Christian G. Diskus

A microwave position sensor with sub-millimeter accuracy

Design and characteristics of a prototype distance sensor are presented. The radar front-end operates at 35 GHz and applies six-port technology and direct frequency measurement. The sensor makes use of both FS-CW and interferometer principles and is capable of measuring distance with 0.1 mm accuracy.

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.

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

Pulse-Based Radar Imaging Using a Genetic Optimization Approach for Echo Separation

This paper describes a novel 3-D ultra-wideband (UWB) imaging technique with the aim of detecting, classifying, and imaging water pipes located inside walls. The target under test was chosen in such a way that the echoes of the front side of the wall and of the water pipes overlap making it impossible to distinguish between them in the raw data. Applying a genetic optimization algorithm for modeling the radar response by a superposition of single echoes it was possible to determine the exact round-trip times of several scatterers. Moreover, the algorithm takes into account the pulse distortion caused by varying angles of incidence at the broad beam antenna.

A 60-GHz MMIC-compatible TED-oscillator

Experimental results achieved with planar GaAs transferred electron oscillators at V-band frequencies are reported in this contribution. The active devices are MESFET-like structures with a Schottky-gate controlling the electron injection into the drift region. The electron injection is adjusted to a level yielding a frequency independent negative differential resistance which is exploited for millimeter-wave power generation. The highest measured CW output power and efficiency are 6.72 mW and 1.3% at 60.33 GHz, respectively. These results are comparable to those obtained with transistor oscillators which are much more difficult to fabricate due to their extremely small dimensions in the 0.1 μm range.

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.