Cebrian Garcia-Gonzalez

Geometry Reconstruction of Metallic Bodies Using the Sources Reconstruction Method

This letter presents a novel application of the Sources Reconstruction Method (SRM) for geometry reconstruction. Foundations of this work are based on the correspondence between the placement of the metallic objects and the highest values of the reconstructed equivalent currents. In order to improve the accuracy of the method, reconstructed equivalent currents, due to different incident waves and working frequencies, are combined. Application examples using simulated data are presented.

Phaseless Synthetic Aperture Radar With Efficient Sampling for Broadband Near-Field Imaging: Theory and Validation

This paper presents a broadband and phaseless synthetic aperture radar (SAR) with efficient sampling. The design relies on a novel phaseless monostatic element comprising a transmitter and a receiver. This element, together with a computationally inexpensive algorithm, can retrieve the phase of the monostatic scattered field at all the working band except for two small safety margins at the lower and upper frequencies. Furthermore, the phase retrieval works independently of the transmitter/receiver position. Consequently, conventional approaches to reduce the number of monostatic acquisition points can be employed. Thus, the proposed strategy is suitable to implement either arrays that benefit from a reduced number of low-complexity elements or raster scan systems that benefit not only from the cost reduction of the scanning components but also from a remarkable speed-up due to the reduced number of acquisition points. Moreover, in contrast to other off-axis schemes, the proposed system does not require neither mechanical nor electrical phase shifting and, therefore, it can be directly adapted to a large number of frequency bands. The performance of the system is validated by simulation and measurement examples in the millimeter-wave band.

Frequency Scanning Based Radar System

A novel imaging technique based on a frequency scanning antenna array is presented. The method is conceived to provide angular information in range-based radar systems which do not allow mechanical or electronic beam steering. The beam steering is changed with frequency, which requires a novel scattered field data processing scheme/algorithm to recover the SAR image. System features, advantages and limitations are discussed, presenting simulation and measurement results, which show the system capabilities to resolve the range and angular position of the objects.

A novel phaseless frequency scanning based on indirect holography

A phase retrieval technique for multifrequency scattered field acquisition is presented in this paper. The proposed setup is based on indirect holography schemes so that it combines the desired signal with a known reference signal. The setup is used together with a two-dimensional frequency scanning (FS) antenna and, therefore, the positions of scatterers can be retrieved without the need of moving either the antenna or the objects.

Interferometric Technique With Nonredundant Sampling for Phaseless Inverse Scattering

A phaseless data acquisition applied on a reduced set of points is presented for inverse scattering problems. The setup is based on the Leith-Upatnieks holography with synthesized reference waves so that the phase of the reference wave can be adjusted to acquire the so-called “reduced field” instead of the regular field. Thus, nonregular sampling techniques can be applied resulting in strong reduction in the number of acquisition points. The technique is validated using simulation and measurement examples at microwave frequencies.

Phaseless Antenna Diagnostics Based on Off-Axis Holography With Synthetic Reference Wave

An antenna diagnostics method based on off-axis holography is presented in this letter. In this novel phaseless antenna measurement setup, the reference wave is synthesized by means of a mechanical phase shifting, and therefore the use of a phase shifter is avoided, yielding an accurate low-cost antenna diagnostics system. The technique is validated by means of simulation as well as measurement. Accurate results prove the system capability for antenna diagnostics tasks.

CHARACTERIZATION OF ANTENNA INTERACTION WITH SCATTERERS BY MEANS OF EQUIVALENT CURRENTS

Antenna characterization in presence of obstacles requires removing multipath efiects in order to retrieve the non-distorted antenna radiation pattern. In this contribution a new approach based on the Sources Reconstruction Method is proposed. The idea is to characterize the Antenna-Under-Test (AUT) and the region where the scatterers are located through a set of equivalent currents. Finally, the reconstructed equivalent currents on the contour enclosing the AUT can be used to recover the AUT radiation pattern, removing most of the distortion efiect due to the presence of the scatterers.

A Modified Phaseless Inverse Scattering Setup Based on Indirect Holography Implemented at Submillimeter-Wave Band

The aim of this communication is to present an enhanced phaseless inverse scattering setup and its implementation at the submillimeter-wave band. This setup is based on a modified indirect holography with synthesized reference signal so that a phase shifter is not required. Thus, a phaseless scanner can be built using a simple power detector resulting in a simplified measurement scheme very suitable to work in the millimeter-wave band and beyond. Mechanical phase shifting is used to bypass the use of electrical phase shifters. In addition, the reference signal is injected by coupling the transmitter and receiver antennas so that directional couplers and power combiners are avoided. New errors introduced by these techniques are analyzed and quantified. The method is validated with simulations as well as measurements at 300 GHz.

Error characterization tool for planar near-field antenna measurement and diagnostics applications

An error characterization tool is presented in this contribution to study the effect of mechanical and positioning errors in the near-field to far-field transformation and the computation of the aperture field processes in different planar measurement setups. Validation of the error simulation tool is made by comparison of the results with a set of measurements in a planar near-field range.

A MULTI-GPU SOURCES RECONSTRUCTION METHOD FOR IMAGING APPLICATIONS

A proflle reconstruction method using a surface inverse currents technique implemented on GPU is presented. The method makes use of the internal flelds radiated by an equivalent currents distribution retrieved from scattered fleld information that is collected from multiple incident flelds. Its main advantage over other inverse source-based techniques is the use of surface formulation for the inverse problem, which reduces the problem dimensionality thus decreasing the computational cost. In addition, the GPU implementation drastically reduces the calculation time, enabling the development of real time and accurate geometry reconstruction at a low cost.