11 documents found, page 1 of 2
Improving the reliability of power LEDs with diamond boards
Mendes, Joana C.; Rodrigues, Luis A.; Kyatam, Sushmitha; Alves, Luis N.; Pereira, LuizHigh power light emitting diodes (LEDs) are much more efficient than conventional light sources like filament bulbs. Nevertheless, heat is still generated, and this directly affects the reliability of these solid-state light (SSL) devices. In order to decrease the operating temperature, these LEDs can be assembled on metal core printed circuit boards (MCPCBs). However, in applications where stability/lifetime i...
Improving the reliability of power LEDs with diamond boards
Kyatam, Shusmitha; Rodrigues, Luis; Maslovski, Stanislav; Alves, Luis N.; Mendes, Joana C.Despite being efficient devices, when compared to other light sources, high power light emitting diodes (LEDs) suffer from heating effects that have a negative impact on their reliability. Power LEDs are typically assembled on metal core printed circuit boards (MCPCBs) to facilitate the extraction of the heat. Diamond boards can also be used for the same purpose, since diamond is the best isotropic conductor of...
A feasibility study on real-time concealed object detection in foliage using ST...
Duarte, Luís; Vala, Mário; Ribeiro, Carlos; Alves, Luis N.; Fernandes, Carlos A.; Caldeirinha, Rafael F. S.This paper reports on the first results of a Swept Time-Delay Cross Correlator (STDCC) based radar performance for the detection of concealed objects in a foliage. The real-time STDCC radar operating at 25 GHz with 500 MHz bandwidth detection capabilities is benchmarked together with a VNA technique using a central frequency of 11 GHz with 18 GHz bandwidth. A set of measurements were performed to assess the att...
Modeling temperature dynamic effects for high‐power light‐emitting diodes
Kyatam, Shusmitha; Rodrigues, Luís; Alves, Luis N.; Maslovski, Stanislav I.; Mendes, Joana C.Temperature is a dynamic variable in most electronic devices. As the device operates, it generates heat, which translates in a temperature increase. Available models commonly disregard these variations due to the fact that they manifest at very large time scales. However, temperature dynamic effects have profound implications on the device model and on our common understanding. This paper discusses implications...
Impact of die carrier on reliability of power LEDs
Kyatam, Shusmitha; Alves, Luis N.; Maslovski, Stanislav; Mendes, Joana C.High power light emitting diodes (LEDs) suffer from heating effects that have a detrimental impact on the devices characteristics. The use of LED carriers with high thermal conductivity promotes extraction of heat away from the LED junction. Different materials can be used for this purpose, such as alumina, aluminium nitride, and silicon. Diamond has also been gaining momentum for demanding heat management appl...
Reconfigurable millimetre-wave RF front-end for radar and 5G applications
Duarte, Luís; Reis, João R.; Leonor, Nuno; Ribeiro, Carlos; Alves, Luis N.; Caldeirinha, Rafael F. S.This paper proposes a reconfigurable RF architecture to cope with radar applications in autonomous driving vehicles and the next generation of communications (5G). A radio front-end architecture operating at frequencies between 24 and 27.5 GHz to deliver a small form-factor design that could easily be changed and ease future improvements, has been developed. Based on X-microwave ecosystem, a fully reconfigurabl...
Estimation of maximum temperature and thermal crosstalk between two active elem...
Kyatam, Shusmitha; Maslovski, Stanislav I.; Neto, Hugo; Alves, Luis N.; Mendes, Joana C.The operating temperature plays a key role in the performance and lifetime of photonic integrated circuits (PICs). Miniaturization and increasing heat dissipation promote thermal crosstalk effects and pose additional challenges to the PIC designer. The European Photonics Industry Consortium recommends thermal modeling during design phase. However, a fully numerical optimization of a particular layout requires a...
DLL architecture for OFDM based VLC transceivers in FPGA
Duarte, Luis; Rodrigues, Luis; Alves, Luis N.; Ribeiro, Carlos; Figueiredo, MónicaThis paper addresses the problem of achieving high bandwidth in a DLL design for OFDM based VLC broadcast systems. It describes the implementation of efficient Data Link Layer (DLL) and Forward Error Correction (FEC) modules in a Xilinx FPGA. The proposed DLL aims at furnishing the adequate means to fragment and route both high data-rate (HDR) and moderate data-rate (MDR) service requests while maintaining a co...
Diamond/ SiC heterojunctions
Mukherjee, Debarati; Mendes, Joana C.; Alves, Luis N.; Neto, Miguel; Oliveira, Filipe J.Diamond and SiC are wide bandgap (WBG) materials which can be used to fabricate high power devices with improved performance. The combination of these materials into one single device is expected to bring some benefits, like a better thermal management with a corresponding increase in the operating power. Diamond films deposited by Chemical Vapor Deposition (CVD) can be doped with boron, making them p-type semi...
Diamond/SiC heterojunctions
Mukherjee, Debarati; Mendes, Joana C.; Alves, Luis N.; Neto, Miguel; Oliveira, Filipe J.Diamond and SiC are wide bandgap (WBG) materials which can be used to fabricate high power devices with improved performance. The combination of these materials into one single device is expected to bring some benefits, like a better thermal management with a corresponding increase in the operating power. Diamond films deposited by Chemical Vapor Deposition (CVD) can be doped with boron, making them p-type semi...