K. H. Awadalla

Microstrip Antenna with Defected Ground Plane Structure as a Sensor for Landmines Detection

A proposed sensor for landmines detection consists of two parallel microstrip antennas placed on the same ground plane and with defected ground structure between them has been investigated. The microstrip patch array with defected ground structure has the advantage of a low mutual coupling compared with the classic one. The Finite-Difference Time-Domain (FDTD) is used to simulate the sensor for landmines detection.

A Single-Feed Cylindrical Superquadric Dielectric Resonator Antenna for Circular Polarization

Circularly polarized superquadric dielectric resonator antenna is investigated. A single coaxial probe is used to excite circularly polarized patterns. Finite element method is used to analyze the problem. Different aspect ratios of the superquadric dielectric resonator cross section for each squareness parameter for circular polarization are calculated.

ELECTROMAGNETIC SCATTERING USING GPU-BASED FINITE DIFFERENCE FREQUENCY DOMAIN METHOD

This paper presents a graphics processing based im- plementation of the Finite-Difierence Frequency-Domain (FDFD) method, which uses a central flnite difierencing scheme for solving Maxwells equations for electromagnetics. The radar cross section for difierent structures in 2D and 3D has been calculated using the FDFD method. The FDFD code has been implemented for the CPU calcu- lations and the same code is implemented for the GPU calculations using the Brook+ developed by AMD. The solution obtained by using the GPU based-code showed more than 40 times speed over the CPU code.

Curved dual- band dielectric resonator tag antenna for RFID applications

This paper presents a new application of dielectric resonator antenna in radio frequency identification system. A curved dual-band dielectric resonator antenna for RFID applications is proposed. The tag antenna is designed to operate at 2.45 GHz (2.25– 2.55 GHz) and 5.8 GHz (5.65– 5.95 GHz) bands. The radiation characteristics of the tag antenna in free space are investigated. The radar cross sections under different loads are obtained. The effect of curvature on the tag antenna performance is explained. Two examples are considered. In the first example, the tag antenna is mounted on cylindrical bottle filled with the Polyethylene material. The effect of the object properties on the radiation characteristics and the radar cross section is investigated. In the second example, the tag antenna is mounted on spherical bottle filled with the Polyethylene material. The radiation and backscattering characteristics are calculated. The Finite Element Method (FEM) is used for simulation and the Finite Integration Technique (FIT) is used to verify the simulated results.

Controlled Radiation Pattern of Circular Antenna Array

This paper presents a seven-element dipole circular array with different lengths and separation between the elements that was used to produce maximum gain in certain directions. The method of moments was used to formulate the problem. The radiation characteristics of the array were calculated, considering that one element acts as an active element while the others to act as parasitic elements. The genetic algorithm was used to optimize the dimensions and the separation between the elements

Transmitarray Using Perforated Dielectric Material for Wideband Applications

In this paper, linearly polarized transmitarray is investi- gated as to avoid the usage of multi-layers for improving the bandwidth of transmitarray. The transmitarray is formed from a single dielectric sheet by perforating selected areas of the material. A perforated dielec- tric layer is divided into square cell elements. Each cell has four holes with the same diameters. Holes with difierent diameters in the cell el- ements are used to allow continuous tuning of the transmitted signals phase over 360 - range with a maximum loss of 3.6dB at 10GHz. The transmission coe-cient versus the diameter of the holes is calculated by using the flnite integration technique. The results are compared with those calculated with transmission line method for veriflcation. The focal-to-diameter ratio of the transmitarray is optimized for lower side lobe level and highest transmitarray gain. A comparison between the transmitarray and the re∞ectarray with the same aperture area is illustrated.

Microstrip antenna with corrugated ground plane surface as a sensor for landmines detection

A proposed sensor for landmines detection consists of two parallel microstrip antennas placed on the same ground plane and with corrugated ground surface between the arrays has been investigated. The microstrip patch array with corrugated ground surface has the advantage of a low mutual coupling compared with the classic arrays. The finite-difference time-domain (FDTD) is used to simulate the sensor for landmines detection.

Homomorphic Enhancement of Infrared Images Using the Additive Wavelet Transform

This paper presents a new enhancement technique for infrared images. This technique combines the benefits of homomorphic image processing and the additive wavelet transform. The idea behind this technique is based on decomposing the image into subbands in an additive fashion using the additive wavelet transform. This transform gives the image as an addition of subbands of the same resolution. The homomorphic processing is performed on each subband, separately. It is known that the homomorphic processing on images is performed in the log domain which transforms the image into illumination and reflectance components. Enhancement of the reflectance reinforces details in the image. So, applying this process in each subband enhances the details of the image in each subband. Finally, an inverse additive wavelet transform is performed on the homomorphic enhanced subbands to get an infrared image with better visual details.

DIELECTRIC RESONATOR ANTENNA MOUNTED ON A CIRCULAR CYLINDRICAL GROUND PLANE

In this paper, the radiation characteristics of the single- element cylindrical dielectric resonator antenna mounted on the surface of a metallic hollow circular cylindrical structure is investigated. The efiect of the radius of curvature on the return loss, input impedance, standing wave ratio, and radiation pattern is explored. Mutual coupling between two identical cylindrical dielectric resonator antennas on a cylindrical structure in difierent conflgurations is determined. To reduce the mutual coupling between the two antennas, the surface of the cylinderical ground plane is defected by cutting slots, or inserting quarter wavelength grooves between the two antennas. The flnite element method and the flnite integration technique are used to calculate the radiation characteristics of the antenna.

Wideband perforated rectangular dielectric resonator antenna reflectarray

A wideband perforated rectangular dielectric resonator antenna (RDRA) reflectarray is presented. The array of RDRA are formed from one piece of material. Air-filled holes are drilled into the material around the RDRA. This technique of fabricating RDRA reflectarray using perforations eliminates the need to position and bond individual elements in the reflectarray and makes the fabrication of the RDRA reflectarray feasible. The ground plane below the reflectarray elements is folded to form a central rectangular concave dip so that an air-gap is formed between the RDRA elements and the ground plane in order to increase the bandwidth. Full-wave analysis using the finite integration technique is applied. Three cases are studied. In the first one, the horn antenna is placed at the focal point to illuminate the reflectarray and the main beam is in the broadside direction. In the second one, the horn antenna is placed at the focal point and the main beam is at ±30 degrees off broadside direction. In the third one, an offset feed RDRA reflectarray is considered. A variable length RDRA provides the required phase shift at each cell on the reflectarray surface. The normalized gain patterns, the frequency bandwidth, and the aperture efficiency for the above cases are calculated.