J. Sachs

Recent Advances and Applications of M-Sequence based Ultra-Wideband Sensors

Ultra-wideband (UWB) sensing is an upcoming technique to gather data from complex scenarios such as nature, industrial facilities, public or private environments, for medical applications, non-destructive testing and many more. Currently it is hard to estimate the full spread of future applications. The measurement approach traditionally used is based on stimulation of the test objects by either short sub-nanosecond impulses or sine waves which are stepped/swept over a wide spectral band. This paper deals with an alternative approach, which uses very wideband pseudo-noise binary signals such as M-sequences for example. Such devices have a very high time stability, enable high measurement speed and do not burden the test objects with high voltage peaks. Furthermore, the device concept promotes monolithic circuit integration in a low cost semi-conductor technology. In what follows, the basic device concept and some extensions will be considered as well as some selected applications will be discussed.

Combining magnetic resonance imaging and ultrawideband radar: A new concept for multimodal biomedical imaging

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and UWB radar. Furthermore, first in vivo experiments have been carried out, utilizing this new approach. Correlating the reconstructed UWB signals with physiological signatures acquired by simultaneous MR measurements, representing respiratory and myocardial displacements, gave encouraging results which can be improved by optimization of the MR data acquisition technique or the use of UWB antenna arrays to localize the motion in a focused area.

Liquid and moisture sensing by ultra-wideband pseudo-noise sequence signals

The use of ultra-wideband signals for moisture sensing by electromagnetic wave interaction provides more information on the material under test compared to single tone or narrowband approaches, regarding spatial and frequency dependent phenomena. Current activities to regulate the emission of electromagnetic waves in the spectral band up to 10 GHz for sensor applications open new perspectives for microwave moisture sensing. Therefore, improved and cost effective ultra-wideband measurement principles will become more and more interesting. The use of short pulses or swept sine waves are classic approaches to cover a large spectral band. However, this paper deals with some variants of an alternative method, which applies pseudo-random codes, namely M-sequences, to stimulate the test objects. The method permits monolithic integration of the RF-electronics in SiGe technology. The signal generation and data capturing are referred to a common stable single tone clock and they are controlled by steep trigger signals. This provides for very stable operation, which allows for measurements in both time and frequency domain. Two versions of an M-sequence approach will be considered and their functioning will be demonstrated by means of simple measurement examples.

Preliminary investigations of chest surface identification algorithms for breast cancer detection

Ultra-wideband sensing and imaging provides perspectives for early-stage breast cancer detection. This paper deals with problems related to the accurate identification of the breast surface. The applicability of the published and recently extended boundary scattering transform (BST) is investigated. In order to reconstruct the whole breast region, the so far planar scanning of the antennas is extended to a spatial scanning. The experimental study is carried out based on metallic test objects and a female dressmaker torso.

Design and application of dielectrically scaled double-ridged horn antennas for biomedical UWB radar applications

Ultra-wideband sensing begins to play an important role in biomedical diagnostic systems. Promising and relevant applications include remotely monitored vital functions as well as the characterization of tissues and organs. The acquisition of such physiological signatures requires small and radiation-efficient antennas, designed for ultra-wideband frequency operation. We have developed physically small and adjustable double-ridged horn antennas with which we could demonstrate the specific advantages of miniaturized, dielectrically matched sensor elements in a direct mode compared to remote sensor applications. As a logical consequence of these results, we have considered to replace the lossy high-permittivity liquid by low-loss high-permittivity solid ceramic material to improve the degree of miniaturization and the radiation efficiency further. Some unexpected peculiarities related to this approach are discussed.

Physically small and adjustable double-ridged horn antenna for biomedical UWB radar applications

Biomedical applications of ultra-wideband radar promise a very important means to remotely characterise tissues and organs. The acquisition of such physiological signatures requires small and efficient antennas, designed for ultra-wideband frequency operation. We have designed and characterised physically small and adjustable double-ridged horn antennas for frequencies from 1 to 10 GHz. The miniaturisation of the radiating elements was accomplished by immersion into a high permittivity liquid dielectric. The effect of dielectric scaling on size, input matching, radiation patterns, and gain has been evaluated by comparison with a double-ridged horn antenna designed for operation in air.

High resolution non-destructive testing in civil engineering by ultra-wideband pseudo-noise approaches

Ultra-wideband sensing provides new and interesting options for testing and inspection in many different fields. The article will deal with some applications for civil engineering. The advantage of UWB-sensing is the good penetration of the sounding waves through the material under test and its high spatial resolution. A flexible UWB-sensor conception will be discussed. Its working principle is based on pseudo-random sounding waves. The examples considered shall indicate the device performance for quite different sensor tasks.

An Ultra-Wideband Pseudo-Noise Radar Family integrated in SiGe:C

Random noise radar attracts interest mainly because of its low interference and its camouflaged operation, as well as the relaxed requirements concerning transmitter power. Its challenge for very wideband operation is the impulse compression in order to gain range resolution. The use of pseudo random codes largely defuses this problem while keeping most advantages of random noise radar. Modern semi-conductor technologies permit the implementation of code generators operating at clock-rates up to tens of GHz at reasonable costs. The resulting range resolutions are to be found in the cm- and sub-cm-range. The implementation of our radar core is based on SiGe:C-technology. An overview of the basic system configurations will be given.

Improved Breast Surface Identification for UWB Microwave Imaging

Electromagnetic ultra-wideband sensing and imaging provides perspectives for early-stage breast cancer detection. This paper deals with problems related to the accurate three-dimensional identification of the breast surface. The SEABED algorithm based on the Inverse Boundary Scattering Transform (IBST) represents a powerful basic approach for surface detection problems.

Ultra-wideband active array imaging for biomedical diagnostics

Ultra-wideband active array imaging has proven extremely valuable for biomedical diagnostics. At the same time, the underlying technologies have achieved a high degree of maturity. Across institutions, we have merged our expertise in M-sequence radar systems, antennas, low-noise and high-power circuitry, to devise an UWB MIMO radar system for breast tumour localisation. Recent progress in UWB imaging and hardware for active antenna arrays is presented.