V.F. Fusco

Polarisation-Reconfigurable Patch Antenna

A tunable hybrid coupler was successfully designed to feed an antenna for full polarisation capabilities. The proposed solution has the advantages of separating the active devices from the radiating element and thus avoiding any unwanted coupling effects. Also, it provides a full set of polarization states by simply changing the DC bias of both a SPDT and two varactor diodes. The feasibility of the concept was fully demonstrated and validated by Sij parameters and radiation pattern measurements

The effect of a SiO/sub 2/ interface layer on CPW lines and Schottky barrier diodes on HRS substrates

Aluminium based CPW lines on high resistivity Si (HRS) substrates, and integrated and implanted Schottky barrier diodes have shown bias-dependent leakage current effects. By incorporating a patterned SiO/sub 2/ interface layer between the line conductors and HRS substrate, excellent CPW line performance in terms of leakage current and dissipation loss, and significantly improved Schottky diode isolation can be achieved.

Antenna Possibilities using 2D Planar Periodic Structures

We discuss possibilities that exist when a 2-D array of wires loaded with linear lumped or with non-linear lumped elements are deployed as passive or as semi-active frequency selective surfaces. We show that such surfaces can act as an EM shutter which allows the flow of transmitted energy to be controlled. In addition it is demonstrated that the inclusion of nonlinear components allow surfaces to be made which could behave as thin planar lenses or as phase conjugating artificial media. Further, the paper discusses the anisotropic propagation properties of textured surface PCBs as means for antenna far-field radiation control

Multiphysics Simulation of Electromagnetic Shielding and Thermal Stressing within Ceramic and Silicon Multilayer Packages for RF Applications

A multiphysics finite element method (FEM) based software, COMSOLtrade has been used to simulate coupled electromagnetic shielding and thermal stress issues for system-in-package (SiP) modules. The ceramic and silicon carriers under study have embedded shielding ground planes. Power HEMT RF devices in GaAs technologies are embedded on and within the carrier causing local thermal hotspots. Thermal cooling is performed using thermal vias. The electromagnetic interaction of thermal vias with the embedded ground plane is studied for hole clearance and via size

Coplanar waveguides on SOI and OPS substrates

Silicon is being investigated as a low cost, low loss substrate for MMICs. The conflicting requirements of low resistivity silicon for active device fabrication and very high resistivity silicon for low microwave transmission losses have been met by two differing technologies. In one technology the low loss CPW lines are fabricated on oxidized porous silicon (OPS) formed on 1-3 (Omega) -cm (100) silicon substrates. In the other technology SOI substrates are produced by bonding 1-3 (Omega) -cm silicon wafers to 2-4 k(Omega) -cm handle wafers which are covered with a layer of silicon dioxide on a layer of polycrystalline silicon. To minimize bowing of the silicon substrate it was found necessary to limit the OPS thickness to 10 micrometers . For the CPW lines the microwave losses on the OPS substrates were 8.5 dB/cm at 30 GHz and on the SOI wafers they were 2.2 dB/cm. The SOI wafers offer considerable promise for reliable low cost low loss MMIC substrates.

Slotline to coplanar waveguide band-stop filter modelling

In this paper an S-parameter matrix reduction scheme based on the dual symmetric properties of a slotline to CPW transition is elaborated. The method suggested can be used in conjunction with any type of EM field solver. This scheme allows a condensed set of scattering parameters for a symmetrical slotline to coplanar waveguide junction to be efficiently calculated. Based on the junction, a compact microwave band-stop filter is realised and its performance discussed.

Self-steered silicon receiver array

A monolithic integrated surface oriented Schottky barrier diode is described. The diode is integrated into a HRS substrate incorporated in a microstrip patch constructed over a patterned SiO/sub 2/ layer. The process technology developed is low cost. The resulting integrated diode is planar and has sensitivity of 1.8 mV/mW/cm/sup 2/ at 15 GHz. By using pairs of elements it is shown how a simple self-tracking receiver can be constructed in integrated all-silicon form.

Quasi-optical beam steering using a MEMS reflector array

In applications such as target tracking the ability to steer the radiation pattern from an antenna array is required. This paper details the theory, design, fabrication and characterisation of a new type of reconfigurable planar antenna reflectarray for operation with circularly polarised signals. Each element in the array comprises a resonant dipole antenna that can be rotated about its axis, each element is positioned at an odd number of quarter wavelengths above a ground plane. An array of fixed antennas was fabricated on a high resistivity silicon substrate with measurements confirming that the silicon exhibits low absorption at quasi-optical frequencies. The demonstrator devices are designed for 100 GHz operation in order to facilitate fabrication of a usable array aperture on a single silicon wafer. Dimensions of the antennae and the thickness of the substrate were selected accordingly. The wide range of micro-machining techniques that are available for silicon based structures enabled the design of a demonstrator array where the elements can be rotated using a rack and pinion arrangement. In such structures, the actuating mechanism is positioned outside the radiating aperture of the array to exclude conducting elements that would otherwise impair antenna functionality. A method of fabricating the reconfigurable array has been developed and successfully implemented.