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Publicações

Publicações por Henrique Salgado

2008

Joint Mitigation of Optical Impairments and Phase Estimation in Coherent Optical Systems

Autores
Pessoa, LM; Salgado, HM; Darwazeh, I;

Publicação
2008 DIGEST OF THE LEOS SUMMER TOPICAL MEETINGS

Abstract
The electrical compensation of chromatic dispersion (CD) and polarization mode dispersion (PMD) in a coherent optical system exploiting polarization multiplexing is discussed in this paper. The benefits of combining a phase estimation algorithm with a decision directed least-mean-square equalizer in a feedback configuration is reported.

2011

Compact Printed Monopole Antenna With Chip Inductor for WLAN

Autores
Luo, Q; Pereira, JR; Salgado, HM;

Publicação
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS

Abstract
One compact printed monopole antenna with a chip inductor for dual-band WLAN is presented. The proposed antenna has a two-armed structure and an electrically small size. The equivalent circuit structure of the chip inductor is studied and a simplified circuit structure is proposed. This simplified circuit structure was introduced into the electromagnetic (EM) simulation model by assigning a boundary condition, and the experimental results show that with this model, the simulation can provide an accurate prediction of the antenna radiation performance. The measurement results show that the proposed monopole antenna has a VSWR 2: 1 bandwidth over 2.41-2.49 and 5.2-5.6 GHz with omnidirectional radiation patterns. The simulation results suggest that the proposed antenna has a directivity around 1.5 dB at both bands with relatively high radiation efficiency. The antenna is designed and optimized by using Ansoft HFSS.

2009

Fractal monopole antenna for WLAN USB dongle

Autores
Luo, Q; Pereira, JR; Salgado, HM;

Publicação
Loughborough Antennas and Propagation Conference, LAPC 2009 - Conference Proceedings

Abstract
This article presents the design and fabrication of a simple printed fractal monopole antenna for WLAN USB dongle applications. The proposed antenna uses the combination of meander line and fractal geometry, which is very simple and easy to fabricate, to achieve a multiband operation characteristic. The parameters of this antenna were optimized through numerical simulations in Ansoft HFSS, after which the antenna has been fabricated and characterized. The measurement results show that the proposed antenna has a -10 dB return loss bandwidth of 2.22 to 2.52 GHz and 5.03 to 5.84 GHz, which covers the entire required band for WLAN 802.11a/b/g standards. Moreover, from the simulation results, it is also observed that this proposed antenna exhibits constant gain of 1.8 dBi with 95% radiation efficiency in the lower band and 2.4 dBi with 94% radiation efficiency in the upper band, respectively. ©2009 IEEE.

2006

Interrogation of a fiber Bragg grating using a mechanically induced long-period fiber grating

Autores
Rego, GM; Salgado, HM; Santos, JL;

Publicação
IEEE SENSORS JOURNAL

Abstract
A fiber-sensing scheme with controlled sensitivity comprising a fiber Bragg grating (FBG) and a mechanically induced long-period fiber grating (MLPFG) is presented. The FBG was written by exposing the fiber to 248-nm UV laser radiation such that the Bragg wavelength is localized on the slope of a resonant band of a mechanical grating, which was produced by winding a nylon string around a fiber/grooved tube set. The strength of that resonant band was altered by applying loads to the MLPFG. For different loads, the FBG was submitted to strain values of up to 2200 mu epsilon, in steps of 200 mu epsilon, during which the Bragg wavelength and the respective transmitted peak power through the MLPFG were recorded. It was demonstrated that by applying a weight with a value of 0.78 kg to the MLPFG, the sensitivity of the FBG interrogation technique to strain variations increased from 2.23 (without load) to 3.20 pW/mu epsilon.

2010

Printed fractal monopole antenna array for WLAN

Autores
Luo, Q; Salgado, HM; R.Pereira, J;

Publicação
Final Program and Book of Abstracts - iWAT 2010: 2010 International Workshop on Antenna Technology: Small Antennas, Innovative Structures and Materials

Abstract
This paper presents the design of a single feed multiband printed monopole antenna array using the 2nd generation of the Minkowski fractal geometry. The multiband operation is achieved by a suitable chosen of the size and iteration of the fractal geometry, which is optimized using the EM simulation tool Ansoft HFSS. During this work, it is found that adding a rectangular stub on the ground plane, the impedance match of the antenna can be improved with little influence on the original resonant frequencies. This finding has been confirmed by both simulation and measurement results. Meanwhile, the antenna array on a PDA size substrate was also designed and fabricated. The experimental results show that it can operate from 2.32 to 2.49 and from 5.1 to 5.88 GHz, which covers the required bands for IEEE 802.11a/b/g (2.41-2.48 GHz, 5.15-5.35 GHz and 5.725-5.875 GHz) applications. Measurements indicate that the maximum gain of this printed monopole array can reach 2.3 dBi at lower band and 5.6 dBi at upper band. The simulation results show that the radiation efficiency of this antenna array is 86% at 2.4 GHz, 82% at 5.2 GHz and 89% at 5.8 GHz. ©2010 IEEE.

2008

Optimum Receivers for Non-Linearly Distorted OFDM Signals in Wireless-over-Fiber Applications: Impact of Antenna Noise

Autores
Oliveira, JMB; Rodrigues, MRD; Salgado, HM;

Publicação
2008 IEEE INTERNATIONAL CONFERENCE ON ULTRA-WIDEBAND, VOL 2, PROCEEDINGS

Abstract
In this paper, we study the effect of uplink wise on the optimality of the receiver structure proposed in [1][2]. This optimum receiver is composed by a demodulator that extracts a set of sufficient statistic, and by an ML detector that uses the demodulator output to estimate the original data, We concentrate on Intensity Modulation/Direct Detection (IM/DD) Radio-over-Fiber (RoF) uplink system when OFDM signals suffer from noise generated by the antenna and photodiode and from nonlinear distortion. The results show that for small and medium modulalion index values, the uplink noise maintains its Gaussian distribution and the optimum receiver still outperforms the conventional.

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