Forward scattering radar power budget analysis for ground targets

An accurate approach to power budget analysis for forward scattering radar with application to the detection of ground targets is presented. A modification of the range equation is used, and the results of experimental testing for its confirmation are given.     

A noncontact method for detecting acoustic emission using a microwave Doppler radar motion detector

A noncontact method for detecting acoustic emission was developed, using a microwave Doppler radar detector and an active band-pass filter. A theoretical model was developed and a prototype sensor was built and tested. The prototype responds to acoustic emissions (AE), from pencil lead break tests, at ranges up to 1.5 feet.     

Uniform rotational motion compensation for inverse synthetic aperture radar with non-cooperative targets

In the current scenario of high-range resolution radars, the rotational motion of the target usually generates migration through resolution cells (MTRC) in the inverse synthetic aperture radar (ISAR) images. A technique to correct the MTRC in the case of uniform rotation rate is proposed. An estimation of the rotation vector of the non-cooperative targets is not required. The approach compensates the rotational motion in two steps: the slant-range rotation compensation (SRRC) and the cross-range rotation compensation (CRRC). CRRC is based on an extension of phase difference (PD) and on a robust method to delete outliers. The technique is verified both with simulated and live data from a millimetre-wave linear frequency-modulated continuous wave radar. A comparison with a minimum entropy-based technique is also made.     

Tracking severe weather storms in Doppler radar images

We describe an automatic storm-tracking system to help with the forecasting of severe storms. In this article, we present the concepts of fuzzy point, fuzzy vector, fuzzy length of a fuzzy vector, and fuzzy angle between two nonzero fuzzy vectors, that are used in our tracking algorithm. These concepts are used to overcome some of the limitations of our previous work, where fixed center-of-mass storm centers did not provide smooth tracks over time, while at the same time, their detection was very threshold sensitive. Our algorithm uses region splitting with dynamic thresholding to determine storm masses in Doppler radar intensity images. We represent the center of a hypothesized storm using a fuzzy point. These fuzzy storm centers are then tracked over time using an incremental relaxation algorithm. We have developed a visualization program using the X11 Athena toolkit for our storm visualization tool. The algorithm was tested on seven real radar image sequences obtained from the Atmospheric Environment Service radar station at King City, Ontario, Canada. We can obtain storm tracks that are long and smooth and which closely match an expert meteorologist's perception. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 201–213, 1998     

Sensitivity and validity of visual search models for multiple targets

This study proposes two search models for multiple targets (random search and systematic search) in an unstructured search field, derived by generalizing search models for single target search. Whilst the probability of locating a single target in the random search model is typically exponentially distributed, the probability of locating multiple targets was found to be distributed hypo-exponentially. The systematic search model was extended from a piecewise-linear function for a single target to a piecewise-curve function for multiple targets. To test whether these search models could predict human search performance, first, visibility area in a fixation, a main component of search models, was investigated at various fixation durations. Sensitivity analysis of this data indicated that using short fixation duration and a small fixation overlap would produce better search performance. Next, the visibility area data was combined with the search models and compared to human performance on a free search field with three targets. The systematic and random models provided upper and lower boundaries of actual human search performance. Additionally, at the start of the search task for multiple targets, search performance was close to the systematic search model, while for late targets, performance approached the random search model. Observers may have changed their search strategy during this multiple-target visual search task.     

Analysis and synthesis of detection devices for radar systems of laser Doppler velocimeters

The principles have been worked out for a systems approach to the choice of technical designs for detection devices of radar systems of laser Doppler velocimeters.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 50–53, November, 1993.     

Reflection of radar signals from multiple phase-modulated surfaces

A phase-modulated surface (PMS) has been shown to provide an effective method of dynamically controlling the scattering from simple planar or cylindrical targets. Real radar targets however have complex geometry comprised of many scattering centres, and multiple interactions may occur between these. Therefore, the authors explore whether the PMS technique is still effective when applied to more realistic target geometries     

Comparison of avalanche-velocity measurements by means of pulsed Doppler radar,continuous wave radar and optical methods

Velocities of mixed dense-flow/powder-snow avalanches have been measured by means of pulsed Doppler radar and by continuous wave radar at the full scale avalanche test site Vallée de la Sionne. From the radar data, we derive velocities of the saltation layer and of the powder part of the avalanche. The results obtained by the two different radar measurement techniques are compared and also are checked against the velocity data obtained by opto-electronic velocity sensors installed at different heights on the 20 m high mast in the avalanche track and against videogrammetry velocity data. We demonstrate that the measurements are consistent and discuss how information about the avalanche structure can be derived from the measurements.     

Comparison of avalanche-velocity measurements by means of pulsed Doppler radar, continuous wave radar and optical methods

Velocities of mixed dense-flow/powder-snow avalanches have been measured by means of pulsed Doppler radar and by continuous wave radar at the full scale avalanche test site Vallée de la Sionne. From the radar data, we derive velocities of the saltation layer and of the powder part of the avalanche. The results obtained by the two different radar measurement techniques are compared and also are checked against the velocity data obtained by opto-electronic velocity sensors installed at different heights on the 20 m high mast in the avalanche track and against videogrammetry velocity data. We demonstrate that the measurements are consistent and discuss how information about the avalanche structure can be derived from the measurements.     

Photoacoustic imaging of multiple targets using gold nanorods

Photoacoustic (PA) imaging has been used mainly for anatomical and functional imaging. Although functionalized nanoparticles also have been developed for PA molecular imaging, only single targeting has been demonstrated. In this study, PA imaging of multiple targets using gold nanorods is demonstrated experimentally using HER2 and CXCR4 as target molecules. The two corresponding monoclonal antibodies were conjugated to two types of gold nanorod with different aspect ratios. Gold nanorods with mean aspect ratios of 5.9 and 3.7 exhibited peak optical absorptions at 1000 and 785 nm, respectively. Appropriate selection of laser irradiation wavelength enhances PA signals by 7-12 dB and allows signals from gold nanorods corresponding to specific bindings to be distinguished. This approach potentially allows the expression levels of different oncogenes of cancer cells to be revealed simultaneously.     

Instantaneous derivatization technology for simultaneous and homogeneous determination of multiple DNA targets

There are potential advantages, in terms of simplicity and speed, for detecting DNA hybridization steps directly without using any external labels, especially for the multiplexed assays. In the current paper, we describe the use of a carrier-resolved label-free multiplexed assay for the simultaneous detection of multiple DNA targets. Herein we demonstrate that this protocol, using three homogeneous carriers thermosensitive poly(N-isopropylacrylamide), polystyrene beads, and magnetic beads, respectively, for simultaneous determination of three short DNA fragments specific to hepatitis B virus. Briefly, one hybridization occurs between a mixture of three different capture probe DNAs immobilized onto three carriers and three targets in a single vessel, and then chemiluminescence (CL) detection proceeds via an instantaneous derivatization reaction between the specific CL reagent 3,4,5-trimethoxylphenylglyoxal (TMPG) and the guanine nucleotide-rich regions within the target DNA. An excellent linearity is found within the range between 0.1 and 6.0 pmol with the lowest detection limit of 100 fmol. In contrast to current encoding strategies, every hybridization signal for the corresponding DNA target in our protocol is uniquely immobilized onto one carrier vehicle with a unique and intrinsic physical-chemical signature. Moreover, an instantaneous derivatization reaction is employed for the label-free determination of three targets in a single vessel. In addition, a simple CL setup is employed to read the carrier code instead of an expensive and complicated flow cytometer or imaging system commonly used for multiplexed assays. Further signal amplification is achieved by employing three amplified DNAs for second hybridization, which include a guanine nucleobase-rich sequence domain for the generation of light and an additional tethered nucleic acid domain complementary with one of the target DNA as an amplification platform. Such simple amplified CL transduction allows detection of DNA targets down to the 15-fmol level. This new protocol also provided a good capability in discriminating perfectly complementary DNA from single-base mismatches and noncomplementary sequences. Overall, the protocol described here may have value in a variety of clinical, environmental, and biodefense applications for which the accurate quantitative analysis of multiple DNA targets is desired.     

基于多普勒频移的水下运动目标测距技术

研究了基于多普勒频移的水下运动目标测距的方法及关键技术,采用了基于Hilbert变换的信号平稳化方法,结合频率匹配和PMTM多锥度法功率谱估计改善处理增益并提高线谱的短时频率估计精度,并结合几何模型及频率导数求解目标斜距。对算法进行了仿真,仿真结果表明,算法正确可行,在谱级信噪比不低于10dB条件下能有效提高被动式水下运动目标测距的精度。最后给出一个应用实例。     

Approximate Cramer-Rao bound on Doppler error in correlation-processing relatively narrowband noise radar

Limitations on accuracy of Doppler estimation in continuous-wave noise radar with correlation processing are studied. Second-order properties of output of the correlation receiver are evaluated and an approximate Cramer-Rao bound on errors of Doppler measurement is derived. The accuracy of Doppler measurements is found to be affected by the following factors: power spectral density of noise signal, frequency response of the low-pass filter in correlator, observation time, velocity of the target and signal to noise ratio. It is shown that the random nature of the transmitted signal induces additional fluctuations at the output of correlator which limit the accuracy even in the infinite signal to noise case. Qualitative extension of the results to a case covering multiple targets and clutter is made. It is argued that the performance will decrease and that increasing transmitted power may not provide significant improvement when clutter is present.     

Cluster-based centralized data fusion for tracking maneuvering targets using interacting multiple model algorithm

The interacting multiple model (IMM) algorithm has proved to be useful in tracking maneuvering targets. Tracking accuracy can be further improved using data fusion. Tracking of multiple targets using multiple sensors and fusing them at a central site using centralized architecture involves communication of large volumes of measurements to a common site. This results in heavy processing requirement at the central site. Moreover, track updates have to be obtained in the fusion centre before the next measurement arrives. For solving this computational complexity, a cluster-based parallel processing solution is presented in this paper. In this scheme, measurements are sent to the data fusion centre where the measurements are partitioned and given to the slave processors in the cluster. The slave processors use the IMM algorithm to get accurate updates of the tracks. The master processor collects the updated tracks and performs data fusion using ‘weight decision approach’. The improvement in the computation time using clusters in the data fusion centre is presented in this paper     

Selectivity toward multiple predetermined targets in nanoparticle capillary electrochromatography

Two unique methods to achieve selectivity toward multiple predetermined targets employing molecular imprinting technology have been developed. Partial filling capillary electrochromatography (CEC) was utilized to evaluate and compare the two techniques. The first approach, the mixed singly templated molecularly imprinted polymer (MIP) nanoparticle approach, is based on the mixing of two types of MIP nanoparticles with inherently different selectivity. The second approach, the multiply templated MIP nanoparticle approach, is based on the incorporation of two different templates during the preparation of the MIP nanoparticles. The use of MIPs in analytical chemistry applications has been extensively investigated during the past years. However, MIP nanoparticles with tailored multiple selectivity toward predetermined enantiomers has not yet been explored. The relative amounts of the two templates studied, i.e., (S)-ropivacaine and (S)-propranolol, were found to strongly affect the affinity of the multiply templated MIP nanoparticles for the predetermined targets. The amount of (S)-propranolol template had to be decreased to concentrations rarely applied in MIP synthesis in order to achieve 2-fold selectivity. Even though strongly decreased to 10% of the usual concentration employed, the MIP could efficiently separate the enantiomers of propranolol when applied in partial filling CEC. This opens up for new possibilities to decrease the need for an initial high amount of template in order to be able to produce an efficient MIP. The multiple enantiomer separation ability of the multiply templated MIP nanoparticles was compared with that of singly templated MIP nanoparticles that were mixed prior to analysis. It was concluded that the multiply templated MIP potentially can offer many new and interesting applications in chromatography as well as in sensor technology and solid-phase extraction.     

A range profiling technique for synthetic wideband radar

A technique is proposed for reconstructing wide range profiles using stepped-frequency waveforms (SWFs). The technique is based on reconstructing range sub-profiles. With respect to previous methods, the proposed technique can be applied to any kind of SWFs. Moreover, for a given range resolution, long range profiles can be formed without increasing the number of transmitted frequencies. Theoretical results are also derived that provide a correct setting of waveform and processing parameter. Finally, as case studies, the proposed method is applied to three SFWs, namely short-pulse stepped-frequency, linear frequency modulated stepped frequency and phase-coded stepped-frequency waveforms. Simulations prove the effectiveness of the proposed range profile reconstruction.     

Automatic identification of bird targets with radar via patterns produced by wing flapping.

Bird identification with radar is important for bird migration research, environmental impact assessments (e.g. wind farms), aircraft security and radar meteorology. In a study on bird migration, radar signals from birds, insects and ground clutter were recorded. Signals from birds show a typical pattern due to wing flapping. The data were labelled by experts into the four classes BIRD, INSECT, CLUTTER and UFO (unidentifiable signals). We present a classification algorithm aimed at automatic recognition of bird targets. Variables related to signal intensity and wing flapping pattern were extracted (via continuous wavelet transform). We used support vector classifiers to build predictive models. We estimated classification performance via cross validation on four datasets. When data from the same dataset were used for training and testing the classifier, the classification performance was extremely to moderately high. When data from one dataset were used for training and the three remaining datasets were used as test sets, the performance was lower but still extremely to moderately high. This shows that the method generalizes well across different locations or times. Our method provides a substantial gain of time when birds must be identified in large collections of radar signals and it represents the first substantial step in developing a real time bird identification radar system. We provide some guidelines and ideas for future research.