We report on fabrication of periodic arrays of polyethylene glycol diacrylate (PEG-DA), a biocompatible hydrogel,
useful in biomedical applications. The structures were produced by means of multi beam laser interference lithography
with both nanosecond (266 and 355 nm of wavelengths with pulses lasting 10 ns) and femtosecond pulsed lasers (800
nm of wavelength and 90 fs laser pulses). Configurations involving two, four and five laser beams were utilized
obtaining a wide variety of patterns with different feature sizes in the micrometer scale. Through this technique, we
demonstrated the ability to fabricate high feature density patterns over large areas without the use of templates or masks.
In addition, resolution and geometrical characteristic of the periodic arrays are discussed as function of pulse duration
and laser processing parameters. The photopolymerization nature of the process was also investigated.
KEYWORDS: Detection and tracking algorithms, Optical correlators, Error analysis, Signal to noise ratio, Receivers, Signal attenuation, Telecommunications, Modulation, Sensors, Systems modeling
This paper addresses hardware design issues of a mobile receiver for future generation direct sequence CDMA wireless communication systems. In the design of a mobile unit, fixed-point hardware is an attractive alternative because of increased speed, reduced power consumption, and reduced hardware cost. In this paper, we focus on the fixed-point implementation of 'blind' algorithms, wordlength requirements, and the operation count required for implementation of such algorithms, wordlength requirements, and the operation count required for implementation of such algorithms are evaluated. Our results show that the blind maximum likelihood channel estimation along with the blind MMSE detection algorithm can achieve approximately five times improvement in performance over the conventional correlator based receivers. These newer algorithms require slightly higher worklength but similar computational complexity.
This paper investigates methods to reduce the amount of computation needed to detect information bits using a linear detector for a CDMA system. We show windowing technique coupled with pipelining can reduce the amount of computation without significantly sacrificing the performance of linear feedback detector. We also describe efficient techniques to adapt to a dynamic system where the system parameters vary due to the change in delays associated with individual users.
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