or asymptotic evaluation. © 2010 IEEE.