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Modern radar sensors are gaining more and more relevance for several industrial measurement applications. To achieve the required range resolution and measurement accuracy, the use of higher frequencies beyond 100 GHz is beneficiary. A commonly used signal generation concept in fully integrated radar transceivers is to use a fundamental oscillator with subsequent frequency multiplication. Depending on the overall system concept, this type of signal generation suffers from a fundamental feed-through signal which generates false targets in frequency modulated continuous wave operation. Additionally, those unwanted signal components radiated by the sensors might be problematic for legal conformity or electromagnetic (EM) interference compliance. This paper presents a novel concept for frequency filtering dielectric lens antennas, to suppress unwanted signal components at harmonic frequencies based on interference filtering effects. Besides the EM simulations to theoretically prove this concept, multiple prototypes of filtering lens antennas were fabricated by conventional mechanical and additive manufacturing. Using a self-developed, ultra-compact radar sensor, measurements were taken to compare the lens antenna prototypes in terms of filtering performance and how the material characteristics affect the filtering performance. Within these measurements, the successful suppression of false targets caused by fundamental feed-through signals is demonstrated.
The development of a millimeter-wave transparent antenna integrated inside a headlamp for automotive radar application is presented. The antenna consists of two radiating elements: the primary and secondary ones. The primary antenna is the one that is fabricated on RF PCB material (e.g., patch, slot, sectoral horn) and connected directly to the transceiver chip, while the secondary antenna is made of optically transparent materials such as glass, but with a optical transparent electrically conductive coating, well known as transparent conductive oxide (TCO). This antenna is realized as a planar offset reflector to collimate and shape the incoming wave from the primary antenna. This reflector is designed based on the Fresnel theory and the reflectarray concept. The division of the primary and secondary antenna enables the placement of the radar module (that contains the primary antenna) at the base of the headlamp, and therefore it is concealed from the surroundings and hidden from the optical path of the light. The secondary antenna is inserted in the space between the headlamp cover and the light unit. The main challenge here is to provide a maximum on transparency in the visible range of the spectrum with a specially designed and laser-based generated microstructure for the resonant reflection of the radar wavelength. An antenna demonstrator has been fabricated, and together with the headlamp cover, the radiation pattern and realized gain are measured. We reported here the measurement results for several reflector designs and concluded that the headlamp cover gives minimal influence on the antenna performance.
Standards IEC 62288:2014 and MSC.191(79) require information on the displays of shipboard navigation systems to be logically grouped, but only provide limited specification for this ‘logical’ criterion. Meanwhile, complex interfaces and information overload remain as major design issues, being connected to several maritime accidents. To address this matter, a three-phase study was conducted to develop a pattern to organise essential information on Radar and Electronic Chart Display and Information System (ECDIS) displays and their equivalent modules on integrated navigation systems and integrated bridge systems. The first phase involved identifying the information most essential for safe navigation using cognitive task analyses, equipment performance standards and frequency of use. The second phase involved a card-sorting experiment with seafarers (n = 63) to develop an initial grouping pattern for the identified essential information. The third phase involved validating the initial grouping pattern with a new sample of seafarers (n = 35). The result is a pattern to group 48 types of information on shipboard navigation displays into 13 groups. The paper details the selected methods and the findings, and provides implications for future research.
In this paper, a wideband ultrathin metasurface absorber is investigated. The proposed absorber comprises a periodic array of a unit cell ring structure. The ring structure and patch inside are tuned to realize the desired frequency bandwidth. The structure has a frequency bandwidth of 7.4 GHz with a center frequency of 15 GHz and fractional bandwidth of 50%. Simulated and measured results show that the absorption at normal incidence is above 90% in the frequency range of 11.3–18.7 GHz. Furthermore, the thickness of the structure is 1.6 mm. The physical mechanism of the metasurface absorber has been analyzed and justified experimentally.
This paper introduces a new maritime search and rescue system based on S-band illumination harmonic radar (HR). Passive and active tags have been developed and tested while attached to life jackets and a small boat. In this demonstration test carried out on the Baltic Sea, the system was able to detect and range the active tags up to a distance of 5800 m using an illumination signal transmit-power of 100 W. Special attention is given to the development, performance, and conceptual differences between passive and active tags used in the system. Guidelines for achieving a high HR dynamic range, including a system components description, are given and a comparison with other HR systems is performed. System integration with a commercial maritime X-band navigation radar is shown to demonstrate a solution for rapid search and rescue response and quick localization.
Next-generation automotive radar sensors are increasingly becoming sensitive to cost and size, which will leverage monolithically integrated radar system-on-Chips (SoC). This article discusses the challenges and the opportunities of the integration of the millimeter-wave frontend along with the digital backend. A 76–81 GHz radar SoC is presented as an evaluation vehicle for an automotive, fully depleted silicon-over-insulator 22 nm CMOS technology. It features a digitally controlled oscillator, 2-millimeter-wave transmit channels and receive channels, an analog base-band with analog-to-digital conversion as well as a digital signal processing unit with on-chip memory. The radar SoC evaluation chip is packaged and flip-chip mounted to a high frequency printed circuit board for functional demonstration and performance evaluation.
In this work, the scattering characteristics of 3D-printed samples are being investigated by using a single-polarized and a cross-polarized radar system. The 3D-printed technology participates in a wide range of applications nowadays. The idea of synthetic aperture radar (SAR) has been utilized to investigate the reflected electromagnetic energy from the 3D-printed samples by setting each of the radar systems in a fixed position and the mounting sample on an x-y positioning table which has been used to achieve rectangular-scan mode for SAR. The data have been ported and processed by the matched filter approach. For better image interpretation, the data have been further processed by the median filter in order to reduce noise level while preserving the main image details. Afterwards, the data have been further investigated for determining and classifying any possible defects. This process has been accomplished by deploying the unsupervised learning concept to cluster the SAR responses into two groups, compromising the defected positions responses and the non-defected responses. The obtained results of both radar sensors have been compared and evaluated using different quality assessment factors. Moreover, unsupervised learning techniques have been investigated and the obtained results show a high degree of efficiency in clustering the SAR responses.
This paper considers the ability of polarization measurements for microwave remote sensing of clouds and precipitation. The simulation of reflections from liquid hydrometeors with a multi-polarization radar system is presented. The mathematical expression of energy received by a radar antenna with arbitrary polarization is obtained. The simulation of the energy redistribution of the signal reflected from liquid hydrometeors assembled over the antennas of multi-polarimetric radar for different wind conditions and different drop-size distributions is obtained and analyzed. The simulation results demonstrate the possibility to register wind and wind-related phenomena by polarimetric radar. The results of the paper can also be used to exclude an impact of drop vibration or oscillation into the radar signal to eliminate errors and underestimation during parameter measurements. The approach to segregate the reflected signal magnitude variations due to the wind-related phenomena from other factors is discussed.
This chapter contains a broad overview of the technical and environmental issues to be addressed in the construction of onshore wind energy projects. The former include ecological considerations, including birds and mammals; the requirements of typical pre-construction ornithological surveys are described with an example. Public safety and acceptance is discussed in the context of catastrophic damage to wind turbines, visual impact, shadow flicker, and noise nuisance. In the last case, equations and simple rules for noise assessment are given in the context of typical planning guidelines. Sound power levels for a range of commercial wind turbines are compared, and empirical relationships are given relating noise to rated output, rotor size, and tip speed. Risks to aviation are discussed, covering aircraft collision and interference to radar systems, including both primary and secondary surveillance radars. The concept of ‘stealthy’ wind turbine blades is discussed and described in outline. Other siting criteria include avoidance of RF and microwave communications beams and television interference. Rules are given to avoid interference, while minimising required separation distances.
This chapter reviews key findings from analyses of spectral reflectance measurements of Mercury taken by the MESSENGER mission. Mercury’s crust lacks the 1-µm crystal field absorption due to ferrous iron that is common on other silicate bodies, yet is unusually low in reflectance. The most likely darkening phase is carbon as graphite. Variations in reflectance and color reveal that volcanic plains averaging >5 km in thickness overlie graphite-rich low-reflectance material, which may have originated as a graphite flotation crust from a magma ocean. The one unambiguous absorption due to an oxidized transition metal, an ultraviolet oxygen–metal charge transfer band in bright, pyroclastic deposits, may originate by oxidation of carbon and sulfides, reducing 0.3–1 wt.% ferrous iron in silicates to a metallic state, unsaturating the very strong oxygen–metal charge transfer band.
The advent of multiple orbital and in situ missions to planetary bodies beyond Earth has enabled characterization of extraterrestrial shallow crustal processes. We describe examples of interpreting geochemical, isotopic, and radar properties from multiple remote datasets, supplemented with in situ observations from rovers and landers, meteorites, and lunar samples. Given the availability of distinct data types and the relevance to bulk-silicate bodies in the Solar System, we present five case studies for the Moon and Mars. The first involves lunar magmatic processes in relation to TiO2 and radargram-derived physical properties. Next, O and Fe isotope variations relative to the Mg number provide insight into the degree of fractional crystallization in lunar lava flows. Physical mixing of endmembers and chemical weathering processes in Gusev crater soil on Mars are discussed. Effective use of the Chemical Index of Alteration (CIA) is also considered by comparing mineralogic observations across Mars with terrestrial references. Lastly, the nature of bulk soil hydration on Mars is described by assessing chemical variations with Principal Component Analysis (PCA). This chapter describes in situ analyses and mapping across local and regional scales. Data synthesis also involves contrasting depth scales from tens of microns to multiple kilometers.
Radar has proven to be a powerful tool in planetary exploration. Most of the major solid bodies of the Solar System have been observed with radar, either from Earth or from spacecraft. Planetary radar studies are reviewed in this chapter, with information on the various techniques of radar remote sensing provided along with key results. Recent radar results are emphasized. Concluding remarks are provided on future directions in planetary radar remote sensing.
Imaging radars are all-weather instruments that can image planetary surfaces regardless of local atmospheric or solar illumination conditions. Radar images provide information about surfaces that are complementary to the chemistry usually inferred from visible and infrared images. Instead, radar images are strongly influenced by surface roughness and geomorphology, and to a lesser extent by the bulk electrical properties of the surface. This chapter describes the basic principles of high-resolution synthetic aperture radars (SARs), as well as advanced SAR implementations. Radar polarimetry provides information about surface roughness and electrical properties, while radar interferometry allows the measurement of surface topography and surface deformation following events such as earthquakes or volcanic inflation. Radar imagers have returned spectacular information about the surfaces of both Venus and Titan, bodies with dense, opaque atmospheres that are difficult to image using traditional camera systems. Examples of both planetary and Earth observations with SAR are discussed to illustrate the utility of these images.
This paper presents a comparative cyber security resilience estimation of shipboard radars that are implemented on two oil/chemical tankers certified as SOLAS ships. The estimated radars were chosen from the same manufacturer, but belonged to different generations. The estimation was conducted by means of ships' crew interviews and computational testing of the radars using a widely deployed vulnerability scanning software tool. The identified cyber threats were analysed qualitatively in order to gain a holistic understanding of cyber risks threatening shipboard radar systems. The results obtained experimentally indicate that potential cyber threats mainly relate to maintenance of the radars' underlying operating system, suggesting the need for regulatory standardisation of periodic cyber security testing of radar systems.
We derive the surface and basal radar reflectance and backscatter coefficients of the southern McMurdo Ice Shelf (SMIS) and part of the nearby Ross Ice Shelf (RIS), Antarctica, from radar statistical reconnaissance using a 60-MHZ airborne survey. The surface coefficients are further inverted in terms of snow density and roughness, providing a spatial distribution of the processes contributing to the surface boundary conditions. We disentangle the basal coefficients from surface transmission losses, and we provide the basal coherent content, an indicator of the boundary geometric disorder that is also self-corrected from englacial attenuation. The basal radar properties exhibit sharp gradients along specific iso-depths, suggesting an abrupt modification of the ice composition and geometric structure. We interpret this behavior as locations where the pressure-melting point is reached, outlining fields of freezing and melting ice. Basal steps are observed at both SMIS and RIS, suggesting a common geometric expression of widespread basal processes. This technique offers a simultaneous view of both the surface and basal boundary conditions to help investigate the ice-shelf stability, while its application to airborne data significantly improves coverage of the difficult-to-observe ice–ocean boundary. It also provides constraints on thermohaline circulation in ice shelves cavities, which are analogs for ice-covered ocean worlds.
This paper presents a novel approach for the determination of True-Speed-Over-Ground for trains. Speed determination is accomplished by correlating the received signals of two side-looking radar sensors. The theoretically achievable precision is derived. Test measurements are done in two different scenarios to give a proof of concept. Thereafter a series of field measurements is performed to rate the practical suitability of the approach. The results of the measurements are thoroughly evaluated. The test and field measurements are carried out using a 24 GHz frequency modulated continuous wave radar.
This paper presents a W-band MIMO radar transceiver chipset for automotive applications, based on a Silicon Germanium technology. It consists of a reference VCO, operating at a center frequency of 38 GHz and a companion IC that comprises a complete millimeter-wave transceiver at 76 GHz. This chipset enables building multipurpose MIMO radar systems that can be scaled in terms of transmitter and receiver count. What makes this system innovative is the fact that it is able to handle more broadband signals than systems presented in current literature and is furthermore not limited to one modulation scheme. The chipset is capable of transmitting and receiving any signal waveform. The main goal of this work was to create a functional version of a VCO and a one-channel transceiver MMIC. Furthermore a demonstrator for a proof of concept was designed to test the MMICs on a system level. The realized VCO MMIC achieves a tuning frequency range of 6 GHz with a center frequency of 38 GHz and consumes 152 mW from a 3.3 V supply. The transceiver MMIC is fully functional and achieves a saturated output power of 11.5 dBm while drawing 670 mW from a 3.3 V supply.