A highly miniaturized and commercially available millimeter wave (mmw) radar sensor working in the frequency range between 121 and 127 GHz is presented in this paper. It can be used for distance measurements with an accuracy in the single-digit micrometer range. The sensor is based on the frequency modulated continuous wave (CW) radar principle; however, CW measurements are also possible due to its versatile design. An overview of the existing mmw radar sensors is given and the integrated radar sensor is shown in detail. The radio frequency part of the radar, which is implemented in SiGe technology, is described followed by the packaging concept. The radar circuitry on chip as well as the external antennas is completely integrated into an 8 mm $\times \,\, 8$ mm quad flat no leads package that is mounted on a low-cost baseband board. The packaging concept and the complete baseband hardware are explained in detail. A two-step approach is used for the radar signal evaluation: a coarse determination of the target position by the evaluation of the beat frequency combined with an additional determination of the phase of the signal. This leads to an accuracy within a single-digit micrometer range. The measurement results prove that an accuracy of better than $\pm 6~\mu \text{m}$ can be achieved with the sensor over a measurement distance of 35 mm.

Miniaturized Millimeter-Wave Radar Sensor for High-Accuracy Applications

Airborne applications demand exceptional overall radar system performance and eminently high output power for high range target detection. The frequency modulated continuous wave (FMCW) radar system presented in this article is capable of achieving this task due to its high output power at 94-GHz center frequency with over 26-GHz tuning range. Nevertheless, the radar still provides a small form factor and low power consumption of 4.25 W at 5 V single Universal Serial Bus (USB) supply. The key system component is a Silicon Germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) monolithic microwave integrated circuit (MMIC) that contains a 94-GHz voltage-controlled oscillator (VCO), and a 27-GHz VCO for dual-loop phase-locked loop (PLL) stabilization, a power amplifier (PA), and two receive mixers. It generates frequency ramps between 83- and 109-GHz with a maximum output power of 19.7 dBm at its output after the bond wires on the printed circuit board (PCB) and 14.8-dBm output power at the radar’s transmit (TX)-waveguide WR-10-flange. The sensor was also tested in a temperature range from −40 °C to +70 °C with menial deviation. Thus, the system offers high system dynamic range and far distance target detection range. Following a detailed system description, we finally present the FMCW range and Doppler measurements performed with the presented radar sensor as well as the application on unmanned aerial vehicles (UAVs) for flight altitude control and as airborne collision avoidance system (ACAS).

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Versatile Dual-Receiver 94-GHz FMCW Radar System With High Output Power and 26-GHz Tuning Range for High Distance Applications

This article presents a fully integrated 100-GHz continuous-wave Doppler radar transceiver with the double-sideband low-intermediate-frequency (IF) architecture for mechanical vibration and vital sign detection. Fabricated in a 65-nm CMOS process, the whole radar chip transceiver consumes 262 mW with a size of 0.9 mm $\times2.0$ mm. Instead of utilizing a fundamental 100-GHz voltage controlled oscillator (VCO) in the chip, a push–push frequency doubler with the 50-GHz external source is adopted to drive the transceiver. Under a dedicated design on the system architecture and circuit blocks, the chip could transmit 4-dBm saturated power ( $P_{\mathrm {sat}}$ ) over 93–105 GHz with a 40-mV 1-kHz IF carrier and achieve good I/Q performance of phase mismatch $\mu \text{m}$ displacement from 1.5 m, the human vital-sign signal from 2 m, and even a small bullfrog’s hybrid respiratory motion from 0.6 m. To the best of our knowledge, this is the first 100-GHz CMOS Doppler radar transceiver chip with the low-IF architecture for the biological vital sign detection.

Design of a 100-GHz Double-Sideband Low-IF CW Doppler Radar Transceiver for Micrometer Mechanical Vibration and Vital Sign Detection

Ahstract- Current developments in ankle prosthetics are focusing on integrated actuators to fully control torques and angles. This enables terrain adaptive strategies e.g. for stairs and ramps. EMG and motion sensor input are state of the art approaches to classify different terrain or terrain changes, but these approaches have limited capabilities and detection accuracy. We present a novel approach for the detection of obstacles using a wearable Frequency-Modulated Continuous Wave (FMCW) radar integrated into a lower limb prosthetic device. With the continuous rotational motion of the tibia during the swing and stance phase, the radar scans the profile of the terrain in sagittal plane in front of the prosthesis. Gait phases are detected using a neural network classifiers based on inertial sensor data. Performance of the system is demonstrated in a single stair detection scenario.

A Radar-Based Terrain Mapping Approach for Stair Detection Towards Enhanced Prosthetic Foot Control

Modern lower limb prostheses have the capability to replace missing body parts and improve the patients’ quality of life. However, missing environmental information often makes a seamless adaptation to transitions between different forms of locomotion challenging. The aim of this review is to identify the progress made in this area over the last decade, addressing two main questions: which types of novel sensors for environmental awareness are used in lower limb prostheses, and how do they enhance device control towards more comfort and safety. A literature search was conducted on two Internet databases, PubMed and IEEE Xplore. Based on the criteria for inclusion and exclusion, 32 papers were selected for the review analysis, 18 of those are related to explicit environmental sensing and 14 to implicit environmental sensing. Characteristics were discussed with a focus on update rate and resolution as well as on computing power and energy consumption. Our analysis identified numerous state-of-the-art sensors, some of which are able to “look through” clothing or cosmetic covers. Five control categories were identified, how “next generation prostheses” could be extended. There is a clear tendency towards more upcoming object or terrain prediction concepts using all types of distance and depth-based sensors. Other advanced strategies, such as bilateral gait segmentation from unilateral sensors, could also play an important role in movement-dependent control applications. The studies demonstrated promising accuracy in well-controlled laboratory settings, but it is unclear how the systems will perform in real-world environments, both indoors and outdoors. At the moment the main limitation proves to be the necessity of having an unobstructed field of view.

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Relying on more sense for enhancing lower limb prostheses control: a review.

In this paper, a compact W-band radar module will be presented, design aspects will be discussed and some measurement results of the finally realized module will be shown. The module features an integrated signal generation, full signal processing and power distribution. The signal generation is based on a phase-locked loop, optimized for linear frequency-modulated continuous-wave operation. A digital signal processor also works as internal controller and provides the digital interfaces. Due to the integrated power distribution, a single 7 to 15V power supply is necessary. In contrast to most state-of-the-art W-band systems using waveguides, a liquid crystal polymer based printed circuit board with integrated antenna and dielectric lens is used to realize a very compact module size of 42mm × 80mm × 27mm and low weight of 160 g. The total power consumption is 5 W, the radio frequency output power is 3dBm and the linear frequency-modulated contimuous-wave radar bandwidth is 14 GHz. The evaluated distance measurement repeatability of the module is 5 ppm (5µm deviation per meter target distance).

Christof Giers

Papers

A compact W-band LFMCW radar module with high accuracy and integrated signal processing