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Multiple beam antennas (MBA) for satellite communications usually provide a contiguous coverage over a specified field-of-view by using high gain overlapping spot beams. The common design objective for all MBAs is to maximize the minimum gain within the coverage region. If the MBA has uniform beams arranged in a hexagonal grid, the minimum gain occurs at the triple beam cross-over and the gain variation...
Cylindrical dipole antenna is the basic element in antenna and scattering analysis. Here, a symmetrical cylindrical dipole antenna analyzed and measured by, 1) Analyzed by MM (Moment Method) based on NEC (Numerical Electromagnetic Code), 2) Analyzed by a separate M M program based on PWS (Piece Wise Sinusoidal) basis and PWL (Piece Wise Linear) base function. 3) Measured a typical monopole over RF...
Numerical results presented recently show that the stochastic inversion method is one of the promising spatial domain methods for reconstructing dielectric permittivities, especially in a noise contaminated environment [1],[2]. The stochastic inversion algorithm is developed based on statistical considerations, with the generated reconstructions and the noise modelled in terms of stochastic or random...
The increasing demand for mobile, broad bandwidth, cost-effective communications has led to the development of novel integrated active antennas operating at mm-wave frequencies. A design methodology is presented for a GaAs monolithic 30 GHz amplifier/antenna consisting of a HEMT device integrated with a slot radiator. Both antenna numerical analysis techniques and microwave circuit CAD tools are employed.
Based on an exact solution of the pertinent boundary-value problem, a method is presented for finding the electromagnetic fields scattered or guided by dielectric gratings having arbitrary profiles. This method unifies the treatment of both perpendicular (TE) and parallel (TM) polarization by using the Boundary Element Method (BEM). To illustrate the method, the results are presented for a four layer...
The dual-polarized patch element is useful in indoor wireless networks for broad bandwidth and modest gains. The focus of this paper is placed on an inset matching network used with a patch element. The purpose of the design is to increase the bandwidth of a microstrip patch by using a thicker substrate with low dielectric constant. However, with such a combination, the input impedance of the antenna...
The finite-difference time-domain technique (FDTD) is used to model electromagnetic systems with lumped elements. The FDTD equations are modified to account for the presence of lumped elements such as R, L, and C and current or voltage sources inside the grid. FDTD equations that include nonlinear elements, i.e., diodes and transistors arc derived.
This paper concerns the calculation and measurement of the RCS of a trihedral corner reflector. The calculations are performed using the moment method and the Uniform Theory of Diffraction (UTD). The measurements are performed at 2–18 GHz in an anechoic chamber. Comparison between the measurements and the calculations shows a good agreement. The results show that as the angle of incidence is increased,...
In recent years, the range of applications for microstrip antennas has been expanding rapidly and so has the complexity of the antenna configuration. Multilayer printed-circuit antennas have been gaining much attention because they can improve antenna characteristics such as bandwidth and side lobe levels. They are also well-suited for multi-frequency operation as well as dual polarization. Frequency...
Three V band and one Ka band low noise amplifier designs have been completed using a GaAs PHEMT process. The two-stage Ka band device demonstrated a 23 dB gain with a noise figure of less than 3,7 dB over the 26 to 33 GHz range. The V band designs have achieved their respective simulated bandwidths of 2, 7 and 10 GHz, Though full testing of the wide band designs has not been completed, the two-stage...
The equivalence principle and the moment method are used to present a solution for the scattering matrix when a number of waveguide junctions (more than one) are considered together in a cascade. This solution presents each two consecutive waveguide junctions by their scattering matrix. The overall scattering matrix of a cascade of waveguide junctions can be obtained by the multiplication of the scattering...
Usual measurement techniques determine amplitudes and phases of signals at the ports of a device and in the far field of an antenna. They do not show what happens within the device or close to the antenna, how signals travel along lines and across junctions, sometimes disappearing mysteriously at some ports, and which edges of an antenna actively contribute to radiation.
A simple cavity resonator is described for measuring surface resistance (Rs) of high temperature superconductor (HTS) thin films. The cavity is a one-half wavelength of WR-28 waveguide with the HTS forming a short across one end. A choke ring reduces the need for low resistance contact. Quantitative Rs measurements can be made over the range of 10 mΩ to 500 mΩ at liquid nitrogen temperature and at...
One future opportunity for satellites is to extend the reach of the planned “information superhighway” to areas not served or underserved by terrestrial networks. Future satcom systems, such as the proposed Canadian advanced satcom system, the Hughes Spaceway system in the U.S., and the global Teledesic system all aim to provide digital wideband multimedia communications to off-net users. To that...
Passive 180° phase-shifters (rat-race or monolithically integrated equivalent) have usually a frequency bandwidth narrower than an octave. A differential amplifier structure provides a very large operating bandwidth, and allows an easy MMIC integration.
Parallel dielectric waveguides are used as optical directional couplers. In this paper for two identical rectangular parallel dielectric waveguides, the propagation constants are calculated by the perturbation feedback method.
This paper describes a model for a GaAs/AlGaAs Heterojunction Bipolar Transistor (HBT). The model is based on the Gummel-Poon topology with modifications to account for self-heating and transit time effects. The model is capable of predicting the DC and small signal S-parameters from 1–40GHz. The simulated and measured load pull characteristics showed a 1–2dB discrepancy.
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