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A reliable low-cost method for accurate characterization of antennas in the domain

Cataldo A., Monti G., De Benedetto E., Cannazza G.

Metrology and Measurement Systems

2008

Vol. 15, nr 4

571-583

In this paper, a time domain-based approach to practical characterization of antennas is presented. The goal is to prove that time domain-based approach, after appropriate processing, represents an accurate and more practicable alternative to the typically used (yet highly expensive) antenna characterization measurements that are performed in anechoic chamber through a Vector Network Analyzer (VNA). To this purpose, two commercial antennas, differing in operating frequency band, are considered as significant test-cases. Reflectometric measurements performed in Time Domain (TD) are subsequently transformed in Frequency Domain (FD), and compared with VNA reference measurements directly obtained in anechoic chamber. Results demonstrate that the preliminary choice of an optimal time window is the main factor leading to a substantial enhancement of the overall measurement accuracy, which is comparable to that provided by VNA measurements in anechoic chamber. This demonstrates that a good insight into the antenna characteristics can be obtained even without using highly expensive facilities.

Fluorescence detection of biological objects with ultraviolet and visible light-emitting diodes

Kurilcik N., Vitta P., Zukauskas A., Gaska R., Ramanavicius A., Kausaite A., Jursenas S.

Optica Applicata

2006

Vol. 36, nr 2-3

193-198

Recent progress in fabrication of semiconductor light emitting diodes (LEDs) allows these devices to be used for excitation of fluorescence of aromatic amino acids and other biofluorophores. In our work, a deep-UV UVTOPTM LED (280 nm) developed by Sensor Electronic Technology, Inc., was used for fluorescence characterisation of natural protein fluorophores in enzyme glucose oxidase (GOx) and in Bacillus subtilus dry spores (B. subtilus). A longer-wavelength Nichia LED (375 nm) and high-power LuxeonTM LED (450 nm) were used for fluorescence detection of enzyme cofactors. Combined spectral and fluorescence lifetime measurements using selective LED excitation enabled us to recognise the impact of specific autofluorophores in complex biological systems. Inexpensive LED-based fluorescence detectors can be used in designing biosensors and detect-to-warn systems.