M. Helbig

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.

Time-variant non-linear phase-coupling analysis of EEG burst patterns in sedated patients during electroencephalic burst suppression period

OBJECTIVES The quadratic phase-coupling (QPC) within burst patterns during electroencephalic burst suppression has been quantified. METHODS It can be shown that a QPC exists between the frequency ranges 0-2.5 and 3-7.5 Hz and between the frequency ranges 0-2.5 and 8-12 Hz. By means of time-variant bicoherence analysis, a strong phase-locking between the modulating and the modulated component can be identified. The phase-locking is demonstrable within the first 250 ms after the burst onset and comes up to the maximum between 750 and 1250 ms. RESULTS The effect is maintained over the whole first part of the burst (2 s) with a decreasing tendency after 1250 ms. All these effects cannot be found in the EEG before entering the burst suppression period (BSP). The transient coupling phenomena in the EEG bursts during BSP can be regarded as indicators for short-term interrelations between the underlying electrophysiologic processes. CONCLUSIONS It can be suggested that the method introduced for the quantification of the sedation depth should be used.

Remote vital sign detection for rescue, security, and medical care by ultra-wideband pseudo-noise radar

The vitality of a human being is closely connected to temporal variations of its body geometry. This is quite obvious in the case of walking. But also when resting, the motion of inner organs such as lung or heart causes geometric alterations which may be registered by high-resolution ultra-wideband radar. Since the radio waves radiated by such radars are absolutely harmless, they may be deployed for monitoring of resident activities helping to ensure health, safety, and well-being of aged or needy people. These waves may also penetrate most of building materials and snow which makes them useful to detect earthquake and avalanche survivors, too. The most challenging task is the registration of respiration activity of an unconscious person. The principle of breathing motion detection by radar is explained and the major handicaps as well as appropriate counter measures are discussed. The possible structure of a survivor and residential injury detection radar system is considered and some results from field trials are summarized.

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.

On the rhythmicity of quadratic phase coupling in the tracé alternant EEG in healthy neonates

The time-variant quadratic phase coupling (QPC) in trace alternant (TA) EEG patterns in healthy full-term neonates (quiet sleep) was investigated by means of time-variant bispectral analysis. The frequency plain 1-1.5 Hz <=> 3.5-4.5 Hz was used as the region-of-interest. QPC rhythms with a frequency of approximately 0.1 Hz were found in all neonates (n = 6). It can be demonstrated that the QPC rhythm of the TA is generated by a pattern-spanning time-variant phase-locking process characterising early functional interactions in the immature brain.

Quantification of transient quadratic phase couplings within EEG burst patterns in sedated patients during electroencephalic burst-suppression period

The time dynamics of the quadratic phase coupling within burst patterns during electroencephalic burst-suppression has been quantified. It can be shown that a transient quadratic phase coupling (QPC) exists between the frequency ranges 0 to 2.5 and 3 to 7.5 Hz and between the frequency ranges 0 to 2.5 and 8 to 12 Hz. The QPC can be explained by an amplitude modulation, where the slow rhythm modulates the rhythmic activities with a higher frequency. By means of time-variant bicoherence analysis, a strong phase-locking between the modulating and the modulated component can be identified. The phase-locking is demonstrable within the first 250 ms after the burst onset and comes up to the maximum between 750 and 1250 ms. The effect is maintained over the whole first part of the burst (2 s) with a decreasing tendency after 1250 ms. All these effects cannot be found in the EEG before entering the burst suppression period (BSP). The transient coupling phenomena in the EEG bursts during BSP can be regarded as indicators for short-term interrelations between the underlying electrophysiologic processes.

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.

Trapped victim detection by pseudo-noise radar

Radar based detection of earthquake survivors exploits the modulation of the backscattered signal by body motions of the victim. The most challenging task is the detection of respiration activity of an unconscious person. The principle of breathing motion detection by radar is explained and the major handicaps as well as appropriate counter measures are discussed. The possible structure of a survivor detection radar system is considered and some results from field trials are summarized.