A.J. Parfitt

Electromagnetic design aspects of packages for monolithic microwave integrated circuit-based arrays with integrated antenna elements

Reliable and cost-effective packaging of monolithic microwave integrated circuits (MMICs) is an important aspect of the design of phased array systems. At millimeter wavelengths, where small dimensions make machining and assembly a complex matter, the interconnections between the modules housing the MMIC components and the antenna elements are a source of unreliability as well as a potential problem in terms of electromagnetic losses. One solution involves the integration of antenna elements onto the MMIC chips. The paper addresses the issues involved in packaging and housing MMIC chips with integrated antenna elements and presents some insights into the electromagnetic design of such packages. >

Helicon Double Layer Thrusters

The Helicon Double Layer Thruster is a new type of magneto-plasma thruster which combines the helicon technology for an efficient coupling of the electrical power to the plasma and a current-free double layer (formed spontaneously in the physical and magnetic nozzle of the thruster) for an optimized acceleration of the plasma ions. A large area, low divergence supersonic ion beam (the source of thrust) is measured in the nozzle for various propellants (xenon, argon and hydrogen). In addition to the scalability in geometry and electrical power, the simplicity, the absence of any moving parts, electrodes, or neutralizer give the HDLT an infinite lifetime.

Analysis of infinite arrays of substrate-supported metal strip antennas

An electric field integral equation method is applied to a metal strip antenna on an electrically thick dielectric substrate of finite size in a uniform infinite array environment. An efficient solution is found using the method of moments. Metal strip folded dipole antennas are analyzed both with and without a coplanar strip feed line, and the effects of the substrate and feed line are investigated. A technique for minimizing the effect of feed line scattering is presented, and arrays of these elements are shown to be capable of good scanning performance over a wide range of beam-steer angles. A phased array simulator experiment is described and the measured results show good agreement with those obtained by analysis. The class of antenna elements studied may be fabricated using monolithic microwave integrated circuit (MMIC) technology, and the analysis described illustrates the expected characteristics for millimeter-wavelength phased arrays of this type. >

On the modeling of metal strip antennas contiguous with the edge of electrically thick finite size dielectric substrates

A solution to the problem of radiation by a narrow metal strip antenna contiguous with the edge of a dielectric substrate is presented where the substrate has parameters such that its electrical thickness is appreciable. Such an antenna may be useful at millimeter wavelengths as an integrated phased array element forming a part of a monolithic microwave integrated circuit (MMIC). A suitable geometry for this application is illustrated and an efficient computational procedure developed. Comparisons with experimental results for the input impedance and far-field radiation patterns show excellent agreement. The influence of the dielectric substrate on the performance of an antenna designed to operate at approximately 60 GHz is discussed. Two examples, the first involving the analysis of a coplanar strip transmission line fed antenna and the second involving impedance matching and control of cross-polarized radiation using a folded strip dipole, are given to illustrate practical applications of the analytical method to design problems. >

Mutual coupling between metal strip antennas on finite size, electrically thick dielectric substrates

An analysis of the mutual coupling between metal strip antennas which are contiguous with the ends of finite-size, electrically thick dielectric substrates is outlined. Such antennas have been proposed as useful monolithic microwave integrated circuit antennas for millimeter-wavelength applications. The analysis presented was verified experimentally, and the results are applied to three-element arrays of metal strip folded dipoles with coplanar strip feed lines. The effect of the electrically thick, finite-size dielectric substrates on the mutual coupling between elements of the arrays is described. >

A dual-polarised wideband planar array for X-band synthetic aperture radar

This paper describes the design and performance of a wideband planar array panel for use in a dual linear-polarisation antenna for the Australian Defence Science and Technology Organisation (DSTO) Ingara X-band airborne synthetic aperture radar (SAR). The final array aperture is approximately 1200 mm by 200 mm and comprises 192 dual-fed microstrip patch elements divided into three panels, each panel with an integrated microstrip feed network. To accommodate high power operation, a coaxial power distribution network is used to feed the panels. The primary objective of the design was to achieve on-axis cross-polarisation radiation in each polarisation at least 25 dB below the co-polarised radiation over a 600 MHz bandwidth.

Experimental results for a focal plane array, synthesized with conjugate field method

The study analyses the performance of a focal plane array in combination with reflector systems of small F/D parameter (F/D<0.5). The geometries of two radio telescope reflector antennas (WSRT and Parkes) were used while the array feed was optimised for the WSRT reflector antenna only. Synthesis of the array feed was done with a dense Vivaldi array operating in a frequency band of 2-5 GHz. Conjugate field matching (CFM) in the focal area of the reflector was applied to determine the required number of array elements, arrangement and the optimal excitation coefficients. To verify the theoretical model, measurements of the array feed were carried out with a near-field scanner. The experimental results were used as an input source in the GRASP simulator to predict the far-field patterns of the WSRT and Parkes reflector antennas.

Operating the Helicon Double Layer Thruster in a Space Simulation Chamber

A prototype of the helicon double layer thruster (HDLT) is designed and manufactured. Initial tests with the thruster mounted on a small vacuum chamber (pumping speed of 700 l ldr s-1) show successful operation in xenon with the formation of the double layer which generates a low divergence ion beam, which is the source of thrust. The prototype is subsequently inserted inside a much larger space simulation chamber (pumping speed of 7000 l ldr s-1). A high-density blue mode is found when increasing the RF power above 380 W, and measurements with a Langmuir probe give an estimated density of 1012 cm-3 in the thruster. An image of the HDLT operating in the high-density blue mode is presented.

The Luneburg lens as a radio telescope element

Serious consideration of the scientific objectives for the next generation decimeter radio telescope includes, as a major objective, the desire to study interstellar hydrogen in the early universe occurring at large red-shifts. This has led to the proposal for a Square Kilometre Array (SKA). Among the primary specifications are large collecting area (the square kilometre relates to the effective collecting area of the telescope at 1.4 GHz), wide frequency coverage (200 MHz to 2 GHz minimum), large dynamic range, full sky coverage and the possibility of forming multiple simultaneous beams on the sky. A lens can have both a wide field-of-view and a high aperture efficiency. Indeed, only a lens appears to offer the possibility of maintaining a constant collecting area for all viewing directions and thereby allowing a multiple beam capability through the use of a fixed focal plane array or lightweight movable feeds. We propose the consideration of a Luneburg lens to meet the requirements of the antenna element for the SKA.

Extension of the insect-vision paradigm to millimeter waves

A novel motion detector utilizing a millimeter-wave array front-end, with signal processing that mimics insect vision, is described. The use of passive millimeter-wave detection enables a significant improvement over optical or IR wavelengths, when a colliding object is obscured by rain, steam or other aerosols. This, for instance, used as a blind-spot detector, will enhance driver safety in poor weather conditions. As insect vision techniques do not attempt to process an image, but rely on tracking moving edges, the processing tasks are less hardware intensive, resulting in a compact low-cost solution.