Have you read everything about direction-of-arrival estimation in textbooks but are still uncertain how to realize it in practice? This tutorial-like article will help to link the theory with a practical approach for direction-of-arrival estimation using millimeter-wave (mm-wave) radar systems, and it deals with arising challenges. Step by step, it is explained how to move from the measured time domain data to the estimated angular position of the target. Since the target angle estimation is usually carried out after range-velocity processing, the required preprocessing steps are described.

Calibration and Direction-of-Arrival Estimation of Millimeter-Wave Radars: A Practical Introduction

This paper presents a fully packaged 140-GHz dielectric waveguide (DWG) communication link using a foam-cladded fiber. A novel frequency shift keying (FSK) demodulator topology is proposed with a low-frequency feedback loop for optimal FSK demodulation under process, voltage, and temperature variation. The introduction of phase shifters and an on-chip local oscillator relaxes the design requirements and the IF-stage benefits from larger gain. The transmitter is based on a fundamental oscillator at 140 GHz with a transformer-coupled buffer to decrease capacitive loading. Both chips are implemented in a 28-nm bulk CMOS design with a nominal supply of 0.9 V and a combined power consumption of 230 mW. An analysis of the DWG data capacity limitations is presented and compared with measurement results. Data rates of 12 Gb/s/10 Gb/s/7 Gb/s over 1 m/2 m/4 m of touchable polytetrafluoroethylene (PTFE) fiber are achieved.

Analysis and Design of a Foam-Cladded PMF Link With Phase Tuning in 28-nm CMOS

Fast Algorithms for Signal Processing: Bibliography

Automotive radar sensors play a vital role in the current development of autonomous driving. Their ability to detect objects even under adverse conditions makes them indispensable for environment-sensing tasks in autonomous vehicles. As their functional operation must be validated in-place, a fully integrated test system is required. Radar Target Simulators (RTS) are capable of executing end-of-line, over-the-air validation tests by looping back a received and afterward modified radar signal and have been incorporated into existing Vehicle-in-the-Loop (ViL) test beds before. However, the currently available ViL test beds and the RTS systems that they consist of lack the ability to generate authentic radar echoes with respect to their complexity. The paper at hand reviews the current development stage of the research as well as commercial ViL and RTS systems. Furthermore, the concept and implementation of a new test setup for the rapid prototyping and validation of ADAS functions is presented. This represents the first-ever integrated radar validation test system to comprise multiple angle-resolved radar target channels, each capable of generating multiple radar echoes. A measurement campaign that supports this claim has been conducted.

Radar Target Simulation for Vehicle-in-the-Loop Testing

River discharge is an important variable to measure in order to predict droughts and flood occurrences. Once the cross-sectional geometry of the river is known, discharge can be inferred from water level and surface flow velocity measurements. Since river discharges are of particular interest during extreme weather events, when river sites cannot be safely accessed, noncontact sensing technologies are particularly appealing. To this purpose, this work proposes a prototype of a low-cost continuous wave (CW) Doppler radar sensor, which is able to monitor the surface flow velocity of rivers. The prototype is tested at two gauged sites in central Italy, along the Tiber River. The surface flow velocity distribution across the river is monitored by means of the analysis of received Doppler signal. The surface velocity statistics are then extracted using a novel algorithm that is optimized to run on a microprocessor platform with minimal computing power (ArduinoUNO). In particular, the radar measurements are used to initialize a 2-D entropy-based velocity model (EVM) that is able to estimate river discharges in any flow condition. Finally, the results concerning the observed discharge provided by the EVM prove to be comparable with those obtained with more expensive commercial solutions. The results are important since the described methodology can be extended to small-size Doppler radar sensors onboard unmanned aerial vehicles (UAVs), the latter providing a method for mapping surface velocity of rivers.

Noncontact Measurement of River Surface Velocity and Discharge Estimation With a Low-Cost Doppler Radar Sensor

In this letter, a radar target simulator (RTS) for the generation of targets for frequency modulated continuous wave (FMCW) chirp sequence radar in the close range of a vehicles surroundings is presented. Key interest is the reproduction of micro-Doppler signatures of vulnerable road users, for example, pedestrians or cyclists. The received $E$ -band radar signal is first converted from the RF band to an IF band, in which the target is manipulated by modulating a range and velocity profile with an IQ modulator. To generate arbitrary signals forms, a PC controlled digital to analog converter (DAC) is used. The RTS has no delay lines to simulate the range, instead it is modulated directly. This allows the distance to be set individually for a large number of targets. In this contribution, the system itself and the underlying concept for the range generation are presented. Finally, measurements of generated static targets and micro-Doppler-signatures are shown.

A Near-Range Radar Target Simulator for Automotive Radar Generating Targets of Vulnerable Road Users

In radar measurements, the observed area is limited by the antenna beamwidth, and due to the usually fixed transceiver position, only unhidden targets in a small observation area can be detected. Furthermore, bulky lens dimensions prevent the use of radar systems in constricted surroundings despite the small dimensions of microwave monolithic integrated circuit (MMIC) radars. To avoid this issue, a new system concept for a flexible and low-cost 160-GHz radar sniffer probe is presented. The flexible sniffer probe is an extremely low-loss dielectric waveguide with a dielectric elliptical lens (28 dBi) at the end. The dielectric waveguide has dielectric losses of 4.5 dB/m at 160 GHz and high flexibility, supporting bending radii of 1.5 cm with negligible losses. To feed the dielectric waveguide, a metallic waveguide with a duplexer is used, which is fed by a special MMIC-to-metallic waveguide transition. The proposed system expands the known radar measurement scenarios with new industrial, medical, and security applications.

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A 160-GHz Radar With Flexible Antenna Used as a Sniffer Probe

Flexible antennas in radar applications enable the user to go around obstacles or detect targets at hidden places In this paper, two elliptical lenses of different size made of high density polyethylene and stacked on a flexible dielectric waveguide are designed and measured from 140 GHz to 180 GHz The feeding dielectric waveguide and the mode transition from metallic waveguide to dielectric waveguide was investigated with full wave simulations The elliptical lenses were designed with a geometrical optics approach The realized antennas have a gain larger than 24 dBi and 27 dBi and a maximum side lobe level below −158 dB

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A dielectric lens antenna fed by a flexible dielectric waveguide at 160 GHz

In this contribution an approach for fluid surface velocity estimation is presented. In order to achieve estimation results, the lag of directly backscattered characteristic surface changes is determined. The evaluation of the surface velocity which will be discussed, too, bases on a cross correlation of two radar signals. These two signals are generated using two 77 GHz radar sensors, which have been developed in our laboratory. The measurements shown at the end of the paper result from an artificial flow passage. Further observable ambiguities in the cross correlation function are discussed in the paper.

Time-domain correlation radar for fluid surface velocity estimation using a 77 GHz sensor platform

In this contribution, a radar target simulator for generating time-varying Doppler shifts to simulate micro-Doppler signatures of vulnerable road users, is presented. The radar target simulator is designed to evaluate automotive radar sensors used in the near surroundings of vehicles. The maximum bandwidth of the radar signals that can be tested is 1.5 GHz. By using a DAC it is possible that arbitrary micro-Doppler signatures can be generated.

Johannes Iberle

Papers

A Near-Range Radar Target Simulator for Automotive Radar Generating Targets of Vulnerable Road Users

A 160-GHz Radar With Flexible Antenna Used as a Sniffer Probe

A dielectric lens antenna fed by a flexible dielectric waveguide at 160 GHz

Time-domain correlation radar for fluid surface velocity estimation using a 77 GHz sensor platform

A Radar Target Simulator for Generating Micro-Doppler-Signatures of Vulnerable Road Users