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Publications

Publications by CTM

2011

A Photon Counting Estimates Distribution of the Average Number of Photons in Coherent Pulses

Authors
De Sousa e Castro, JCDE; Salgado, HM;

Publication
2011 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
A statistical model linking the probability of detecting photons in a photon counting experiment to the average number of input photons is used to analytically derive an error distribution of the estimates of the average number of photons in coherent input pulses. The estimates distribution determines the required number of experimental count runs required for an acceptable measurement error, for any value of the average number of input photons. An expression for the minimum detectable power by photon counting is obtained, fully capturing the effect of the photon counting statistics thereby completing an earlier analysis.

2011

Clock Recovery of an Injection-Locked Resonant Tunneling Diode Microwave-Photonics Oscillator

Authors
Romeira, B; Pessoa, LM; Salgado, HM; Silva, S; Figueiredo, JML;

Publication
2011 13TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON)

Abstract
We show experimental results of clock recovery from return-to-zero (RZ) format data by using injection locking of a free-running optoelectronic oscillator (OEO) circuit, which consists of a resonant tunneling diode (RTD) oscillator integrated circuit with both a detector and optical source. Error free extraction of a clock signal from the RTD-OEO is shown under both optical and electrical injection. The clock recovery performance at similar to 1.25 Gb/s is analyzed in terms of timing jitter, phase noise and locking bandwidth.

2011

Compact printed monopole antenna array for dualband WLAN application

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

Publication
EUROCON 2011 - International Conference on Computer as a Tool - Joint with Conftele 2011

Abstract
This paper presents a printed two C-shaped monopoles antennas array for dual-band WLAN application. The two antenna elements are closely spaced at a distance of only 0.09 2.4GHz. High isolation between these two radiation elements is achieved by using the neutralization technique, which has been demonstrated as an effective way to increase the isolation for single band PIFA antennas [1, 2]. In this work, the neutralization technique has been implemented to the printed monopole antenna design. We demonstrate that by introducing two RF switches, we can not only design a compact monopole antenna array with high isolation for single band operation but also can extend this method to design a compact dual band antenna array. The proposed antenna array contains two C-shaped monopoles with a shorting line, on which two RF switches were integrated, connecting two arms of the antenna elements. Experiment results indicate that the proposed antenna array has a 10dB bandwidth that covers the required frequencies for dual-band WLAN applications (2.4/5.2GHz) with isolation higher than 15dB over both operation bands. The proposed antenna has been designed and optimized using Ansoft HFSS. © 2011 IEEE.

2011

Assessment of noise impact on UWB signals in R-EAM based optical links

Authors
Pessoa, LM; Coelho, D; Oliveira, JMB; Castro, JCS; Salgado, HM;

Publication
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

Compact Printed C-shaped Monopole Antenna with Chip Inductor

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

Publication
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%.

2011

Cooperative clustered architecture and resource reservation for OBS networks

Authors
Haq, IU; Salgado, HM; Castro, JCS;

Publication
International Congress on Ultra Modern Telecommunications and Control Systems and Workshops

Abstract
Resource contention is a major concern in Optical Burst Switching networks that leads to relatively high burst loss probability. This article presents a clustered architecture for OBS networks, called Cooperative Clustered Optical Burst Switching (C2OBS) network architecture. In this architecture, the network is divided in overlapping zones/clusters with a zone/cluster head having the knowledge of available resources within the zone called Zonal Base (ZB) and maintains a short resource usage history called Short History Base (SHB). A resource reservation strategy for the proposed Cooperative Clustered OBS network architecture (C2OBS-RR) is also presented which is centralized within the zone and distributed in the overall network, for combining the benefits of both the centralized and the distributed resource reservation schemes. This novel approach uses the local state of the resource availability within the zone (ZB) so that the bursts originating at the ingress nodes in the same part of network having been assigned the same wavelength, can be assigned different time offsets. This will proactively reduce the probability of contention at the intermediate nodes within a zone and is expected to significantly reduce the overall network burst loss probability. For illustration purpose, the proposed C2OBS architecture has been applied to the European Optical Network. © 2011 HTE.

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