2008: Vol 99 No 2

Download the this issue (complete journal, excluding cover) (~5.6 MB).

Jump to:

1. Cryogenic CMOS-based Control System for Superconductor Electronics
2. RF-MEMS Dielectric Charging: Dependence on Dielectric Film Polarization Procedures
3. Repeat-Puncture Superorthogonal Convolutional Turbo Codes on AWGN Channels
4. A Comparison of Planar EM Bandgap Structures for Printed Circuit Board EMC

Cryogenic CMOS-based Control System for Superconductor Electronics by P.C. van Niekerk and C.J. Fourie
Abstract: This article describes the design and evaluation of a CMOS-based control system for use in Cryogenic vacuum environments. A control system, with accompanying software, was designed to interface superconductive digital and sensor circuits in a cryocooler to portable computers at room temperature. It is designed to operate as close as possible to the superconductors to reduce thermal noise. The controller connects via a fibre optical RS-232 interface to any USB connector on a computer at a data rate of 1 Megabaud. The interface to the superconductor electronics consists of 16-bit ultra low-noise analogue-to-digital converters and digital-to-analogue converters. Extensive research and testing was done on all components - both active and passive - to validate operation at 60 K. An integrated temperature control system was designed to ensure a stable temperature environment. Results are shown and discussed.
Download Paper (~1.5 Mb)

RF-MEMS Dielectric Charging: Dependence on Dielectric Film Polarization Procedures by G. Papaioannou, J. Papapolymerou, P. Pons and R. Plana
Abstract: The paper demonstrates the advantages arising from the simultaneous assessment of radio frequency micro-electromechanical systems capacitive switches and MIM capacitors. The application of simple capacitive-voltage characteristics and thermally stimulated depolarization current methods, respectively, allow the discrimination of the contribution of injected charges induced space charge polarization and the dipolar polarization. The proposed method allows the direct determination of device degradation sources and can be used for the dielectric material improvement.
Download Paper (~1.2 Mb)

Repeat-Puncture Superorthogonal Convolutional Turbo Codes on AWGN Channels by N. Pillay, H. Xu and F. Takawira
Abstract: The performance of turbo codes have been shown to be near the theoretical limit in the additive white Gaussian noise channel. By using orthogonal signaling, which allows for bandwidth expansion, the performance of the turbo coding scheme can be improved even further. Since this is a low-rate code, the code is mainly suitable for spread-spectrum modulation applications. In classical turbo codes the frame length is set equal to the interleaver size, however, the codeword distance spectrum of turbo codes improves with an increasing interleaver size. It has been reported that by using repetition and puncturing the performance of turbo codes can be improved. Repeat-Punctured Turbo Codes has shown a significant increase in performance at moderate to high signal-to-noise ratios. In this paper, we study the use of orthogonal signaling and parallel concatenation together with repetition and puncturing to improve the performance of superorthogonal convolutional turbo codes for reliable and effective communications. Simulation results for the additive white Gaussian noise channel are presented together with analytical upper bounds, which have been derived using transfer function bounding techniques.
Download Paper (~1.6 Mb)

A Comparison of Planar EM Bandgap Structures for Printed Circuit Board EMC By R. Geschke and E. Laubscher
Abstract: This paper investigates the suppression of parallel-plate modes on printed circuit boards via electromagnetic bandgap structures. We consider planar structures on ground or power planes. Two unit-cell geometries are used to create a 4x4 lattice on two simple test boards, where connector ports represent vias. This is compared to a reference test board without these structures. Measured results show that, even with a simple arrangement, it is possible to suppress parallel-plate modes very effectively.
Download Paper (~1.2 Mb)