In this paper, an extremely fast technique is introduced to evaluate the shielding effectiveness of a rectangular enclosure of finite wall thickness and numerous square or circular small apertures subject to a normally incident plane wave. The technique is based on the traditional waveguide circuit model where the enclosure is replaced with an equivalent shorted transmission line. In the proposed circuit model, the perforated thick wall is represented by an equivalent impedance which is derived from the reflection coefficient. The computation results are in very good agreement with measurements. Additionally, further results are compared to a generalized modal MoM technique which are in excellent agreement as the number of apertures increase. Besides accuracy, the method is extremely efficient and easy to implement compared to the numerical techniques.
A geometrical high-frequency approximation method for solving the propagation of electromagnetic wave through the quartic Wood lens into an uniaxial crystal is presented in this paper. Caustic problem of electromagnetic wave is translated into non-caustic problem by using the hybrid space. The drawback that the solution in the caustic region cannot be obtained with geometrical optics is overcome by this method known as Maslov's method. The high-frequency approximation solution that is valid around caustic region is obtained by using this method which combines the simplicity of ray and generality of the transform method. And the results are compared with those obtained by Huygens-Kirchhoff's expression.
We propose an exact synthesis method which allows the design of dual-band transformers with an arbitrary even number of uniform sections giving equi-ripple impedance matching in two separate bands centered at two arbitrary frequencies. This method is a generalization of the exact Collin-Riblet synthesis of Chebyshev single-band transformers. As compared to a single-band Collin-Riblet transformer encompassing both required passbands, the proposed design yields significantly better performance in terms of passband tolerance and width.
A low complexity wavelet packet transform-based least mean square (LMS) adaptive beamformer is presented in this paper. This beamformer uses wavelet packet transform as the preprocessing, reduces the signal dimension in wavelet packet domain for low complexity and denoising, and employs least mean square algorithm to implement adaptive beamformer. Theoretical analysis and simulations demonstrate that this algorithm with better beamforming performance converges faster than the conventional adaptive beamformer and the wavelet transform-based beamformer. Finally, our proposed algorithm has the low complexity, and it can be easy to implement.
The problem of diffraction of a plane electromagnetic wave by a slot in a planar perfectly conducting screen of arbitrary thickness in the presence of a half-infinite dielectric arranged at a distance from a screen is solved rigorously on the bases of eigenfunction expansion and mode matching technique. The calculation algorithm for various components of the electric and magnetic field vectors in the entire space is presented, and a simple computation method for corresponding diffraction integrals is described. Just one more method of field visualization is demonstrated, which utilizes a picture of the energy-flux lines.
This paper presents the design and construction of an advanced wideband, automated radar system. With the aid of Vector Network Analyzer (VNA), a wideband ground-based system can be achieved with proper Radio Frequency (RF) circuitry integration. The RF circuitry is designed specifically to configure the proposed system to be able to measure full linear polarimetric scattering matrices of the area of in terest. Besides, quasi-monostatic horn antenna configuration is chosen to transmit and receive the electromagnetic wave. The goal of this paper is to demonstrate the real and synthetic aperture capabilities of the system in outdoor measurement with the microwave frequency range from 2 to 7 GHz. Coupled with the integration of the Automatic Antenna Positioning System (AAPS), the constructed system is able to perform real and synthetic aperture radar measurements. A series of measurement was done on real aperture radar measurement using point target for validity purpose. The overall results show good agreement with the theoretical values. On the other hand, the proposed system is capable to performing a radar imaging measurement. A preliminary analysis is done on a 45 days old rice field. A three dimensional (3-D) radar image has also been constructed successfully with Range Migration Technique (RMA). The result shows good potential ofthe system in constructing radar imaging ofnatural target.
Making use of the Toeplitz structure of the mutual coupling matrix of the Uniform Linear Array (ULA), estimating the direction-of-arrival (DOA) of the sources as well as the mutual coupling coefficients of the array can be formulated as a linear inverse problem, where the solution is given by the Kronecker product of the vectors with respect to the DOAs and the mutual coupling coefficients. Through mathematical manipulation, these solution vectors can be decoupled. Estimation of the DOAs is cast into the framework of sparse solution finding. To derive the solution, an alternating minimization technique is presented. The proposed method is firstly developed based on the noise free observation covariance matrix, and can be generalized to directly using the snapshots. Using the proposed method, DOA estimation is feasible even in single snapshot case. The performance of the proposed methods with covariance matrix, single snapshot and multiple snapshots are illustrated by computer simulations. Their ability to resolve closely spaced targets and the applicability to correlated sources have also been demonstrated.
This study includes three parts: First is fuzzy modeling of scattered field from unloaded dipole antenna. In second step a fuzzy model for scattered field from a linearly loaded thin dipole antenna is introduced. In both parts, knowledge bases of diameter and load impedance are separately extracted and saved as very simple curves. It is shown that the behavior of scattering dipole antenna is well approximated with the single transmitting dipole antenna obtained in our previous study. In the third step, using the concept of spatial membership functions, two obtained knowledge bases are combined so that the spatial knowledge base including simultaneous effects of diameter and load impedance is extracted. As a result, these spatial knowledge base as well as the behavior of single transmitting dipole antenna are used instead of time consuming and repetitive computations in accurate methods. With the use of this spatial knowledge and behavior of single transmitting dipole antenna, the scattered field from dipole antenna for any load impedance and diameter is predicted. Comparing the predicted results with accurate ones shows an excellent agreement. Moreover the computation time is considerably reduced.
The electrodynamical rigorous solution of Maxwell's equations related to the microwave pulse propagation inside a threedimension heart model is presented here. The boundary problem was solved by using the singular integral equations' method. The carrier microwave frequency is 2.45 GHz. The pulse durations were always equal to 20 ms. The modulating signals are triangular video pulses with the on-off time ratio equal to 5 and 100. The model heart was limited by a non-coordinate shape surface and it consisted of two different size cavities. The heart cavities were schematic images of the left and right atriums and ventricles. In our calculations the cavities were filled with blood with the permittivity ε2 = 58 − i19 and the walls of the heart consisted of myocardium tissue with the permittivity ε1 = 55 − i17. Microwave electric field distributions were analysed at four longitudinal cross-sections of the heart model.
This paper links joint direction of arrival (DOA) and frequency estimation problem to the trilinear model and derives a novel blind joint angle and frequency estimation algorithm. The proposed algorithm has better performance than ESPRIT algorithm. Our proposed algorithm is thought of as a generalization of ESPRIT. The useful behavior of the proposed algorithm is verified by simulations.
This paper presents a novel resistively loaded antenna design for microwave breast cancer detection. The antenna is planar and ultra-compact,and can be easily manufactured using PCB technology with embedded thin-film resistive layers. Through numerical simulations,the antenna demonstrates a return loss below -10 dB over a wide frequency range from 2 to 35 GHz. For pulse radiation in the ultra-wideband (UWB) range in a biological medium, the antenna shows an excellent fidelity above 0.95 and a relatively high radiation efficiency of 39.21% in comparison to resistively loaded antennas. In addition,a design rule guideline is presented for designing the antenna to radiate in a specific background medium and with a given lower operating frequency. Finally,a complete microstrip feed design is presented for the antenna operating in the UWB range.
In this paper a novel rose leaf shape microstrip antenna with capacitively coupled rectangular fed is presented. Various shapes of capacitive coupled fed are compared and optimized by successive iterations of a computer-aided analysis. The Ansoft HFSS is employed for analysis at the frequency band of 4.3 GHz-8.3 GHz. The antenna is fabricated and measurement results show a very good agreement with the simulation results. The proposed antenna is able to achieve an impedance bandwidth about 69%. Effects of varying the parameters on the performance of the antenna have also been studied. The proposed antenna can be used in wireless ultra-wideband (UWB) communication.
A two-slot array antenna on a concentric sectoral cylindrical cavity excited by a coupling slot is investigated. The electromagnetic fields and Q factors for the first few modes of a concentric sectoral cylindrical cavity are presented. It shows that the appropriate mode for a slot array antenna on a concentric sectoral cylindrical cavity is the TM110 mode. The correlations between each mode distribution and the magnetic field distributions inside the cavity are presented. The antenna design and the parametric study of a two-slot array antenna on a concentric sectoral cylindrical cavity for a single sector are illustrated. Simulated results are validated by measurements. The results provide useful information for the design of a switched-beam slot array antenna on the concentric sectoral cylindrical cavities.
In this paper, a general symmetry-based approach to the electrodynamics of a class of low-dimensional structures, carbon nanotubes, is proposed. The contribution of the microscopic configuration is handled using the symmetry group of the structure under consideration. An explicit form of the electromagnetic field is derived starting from a general nonlocal linear susceptibility model expressed as a low-dimensional phenomenological response function. The general form of the field obtained is used to devise new theoretical insights by providing a framework for the computation of the nanotube Green's functions.
In this paper, we study in detail both the trapped surface wave and lateral wave excited by a dipole antenna parallel to the plane boundaries of a three-layered region in spherical coordinate. An approximate formula is obtained for the solution of the electrictype pole equation when a condition is satisfied by √k21-k20l≤0.6. Similarly, an approximate formula is obtained for the solution of the magnetic-type pole equation when a condition is satisfied by √ k21-k20l-π/2≤1. Furthermore, because of its useful applications in microstrip antenna, the radiation patterns of a patch antenna with specific current distributions are treated specifically. Analysis and computations are carried out in several typical cases. It is seen that, for the component E0Θ, the total field is determined primarily by the trapped surface wave of electric type, and, for the component E0Φ, the total field is determined primarily by the trapped surface wave of magnetic type.
A microstrip circular patch antenna with two shorting pins is proposed as an antenna with reduced surface wave and lateral wave excitation. Theoretical analysis of the cavity modes of the patch lead to a design procedure for the antenna. Simulation results using the IE3DZeland software support the theory and verify the reduced surface wave capability. By using four shorting pins instead of two, we demonstrate the possibility of achieving circular polarization with high polarization purity in addition to the reduced surface wave. It is demonstrated that a discrimination against the lateral wave of 30dB or more is achievable. Applications include design of large patch arrays with reduced coupling and GPS receiving antennas that reduce low angle interfering signals.
This paper presents the design and construction of a complete near real-time scatterometer system for in-situ measurement. The full polarimetric system is comprised of inexpensive Frequency Modulated Continuous Wave (FMCW) radar that is efficiently constructed from a combination of commercially available components and in-house fabricated circuitry. An automated advanced antenna positioning system (AAPS) is included in the development of the system, giving rise for a more practical measurement. The backscattering matrices of a 4'' × 8'' dihedral corner reflector are rotated and measured at different angles to provide different sets of polarimetric data. The backscattering matrices of 8'' sphere, 12'' sphere and 16.5'' trihedral are also measured and the results are presented in this paper. In order to verify the effectiveness of the calibration technique, the results are compared with the theoretical values. Consideration on the challenges of measurement in outdoor environment is countered with external and internal calibration. As a result, the proposed scatterometer system has shown good correlation between measurement and theoretical results.
An improved E-plane power divider for compact waveguide triplexers with large separation between channels is presented. The configuration of the divider aims to exploit the different behavior of the device for frequency bands with large separation, leading to a very asymmetric E-plane junction. H-plane filters with inductive windows are used for each channel, in order to obtain reduced insertion losses and lower sensitivity than in metal-insert E-plane filters. The resultant triplexer configuration is very compact, and its design is analyzed and optimized by Mode-Matching. The experimental results of a full Ku-band prototype for communications satellite systems show a very good agreement with the expected simulated response.
A novel blind Direction of arrival (DOA) and polarization estimation method for polarization-sensitive uniform circular array is investigated in this paper. An analysis of the received signal of the polarization-sensitive uniform circular array shows that the received signal has trilinear model characteristics, and hence trilinear decomposition-based blind DOA and polarization estimation for polarization sensitive uniform circular array is proposed in this paper. Our proposed algorithm has better DOA and polarization estimation performance. Our proposed algorithm can be thought of as a generalization of ESPRIT, and has wider application than ESPRIT method. The useful behavior of the proposed algorithm is verified by simulations.
In this paper we develop a new impulse-radio-based RF front-end module for ultrawideband communications. The proposed transceiving module is designed based a novel compact microwave sampler. The microwave sampler consists of a multilayered magic-T and a balanced sampling bridge. By utilizing a wideband microstripto-slotline Marchand balun, the newly proposed magic-T features an improved bandwidth of 94.2%. The design concept, circuit topology, and experimental results of the magic-T and microwave sampler are investigated in the first half of this paper. By utilizing the equivalent time sampling theory, in the second half of this paper we investigate an impulse-radio-based ultrawideband transceiving front-end module. Two transmission data rates, 90 and 270 Kbps, are demonstrated with various bit patterns. The experimental results reveal that the transceiving module has a coverage range up to 4.5 m. The circuit configuration, modulation scheme, and system performance of the front-end module are discussed thoroughly. The tradeoff for increasing the data rate is discussed at the end of this paper as well.
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