Browsing by Author "Sismeiro, Luis"
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- Hybrid FSS and Rectenna Design for Wireless Power HarvestingPublication . Ferreira, David; Sismeiro, Luis; Ferreira, Adelino; Caldeirinha, Rafael F.S.; Telmo R. Fernandes, Telmo R.; Cuinas, Inigo; Caldeirinha, RafaelThis communication presents a hybrid frequency selective surface (FSS) and rectenna design for wireless power harvesting. To this extent, the center of the original FSS structure acts as a probe-fed patch antenna and an additional layer was added to the rear of FSS structure to mimic the required antenna ground plane, while minimizing its impact on FSS performance. The proposed hybrid solution yields a bandpass frequency response at GSM 900-MHz frequency band, with band reject behavior at 2.4 GHz and, on the other hand, act as a energy harvesting system through the antenna element at the 2.4-GHz ISM band, e.g., for recycling ambient Wi-Fi energy. The developed prototype, consisting of an array of 12 unit cells, was able to power a 56-mW LED at a 2-Hz rate from an incident power level of−10 dBm, resulting in an average output power of 300 μW and an unit cell RF–DC conversion efficiency of 50%.
- A mm Wave solution to provide wireless Augmented Reality in classroomsPublication . Gomes, Rodolfo; Sismeiro, Luis; Ribeiro, Carlos; Sanchez, Manuel G.; Hammoudeh, Akram; Caldeirinha, Rafael F. S.This paper presents a very high throughput wireless data transmission solution for Augmented Reality (AR) Head Mounted Devices (HMDs) in the 60 GHz band. Its feasibility is assessed in an Orthogonal Frequency Division Multiplexing (OFDM) downlink communication towards five User Equipment (UE) devices, placed at different locations inside an indoor classroom environment scenario. Key Performance Indicators (KPIs) as Error Vector Magnitude (EVM), Signal-to-Noise Ratio (SNR), and path loss are considered for Quality of Service (QoS) assessment. Experimental results demonstrate the reliability of the proposed mmWave system, where a data rate of 312.5 Mbps is achieved over distances of 1, 2.4 and 4.1 m, regardless the UE position.
- Will COTS RF Front-Ends Really Cope With 5G Requirements at mmWave?Publication . Gomes, Rodolfo; Sismeiro, Luis; Ribeiro, Carlos; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.; Garcia Sanchez, Manuel; Hammoudeh, Akram; Caldeirinha, RafaelIn this paper, the real-time over-the-air multi-gigabit wideband wireless orthogonal frequency division multiplexing (OFDM) system performance, using two distinct radio frequency (RF) front-ends designed for the millimetre frequency band (mmWave), is evaluated. A thorough comparative analysis between 60-GHz cutting-edge commercial off-the-shelf and reference RF front-ends, taking into account their intrinsic RF impairments and their impact on the overall system performance degradation, is presented. With this, it is possible to verify whether system on chip technology for RF circuits is ready for 5G systems. Due to the large available bandwidth, the mmWave band is very attractive for future 5G wireless communication systems, which might provide transmission data rates over 10 Gb/s and network latency below 1 ms. However, non-linearities of RF front-ends, at these frequencies, severely affect the performance of transmission schemes. In fact, this is the main cause for performance degradation on OFDM systems. It causes significant limitation on both maximum spectral efficiency and data rate of the wireless communication link. Therefore, the OFDM performance degradation due to the non-linearities from both analogue stages of upconversion/downconversion is evaluated considering important key performance indicators for quality of service in digital communications considering 4-, 16-, 64- and 256-quadrature amplitude modulation. Furthermore, based on the results obtained from appropriate RF measurements, a practical EVM link budget formulation for mmWave systems, which takes into account both PA and PN impairment effects, is proposed.