A High-Power Microwave Reflectarray Antenna Based on Perforated Dielectric Substrate

A high power microwave antenna based on the reflectarray concept is designed and investigated in this paper. The reflectarray aperture is directly driven by an azimuthally symmetric mode and a directional boresight beam is realized through azimuthally introducing a phase shift of 90 to the phase shift profile of reflectarray unit cells. A sample model operating at X-band is designed to verify the validity of the proposed approach. Variable diameter air-filled holes through a host dielectric material are exploited as the phase-shifting unit cells because of the advantage of higher power handling capacity. Theoretical analysis and full-wave simulations are accomplished and results are in good agreements. A collimated beam of circular polarization with peak gain of 20.2 dB and axial ratio of 1.3 are achieved at the boresight direction for the design frequency of 10 GHz. The radiation performance of the proposed antenna as well as its compact structure makes it a potential candidate for high gain high power applications

Modeling a Planar Coupled Microstrip Lines using various Wavelets and Method of Moments

In this paper, we apply a several wavelets basis functions to the method of moments to modeling the parallel-coupled microstrip lines. The first set of equations is for the shielded microstrip line solved with moment’s method and wavelets. The Green’s function is obtained from the theory of images. The second set are for the parallel-coupled microstrip lines operating in the TEM mode or when the analysis can be based on quasi-static approximation, the properties of coupled lines can be determined from the self- and mutual inductances and capacitances for the lines. To demonstrate the effectiveness and accuracy of the proposed technique, numerical results of even- and odd-mode characteristic impedances, coupling coefficient, percentage sparsity achieved in the impedance matrix, the CPU Time to reverse impedance matrix, and error relative for Daubechies, Coiflets,   Biorthogonal and Symlets wavelets are presented. Numerical results are in good agreement with those in previous publications

Characterization of Transmission and Reflection of Ku Band Split Ring Resonator Reflectarray using Waveguide Method

In this paper, the analysis, design, and measurement of a split ring resonator reflectarray is presented. The 6 different designs of reflectarray are simulated to analyze the effect of splits position on resonance frequency. The SRR reflectarray which covered highest frequency bandwidth at Ku-band is fabricated and tested. In the fabrication, FR4 substrate is used. The S-parameter measurements of the fabricated reflectarray are performed by waveguide method. The obtained results have good reflection characteristics for a wide frequency range from 12 GHz to 16.5 GHz in Ku-band. The maximum value of reflection is achieved approximately at 15.3 GHz frequenc

Mutual Coupling Reduction of DRA for MIMO Applications

In this paper, A multiple input Multiple Output (MIMO) antenna using two Square Dielectric Resonators (SDRs) is introduced. The mutual coupling between the two SDRAs is reduced using two different methods; the first method is based on splitting a spiral slot in the ground plane, then filling the slot with dielectric material, "E.=2.2". The second method is based on inserting a copper parasitic element, having the same shape of the splitted Spiral, between the two SDRAs.  The effect of replacing the copper parasitic element with Carbon nanotubes (CNTs) parasitic element "SOC12 doped long-MWCNT BP" is also studied. The antenna system is designed to operate at 6 GHz. The analysis and simulations are carried out using finite element method (FEM). The defected ground plane method gives a maximum isolation of l8dB at element spacing of 30mm (0.6λo), whereas the parasitic element method gives a maximum isolation of 42.5dB at the same element spacing

Enhanced Accuracy of Breast Cancer Detection Based on UWB Compact Slotted Monopole Antennas

This work presents a new breast tumor detection system based on an omnidirectional microstrip ultra wideband antenna. The localization coordinates of the tumor are studied in detail for better tumor detection. The coordinates of the corresponding maximum value of SAR are identified in order to accurately detect different locations of tumor inside the breast. The results show that relying on these coordinates; the tumor can be detected with high accuracy. The possibility of mutual interferences with other systems operating at the FCC frequency band is considered as a major issue in UWB systems. Therefore, rejected out-band interference signals is introduced by etching single and double U-shaped slots on the radiating element, then a first and second frequency band are successfully produced respectively. The proposed antenna is a compact antenna that can be used on microwave imaging detection. The antenna gain was larger than 2 dbi with an omnidirectional radiation pattern over the whole frequency-band. A relatively flat group delay of the antenna response is also achieved. Antenna prototype has been manufactured and measured, results prove the performance of the proposed antenna

Application of the Shifted Frequency Internal Equivalence to Two Dimensional Lossy Objects

Performance of a new method, Shifted Frequency Internal Equivalence (SFIE) is studied in the analysis of scattering from two dimensional lossy objects. This method finds the solution of a wideband scattering problem faster than classical approaches.By introducing conductivity, loss shows itself as imaginary electrical permittivity. Changing conductivity also changes the distribution of electromagnetic waves and modifies RCS plots. In this study homogeneous and inhomogeneous conductive media are investigated to widen the usage of SFIE method. By increasing conductivity skin effect phenomenon is observed, electrical dimensions are decreased and RCS plots are flattened as expected.Numerical results obtained by SFIE are compared to the ones obtained by Method of Moments and the differences are shown

Analysis of the Effect of a Gyrotropic Anisotropy on the Phase Constant and Characteristic Impedance of a Shielded Microstrip Line

In this work, we present an analytical modeling of a highly complex medium-based shielded microstrip line. The study aims at a numerical evaluation of the characteristic impedance and the dispersion characteristics of the dominant hybrid mode in the microstrip line printed on an anisotropic medium. The newly considered complex anisotropy has a full 3×3 tensor form of permittivity and permeability. The study is based on the derivation of the Green's functions of the general complex-medium-based structure in the Fourier domain. The spectral Method of Moments (MoM) and the Galerkin's procedure are combined to solve the resulting homogeneous system of equations. The effect of the gyrotropic anisotropy on the phase constant and the characteristic impedance is particularly investigated. Original and interesting numerical results are obtained and discussed. Our results are found to be in good agreement with available isotropic case data reported in literature

Study of Stacked High Tc Superconducting Circular Disk Microstrip Antenna in Multilayered Substrate Containing Isotropic and/or Uniaxial Anisotropic Materials

In this paper, we present a rigorous full-wave analysis able to estimate exactly the resonant characteristics of stacked high Tc superconducting circular disk microstrip antenna. The superconducting patches are assumed to be embedded in a multilayered substrate containing isotropic and/or uniaxial anisotropic materials (the analysis is valid for an arbitrary number of layers). London’s equations and the two-fluid model of Gorter and Casimir are used in the calculation of the complex surface impedance of the superconducting circular disks. Numerical results are presented for a single layer structure as well as for two stacked circular disks fabricated on a double-layered substrate

A Low Profile Wideband Log Periodic Microstrip Antenna Design for C-Band Applications

In this study, a wideband low profile microstrip antenna design for C-band applications is presented. The proposed antenna consists of a monopol log periodic patch in the equilateral triangular dimensions with the microstrip line fed and a rectangular ground plane. The antenna has 9×19.8 mm2 overall size, thickness of 1.6 mm and 4.3 dielectric constant. According to the simulation results, the proposed antenna has a very wide bandwidth while operating in the frequency band of 4.25-7.95 GHz and 5 GHz resonance frequency. The proposed antenna was also prototyped on FR4 substrate with the 0.02 tangent loss and the measurement results were quite similar by the simulated results

Analysis of Current Distributions and Radar Cross Sections of Line Source Scattering from Impedance Strip by Fractional Derivative Method

In this paper, we have studied the analysis of current distributions and radar cross sections of line source scattering from impedance strip. The problem was solved with fractional derivative method previously. Here, the specific case of fractional derivative method is investigated. The problem under consideration on the basis of various methods is studied well, however, they are mainly done by numerical methods. The fractional derivative method, allows an analytical solution in a specific situation. This method allows to obtain analytical solution of impedance strip for a special case which is fractional order  is equal to 0.5. When fractional order is 0.5, there is an analytical solution which is explained and current distribution, radar cross section and near field patterns are given in this paper. Here, as a first time, current distribution, bi-static radar cross section and near field for the upper and lower part of the strip are studied