Alexander Reisenzahn

Through-Wall Imaging With a 3-D UWB SAR Algorithm

Ultra-wideband (UWB) radar systems become more and more important for material penetrating and imaging applications. Many conventional UWB signal processing algorithms for image generation are commonly based on migrations techniques which are not optimal in terms of object identification capability and calculation time. Thus, a surface reconstructing imaging algorithm has been implemented and verified by real radar data. It offers two crucial advantages with respect to the conventional algorithms: an extensive reduction of the calculation time and the ability to identify targets by the shape of the object. Several examples are given demonstrating the efficiency of this approach. It is based on a preselection of the received C-scan yielding the quasi-wavefronts of the object.

Ultra-wideband transceivers for cochlear implants

Ultra-wideband (UWB) radio offers low power consumption, low power spectral density, high immunity against interference, and other benefits, not only for consumer electronics, but also for medical devices. A cochlear implant (CI) is an electronic hearing apparatus, requiring a wireless link through human tissue. In this paper we propose an UWB link for a data rate of Mbps and a propagation distance up to 500 mm. Transmitters with step recovery diode and transistor pulse generators are proposed. Two types of antennas and their filter characteristics in the UWB spectrum will be discussed. An ultra-low-power back tunnel diode receiver prototype is described and compared with conventional detector receivers.

A Wave Front Extraction Algorithm for High-Resolution Pulse Based Radar Systems

The resolution of a pulse based radar system is restricted by the pulse width. Overlapping echoes in time domain of adjacent objects make a wave front evaluation of B-scans difficult. In this paper, a new algorithm for the wave front detection is proposed. Based on a reference impulse response of a large metal plate, the algorithm is able to determine the number of targets. Furthermore, two narrow adjacent spheres were detected as two different objects although the pulses of the two targets were overlapping. In the resulting radar image their shapes could be reconstructed.

Comparison of UWB Target Identification Algorithms for Through-Wall Imaging Applications

In this paper an ultra-wideband imaging radar system using B-scans is proposed. Two imaging algorithms for shape recognition are explained and compared. Furthermore, for the first time the two dimensional inverse boundary scattering transform was successfully applied for through-wall imaging applications. The measured radar data of a cylinder behind a wall demonstrate that only 24 different positions of the antennas were sufficient to reconstruct the target curvature

An ultra low power transcutaneous impulse radio link for cochlea implants

The big potential of ultra wideband radio, in particular low power consumption, low power spectral density, high immunity against interference, affords many benefits, not only for consumer electronics, but also for medical devices. A cochlea implant is an electronic hearing apparatus, where a wireless link through human tissue is required. We propose a UWB link for a data rate of 1.2 Mbps and a propagation distance up to 500 mm. Transmitter, antennas and receivers are described and proposals for semiconductor integration are made.

Phase-synchronization in UWB receivers with sampling phase detectors

Ultra wideband (UWB) radio offers low power consumption, low spectral density, high immunity against interferences and other benefits, but for synchronous transmission of data the transmitter and the receiver clocks have to be synchronized. One possibility to realize this is the use of a broadband mixer which is difficult to fabricate and hence expensive. An alternative is the use of a sampling phase detector which is not only cheaper, but also yields a simpler circuitry. In this paper the two methods are compared and the advantages of synchronization with a sampling phase detector are shown.

An UWB Wall Scanner Based on a Shape Estimating SAR Algorithm

This paper describes a complete pulse based high-resolution radar system. This includes the transmitting and receiving unit as well as the signal processing of the down-sampled echoes. The main focus of the hardware design was on the usage of low-cost components. The signal evaluation is based on the shape reconstruction of simple targets in order to use the proposed radar system for wall scanning applications, e. g. the detection of water pipes.

A Low-Cost UWB Radar System for Sensing Applications

A new low-cost pulse based ultra-wideband radar system working up to 6.4 GHz has been developed. The main focus was on the use of cheap off the shelf components. Pulse generation in the transmitter was solved with a simple transistor circuitry. The down conversion in the receiver is realized with a sampling phase detector combined with a direct digital synthesizer. To control the radar system and for transmitting the digitized data to the PC a USB-controller is used

Ultra-wideband sampling down converter with sampling phase detector

Ultra-wideband radar is an excellent tool for nondestructive examination of walls and highway structures. Therefore often steep edged narrow pulses with rise-, fall-times in the range of 100 ps are used. For digitizing of the reflected pulses a down conversion has to be accomplished. A new low cost sampling down converter with a sampling phase detector for use in ultra-wideband radar applications is presented.

UWB Radar Calibration Using Wiener Filters for Spike Reduction

Ultra wide band (UWB) radar systems are used to get information from a detected target. This can be done by studying the shapes of incident and reflected pulses. To evaluate the target transfer function, a calibration is necessary to eliminate the influences of the system and the environment. The calibration includes deconvolution operations producing spike artifacts. In this paper a calibration approach for spike suppression by using Wiener filters in the deconvolution process is introduced