2011
Autores
Pessoa, LM; Coelho, D; Oliveira, JMB; Castro, JCS; Salgado, HM;
Publicação
2011 IEEE Avionics, Fiber- Optics and Photonics Technology Conference, AVFOP 2011
Abstract
The measured characteristics of a R-EAM, acting as a base station, were used to assess the performance of a radio-over-fiber uplink for possible provision of wireless services within aircrafts. The specific case of deployment of UWB signals was analyzed. We conclude that laser RIN is a performance degradation factor that imposes a limit on the achievable SNR, especially for a zero biased modulator. A laser RIN of -160 dB/Hz would be required in order to avoid the RIN limitation. Additionally, in this case the performance becomes limited by shot noise. Although the zero bias case seems limitative, the R-EAM can be optimum biased using a small battery, which can last for several months, allowing the base-station to operate as a passive device. © 2011 IEEE.
2011
Autores
Luo, Q; Salgado, HM; Pereira, JR;
Publicação
2011 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (APSURSI)
Abstract
This paper presents one compact printed monopole antenna with one chip inductor embedded on the radiation elements. By introducing the chip inductor, the resonant frequency of the original antenna can be decreased by more than 37% while there is no significant influence on its radiation characteristics including radiation efficiency and antenna gain. Meanwhile, after adding the chip inductor, the higher mode of the original antenna can also be brought down to a lower frequency, which makes the proposed antenna resonate at the dual frequency band and simultaneously have a compact size. This antenna has a C-shaped geometry and its parameters including the location of the chip inductor are optimized by doing parametrical studies in Ansoft HFSS. The measurement and simulation results show that the proposed C-shaped monopole antenna can operate at 2.55-2.65GHz and 5.1-5.3GHz with peak gain of 2.2 and 4.7dB, respectively. Moreover, according to the simulation results, the radiation efficiency of this antenna at both bands is around 90%.
2010
Autores
Luo, Q; Salgado, HM; Pereira, JR;
Publicação
2010 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM
Abstract
In this paper, a printed two C-shaped monopoles array for WLAN MIMO application has been proposed. By using the neutralization technique, high isolation between the two antenna elements has been achieved while the distance between them is only 0.09(lambda 2.4GHz). The experiment results indicate that the proposed antenna array has -10dB bandwidth from 2.34 to 2.55 GHz and has an isolation less than -12 dB over the entire required operation band. The proposed antenna has a compact size of 30x14 mm(2) and can be easily integrated into wireless devices.
1997
Autores
Salgado, HM; Ferreira, JM; OReilly, JJ;
Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS
Abstract
A new technique is described for the extraction of the intrinsic semiconductor laser parameters from intermodulation measurements of composite second-order (CSO) and composite third-order (CTB) distortion products. The effect of the parasitics elements are eliminated, by taking the distortion measurements at constant optical modulation depth, which enables one to obtain the laser parameters on packaged laser diodes. An optimization algorithm is then described that extracts the relevant laser parameters from the distortion data. This method was applied to a commercially available packaged laser diode and very good agreement was obtained between the measured and theoretical results.
1999
Autores
Griffin, RA; Salgado, HM; Lane, PM; O'Reilly, JJ;
Publicação
Journal of Lightwave Technology
Abstract
We consider the performance of a hybrid radio-over-fiber distribution system with a remote phase-locked loop (PLL) providing the local oscillator for upconversion to millimeter (mm)-wave frequencies. The reference signal for the PLL is transmitted together with digitally modulated subcarriers over a fiber link, allowing centralization of radio processing. Through analysis and simulation, we identify the relationship between the phase noise requirement for the PLL and the data capacity of the fiber link. For a practical link, we provide an upper limit on system capacity for transmission of 16 quadrature amplitude modulation (QAM) subcarriers.
1996
Autores
Salgado, HM; Castro, JCS; O'Reilly, JJ;
Publicação
IEEE Journal of Quantum Electronics
Abstract
The FM intermodulation characteristics of directly modulated semiconductor lasers of relevance to the design of subcarrier multiplexed applications are investigated. "Adiabatic" chirp which has previously not been considered is shown to have a large impact on the reduction of the distortion levels at frequencies below half the resonance frequency of the laser. Results are presented showing that, in contrast to previous suggestions, FM modulation may be advantageous, imposing less requirements on laser linearity than IM modulation.
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