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A low cost transportable short range Synthetic Aperture Radar (SAR) measurement system is constructed by placing a linear positioner on the bed of a truck. The radar system is based on a network analyzer and a pair of standard horn antennas. The SAR system gives a resolution of 0.3 m at X-band frequencies and 100 m measurement distance. By using the terrain the objects can be measured at depression angles up to at least 10. . The near field SAR images are processed using back projection algorithms. The system can be used to estimate camouflage efficacy in realistic environments. Flexible software based entirely on open source components is developed for the data processing, presentation and analysis of the SAR images. Results from the evaluation of two generic camouflage nets using reference targets in different backgrounds and SAR images of vehicles are presented.
In this paper we present an optical imaging tool, the Overlay Imaging Aligner (OIA), developed to aid in the mechanical alignment of antenna components in the mm-wave and low-THz frequency regimes (50-500 GHz) where the millimeter and sub-millimeter wavelengths pose significant challenges for alignment. The OIA uses a polarization-selective, machine-vision approach to generate two simultaneous and overlaid real-time digital images along a common axis. This allows for aligning two antenna components to within fractions of a wavelength in the mm-wave and THz frequency regimes. The overall concept, optical design, function, performance characteristics and application examples are presented. Preliminary data at specific frequencies in the WR-2.2 band are presented that compare the alignment achieved with the OIA to an electrical alignment.
A novel electromagnetic measurement technique using an active screen is presented. The main advantage of this technique is that it can remove contributions from non-stationary or fluctuating backgrounds, even if they are within the same measurement range gate of the target. This technique is particularly useful in cases where the beam width of the measurement antenna has to be wide enough to encompass the cross-range extent of the target. The technique is demonstrated for scattering measurement.
The 2D full wave finite difference frequency domain (FDFD) method can provide propagation constant and eigenmode information for various guided wave structures. In addition, the mode information is well suited for exciting the waveguides and extracting the modal S-parameters in 3D FDTD simulation. However, most 3D full wave FDTD solvers have used conformal techniques to improve the accuracy and efficiency. To match these two methods and take advantage of the conformal features, it is necessary to apply the conformal techniques to the 2D FDFD method. In this paper, a conformal 2D FDFD eigenmode method is derived for solving arbitrarily shaped waveguides or transmission lines. The numerical results showed that the propagation constants obtained by the proposed method agree well with those obtained by the analytical solutions and commercial circuit solvers. The eigenmodes obtained by the developed conformal 2D FDFD eigenmode solver can be used to excite various transmission lines and to extract the modal S-parameters in 3D conformal FDTD simulation. Some examples such as horn antennas, circular waveguide filters and differential pairs are presented to show the capabilities of the developed conformal 2D FDFD eigenmode solver. The simulation results are also verified by some measurement results.
ABSTRACT
There are various electrical high power cables around and within semiconductor foundry. These cables are the source of extremely low frequency (ELF < 300 Hz) magnetic fields that affect the tools which are operating by the function of electronic beam. Such as electron microscopes (included SEMs, TEMs, STEMs, FIB and E-Beam writers) are very susceptible to ELF magnetic fields emanating. The miss operation (MO) happens because of ELF magnetic fields inducing the beam shift during the measurement or process for cutting-edge chips below 40 nanometer process. We present optimal permutation of power transmission lines to reduce electro-magnetic influence at high technology nano-Fab. In this study, the magnetic field was lessened by mirror array power cable system, and simulation of results predicted the best permutations to decrease electromagnetic influence (EMI) value below 0.4 mG at working space without any shielding. Furthermore, this innovative method will cost down at high technology nano-Fab especially for 28 nanometer process. Through the theoretical study and numerical simulation, we predict the best permutation for mitigating EMI noise from three-phase electric power lines system without any shielding system down to 1.2 mG in 3.0 m distance from applying I=150 A at 60 Hz with 12 series cable tray system. Followed above discussions, this study indicated different and new perspectives with before opinions of some researcher. The measured magnetic field values on the nano-Fab are in good agreement with this simulation results. These good results give more confident to apply in new building nano-Fab system. Furthermore, this innovation will cost down for EMI shielding at high technology nano-Fab especially for 40 (and below) nanometer process.
From measurements of RCS of a target as a function of the frequencies and the bearings, it is possible to make RADAR imagery. A common way is to use a bi-dimensional Fast Fourier Transform (FFT2) while this algorithm being very fast. Yet this algorithm demands that the grid on which the RCS is known fulfils some particular conditions. Now such conditions are not respected by the grid of measurement. Consequently an interpolation of this grid is necessary in order to be able to apply the FFT2 algorithm. The choice of the method of interpolation will directly impact the quality of the calculated RADAR image. In this article we propose to study this impact while giving the analytical expression of the interpolation then while giving the analytical expression of the RADAR image calculated from the interpolated RCS and while specifying eventually the method interpolation which limits the degradation of quality of the calculated RADAR image.
The installation of power-generating wind turbines near outdoor radar cross-section measurement ranges for low-observable targets presents a number of problems for accurate measurements on those ranges. The turbines, with towers up to 100 meters tall and blades 45 meters long, are enormous scatterers that raise clutter levels well above returns from LO targets. The movement of the rotors, rotating about both a horizontal and vertical axis, generates a dynamic and unpredictable Doppler smear that cannot be mitigated with phase coding techniques or Doppler filtering. Lastly, the large wind farms over which the turbines are installed lowers the unambiguous-return PRF to extremely low levels, raising test times and dropping rotation speeds below acceptable levels. A method of varying pulse spacing into a burst mode is presented that maintains data throughput in RCS collection while avoiding the clutter returns of downrange wind turbines. This burst mode has the radar transmit and receive a string of closely-spaced pulses, and then idle while that string of pulses propagates through the wind farm. By careful selection of timing parameters, clean-range clutter levels can be maintained with little to no degradation in test time.
In this paper, we present a three-antenna reverberation chamber method that allows for the determination of the antenna efficiency. While reverberation chambers have been used in the past for determining antenna efficiency, the previous approaches required knowledge of the efficiency of a reference antenna. The approach discussed in this paper allows one to determine the efficiency of one or all three antennas, and does not require one to know the efficiency of any of the antennas under test before hand. The technique combines both time-domain and frequency-domain processed data collected in reverberation chamber experiments. Combining data in these two domains for three sets of experiments (a set for each two-antenna combination of the three antennas under test) allows for the determination of the efficiency of the three unknown antennas. In this paper we present the technique and present experimental data in order to illustrate its validity.
Abstract: This paper describes methods of computational testing of radomes in combination with their associated antennas. Physical testing has the disadvantage that it re-quires facilities capable of handling full-scale assets and possibly classified frequencies, and requires the full-scale parts to be available. Computational testing is promoted as an alternative and supplement to physical testing, having the ability to overcome these problems, as well as being able to examine notional configurations. A suite of compu-tational programs are now available that can be applied both during the design or proposal phase when changes can more readily be made to designs, and during the production and post-production phases to analyze changes. Full physi-cal testing can then be restricted to situations where physi-cal testing is actually required.
Large phased arrays have stringent beam-pointing accuracy requirements over their scan volume. Measuring the beam-pointing accuracy of a phased array with a planar near-field scanner is convenient but can lead to erroneous results if the near-field sampling grid is not well controlled. This paper describes numerical experiments that were carried out to assess the impact of various types of grid errors on the measurement of beam-pointing accuracy. The types of grid errors considered include skewing and curvature in the plane of the grid. The numerical experiments use infinitesimal dipoles as the radiating elements and assume an ideal probe. It is shown that beam-pointing errors induced by grid errors that can be described by an affine transformation can be estimated in closed form. For more complicated grid errors, the model is shown to be a useful tool in estimating their impact on measuring beam-pointing error. Finally, the amount of over-scan required for accurate beam-pointing measurements over a large scan volume is examined.
Snow attenuation depends on many factors which are hard to observe and identify or classify. Modeling of snow attenuation is relatively complex. Modeling should be done to reach the best estimate for each frequency and location. There are two main classes of methods used in snow attenuation prediction: the empirical method and the physical method. Physical method which we used in this work focuses on reproducing the physical behavior of factors involved in the process. In this study, the attenuation in the frequencies of mobile communication due to snow is simulated using Discrete Propagation Model. For this modeling, certain ice-crystal categories are chosen to be investigated. Needles, plates and branches are the main 3 groups which are focused, and 13 different models of snow particles in total are chosen to represent snow. The element in each group is chosen according to similar physical characteristics of ice crystal. It was found that attenuation due to snow is higher than rain attenuation specifically due to differences in particle size. In our simulations, frequencies of GSM communication, 900MHz, 1800MHz and 2270MHz, are used for calculation and discussion of attenuation.
In this paper, we report a calculation of the microwave fields within a model of the human eye. FEM with web-spline computer modeling have been applied to study the corneal surface temperature increase during microwave irradiation. The mechanism of heat transfer from the eye and the selection of the thermal parameters of the media of the eye are also discussed. The implementation of these parameters in the web-spline solution of the heat conduction is then developed. Furthermore, temperature rises calculated are compared with the values found in the literature pertaining to microwave-induced cataract formation.
Large size, light weight, broadband convex RF lens was developed to meet far-field requirements for antenna measurements. The Lens was fabricated from low loss, low density meta-materials and has diameter of D=2 m, focusing distance 2.4m and weight of just 50 kg with operational frequency 0.8 to 6 GHz. The lens is able to produce a plane-wave zone with an approximate size of 0.7D, allowing a 2m diameter lens to test antennas up to 1.4m in relatively small anechoic chamber. Another possible application of large size, lightweight RF lens is RCS measurements that include bi-static measurements. Results of quiet zone measurements for different frequencies are presented.
Accurate knowledge of the wake-up power and the corresponding input impedance of an RFID IC is valuable for RFID tag and IC designers, as it enables the design of performance-optimized tags using a specific IC and provides means for validation of both tag and circuit designs. However, the IC’s power-dependent front-end makes it difficult to measure this information. This article presents a method, based on the joint use of computational electromagnetics, wireless RFID tag measurements and Monte Carlo simulations, to determine the wake-up power and the corresponding input impedance of a mounted RFID IC.
The radiation pattern of an antenna can be determined accurately by near-field measurement and transformation techniques. Low numerical complexity, full probe correction capabilities, and high accuracy of the transformed far-field pattern are important features of near-field transformation algorithms. The multilevel plane wave based near-field transformation algorithm achieves an efficient full probe correction by plane wave representations of antenna and field probe and realizes the low numerical complexity by hierarchical grouping of measurement points. Field translations are carried out to the boxes on the coarsest level and are further processed to the measurement points by disaggregation and anterpolation. Disaggregation is a simple phase shift of the plane waves and anterpolation reduces the sampling rate corresponding to the spectral content of the plane wave spectra on the various levels. The accuracy of the transformation is influenced by several variables where the number of buffer boxes between antenna and measurement point groups is crucial. A higher accuracy due to more buffer boxes can be achieved at the cost of increased computation time. Adaptive field translations structure the measurement setup such that individual groups are transformed with the required accuracy at lowest costs. A detailed investigation for a planar near-field measurement will be shown.
Scattered field . Escatt A profile reconstruction method using a surface acquisition domain inverse currents technique is presented. The method makes use of the internal fields radiated by an . equivalent currents distribution retrieved from scattered field information collected from multiple incident fields. The main advantage of this method with respect to other inverse source-based techniques . E is the use of surface formulation for the inverse problem, which reduces the problem dimensionality thus decreasing the computational cost
Two of the three algorithms require an estimate of the element pattern, which they assume to be common to all the elements. We describe our measurement of our array’s element pattern, as well as the use of the IsoFilter™ to center the element pattern and limit the edge effects.
This paper validates the sub-reflectarray technique for main reflector antenna distortion compensation through simulations and measurements. First, axial defocusing of the feed creates spherical aberration distortion and it is corrected using sub-reflectarray by conjugate field matching method. Then, a ring-type distortion is created on the main reflector and it is also compensated using a similar approach. A hybrid HFSS/PO simulation approach was used for the design and analysis. Bipolar planar near-field measurements are performed to validate the compensation technique and back projection holography is used to locate the position of distortions and to study the effects of the distortion on the antenna performance.