Prototype Radar System Research Articles

Verification of Applicability of 90 GHz Band Millimeter‐Wave for Obstacle Detection to Railway

AbstractObstacles on railway tracks are a factor hindering safe and stable operation. For this reason, obstacle detection systems have been introduced at level crossings, slopes and under platforms. However, they have been introduced only in limited sections for limited applications. Therefore, the authors considered to introduce an obstacle monitoring system that combines 90 GHz band millimeter‐wave and Radio over Fiber (RoF) technology, as an obstacle monitoring system over tracks to monitor the entire line. Since the millimeter‐wave band has a wide bandwidth, high precision detection is possible when they are used in radar. In addition, since radar control units can be grouped in one place by introducing the RoF technology, we can build a system at a low cost. In order to study the feasibility of introducing a new obstacles monitoring system combining 90 GHz band millimeter‐wave and RoF technology in railway environment, a field test using prototype equipment was conducted on a railway track. As a result, it was confirmed that the prototype radar system could detect humans and non‐metallic objects entering a track at a distance of about 200 m from the location of the prototype system. These results shows that the proposed system has the potential to be introduced as a new railway obstacle monitoring system using 90 GHz band millimeter‐waves and RoF technology. © 2023 The Authors. IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Drone-mounted UWB snow radar: technical improvements and field results

Drone borne radar systems have seen considerable advances over recent years, and the application of drone-mounted continuous wave (CW) radars for remote sensing of snow properties has great potential. Regardless, major challenges remain in antenna design for which both low weight and small size combined with high gain and bandwidth are important design parameters. Additional limiting factors for CW radars include range ambiguities and antenna isolation. To solve these problems, we have developed an ultra-wideband snow sounder (UWiBaSS), specifically designed for drone-mounted measurements of snow properties. In this paper, we present the next iteration of this prototype radar system, including a novel antenna configuration and useful processing techniques for drone borne radar. Finally, we present results from a field campaign on Svalbard aimed to measure snow depth distribution. This radar system is capable of measuring snow depth with a correlation coefficient of 0.97 compared to in situ depth probing.

Multiple Object Localization and Vital Sign Monitoring Using IR-UWB MIMO Radar

We consider 2-D localization and noncontact vital sign monitoring (i.e., determining the 2-D locations and estimating the rates of respiration and heartbeat) of multiple human objects via developing an impulse radio ultra-wideband (IR-UWB) distributed multi-input multi-output (MIMO) prototype radar system. A modified back projection algorithm is used to localize multiple objects. We also formulate the chest skin range displacement estimation problem caused by respiration and heartbeat into a sinusoidal frequency estimation problem, which can be solved efficiently via the fast Fourier transform method. Then, the robust, high resolution, and low sidelobe iterative adaptive approach (IAA) is adopted to obtain the IAA spectrum of the chest skin range displacement signal. Both respiration and heartbeat rates can be reliably determined from the IAA spectral estimates. Further, we solve the random body movement problem by developing a 2 × 2 IR-UWB distributed MIMO prototype radar system to obtain measurements from both the front and back of the human torso simultaneously. Finally, numerical and experimental results based on the prototype hardware radar systems we develop are presented to demonstrate the performances of the proposed 2-D localization and noncontact vital sign monitoring systems and the corresponding algorithms.

Preliminary experimental results by the prototype of Sanya Incoherent Scatter Radar

In the past decades, the Incoherent Scatter Radar (ISR) has been demonstrated to be one of the most powerful instruments for ionosphere monitoring. The Institute of Geology and Geophysics at the Chinese Academy of Sciences was founded to build a state-of-the-art phased-array ISR at Sanya (18.3°N, 109.6°E), a low-latitude station on Hainan Island, named the Sanya ISR (SYISR). As a first step, a prototype radar system consisting of eight subarrays (SYISR-8) was built to reduce the technical risk of producing the entire large array. In this work, we have summarized the preliminary experimental results based on the SYISR-8. The amplitude and phase among 256 channels were first calibrated through an embedded internal monitoring network. The mean oscillation of the amplitude and phase after calibration were about 1 dB and 5°, respectively, which met the basic requirements. The beam directivity was confirmed by crossing screen of the International Space Station. The SYISR-8 was further used to detect the tropospheric wind profile and meteors. The derived winds were evaluated by comparison with independent radiosonde and balloon-based GPS measurements. The SYISR-8 was able to observe several typical meteor echoes, such as the meteor head echo, range-spread trail echo, and specular trail echo. These results confirmed the validity and reliability of the SYISR-8 system, thereby reducing the technical risk of producing the entire large array of the SYISR to some extent.

Diurnal evolution of wind structure and data availability measured by the DOE prototype radar system

A new Doppler radar prototype has been developed and deployed at Texas Tech University with a focus on enhancing the technologies’ capability to contribute to wind plant relevant complex flow measurements. In particular, improvements in data availability, total data coverage, and autonomous operation were targeted to enable contributions to a wider range of wind energy applications. Doppler radar offers rapid scan speeds, extended maximum range and excellent along-beam range resolution allowing for the simultaneous measurement of various wind phenomena ranging from regional and wind plant scales to inflow and wake flow assessment for an individual turbine. Data examples and performance improvements relative to a previous edition of the technology are presented, including insights into the influence of diurnal atmospheric stability evolution of wind structure and system performance.

Concept and Implementation of a PLL-Controlled Interlaced Chirp Sequence Radar for Optimized Range–Doppler Measurements

In this paper, we introduce a novel concept for frequency-modulated continuous-wave radar. The approach is based on an interlaced chirp sequence waveform, which is controlled by phase-locked loops (PLLs). The use of PLLs improves frequency chirp linearity and reduces phase noise compared with open-loop voltage-controlled oscillators commonly used to generate the fast chirps. In contrast to basic range-Doppler processing, it enables higher target velocities to be detected unambiguously at the same resolution, which makes it suitable for automotive applications. Separate frequency synthesizers generate the interlaced ramps in the system. An RF switch combines these two signals to suppress transients caused by oscillator overshoot and to avoid incoherencies due to programming times of the PLL ICs. We built a prototype radar system in K-band. The test results are promising and bode well for other applications.

A W-Band Heterodyne FMCW Radar Based on TX IQ-Modulation

In this paper a method to realize a heterodyne frequency-modulated continuous-wave (FMCW) radar is presented. The proposed principle relies on the use of an inphase/quadrature (IQ)-modulator as single-sideband-mixer to shift the frequency of the FMCW-output away from dc. Since in any IQ-modulator phase and amplitude imbalances occur, the effect of these imbalances will be investigated by deriving the corresponding signal model. Based on this analysis, a method to compensate the imbalances by a predistortion of the modulation signal will be derived. The presented method does not require special test signals or additional hardware, but relies on a standard FMCW measurement onto a calibration target. A prototype radar system was built and used in test measurements to verify the proposed principle. The measurement results show that a suppression of unwanted signal components caused by IQ-imbalances better than 45 dB is achievable.