Butler matrices can be used in antenna beam-forming networks to provide a linear phase distribution across the elements of an array. The development of an 8 to 18GHz micro-strip implementation of a 4-input 4-ouput Butler matrix is described. The designed Butler matrix uses March hybrids, Schiffman phase shifters and wire-bond crossovers integrated on a single 60mm x 70mm alumina substrate.
Accurate characterisation of transmission lines is essential in enabling the design of Monolithic Microwave Integrated
Circuits (MMICs) or Radio Frequency Integrated Circuits (RFICs). One RFIC technology currently being pursued is
Silicon on Sapphire Complementary Metal Oxide Semiconductor (CMOS) technology. CMOS processes typically
involve stacked metal layer structures and the correct method of modelling coplanar waveguides in CMOS is unclear.
This paper reports on preliminary studies into electromagnetic design, with an emphasis on correctly predicting losses
associated with these structures.
The increasing requirements for antenna apertures with multiple functions in terms of frequency diversity, beam steering and beam shaping have lead to the concept of re-configurable antennas. RF MEMS switch technology is promising to enable the development of such structures. Through electromagnetic analysis, this research demonstrates the feasibility of using RF MEMS switches to facilitate the phase shifting required for phased array beam steering. A particular problem associated with the practical implementation of RF MEMS switches, the substrate choice, was investigated. Ceramic substrates have appropriate loss tangent coefficients and dielectric constant, however, the thermal mismatch between silicon nitride and other materials used to construct the mechanical parts of the switch introduces thermal mismatch stress and process problems during fabrication. Micro RF relay switches on a ceramic substrate have been fabricated and their pull-in voltage characteristics were measured and compared to the theoretical results for the RF relays.
Microstrip patch antenna arrangements offer many advantages. They provide low profiles, are light-weight and are easily integrated with the monolithic circuitry that has been embraced for miniaturised RF sensing systems. This paper presents the designs of 8-16 GHz bandwidth log-periodic and aperture-stacked based antenna arrangements. These antennas are examined in the light of the existence of alternatives (e.g., a Vivaldi tapered slot sensor) for operation as broadband sensing elements.
Frequency-scanned slotted-waveguide and microstrip travelling-wave arrays, for detecting mm-wave (10-110GHz)thermal emissions via acousto-optic Bragg cell processors, are being considered in defence and civilian security-related remote sensing applications. The optical processing of RF signals is significant because it promises affordable RF operating staring multi-beam arrangements. Optical processing circumvents the need to assemble expensive miniaturised RF receiver elements in phased array configurations by allowing RF information to be processed using optical-video and CCD techniques. This paper considers the design and fabrication of microstrip travelling-wave based sensors for Ka (~35 GHz) -band operation.
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