Werner Scheiblhofer

A 77-GHz Cooperative Radar System Based on Multi-Channel FMCW Stations for Local Positioning Applications

In this paper, a radar system for local positioning applications is presented. The system consists of frequency modulated continuous-wave (FMCW) stations operating in W-band that are loosely coupled using time-delayed ramp start signals. A centralized signal processing approach allows to relax the required synchronization accuracy between the stations and further leads to a cancellation of phase noise and phase distortions caused by imperfect FMCW ramps. All stations are equipped with an antenna array and multiple receivers. Thus, a signal processing approach is developed in this work that combines the positive effects from the centralized processing with the information from the antenna array in a digital-beamforming based approach to improve the multipath robustness of the overall system. The developed theory is confirmed in measurements carried out with a prototype system consisting of two stations. Various measurements in multipath environments confirm the improved robustness leading to a worst-case root-mean-square position error of 15 mm under strong multipath conditions which were simulated inside an anechoic chamber.

A high-precision long-range cooperative radar system for gantry rail crane distance measurement

We present the implementation of a cooperative radar system on a gantry rail crane for distance measurements in an industrial environment. The measurement approach is based on the dual-ramp frequency-modulated continuous-wave principle, using identical sensor-nodes at the endpoints of the range of interest. Pseudo-range information is exchanged via a dedicated data-link between these stations. At the sensor-node a flexible high-performance signal processing and remote management engine is implemented. The system setup is controlled by a single host-PC, which is used as a man–machine interface for configuration of the remotely controlled measurement stations, system surveillance, and visualization of the measurement data. Indoor characterization of the developed hardware is sufficient for an efficient calibration of the system, minimizing distance offsets. On-site measurements at distances up to 1000 m with an accuracy better than 2 cm confirm the performance of the ranging system. Furthermore, the results are verified by simulation.

Hardware and Signal Processing for a Novel Multi-Lap-Joint Measurement System for Automated Welding Applications

This paper presents a radar system for measuring the position of edges with good electrical conductivity in automated welding applications. The sensor consists of a frequency-modulated continuous-wave radar system which operates in the W-band. To estimate the position of the edge, we focus on polarimetric scattering effects introduced by discontinuities in the shape of a conducting plate. In addition to hardware designs, we propose signal models for single- and multi-step scenarios. The signal models are calculated using a field simulation tool we developed. The proposed models were used to derive a novel position estimation algorithm that allows real-time operation. Further, the accuracy limits of our concept were investigated using an analytically derived Cramér-Rao lower bound and simulations for multi-step scenarios. The simulation results were verified by measurements. Electromagnetic influences of the welding arc on the system during operation were also investigated by measurements.

Simultaneous localization and data-interrogation using a 24-GHz modulated-reflector FMCW radar system

In this paper, the integration of a communication link for a modulated-reflector radar is presented. This kind of radar system is intended to determine the position of multiple semi-passive backscatter reflector nodes, designed to be mounted on different objects of interest. A method to transport information from these objects back to the radar-basestation is sketched, using the available hardware-resources of the nodes. In addition a technique minimizing the influence of this communication link on the localization capability of the system is presented and validated by measurements.

In-chirp FSK communication between cooperative 77-GHz radar stations integrating variable power distribution between ranging and communication system

We present the realization of a cooperative radar system for ranging applications with integrated data-transmission capability. The simultaneous transmission is performed by the radar-hardware without the necessity of additional components or an auxiliary data-link. Therefore, the data are directly embedded in the transmitted chirp of a frequency-modulated continuous-wave radar sensor. A second station, acting as receiver, uses an identical, but unmodulated chirp for down-conversion. The resulting signal then is processed by a non-coherent demodulator setup, extracting the communication data. Measurement results from transmission of messages with different bit-rates are shown. By utilizing existing radar-hardware a transmission rate of up to 256 kbps is possible, without the need of a dedicated transceiver. Additionally, a method to optimize the ranging results by variable distribution of the available signal power between distance-measurement and communication system is presented.

Polarimetric measurements with integrated sensors at mm-wave frequencies

We present a fully polarimetric frequency-modulated continuous-wave (FMCW) radar prototype and show its performance by polarimetric measurements of a dihedral corner reflector. The radar prototype operates at a frequency of 77 GHz and is built up by an FMCW frontend (FE) and a multichannel baseband board. The FE consists of horizontally and vertically polarized transceiver channels to conduct co-polarized and cross-polarized measurements. To demonstrate the capability of the system, we placed a dihedral corner reflector on a turntable facing the radar system. Then measurements of the corners scattering parameter, depending on its rotation angle, were taken. To confirm the measurement results, we ran simulations using a self-developed numerical field simulation tool and compared the results to the measurements.