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As with most antenna measurement techniques, with a spherical near-field system there are many individual sources of error which contribute to an overall inaccuracy of the measured result. These relate to a number of diverse factors, for example positioner readout errors, receiver non-linearity, multipath reflections, dynamic sampling errors, temperature-dependent changes in instrumentation cables...
An exact solution to the problem of scattering of a plane wave by a hemispheroidal boss on an infinite perfectly conducting plane, has been obtained using a similar solution for scattering by a single spheroid in an unbounded space. Numerical results have been presented for perfectly conducting bosses of different sizes, and axial ratios. On the basis of this exact solution, the analysis of electromagnetic...
In this paper, numerical results for the scattering of a plane wave by an infinitely-thin multiloaded perfectly-conducting spherical shell with a circular aperture are studied in order to get an insight of the scattering characteristics of the considered structure. It is found that filling the spherical shell with a dielectric doesn't change its scattering characteristics compared to those of the...
The scattering by a single dielectric sphere with a concentric spherical shell has been analyzed in detail by a number of authors. It was firstly treated by Aden and Kerker [1] by expanding the exterior and interior fields in terms of the spherical vector wave functions. Later, Scharfman [2] used this solution to present numerical results for the special case of a small dielectric-coated conducting...
A uniform solution is obtained for the diffraction of a cylindrical wave by a conducting wedge. This solution is valid within the entire region and the expression of the diffraction integral is obtained by Pauli-Clemmow method. When the source is far from the observation point and from the wedge, this solution reduces to that for the case of a plane wave illumination.
The scattering properties of a homogeneous elliptic cylinder with a nonconfocal dielectric coating are investigated analytically. The method of separation of variables together with the addition theorem for Mathieu functions are used to determine, exactly , the field distributions in each region for the transverse magnetic (TM) excitation. The technique can be easily extended to handle any number...
In conventional phased arrays, antenna elements are usually simple radiators, such as dipoles, slots, dominant mode horns and microstrip patches, etc., that generate broadbeam, low gain and radiation patterns with a desired polarization property. The array beam is then formed and scanned by introducing phase shifts between the elements and modifying the phase shift values. The simplicity of array...
A general study on phased array is undertaken to evaluate the array performance in terms of its lattice structure, gain and sidelobe levels. For the array geometry both rectangular and circular shapes are considered and their performance for fully scanned and switched beam arrays is studied. The performance of arrays in G/T is also studied and estimated costs for each array are provided.
Hyperthennia induced by interstitial microwave applicators has proven to be effective in the treatment of malignant tumors particularly when used in conjunction with ionizing radiation and chemotherapeutic drugs. During hyperthermia treatment the tumor temperature is raised above 42°C at which point many normal cellular functions are impaired. Cancer cells have been shown to be more sensitive to elevated...
Presented is a method to estimate the element gains and phases of an array antenna when specular multipath interference is strong and cannot be ignored. A movable calibration source is used. The element gains are derived from the relative output powers at the array elements. The element phases are obtained by transforming the array snapshots to make the source direction appear fixed and then maximizing...
In this paper we have presented a new approach for pattern synthesis for array antennas of arbitrary geometry. The far-field radiation pattern is matched to one that is prescibed by minimizing a global root-mean-square error. Using the Conjugate Gradient iterative scheme the storage and inversion of a large system matrix is omitted. As shown by numerical test cases presented in this paper, the present...
A permittivity of (51-j31) has been used which is typical of muscle, skin and other tissue having high water content [2) at the frequencies considered here (915 MHz). The radiator has been modeled as a lossy transmission line with empirically determined characteristics. Figures 2 and 3 show the power density along a line parallel to the axis of the applicator at various radial distances with the diode...
The hyperbolic reflector antenna was developed over ten years ago, but little has appeared in the literature on its design and application. In this paper, its application to a multibeam antenna and some general guidelines on the hyperbolic reflector antenna design are presented.
Design and experimental results of an L-Band circularly-polarized microstrip subarray are presented in this paper. A 2 × 2 subarray of vertically-stacked microstrip patches is fed by a microstrip beamforming network in a sequentially phase-rotated fashion. The subarray is composed of space-qualified materials and is intended as a feed element for reflectors on board communications satellites. Measured...
The expression for the far field patterns of conical reflectors with a line source feed in the form of two microstrip comb line arrays, are derived and computed using a numerical integration of the physical optics currents. Representative radiation patterns are computed and presented.
The Magvi, Aerial, a printed vivaldi type slotline element, printed in a ferrite substrate, is introduced. The design of the shape of the edges for the slotline taper will be discussed. The practical results presented by a prototype will be shown and commented. Finally, some conclusions and suggestions for future works will be given.
A recent trend in microstrip antennas, electromagnetic (EM) coupling, is demonstrated using a spiral slot antenna with a triplate transmission line. The microstrip line, which is located between the upper and lower plates of the triplate, feeds the spiral slot without physical contact. A wideband characteristic for the axial ratio is obtained by using a c-shaped slot.
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