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Electrical limitations of the state-of-the-art thin-film high-temperature superconducting (HTS) circuits are examined for microwave and millimeter-wave applications. Some factors adverse to HTS applications are discussed qualitatively. Numerical examples are shown the up-limit of loss advantages and the maximum monomode bandwidth possible for commercial YBCO-LaAlO3 based HTS transmission lines, thereby...
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...
The development of High Temperature Superconducting films has sparked much interest within the phased array antenna community. Using superconducting film for the RF power distribution network of large array antennas can considerably reduce Ohmic losses and hence increase antenna efficiency. In this paper we will discuss the measured results for a capacitivly coupled array antenna design adopted to...
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.
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...
Aperture efficient antennas are required for optimum performance of small satellite terminals. The development of a dual band EHF (30/20 GHz) microstrip antenna will be presented with single Tx and Rx elements as well as sixteen element Tx and Rx subarrays. The design and measured performance of the array are presented, with special focus on the effects of subarray element spacing and fabrication...
The conventional design approach to provide a shaped beam antenna pattern has been to illuminate a paraboloid reflector with a multielement feed array. The beam shaping is achieved by selection of the size and placement of the feed elements in the focal plane of the reflector, and the excitation coefficient which drive the elements. Recent developments at Space Systems/Loral have proven the benefits...
This paper describes the development of the EHF offset reflector antenna system for Personal Communications, Picoterminals. The picoterminal antenna system is an experimental unit designed for personal communications via satellite from any stationary location at an EHF band of 20/30 GHz. The antenna system consists of mechanically steered linearly polarized offset paraboloid reflector that uses a...
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...
The digital radio program is anticipated to be broadcast simultaneously through the Satellite and Terrestrial Stations. To receive the program the ground antenna should have adequate gain for both transmitters. The challenging problem is with the mobile antennas that must maintain its gain during the operation. The broadcast will be in the L-Band, around 1.45–1.5 GHz, and circularly polarized for...
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...
The radiation characteristics of the eccentrically coated axial slot cylindrical antenna is examined. The boundary value method is employed to obtain the solution with the aid of the addition theorem of the Bessel functions. The resulting dual infinite series involved in the solution is then truncated to generate numerical results. Several examples showing the antenna radiation characteristics corresponding...
The characteristics of a prolate spheroidal antenna, excited by a rotationally symmetric narrow slot, have been discussed by Wait [1]. Sinha and MacPhie[2] have discussed the admittance characteristics of an antenna system consisting of two symmetrically center-fed prolate spheroids in parallel configuration. Ciric and Cooray[3] have further investigated such two spheroidal dipole antennas in an arbitrary...
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.
The translational formula for vector spherical harmonics [1-5] is derived in a very simple and straightforward manner using only a few well known results in the irreducible spherical tensor theory [13-15] and recursion relations of spherical Bessel and Hankel functions.
The analysis presented in this paper provides a polarimetric observation over the Kelvin's wake sensed by a SAR in a numerical simulation. A computer simulation of L band SAR images of surface ship wakes is described and the results analysed. The model accounts for the perturbation in the fluid by the ship and the influence of the sea in calm wind conditions. The fluctuations of the Kelvin's waves...
A periodic structure antenna that exhibits traveling wave properties with strong horizontal electric field is analyzed. Input impedance and near field are calculated and are in good agreement with the measurements. Both calculation and measurement show strong radiation around 1.45 GHz.
We study the performance of a chirped sinusoidal surface relief grating in an optical waveguide as a wavelength demultiplexer by means of local normal mode theory. Linear chirp and contrapropagating guided-to-guided mode coupling is considered in phase synchronism. Two first-order differential coupled-mode equations with variable coefficients give approximate solutions for the coupling of the contrapropagating...
A proper Green's function is developed to study the reflective properties of structures composed of two layers of periodic structures printed on the two interfaces of a dielectric slab. Implementation of periodic structures composed of cell elements of different sizes and/or shapes on the two interfaces of a dielectric slab leads to certain interesting characteristics such as: decreasing the angular...
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...
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