MIMO UWB radar for moving target tracking

A novel electronic beam steering is achieved by varying the amplitude of each radiating element in a microstrip array on a curved surface. PIN diodes are used to turn on the radiating patches facing in the intended direction while turning off all other patches. Since the amplitude‐varying antenna does not use expensive phase shifters, the resultant beam‐steering system is much less expensive than conventional phased‐array antennas. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 386–387, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10771

One application of acoustic droplet vaporization (ADV), a method of converting biocompatible microdroplets into microbubbles, is to enhance locally high intensity focused ultrasound (HIFU) therapy. Two objectives are pursued here: (1) the controlled creation of a bubble trench prior to HIFU using ADV and (2) use of the trench for increasing ablation volumes, lowering acoustic powers, and decreasing therapy duration. Thermally responsive phantoms were made with perfluorocarbon emulsion. Compound lesions were formed in a laboratory setting and a clinical magnetic resonance imaging (MRI)-guided HIFU system. Linear and spiral patterned compound lesions were generated in trenches. A larger fraction of the HIFU beam is contained to increase the generation of heat. Using the laboratory system, a 90 mm linear length spiral trench was formed in 30 s with mechanical beam steering. Comparatively, the clinical HIFU system formed a 19.9 mm linear length spiral trench in approximately 1 s with electronic beam steering. Lesions were imaged optically and with MRI. A uniform thermal ablation volume of 3.25 mL was achieved in 55.4 s (4-times faster than standard clinical HIFU and 14-times larger volume versus sum of individual lesions). Single lesions showed a 400% volume increase.

Target tracking is one of the major applications of Wireless Sensor Networks (WSN). In traditional target tracking with directional sensors, the target can be detected only when it is in the field of view (FoV) of a sensor. The target's track is obtained with the help of filtering algorithms/techniques at the base station (BS). These techniques sometimes lead to incorrect location estimation of the target due to measurement errors and noise. It is ideally required that the main sensing lobe/FoV of the sensor follow the target, whenever the target is in the FoV of the sensor. Based on the above considerations, this paper proposes an efficient solution to target tracking with the help of beam steering enabled directional sensors mounted on the nodes for tracking the targets. At every step of beam steering, the sensor node updates the location of the target to the nearest cluster head or base station. Each sensor will continuously monitor the target till it crosses the FoV or sensing range of the sensor. The proposed method has been implemented in OMNeT++ and the performance of the algorithm has been evaluated with directional active and passive sensors. Different target mobilities and different sensor FoV angles have been considered. The results show that the proposed method successfully tracked the target and located the target at every instant of time. Directional active sensors yield more accurate results when compared to passive sensors. It was also seen that the location accuracy of the target was mainly dependent on the FoV angle and FoV/sensing radius of the sensor.

Common clamp-on ultrasonic flow meters consist of two single-element transducers placed on the pipe wall. Flow speed is measured noninvasively, i.e., without interrupting the flow and without perforating the pipe wall, which also minimizes safety risks and avoids pressure drops inside the pipe. However, before metering, the transducers have to be carefully positioned along the pipe axis to correctly align the acoustic beams and obtain a well-calibrated flowmeter. This process is done manually, is dependent on the properties of the pipe and the liquid, does not account for pipe imperfections, and becomes troublesome on pipelines with an intricate shape. Matrix transducer arrays are suitable to dynamically steer acoustic beams and realize self-alignment upon reception, without user input. In this work, the design of a broadband 37×17 matrix array (center frequency of 1 MHz) to perform clamp-on ultrasonic flow measurements over a wide range of liquids ( c=1000-2000 m/s, α ≤ 1 dB/MHz · cm) and pipe sizes is presented. Three critical aspects were assessed: efficiency, electronic beam steering, and wave mode conversion in the pipe wall. A prototype of a proof-of-concept flowmeter consisting of two 36-element linear arrays (center frequency of 1.1 MHz) was fabricated and placed on a 1-mm-thick, 40-mm inner diameter stainless steel pipe in a custom-made flow loop filled with water. At resonance, simulated and measured efficiencies in water of the linear arrays compared well: 0.88 and 0.81 kPa/V, respectively. Mean flow measurements were achieved by electronic beam steering of the acoustic beams and using both compressional and shear waves generated in the pipe wall. Correlation coefficients of between measured and reference flow speeds were obtained, thus showing the operational concept of an array-based clamp-on ultrasonic flowmeter.

A multi-objective plasma reflectarray/transmitarray antenna which reflects/transmits the incident fields radiating from a feed antenna in different directions have been introduced using a single structure. An electronic beam steering is achieved using a DC applied voltage on the array elements. A 13 × 13 unit cell reflectarray/transmitarray antenna covering an area of 13.52 × 13.52 cm2 is proposed. The dimensions of the unit cells are identical with different argon gas density according to the relative phases of the reflected/transmitted wave. Each unit cell consists of two plasma cylindrical ring tubes positioned along the top and bottom of a plasma square ground plane filled with argon gas. The reflectarray is designed for 19.39 GHz, and the transmitarray is operating at 19.75 GHz using a single structure. The plasma frequency of the argon gas is varied by changing the applied ionizing DC voltage at both ends of the dielectric cylinder. The gain and frequency bandwidth for the new configuration are presented. An electronic beam steering plasma transmitarray antenna from −30° to +30° is introduced. The radiation characteristics of the reflectarray/transmitarray are investigated. A compromise between the reflectarray/ transmitarray efficiency and the multi-objective operation of the single structure have been introduced. A full-wave analysis using the finite integration technique (FIT) is applied.

The evolution of the Spaceborne Imaging Radar (SIR) has led to a multipolarization, multifrequency SAR with variable imaging geometry which will be ready for flight on the Space Station Earth Observing System (EOS). Nominally, this SAR will be a three-frequency (L-, C-, and X-band) system with quad polarization available for the L and C bands. It will be capable of acquiring multiincidence-angle data using electronic beam steering, and other imaging geometries by mechanically pitching, yawing, and rolling the antenna. The capabilities of the EOS SAR, particularly acquisition of cross-polarized and high-incidence-angle data, depend on the altitude of the platform on which the SAR flies and improve significantly at lower altitudes. The EOS SAR will provide a unique new data set and will play a key role in understanding the earth's global processes, alone and synergistically with other EOS instruments.

Error field measurement and analysis for a pure permanent magnet FEL wiggler

This paper discusses revolutionary laser system architecture capable of dramatically reducing the complexity of laser systems while increasing capability. The architecture includes 3 major subsystems. The first is a phased array of laser sources. The second provides wavefront control and electronic beam steering. The third is sub-aperture receiver technology. Combining these three technologies into a new laser systems architecture results in a system that has graceful degradation, can steer to as wide an angle as individual optical phased array sub-apertures can steer, and can be scaled to high power and large apertures through phasing of a number of sub-apertures.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Current, minimally invasive, treatments for cardiac arrhythmia use a transvenous radio-frequency (RF) catheter to ablate the malfunctioning cardiac muscle regions. The paper proposes a noninvasive transesophageal cardiac thermal ablation using focused ultrasound. A planar phased array (1 MHz, 60/spl times/10 mm/sup 2/, 0.525 mm element center-to-center distance, 2280 elements) was put in the esophagus. Using electronic beam steering, a matrix of 5/spl times/3/spl times/5 foci in the cardiac muscle was defined in three planes parallel to the transducer surface at short, medium and long (20, 40 and 60 mm) radial ranges and different steering angles. The transmitted ultrasound pressure distribution in a volume of 20/spl times/20/spl times/20 mm/sup 3/ centered at each focus was calculated using a multilayer acoustic wave transmission model. The thermal lesions due to the acoustic energy absorption in cardiac muscle were simulated using the bioheat transfer equation. For short, medium and long (1-, 10- and 20-second) sonications, the acoustic powers needed to achieve 60/spl deg/C and 70/spl deg/C peak temperatures in the cardiac muscle were 89-725, 25-125, 20-86 W and 128-1040, 36-179, 28-123 W, respectively. The simulated tissue lesion (thermal dose >240 min at 43/spl deg/C) lengths at these foci were 2-10, 5-12, 6-14 mm and 3-13, 7-15, 9-17 mm, respectively. The lesion widths were 2-8, 3-10, 4-11 mm and 3-11, 4-12, 5-13 mm, respectively. The simulations show that noninvasive transesophageal cardiac ablation with a planar phased ultrasound array is feasible.

Polarimetric weather radars, such as the Weather Surveillance Radar-1988 Doppler (WSR-88D), improve weather forecasts and provide valuable data for operational and scientific applications. The polarimetric capability adds additional insight into storm microphysics and greatly improves precipitation estimates. Nevertheless, fast-evolving weather events require high-temporal resolution data, which conventional radar systems (mechanical and dish-based) cannot provide. Phased array radar (PAR) offers superior observation capabilities with electronic beam steering and enhanced scanning agility. Furthermore, digital PAR enables 1-D (space and time) processing and overcomes limitations in clutter mitigation compared with the traditional radar systems that only use Doppler processing. Doppler processing is traditionally used to effectively filtering out ground clutter with zero mean velocity. In contrast, space-time processing (STP) enhances clutter mitigation to filter out both stationary and moving clutter through the joint spatial and temporal spectrum. This study aims to apply STP (nonadaptive) and space-time adaptive processing (STAP) to weather radar data and explore their benefits to improve Doppler velocity estimation of meteorological returns. Furthermore, the performance of STP and STAP for different digital PAR back ends, including fully digital and subarray systems, is investigated. Preliminary findings underscore the critical role of radar scanning parameters and environmental conditions, such as sample quantity, clutter-to-signal ratio (CSR), and signal-to-noise ratio (SNR), in the Doppler velocity estimation. Data collected with the recently completed Horus radar system are evaluated using STP and STAP. Results demonstrate the potential for improving data quality, particularly in Doppler velocity estimation within cluttered environments, through the application of STP and STAP techniques. The filtering algorithm with STAP demonstrates a substantial reduction in error within the Doppler velocity estimation, achieving approximately an eightfold improvement compared with the estimation derived from STP with filtering.

Reflector antennas realized by reflectarrays have many attractive features that are unmatched by traditional reflectors. Low-profile planar reflectarrays can be made to have high gain and electronic beam steering. However, they tend to use elements operating near their resonant frequencies for achieving a large phase range, thus limiting their bandwidth significantly. Transformation optics (TO) offers a new way to design tunable reflecting devices while preserving many of the attractive features of a reflectarray antenna. The TO device accomplishes beam collimation by using a 2-D array of sub-wavelength dipoles, which is macroscopically seen as an effective medium, to incur different phase changes of the incident fields. The proposed reflector has a relative gain bandwidth of 150%.

It is estimated that up to 9.3 million persons may be impacted by locomotive horn noise and up to 4.6 million of those may be severely impacted.1 In 2009, there were over 1,900 incidents, over 700 injuries and over 240 fatalities at highway-rail grade crossings.2 The National Academy of Engineering Committee on Technology for a Quieter America has indicated that the public would benefit if train warning horns were more directional and has recommended that research and development be undertaken to better understand the effects on safety and benefits to the public.3 A directive train horn has the potential to focus audible warning signals to desired locations including pedestrians and motorists at highway-rail grade crossings while minimizing noise to the surrounding community and employees in the locomotive cab. As a part of an ongoing Federal Railroad Administration (FRA)-sponsored research and development effort, the authors have examined the feasibility of and recommended an acoustical specification for an optimized train horn that would improve the detectability of the warning signal for motorists at critical positions along the crossing road while reducing the area of environmental noise impact. The detectability, noise impact area and occupational noise exposure have been compared for the optimized horn and several typical standard horns. Near the beginning of most sounding events (1/4-mile from the grade crossing) the optimized horn reduces noise exposure because a narrow beam of sound can be generated and focused at the grade-crossing. As the train approaches the crossing, the beam width must become wider. It is found that detectability could be improved and noise impact area reduced by up to 57%, but the optimized horn must have a directivity pattern and amplitude that dynamically changes as a function of train position relative to the crossing. Current acoustic source technologies which generate directive sound were examined including “acoustic hailing devices” (AHDs) which are recent technological advancements typically used for naval communications. Capable of focusing high amplitudes of sound within a narrow beam and dynamically changing the directivity pattern through electronic beam steering, AHDs have been identified as a feasible means of meeting the required specifications. A critical design issue for the optimized horn is controlling the directivity pattern at low frequencies. Development and testing of a prototype is in progress and actual improvements to detectability and reductions in noise impact will be analyzed. The paper briefly discusses the feasibility of the optimized horn and general information on cost and implementation.

Electronic Warfare (EW) and Radio Detection and Ranging (Radar) are two of the many applications that rely on multi-channel and phase-coherent configurations for signal processing. We provide herein an overview of the complexities and requirements of a multi-channel phase-coherent measurement system. Multiple Input Multiple Output [MIMO] systems have to overcome key technical challenges related to phase, time and frequency synchronization in order to coherently receive and process the data acquired/generated from each input/output. In practical MIMO systems, the radio hardware should be capable of acquiring and/or generating such phase coherent signals across the multiple channels. Further, the systems need to be able to sustain the phase coherence over considerable duration of time, depending on the sensitivity of the system. However, drifts will occur owing to the effects like temperature, thermal expansion, mismatched cable lengths, uncorrelated phase noise, ADC sample clock phase noise and quantization noise. Thus, a calibration process is required to compensate for the drift, whenever it crosses a particular threshold value that defines the accuracy of the phase-coherent system. In this paper, an FPGA based software-defined calibration method is presented for synchronizing the phase and magnitude across multiple channels of a system. This method allows the phase/magnitude drift over time to be periodically monitored and calibrated, when there is a need. With the FPGA built into the system, the calibration can take place remotely without the need of connecting the system to an external calibration kit. Also, measurement results are provided for a state of the art super heterodyne receiver system to show that the phase drift is lesser than ±1 degree across a 500MHz – 26.5GHz frequency range at 23°C ± 5°C for 2 and 4 channels configurations. Such systems can find use in a variety of real-world MIMO implementations such as Direction Finding, Beam Steering, Passive Radars, MIMO and Phased-Array Radar Systems, where phase coherence, alignment and /or synchronization has added advantages to multi-channel systems.

We reported a high average power and energy microsecond pulse erbium-doped fluoride fiber MOPA system centered at 2786.8 nm. The master oscillator was a passively Q-switched erbium-doped fluoride fiber laser based on SESAM in a linear cavity. Then a one-stage erbium-doped fluoride fiber amplifier was used to boost its average output power to 4.2 W and pulse energy to 58.87 μJ. The pulse duration and repetition rate were 2.29 µs and 71.73 kHz, respectively. To the best of our knowledge, the achieved average output power and pulse energy are the recorded levels for the passively Q-switched fiber lasers at 3 μm wavelength region.

We report the observation of efficient steering of a 855MeV electron beam at MAMI (MAinzer MIkrotron) facilities by means of planar channeling and volume reflection in a bent silicon crystal. A 30.5 μm thick plate of (211) oriented Si was bent to cause quasimosaic deformation of the (111) crystallographic planes, which were used for coherent interaction with the electron beam. The experimental results are analogous to those recorded some years ago at energy higher than 100GeV, which is the only comparable study to date. MonteCarlo simulations demonstrated that rechanneling plays a considerable role in a particle's dynamics and hinders the spoiling of channeled particles. These results allow a better understanding of the dynamics of electrons subject to coherent interactions in a bent silicon crystal in the sub-GeV energy range, which is relevant for realization of innovative x-ray sources based on channeling in periodically bent crystals.