In this paper, a novel algorithm named multi-scan mixture particle filter is proposed for joint detection and tracking for a varying number of targets. The posterior distribution of multiple target state in a single-target state space is a multi-mode distribution with each mode corresponding to either a target or clutter. A general global posterior distribution is adopted in this work, which consists of existing components and new components. The new components are generated at each time step to capture the new modes due to newly appeared targets or clutter. In order to distinguish targets from clutter, multiple scan information is incorporated. The history of each component's associate weights is stored in a multi-scan sliding window, which is used to judge whether the component is from a target or clutter. Moreover, a novel sampling method which combines the likelihood sampling and prior sampling is proposed to draw particles from the desired parts of the state space at each time step. From the simulation results, it could be seen that the proposed algorithm can effectively detect the appearance/disappearance of the targets as well as track the existing target.
The problem of detecting point-like sources whose frequency spectrum is unknown is addressed. Limitations of single-frequency approaches are identified by analytical as well as numerical arguments. To overcome these limits, different multifrequency approaches which combine frequency data incoherently are compared. In particular, a novel multifrequency MUSIC-like algorithm based on interferometric idea is proposed. Results show that the algorithm outperforms other methods under comparison.
An improved nonlinear least-square method is presented in this paper. This method changes the traditional least-square method's shortness of being sensitive to its initial conditions. Pattern synthesis for concentric circular arrays using nonlinear least-square method is introduced. The excitation amplitudes and phases of the array elements are optimized. This method can make the design of the feeding network much easier because the excitation amplitudes of the elements placed on the same ring are equal. The number of parameters to be optimized is reduced which leads to a faster simulation speed and makes the simulation results much more accurate. Also, the cost of designing the feeding network is reduced. The simulation results show the good agreement between the synthesized and desired radiation pattern. Also, the peak side lobe level (PSLL) of the synthesized radiation pattern is quite low.
In this paper, a novel moment-matching reduced order model technique termed the multi-dimensional well-conditioned asymptotic waveform evaluation (MDWCAWE) method is presented. The MDWCAWE method can be used to efficiently determine the radar cross section (RCS) of arbitrarily shaped objects, in both the frequency and angular domains simultaneously. Numerical results are given in order to demonstrate the accuracy and robustness of the MDWCAWE method. All scattering problems investigated in this work are formulated using the two-dimensional volume-surface electric field integral equation (EFIE). We consider problems involving scattering from both dielectric dispersive and conducting objects.
The dispersion equation governing the guided propagation of TE and TM fast wave modes of a circular cylindrical waveguide loaded by metal vanes positioned symmetrically around the wave-guide axis is derived from the exact solution of a homogeneous boundary value problem for Maxwell's equations. The dispersion equation takes the form of the solvability condition for an infinite system of linear homogeneous algebraic equations.The approximate dispersion equation corresponding to a truncation of the infinite-order coefficient matrix of the infinite system of equations to the coefficient matrix of a finite system of equations of sufficiently high order is solved numerically to obtain the cut-off wave numbers of the various propagating modes. Each cut-off wave number gives rise to a unique dispersion curve in the shape of a hyperbola in the ω-β plane.
Ramp response technique in low frequency can be used for generating 3-dimensional images of radar targets (even stealthy or buried targets) so as to identify them. This technique uses the target profile function, which is defined as its transverse cross- sectional area versus distance along the observing direction. For mutually orthogonal observing views, reconstructed 3D images are quite accurate. However, in practice, due to the bias introduced from the response in shadow region and from limited non-orthogonal observing directions, reconstructions become distorted.To evaluate the quality of the reconstruction and to further identify objects from their reconstruction, we need to calculate profile functions of 3D reconstructed objects in arbitrary directions. Therefore, in this paper, we propose an algorithm meeting this needs.
In this paper, a novel second-order transmission condition is developed in the framework of non-conformal finite element domain decomposition method to meet the challenges brought by complex and large-scale electromagnetic modeling. First, it is implemented efficiently on the non-conformal interface via a Gauss integral scheme. Then, the eigenvalue analysis of the DDM system show a more clustered eigenvalue distribution of this transmission condition compared with several existing transmission conditions. After that, it is applied to large-scale complex problems such as S-type waveguides in the high frequency band and dielectric well-logging applications in the low frequency band. The final numerical results demonstrate that this transmission condition has high efficiency and huge capability for modeling large-scale problems with multi-resolution in any frequency band.
In this paper, we present a low-profile, compact, ultra-wideband antenna that uses a set of closely coupled radiators. The system of two coupled radiators has two different linearly independent modes of operation with complementary frequency bands of operation. These include the differential mode and the common mode of operation. When the antenna is excited in the common mode of operation, it acts as an ultra-wideband (UWB) antenna covering a broad frequency band. When excited in the differential mode, the antenna operates as a wideband dipole in a frequency range below that of the common mode. Thus, by appropriately combining the two modes using a suitably designed feed network, the bandwidth of the antenna can be extended and its lowest frequency of operation is reduced. Mode combining is achieved with a feed network that employs a frequency-dependent phase shifter. Using this feed network, the two modes of the antenna are combined and a single-port broadband device is achieved that has a bandwidth larger than that of either the common or the differential mode individually. A prototype of the antenna is fabricated and experimentally characterized.
In this paper, an experimental characterization of a MIMO underground channel is presented. A simple statistical model is proposed at 2.45 GHz. The Channel is characterized in terms of path loss, shadowing, RMS delay spread, and capacity. The measurements are carried out in an underground mine, which is a harsh confined environment. The path loss model is extracted from measured data for the line of sight (LOS) and non line of sight (NLOS) scenarios for both MIMO and SISO channels. The path loss exponent in LOS is less than 2 in MIMO and SISO as the environment has a dense concentration of scatterers. A statistical study is carried out to find the delay spread. For MIMO and SISO, there is no relation between the delay spread and the transmitter receiver distance. Furthermore, the delay spread of the MIMO is less than the one of the SISO channel in the LOS measurement campaigns. Aikake information Criteria are used as a goodness of fit for different statistical distributions to represent the delay spread. According to the calculated capacity for a constant signal to noise ratio in LOS case, the transmission performance is significantly improved by using the MIMO scheme over the traditional SISO. Therefore, MIMO is an ideal candidate for future wireless underground communications.
A WLAN band notched compact ultra-wideband (UWB) microstrip monopole antenna with stepped geometry is proposed. A L-slot loaded modified mushroom type Electromagnetic Band Gap (EBG) is designed, analyzed and used to realize notched band characteristics for wireless local area network (WLAN) in the UWB frequency range. The proposed antenna having partial ground plane is fabricated on a low cost FR4 substrate having dimensions 40 ( Lsub ) × 30 (Wsub ) × 1.6 (h) mm^{3} and is fed by a 50-Ω microstrip line. The results show that the proposed antenna achieves impedance bandwidth (VSWR < 2) from 2.3 GHz to 11.4 GHz with band notched characteristics (VSWR > 2) from 4.9 GHz to 6 GHz. Fidelity factor for proposed antenna is also analyzed to characterize time domain behavior. Simulation and measurement results of VSWR are found in good agreement.
This paper presents a high-efficiency ferrite meander antenna (HEMA), which can be used to realize a 2×2 multiple-input-multiple-output (MIMO) communication system when it is used at both the transmitter and the receiver ends. This antenna is designed to operate at 2.45 GHz center frequency (fc). It consists of two spatially separated half-cycle microstrip meander structures. Ferrite material is not used for the entire substrate, only beneath each meander structure. A standard FR-4 substrate is utilized as a system board. Impedance bandwidth and radiation patterns of the fabricated antenna are measured and compared with those of the simulation results. The -10 dB impedance bandwidth of the fabricated antenna is 262 MHz, whereas the simulated bandwidth is 235 MHz. According to the simulations, the gain and efficiency of the antenna are 2.2 dB and 81%, respectively. The efficiency of the antenna is confirmed by measurements. By using the simulated radiation patterns, correlation between the radiation patterns is calculated and employed in the generation of the channel matrix. Mutual impedance of the antennas and antenna efficiency are also included in the channel matrix, which in turn is used in bit error rate (BER) and ergodic capacity simulations. BER and ergodic capacity are utilized as performance metrics. The effect of antenna efficiency, mutual impedance of the antennas, and correlation between radiation patterns on system performance are presented.
This paper presents a new approach to the electromagnetic inverse scattering formulation of the permittivity profile estimation. The proposed approach is particularly effective for the cases where unknown objects are made of a finite number of homogeneous regions. This approach prevents the need for the Born approximation initial guess and updating the internal total electric field iteratively. The solution to the inverse source problem and scattering problem is not unique. To address the non-uniqueness issue, we have defined the non-radiating objective functions. By minimizing this objective function and applying some constraints, we have been able to obtain a unique permittivity profile. The simulation results indicate that the low-contrast and high-contrast permittivity profiles are accurately estimated by the proposed method. The distinguishing feature of the proposed approach is that by including the non-radiating part of the equivalent source, the unknown permittivity profile becomes the solution to a minimization problem, which is much less computationally intensive as compared to existing methods using iterative field calculation over the entire domain, when applied to large (in terms of wavelength) objects. The high performance of the proposed method for noisy measured data has also been verified.
An electromagnetic band gap (EBG) waveguide using holes drilled in a dielectric substrate is investigated in this paper. A broadbanding technique is suggested and implemented through a detailed study of the modal behaviour of the guiding structure. The stop band of the EBG waveguide was adjusted by changing the width of the waveguide to increase its bandwidth. It is shown that the propagating mode is a quasi-TEM by examining the dispersion properties of the propagating mode. An EBG waveguide of 49.1 mm (equivalent to 19 EBG cells) was designed and fabricated. The simulation results show better than -10dB return loss performance from 27 GHz to 31.5 GHz with insertion loss of better than 2.5 dB over the same bandwidth, and also high isolation in the range of -20 dB with an adjacent similar EBG waveguide. There is a good agreement between the measured data and simulation results. A microstrip line was also fabricated and used as a benchmark for comparison with the designed EBG waveguide. The group velocity of this waveguide is nearly constant across its operating frequency band which implies low frequency dispersion and is also a confirmation of the quasi-TEM nature of the EBG fundamental mode. Also, using the physical insight gained from a careful study of the EBG guide, a simple method is suggested for the calculation of the dispersion characteristic of its fundamental mode.
The feasibility of realizing an all-optical AND gate for 320 Gb/s return-to-zero data by incorporating quantum-dot semiconductor optical amplifiers (QD-SOAs) in a Mach-Zehnder interferometer (MZI) is theoretically investigated and demonstrated. The proposed scheme employs the QD-SOA-based MZI in a configuration where the QD-SOA in one MZI arm is subject to the first data sequence, the QD-SOA in the other MZI arm receives no such input but is constantly held in the small signal gain regime, and the second data stream is inserted from the common MZI port acting as enabling or disabling signal. Compared to other approaches adopted for the same purpose this implementation is more general, direct, flexible and affordable as only one strong data signal is required to control switching. By conducting numerical simulation the impact of the critical parameters on the Q-factor is thoroughly assessed. The obtained results are interpreted with the help of a complete characterization of the QD-SOA response to an ultrafast data pulse stream. This allows to specify the requirements that the critical parameters must satisfy to achieve acceptable performance. The extracted design rules are technologically realistic and ensure AND operation both with logical correctness and high quality. The outcome of the numerical treatment extends the range of Boolean functions executed with the QD-SOA-MZI module at sub-Tb/s data rates.
In High-Frequency (HF) Over The Horizon (OTH) radar, the space-time variations of the ionospheric channel, the external noise level (environment and man-made) as well as the transmission channel bandwidth limitations, are among the most critical and challenging aspects for the design and the operational management. Specifically, the knowledge of the ionosphere behaviour in a real time configuration is of primary importance because of the way it influences the frequency selection. This implies that a HF radar must have a high level of adaptability in order to deal with external constraints. For this purpose, a suitable frequency management system is needed. In this paper, a representation of the ionosphere propagation channel from a radar point of view is provided. Specifically, radio-electric parameters of the radar link are revisited by extending the concept of Maximum Usable Frequency (MUF), which is typically used in the communication field. The Ionospheric Propagation Chart (IPC) and Maximum Transmitted Frequency (MTF) are also introduced as new concepts. The present work is supported by simulation results.
Statistical characteristics of multiply scattered electromagnetic waves in turbulent magnetized plasma with both electron density and external magnetic field fluctuations are considered. Analytical expression for phase fluctuations of scattered radiation is derived using the smooth perturbation method. Correlation and wave structure functions of the phase fluctuations, angle-of-arrivals are obtained for arbitrary correlation functions of fluctuating plasma parameters and external magnetic field taking into account the diffraction effects. The evolution of a double-peaked shape in the spatial power spectrum of scattered radiation is analyzed numerically for both anisotropic Gaussian and power-law spectra of electron density fluctuations using experimental data. Phase portraits of external magnetic field fluctuations have been constructed for different non-dimensional spatial parameters characterizing a given problem.
A new method to design a miniaturized ring coupler consisting of multiple open stubs on the inside of the ring is proposed. It is shown that this coupler topology may be seen as fully-distributed composite right/left handed (CRLH) small-size phase shifters, cascaded in a ring configuration. The CRLH phase shifter is analyzed in detail and a design method is proposed, pointing out the condition to obtain a reduction of its length. Using the fully-distributed CRLH based phase shifter, a ring coupler is configured and analyzed in comparison with the traditional ring coupler, showing that both couplers have similar characteristics. To validate the proposed design method, a 3-dB CRLH based ring coupler is designed and fabricated. The experimental results show a very good agreement with the predicted results obtained by electromagnetic simulation. The printed area of the fabricated coupler is 49% smaller compared to the traditional ring coupler.
This paper deals with the finite element analysis and experimental study concerning the influence of the one broken bar and rotor dynamic eccentricity faults on the magnetic field outside a squirrel-cage induction motor. The spatial distribution of the magnetic field, the time variation of the magnetic flux density in a point outside the machine and the time variation of the output electromotive force delivered by a coil sensor are evaluated based on the finite element models of the healthy and faulty states of the motor. The increase of amplitude from the healthy to the faulty states of some low frequency harmonics measured in the nearmagnetic field is emphasized. For the one broken bar fault, the increase of the amplitudes of specific harmonics of the coil sensor electromotive force, with frequency lower than 25 Hz, is experimentally confirmed.
A technique is described for the electromagnetic reconstruction of the location, shape, dielectric constant, and conductivity of buried homogeneous cylinders of elliptic cross-section. The inversion procedure is based on the Differential Evolution algorithm and the forward problem is solved using the single boundary integral method. Simulation results are presented which demonstrate that this hybrid approach can offer a conceptually simple yet efficient and reasonably robust method for the imaging of buried objects and voids.
A through wafer vertical micro-coaxial transition flushed in a silicon substrate has been designed, fabricated, and tested. The transition has been designed using radio frequency (RF) coaxial theory and consists of a 100μm inner diameter and a 300 μm outer diameter, which corresponded to a 1:3 inner/outer diameter ratio. The transition's through silicon structure has been achieved using standard photolithography techniques and Bosch's process for deep reactive ion etching (DRIE). The coaxial vias of the transition have been successfully metalized with a diluted silver paste using a novel filling method. To measure the behavior of the transition at high frequencies, coplanar waveguide (CPW) lines matched at 50 ohms have been integrated on the front and backside of the device. Measurement results show that the transition demonstrate good results with a reflection coefficient better than -10 dB at high frequencies from 15 GHz-to-60 GHz. Results also indicate that the transition has good signal transmission with less than -1.8 dB insertion loss up to 65 GHz. By eliminating the need for rigorous bonding techniques, the transition is a low-cost and durable design that can produce high input/output ratios ideal for commercial products.