Radar Device Research Articles

Transformation electromagnetics and its applications (Invited paper)

In this review, we present a brief introduction on the transformation electromagnetics theory and several novel applications. We mainly focus on a radar illusion device, a microwave bend structure, a flattened Luneburg lens, a planar focusing lens antenna, and a three-dimensional broadband carpet cloak. These devices are designed with either general transformation optics or quasi-conformal mapping, which are implemented using metamaterials and validated by experiments, showing high performances. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22:496–511, 2012.

Complexity of scheduling of coupled tasks with chains precedence constraints and any constant length of gap

Coupled tasks scheduling was originally introduced for modelling complex radar devices. It is still used for controlling such devices and applied in similar applications. This paper considers a problem of coupled tasks scheduling on one processor, under the assumptions that all processing times are equal to 1, the gap has a constant exact length and the precedence constraints are strict. Although it is proven that the problem stated above is NP-hard in the strong sense if the precedence constraints have a form of a general graph, it is possible to solve some of its relaxed versions in polynomial time. This paper contains a solution for the problem of coupled tasks scheduling with an assumption that the precedence constraints graph has a form of chains and it presents an algorithm that can solve the problem with such assumption in time O(n log n).

Temporal and spatial variability of rainfall at the urban hydrological scale

The main objective of this paper is to characterize the spatial and temporal variability of different types of rain events at scales that are consistent with urban hydrological applications. In this way, a total of 24 rain periods have been analyzed according to a geostatistical approach. This analysis has focused on the non-zero rainfall variogram. The studied rain periods were recorded by the weather radar of Treillieres (10 km north of Nantes, France) in 2009. This radar device provides rainfall radar images with a high level of spatial resolution (250 m x 250 m) and instantaneous temporal resolution. Results indicated four different types of rainfall fields, which display very different variability scales, including double structures within the same field. These four types of rainfall fields can be characterized by their climatological variograms, as calculated for increasing time resolutions: instantaneous, 5 min, 15 min, and 30 min, thus making it possible to estimate the decorrelation distance (i.e. range). This study highlights the benefit of radar images featuring high temporal and spatial resolution, which in turn allow studying small-scale variability.

Application of optics-geometrical method in short-range optical radar

The paper describes application of optics-geometrical method in short-range optical radar for measuring reflection characteristics of target and radiator’s angular energy distribution. The possibility of signal sampling in a base-type optical radar device using multi-element photoreceiver is studied as well as ways of improving precision of measurements with respect to linear coordinate up to ∼1 mm. A ratio between reflection coefficient of target’s surface and image coordinate in photoreceiver’s plane is determined. A working equation for calculating radiation pattern of radiator using the method of self-scanning of photoreceiver’s field of view with respect to its flare with precision ±0.5° with respect to angle coordinate is obtained.

RADIOFREQUENCY AND MICROWAVE RADIATION HEALTH EFFECTS AND OCCUPATIONAL EXPOSURE

In the recent years, there have been considerable discussion and concern about the possible hazards of RF/MW radiation. More recently, the growth and development in personal mobile communications have focused attention on the frequencies associated with this technology. A number of studies have examined the health effects of RF/MW electromagnetic fields (EMFs), originating from occupational exposure, hobbies, or residence near the radio or television transmitters. Particularly controversial are the biophysical mechanisms by which these RF fields may affect biological systems. General health effects reviews explore possible carcinogenic, reproductive and neurological effects. Health effects by exposure source have been observed in radar traffic devices, wireless communications with cellular phones, radio transmission, and magnetic resonance imaging (MRI). Several epidemiological surveys have suggested associations with non-specific complaints such as headache, tiredness, sleep disturbance, loss of memory, and dizziness. These findings, which echo reports of illness associated with other types of radiofrequency (RF) radiation, relate not only to the use of mobile phones, but also to residence near the mobile phone base stations and other settings involving occupational exposure. The biological effects suggest that some precautions are necessary, and preventive approaches are highly recommended. Further researches are required to give more information about the effects of microwave radiation on our health, especially in occupational setting and professionally exposed workers.

Behavioural responses of the supralittoral amphipod Talitrus saltator (Montagu) to trace metals contamination

We investigated behavioural responses (locomotor activity and substrate selection) of the amphipod Talitrus saltator after laboratory exposure to different concentrations of Hg, Cu and Cd. Locomotor activity, measured with a microwave radar device, was assessed in animals exposed to contaminated sand and in sandhoppers previously kept for 48h in contaminated seawater and tested in clean sand. The contents of Hg, Cu and Cd in T. saltator tissues were measured at the end of pre-exposure to contaminated seawater and after 7days of exposure to contaminated sand. Substrate selection tests were carried out in a binary choice arena. Tests in contaminated sand showed that sandhopper locomotor activity varied in a dose-dependent manner in the presence of Cu and Hg (at lower Hg concentration they were more active during daytime) but did not show significant changes in Cd-exposed animals except for disappearance of the typical circadian activity pattern. Pre-exposure to trace metals in seawater induced a significant decrease of movements for all metals, although the effects varied according to the toxicity of the metal. Trace metals analyses showed that tissue concentrations of Hg, Cu and Cd were related to their concentrations in the test medium. Substrate selection tests showed avoidance of contaminated sand only when sandhoppers were tested in the presence of both concentrations of Hg and at the higher concentration of Cu. In conclusion, locomotor activity and avoidance behaviour of T. saltator could be used as behavioural biomarkers of trace metals exposure.

Radar illusion via metamaterials

An optical illusion is an image of a real target perceived by the eye that is deceptive or misleading due to a physiological illusion or a specific visual trick. The recently developed metamaterials provide efficient approaches to generate a perfect optical illusion. However, all existing research on metamaterial illusions has been limited to theory and numerical simulations. Here, we propose the concept of a radar illusion, which can make the electromagnetic (EM) image of a target gathered by radar look like a different target, and we realize a radar illusion device experimentally to change the radar image of a metallic target into a dielectric target with predesigned size and material parameters. It is well known that the radar signatures of metallic and dielectric objects are significantly different. However, when a metallic target is enclosed by the proposed illusion device, its EM scattering characteristics will be identical to that of a predesigned dielectric object under the illumination of radar waves. Such an illusion device will confuse the radar, and hence the real EM properties of the metallic target cannot be perceived. We designed and fabricated the radar illusion device using artificial metamaterials in the microwave frequency, and good illusion performances are observed in the experimental results.

Introduction [Measurements Corner

The problem of detecting, locating, and tracking dismounts (moving people), using a distributed collection of simple and cheap narrowband (and, hence, low-resolution) radar devices, is an extremely challenging problem. It has been a topic of considerable research for the past several years. In particular, system performance is dependent upon both the positioning of the devices and the detection/tracking algorithms applied to the raw radar data. This month's Measurements Comer paper describes a novel Bayes-optimal nonlinear filtering technique for the latter. It demonstrates that reasonable dismount tracking can be accomplished with 5–10m bistatic range-resolution systems.

Application of a Terrestrial Laser Scanner (TLS) to the Study of the Séchilienne Landslide (Isère, France)

The active Séchilienne landslide (Isère, France) has been continuously monitored by tacheometry, radar and extensometry devices for 25 years. Indeed, if the 3 mil. m3 of rocks in the active zone named ―Ruines‖ fell down, the debris would dam the Romanche valley. The breaking of the dam by overtopping and rapid erosion would bring a catastrophic flood and other dramatic consequences throughout the valley. Given the rockfall hazard in the most active zone, it is impossible to use targets in this area: Only reflectorless remote sensing techniques can provide information. A time-series of seven Terrestrial Laser Scanner (TLS) point clouds acquired between 2004 and 2007 enable us to monitor the 3D displacements of the whole scanned area, although point coverage is not homogeneous. From this sequential monitoring, the volume of registered collapses can be deduced and the landslide movement along the main geological structures can be inferred. From monitoring associated subsidence and toppling observed on TLS data, it can be deduced that blocks rearrangements are linked to structural settings and that the Séchilienne landslide is complex. To conclude, TLS point clouds enable an accurate monitoring of the evolution of the inaccessible "Ruines" area and, proven its ability to provide reliable kinematic information, even in areas where on-site instrumentation is infeasible.

Radar emitter recognition based on cyclostationary signatures and sequential iterative least-square estimation

Radar emitter recognition plays an important role in electronic warfare (EW). Specific radar emitter recognition is the state-of-art technology of emitter recognition, which can recognize the different radar devices of the same type. It is a composite task that involves radar signal interception, modulation recognition, features extraction and classification. In this paper, first we study the unintentional modulation on pulse (UMOP) features of radar emitter. Then the iterative least-square method is introduced for estimation of the UMOP features. Because of the discriminatory capability and abundant information of cyclostationary signatures, the zero frequency slice of cyclic spectrum is used for specific radar emitter recognition. Based on these, the sequential iterative least-square (SILS) algorithm is proposed for the online recognition of radar emitters. Finally experiments on three simulation radars and eight actual intercepted radars with the same type verify the correctness and validity of the proposed method.

Damage consequence chain mapping after the Wenchuan Earthquake using remotely sensed data

The Wenchuan Earthquake occurred on 12 May 2008 followed by frequent aftershocks. The earthquake suddenly caused heavy damage to roads, bridges, buildings and communication facilities. Two B4101 Citation II remote sensing airplanes from the Chinese Academy of Sciences took off to monitor the region soon after the earthquake and collected images using a synthetic aperture radar (SAR) device and an optical ADS40 sensor. Using images obtained from airborne surveys, a damage consequence chain was mapped that provided information about the type of damage and its extent. This proved to be of great help for rescue operations and after earthquake reconstructions. We present details of airborne survey, images and mapping of damages caused by the earthquake and the use of such information for a rescue operation.

Status of Reliability of GaN-Based Heterojunction Field Effect Transistors

GaN-based heterojunction field effect transistors (HFETs) will play major roles in the high-power, high-frequency military and commercial arenas for microwave and millimeter wave transmitters and receivers used in communications and radar devices. In fact, devices operative in the X-band (7-12.5 GHz) and beyond are already at market and boast quite impressive performances. Having improved the crystal quality now to levels where the reliability [expressed as mean time to failure (MTTF)] is claimed to exceed ten million hours, the work now needs to focus on which of the physical mechanisms responsible for degradation are the most important, and how the existing degradation accelerates subsequent degradation, ultimately resulting in device failure. Available data show that not all devices from the same wafer show similar longevity and the wide spread of activation energies reported for three-temperature extrapolation-based predictions of the lifetime are troubling. If we hope to make consistent, reliable predictions of device lifetimes, particularly when the devices are being pushed in radio-frequency (RF) operation to near their limits, more work will need to be done in characterizing the long term stability of the devices, and new physical models for the failure mechanisms will have to be developed.

Poster Session I, July 14th 2010 — Abstracts Accounting for ball performance differences in golf club fitting

Golf club fitting is becoming a more and more precise science. In the last 10 years, a number of different devices have become available to club fitters for measuring either the flight of the golf ball (e.g. Trackman™ and Flightscope® radar devices) or just the initial launch conditions (e.g. Vector Pro™ and 3Trak® camera devices, Golf AchieverTM laser device). In 2008, PING released the nFlight® fitting software to tie in with any of these devices, capture data, digitally analyze and scientifically compare every aspect of every shot taken by a golfer to provide the best possible golf club fitting.One challenge arising from this approach was how to account for large differences in golf ball construction and performance, both in the initial launch conditions immediately after impact and the resultant ball flight. In particular, many golf courses use various kinds of range balls in practice and fitting areas. To conduct a golf club fitting using data derived from these balls could be misleading and result in inappropriate club choices. For example, a driver fitting using an exceptionally high spin ball could result in a low loft and stiff shaft being chosen to minimize the spin rate when actually the high spin is due to the nature of the ball used in the fitting rather than aspects of the golfer’s swing.To account for these differences and ensure accurate data from a golf club fitting, the nFlight® fitting software provides a way to convert launch data from one category of golf ball into another. So far over 60 different brands of ball have been subjected to static, robot and player comparison testing including at least 1500 shots hit by Ping Man, PING’s robotic testing machine. A cluster analysis was used to group similar golf balls into various categories and C# code in the nFlight® fitting software was used to manage the data conversion. The poster describes the testing conducted, the methods behind the cluster analysis and the patent-pending nFlight® fitting software application of the data conversion.

Introduction [Measurements Corner

The problem of detecting, locating, and tracking dismounts (moving people), using a distributed collection of simple and cheap narrowband (and, hence, low-resolution) radar devices, is an extremely challenging problem. It has been a topic of considerable research for the past several years. In particular, system performance is dependent upon both the positioning of the devices and the detection/tracking algorithms applied to the raw radar data. This month's Measurements Comer paper describes a novel Bayes-optimal nonlinear filtering technique for the latter. It demonstrates that reasonable dismount tracking can be accomplished with 5–10m bistatic range-resolution systems.

Scheduling of coupled tasks with unit processing times

The coupled tasks scheduling problem was originally introduced for modeling complex radar devices. It is still used for controlling such devices and applied in similar applications. This paper considers a problem of coupled tasks scheduling on a single processor, under the assumptions that all processing times are equal to 1, the gap has exact integer length L and the precedence constraints are strict. We prove that the general problem, when L is part of the input and the precedence constraints graph is a general graph, is NP-hard in the strong sense. We also show that the special case when L=2 and the precedence constraints graph is an in-tree or an out-tree, can be solved in O(n) time.

Providing location security in vehicular Ad Hoc networks

It is fair to say that most, if not all, VANET applications rely on accurate location information. It is therefore imperative to provide mechanisms that ensure the integrity, availability, and confidentiality of location information. In this article we present a number of location security mechanisms specifically designed for VANETs. Proposed mechanisms for location integrity range from the use of onboard radar devices and GPS to simpler methods that rely on information fusion. We also address ways to enhance the availability of location information by selecting and maintaining stable routing paths. Finally, we discuss a mechanism that promotes location confidentiality through encryption/decryption and access control using geographical information. Our location information security mechanisms meet the requirements of the Confidentiality, Integrity, and Availability (CIA) information security model.

A rugged 100 W high-voltage vertical MOSFET L-band radar device

The silicon vertical MOSFET RF power amplifier described in this paper is the industry’s first to utilize high-voltage vertical technology. Operating under pulse conditions of 200 µs pulse width and 10% duty cycle, it delivers more than 100 W of peak power. Operating in Class AB with only 50 mA of bias current the device achieves more than 20 dB of gain and 47% power added efficiency at P1dB compression across 200 MHz of bandwidth at L-band from 1.2 to 1.4 GHz. The DC characteristics include a BVdss of 95 V enabling high-voltage operation with a 48 V power supply. The device is inherently rugged and withstands mismatch tolerances of 20:1 voltage standing wave ratio over all phase angles at full rated power and with 3 dB of input power over-drive and 10% greater than nominal voltage.

The Relationships Between Range Of Motion, Performance, And Club Head Speed In Older Female Golfers

Research on range of motion (ROM) of the trunk, shoulder and hip in older amateur female golfers is limited. It is unknown if club head speed (CHS) is related to these physical characteristics or golf performance. PURPOSE: The aims of this study were to: 1) determine the relationships between ROM, performance, and CHS in older amateur female golfers; and 2) evaluate the relationship between ROM and CHS in two age groups of older golfers, middle and senior. METHODS: Twenty-eight healthy, amateur female golfers [mean age ± SD (range), 63.7 ± 7.8, (49-86 years)] who swung right-handed were measured for trunk, hip, and shoulder rotation passive ROM with inclinometers. Trunk rotation was measured in sidelying using dual inclinometers and pelvic stabilization. Hip rotation was measured prone with the contralateral hip in 30° of abduction and pelvic motion prevented. Shoulder rotation was measured supine with the shoulder placed in 90° of abduction and scapula motion prevented. CHS was recorded with a ground level radar device. Each golfer used her driver of choice and swung from a standardized golf mat and tee. A self-report questionnaire was given to record performance data for both 9-hole and 18-hole games and driving distance. ICC values were calculated for repeated passive ROM measures. Relationships between ROM, performance, and CHS were examined with a Pearson product moment correlation coefficient analysis using SPSS v. 16.0. RESULTS: The ICC values for intratester measures were 0.82, 0.88 (trunk: right, left), 0.81, 0.83 (shoulder: internal, external), and 0.95, 0.92 (hip: internal, external). A significant relationship (r = 0.85, p< 0.01) between CHS and driving distance was found. There were also inverse correlations (r = -0.49 to -0.80, p< 0.01) between age, 9-hole score, 18-hole score and CHS. In the middle age group (≤ 60 years of age), left hip external rotation was inversely correlated with CHS (r = -0.70, p< 0.05). No significant correlations were identified between ROM and CHS in the senior group (> 60 years of age). CONCLUSIONS: The ability to produce a greater club head speed was associated with better golf performance and increased driving distance. Club speed was shown to decline with age. Assessment of hip flexibility should be considered for rehabilitation and training programs in older female golfers.

Georadar Measurements for the Snow Cover Density

Ground Probing Radar (GPR) devices is adopted for the analysis of thickness and the mechanical properties (density) of the snow cover in some test site in Alps, in Northern Italy. The performances of standard radar systems for the snow cover characterisation are analysed, the main aim is to assess the reliability of the method to estimate the snow density, the snowpack thickness and the depth resolution in terms of capability to detect thin layers. The main relationships between the electrical permittivity and the density of the dry-snow are applied to estimate the density vertical profiles inferred by the GPR investigation. The data were calibrated and compared with the results coming from direct measurements of the density and thickness.

Deformation of Stromboli Volcano (Italy) during the 2007 eruption revealed by radar interferometry, numerical modelling and structural geological field data

The activity of Stromboli volcano is characterized by very low energy explosions, occurring every 10–15 min, throwing out lava above the crater rim. During 2007, the volcano showed an anomalous activity in which new effusive vents developed (27 February and 9 March) and a major explosion took place on 15 March. This paper presents an integrated study based on a structural geological field survey, interferometric radar monitoring and numerical modelling on the deformations of the upper NW flank of the volcano (Sciara del Fuoco — SdF). The field survey carried out during the 2007 events shows the development of mainly NE-striking fissures and fractures on the northern part of the upper SdF. In January 2007, the ground-based synthetic aperture radar (GB-InSAR), installed on the flank of the SdF, showed a progressive acceleration of movement on the NE crater preceding the eruption of 27 February 2007. By the first half of February, the acceleration also involved the upper portion of the SdF and on 27 February the eruption started with the opening of new vents and deformation rates higher than the measurement capability of the radar device. On 8–9 March 2007, the GB-InSAR highlighted the formation of a bulge on the NW sector of the SdF, preceding the opening of an additional vent. To understand the deformation pattern recorded during the eruption, a numerical simulation was carried out by using the FLAC 3D code. Based on the integration of all the data, the deformations observed in the pre-effusive phase (before 27 February) seem to be related to the intrusion of a SW–NE striking dyke. The bulging recorded before the 9 March vent opening is instead to be associated with the intrusion of a sub-horizontal sill.