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New method is applied on linear phased array in order to increase the inter-element separation. The method is based on using elements of scan capability, where the element pattern has a null at specified direction. Dual mode horns are used here, where the position of the element pattern null is controlled by the relative amplitude and phase of the second mode. In this case if the element pattern null...
Constant width slot antennas(CWSA) and various types of tappered slot antennas(TSA) have attractive features like ease of construction, compatibility with MIC/MMIC technologies, Wider bandwidth,… for focal plane and phased array applications. Radiation and input circuit characteristics of a single isolated TSA/CWSA element has been investigated by several workers, but there are relatively few published...
Reflector configurations suitable for a multibeam EHF satellite communication receive antenna are reviewed in this paper. Four different antenna systems have been studied and their relative performances are compared. Computer simulations have been performed to analyze the co-polar and cross-polar gain contours of the antennas and the results are discussed.
A JPL Fortran program for designing the main reflector and the subreflector of a Galindo-Williams system with a constant intensity over the aperture of the main reflector was modified for use on our computer system. Geometrical Optics and conservation of energy are the basic laws used for designing this type of surface. The basic computation is a numerical solution of three simultaneous differential...
This paper considers the modal current distribution on a loop antenna which is situated coaxially on the interface of a double-layered cylindrically stratified media. The loop is modelled as a ΣNn=1cos nφδ(z) electric current distribution under the influence of a unit amplitude rectangular voltage pulse function. The determination of the modal amplitudes of the current distribution follows an exact...
The performance of an amplitude sensing monopulse radar is largely affected by the hardware imperfections of the receiver. This paper describes an analysis on the effects of the pre-comparator phase and amplitude unbalance on the radar antenna. In this paper an anlaytical antenna model is used, the radiation patterns of the two squinted beams of the monopulse are represented by the Gaussian function...
In high speed and wideband electronic circuit applications, it is desirable to minimize the cross-talk between parallel tracks on the printed circuit board. This paper presents a technique using vias, with which the cross-talk can be reduced by 50 to 90%. A SPICE model combined with the finite element method is developed to predict the performance and is validated with experimental results.
Microwave Neural Networks are introduced. These are microwave subsystems, designed on basis of the emerging Artificial Neural Network Theory, that together with inhomogenous antenna arrays, are able to perform identification tasks of radar emitters, in real time. A model is presented and its properties are commented. Considerations about the physical realization of such systems are given.
Advanced multi-function Ku-band feed systems for satellite or earth station application require a number of operational features such as wide bandwidth, dual polarization, frequency reuse and polarization re-orientation. When built for satellite application, the feed system must also be compact, environmentally rugged and light weight. The realization of such a feed system calls for the development...
Location and identification of compact ferrous objects is of major concern for detection of vehicles, submarines, achaeological objects, buried or hidden explosive objects, geological ore inclusions and inclusions in the human body. In principle, measurement of the spatial variation of the magnetostatic field associated with a compact ferrous object may be used to locate and identify the object and...
Microwave components carrying medium or high powers in the space environment may suffer from multipactor breakdown. The resulting discharge can seriously affect the performance of communications equipment, so effective multipactor detection is essential in the development and qualification stages of flight hardware. This paper presents an extremely sensitive method of detection by means of a travelling...
Electromagnetically coupled (EM fed) microstrip patches have their feed structure fabricated on a thin substrate located between the patch antenna and its ground plane as shown in Figure 1. This dual layer design has two main advantages over conventional single layer microstrip antennas. First, spurious radiation from the feed network can be reduced by decreasing the height and increasing the dielectric...
In this paper, the electromagnetic wave scattering from a infinite array constituted by wires with finite length is analysed by using a moment method and Floquet's theorem. When the period of the grating is far greater than the length of each wire, the numerical results are in good agreement with that for a single wire. Some numerical results for different periods and incident angles are presented.
There are now many new microstrip antennas being produced in industrial centres throughout the world for a host of applications. However there still remains significant challenges in full exploitation of the unique capabilities of these printed antennas. Cost reduction and tolerance control to allow realistic mass production, exploitation of the conformal nature of microstrip and further integration...
In this paper, an enhanced precision “Thru-Reflect-Line” (TRL) calibration technique is presented which allows highly accurate, de-embedded measurements to be made for a microstrip line-fed patch antenna with an arbitrary feed line characteristic impedance. This technique provides tremendous design flexibility and reduces the phase uncertainty to about 1 degree for the low dielectric constant material...
The field transient response of a circular cylinder illuminated by a plane wave having a step function wave form in the time domain is computed using the Finite Difference-Time Domain (FD-TD) numerical technique. Both cases of conducting and dielectric circular cylinders are considered and correspondence between the transient response and the rise time of the excitation wave are investigated.
Transverse problem in coaxial regions leads to the well known Bessel equation. Solution of this equation is in the form of Fourier-Bessel expansion of which eigenvalues are determined by the appropriate transcendental equations. In electromagnetics, two symmetric cases: Dirchlet-Dirichlet (D-D) and Neumann-Neumann (N-N) are fundamental both from practical and theoretical points of view. The first...
Null steering methods usually involve costly and complicated amplitude and/or phase control systems. A new technique is presented for null steering based on the element positions perturbations. This method possesses an even symmetry pattern cancellation, which allows nulls to be imposed at symmetrical positions around the main beam. Also it frees the phase shifters to be used solely for steering the...
This article presents both theoretical and experimental aspects of the imaging of near fields of printed circuit boards (PCB). Selected aspects of sensor performance and imaging of reactive fields of simple PCB boards are also presented.
A simple model is used to explain spatial response characteristics of an electromagnetic induction detector as it scans over a metallic object. The technique is illustrated with numerical and experimental data for two mechanically identical prolate spheroids, one made of steel and the other of aluminium. Some basic differences in the response characteristics of a permeable and a non-permeable object...
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