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Helical antenna is a practical electromagnetic radiator constructed by winding a conducting wire in the form of a screw thread. In most applications, the helix antenna is mounted on a ground plane as shown in Fig. 1. The radiation characteristics of the helix antenna are critically dependent on the electrical size of its geometrical properties. The input impedance is dependent upon the pitch angle...
Electromagnetic field scattering problems can be solved by either an analytical or numerical method. With the advancement of computers, the numerical method has lately received a lot of attention. However, in some aspects, an analytical method can still offer certain advantages over the numerical approach. This includes a better physical insight into the problems and a better computational efficiency...
Future satellite based, personal communications systems operating in the 20/30 GHz frequency range will require small and reliable RF components capable of being manufactured in large quantities. Suitcase sized terminals are expected to be available and phased array antennas appear to be an attractive way of realizing the necessary planar antenna configuration. Integrated circuit technologies such...
Computer modeling and numerical techniques provide valuable results in the area of bioelectromagnetics. In this paper, advantages and limitations of three numerical techniques, namely the method of moments (MoM), the finite-difference time domain method (FDTD) and the spherical wave expansion functions are addressed and discussed. Examples of the results obtained with the FDTD for the interaction...
This paper presents the design and performance of a hybrid semiconductor/superconductor amplifier and filter integrated circuit. The circuit combines the high frequency, low noise advantages of a cryogenically cooled GaAs HEMT with the low loss, high Q properties of a narrowband HTSC filter and matching networks. The HTSC filter/amplifier combination produced 7.2dB gain at the passband centre frequency...
A multi-layer patch antenna that is fed by a gap discontinuity within a microstrip feed line is investigated. The feed line is located on the lower layer of the structure, while a rectangular patch is centred above the gap discontinuity on the upper layer. The structure is analyzed by the moment method in the spatial domain and employs a matched load simulation technique. Comparison with experimental...
This paper will present codes whose function is to pre- and post-process information used by the Numerical Electromagnetic Code Basic Scattering code and the Richmond Thin Wire code. The processor uses the MATLAB environment for the fundamental graphical functions. The Basic Scattering Code uses the principles of ray optics as well as the geometrical theory of diffraction. The Richmond code uses a...
There are many ways to apply the finite difference method to the time domain Maxwell equations. One of the first applications was the time-space centered algorithm formulated by Yee [1] which is now usually refered to as the finite difference time domain (FDTD) method. In this paper we will be using the term FDTD in the more general sense to include any other finite difference technique which can...
The UHF antenna for the Skynet communications satellite comprises a circularly polarized helix radiator. In the CAL design (Fig, 1), the helix conductor is realized as an aluminum tape conductor supported at one end by an extendible structure designated as the bistem. This central conducting tube, along with a set of longitudinal support tapes, allows the helix to be deployed in orbit. At the base...
Transient propagation of Gaussian pulses on superconductive conductor-backed coplanar waveguides are investigated by a modified Finite Difference Time Domain method (FDTD). The two-fluid model is used to describe the superconductor. The frequency-dependent negative imaginary part of the conductivity is modeled with the FDTD by storing the electric field history. A variable mesh with second order accuracy...
This paper describes the measurement and computation of the resonant frequencies and the associated Q factors of dielectric parallelepipeds made of high-permittivity, low-loss ceramic materials. The radar cross-section(RCS) is measured separately near each resonance peak with a fine frequency step. A curve-fitting method is used to accurately estimate the resonant frequency and the 3 dB bandwidth...
The stacked quad EMC super patch with probe feeding was first proposed in [1] and a number of design results for personal communication terminals were provided in [2]. It has wide bandwidth of stacked microstrip antennas and higher gain due to the radiation of subarray. On the other hand, aperture coupling[3] can reduce the interaction between the antenna and feeding network, and the feed can be placed...
To reduce the angular and polarization sensitivity of FSS structures, various novel geometries such as double layered periodic structures composed of open or shorted square rings are proposed as cell elements. Results are presented to demonstrate the feasibility of removing the angular constraints upon the “reflective characteristics” of a resonating FSS. Logical steps that led to the proposed geometry...
In this paper, we report the results of our experimental investigations on microstrip-fed series dielectric resonator arrays. The antennas have been fed by proximity coupling between the microstrip line and the dielectric resonator. The performance of three and twelve element arrays is discussed.
The MMP modeling of different scattering structures is discussed. It is shown, that highly accurate near and farfield simulations are possible, not only for simple academic structures such as spheres or cubes, but also for a multiturn helical wire of finite thickness and an absorbing ferrite cylindre placed on a cable. Although the amount of calculation increases when edges or tips are present, rather...
The original ideas which lead to the development of MMP-3D are still very much in use. However during the past years, there has been some recent improvements which lead to both the hybridization and generalization of the method. In particular, there has been a generalization for the sources or basis functions, to allow the computation of special geometries. Also, a combination with line theory has...
Relationships are presented for use in determining material properties of dielectric objects, including permittivity, density, moisture content, and mass, from measurements of frequency shift and change in cavity transmission characteristics when a small object is inserted into a microwave resonant cavity. Results are presented for such measurements of moisture content of individual soybeans and cereal...
In [1], a new method has been developed to minimize the cost and memory requirements of the integral equation method (IEM) for the capacitance calculation of multiconductor system embedded in a homogeneous dielectric medium. In this paper, the method has been extended to the calculation of the capacitance matrix for integrated circuits applications.
Much attention has been paid to circular polarized self-diplexing antennas[1]-[3], for mobile satellite communications. Among them, the two-layer configuration[2]-[3] seems to be suitable for reduction of the array size. Most self-diplexing antennas described earlier are either direct microstrip line-fed or probe-fed. For the application to higher frequencies, such as Ka-band or millimeter wave band,...
A coplanar waveguide (CPW) is an attractive transmission line for superconducting applications because the presence of the CPW ground and centre strip in the same plane eliminates the need for via holes. These via holes may break the fragile substrate, lanthanum aluminate, most often used with superconductors.
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