Jan Barowski

On the usability of low-cost inertial navigation systems for free-hand SAR imaging at GPR-frequencies

This contribution investigates the influence of Inertial Navigation System (INS) uncertainties for antenna positioning on Synthetic Aperture Radar (SAR) imaging. Therefore, a SAR simulator, which provides predefined positioning uncertainties is introduced. Two parameters of the resulting SARimage, i.e., the spatial resolution and the detection shift of a point target are investigated in range and azimuth direction. Moreover, a simple INS, which relies on an accelerometer, is introduced and the particular positioning method is discussed in detail. The applicability of the presented INS is investigated by means of SAR-measurements, which were performed with a Ground Penetrating Radar (GPR) antenna and a Vector Network Analyzer (VNA). Moreover, the resulting SAR images are evaluated by the defined properties and compared to SAR images, which rely on the same raw data, but utilize a positioning vector gathered by a high precision mmWave-radar.

Ground penetrating synthetic aperture radar imaging providing soil permittivity estimation

In this paper a combined Ground Penetrating Radar (GPR) and Synthetic Aperture Radar (SAR) technique is introduced, which considers the soil surface refraction and the wave propagation in the ground. By using Fermats principle and the Sober operator, the SAR image of the GPR data is optimized, whereas the soils permittivity is estimated. The theoretical approach is discussed thoroughly and measurements that were carried out on a test sand box verify the proposed technique.

Characterizing Dielectric Materials using Monostatic Transmission- and Reflection-Ellipsometry

Abstract The characterization of dielectric materials at microwave frequencies can be done by various measurement principles. Free space methods are a commonly used approach if the material under test (MUT) has to be characterized in-situ or in a non-destructive manner. Since the transmission and reflection parameters of a finite sized dielectric slab typically depend on its thickness, accurate knowledge about this parameter is of high importance. The ellipsometric approach presented in this paper eliminates the thickness dependence and thus allows to reduce a major source of error. This is achieved by performing four measurements. These measure the transmission and reflection factors of the MUT in both polarizations at an incident angle of 45°. The high stability of the measurement allows a simple monostatic setup utilizing a single antenna. The measurements in this paper are performed using Polytetrafluoroethylene (PTFE) and Polyvinylchloride (PVC) blocks in the frequency range from 22 GHz to 26 GHz.

Dielectric phantom materials for broadband biomedical applications

In this contribution, we present broadband microwave measurements on developed biomedical phantom materials. Therefore, we illustrate the reproducible mixing process of the realized phantom materials that are generated in different shapes with a potting compound and barium titanate. Moreover, three microwave measurement systems, including a coaxial probe, a microwave tomography system, and a radar ellipsometry system, characterize the dielectric behavior of the samples in different frequency bands.

Real-time imaging system for millimeter wave synthetic aperture radar sensors

In this contribution, a real-time imaging system alongside its processing chain for millimeter wave (mmWave) synthetic aperture radar (SAR) sensors operating at 240 GHz is presented. In addition to real-time capability, the SAR imaging system is manually moved on a linear track without precise stepper motors. Instead, the current position is obtained by a second radar measurement at a far lower frequency with an additional reference target. By this means, the image of the considered scene can be obtained in mere seconds. To allow real-time processing of the measurement data, a signal processing chain based on separate threads is established and further enhanced by using a graphics-processing unit (GPU). Due to the large imaging bandwidth of 50 GHz, the image system can be used to obtain high-resolution sub-surface images of e.g. construction materials.

Active contour extraction method for objects with a rough surface using single-chip FMCW radars

In this paper a method for contour extraction of objects with a high degree of surface roughness in the range of 60 GHz Radar is presented. The proposed algorithm is based on an active contour model (snake) with external forces called component normalized gradient vector flow (CN-GVF). The snake algorithm extracts the contour of the object under test (OUT) based on wavefront Radar imaging methods. Experimental validations were performed with two fully integrated wideband frequency modulated continuous-wave (FMCW) single-chip Radar transceivers with an operational band from 57 GHz to 64 GHz, a corner cube retroreflector and a target object with a high degree of surface roughness.

Monostatic and thickness-independent material characterisation based on microwave ellipsometry

Material characterization utilizing microwave ellipsometry is based on the fact that the reflection coefficients of a wave impinging on a material depend on the incident fields polarization. Due to multiple reflections that occur in case of a material slab with finite dimensions these coefficients also strongly depend on the materials thickness. This paper describes an approach to determine the electromagnetic properties of a material under test by applying an ellipsometric measurement without knowledge of the materials thickness. The paper shows that the additional measurement of the transmission coefficients allows to perform an exact measurement of the complex permittivity since the thickness dependencies in reflection and transmission coefficients are removed. The measurements are done in the frequency range from 22 GHz to 26 GHz by using a vector network analyzer setup with a conical horn antenna.

Development and analysis of a modified Saleh-Valenzuela channel model for the UHF band

This contribution deals with the analysis of a modified Saleh-Valenzuela channel model for the UHF band. The development of the channel model is based on indoor channel measurements within a large exhibition hall in a line-of-sight scenario in order to study new cognitive radio systems. Contrary to the conventional modeling, the path voltage gain is modeled by a Rayleigh probability density function. Due to the broad-band consideration the channel model can be used for a variety of different operating frequencies.

A system simulator including channel and frontend models for cognitive professional wireless microphones

In this paper a simulation environment for indoor transmissions in the ultra high frequency band is presented. The simulator comprises hardware as well as channel models that were derived from extensive measurement campaigns. In case of hardware modeling, nonlinear memory-polynomial models are used in order to accurately describe the intermodulation between multiple receive signals. The presented channel model is structured into three layers for indoor line of sight, non line of sight as well as outdoor to indoor transmissions. The indoor models utilize a Saleh-Valenzuela approach and a Clarkes model, while the outdoor model makes use of a Hata model.