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- Enabling spatial diversity and beamsteering with reduced RF-chains using reconfigurable transmitarraysPublication . João R. Reis; Caldeirinha, Rafael F. S.; Fernandes, Telmo R.; Hammoudeh, AkramThis manuscript introduces a new vision on the implementation of spatial diversity with beamsteering capability, by suppressing the typical beamforming networks of antenna phased arrays and replace them by Reconfigurable Transmitar- rays. Consequently, the radio frequency components, i.e. RF- chains that compose such systems, were replaced by a device with the capability to perform two-dimensional beamsteering relying on single antenna source, hence reducing the number of associated RF hardware in comparison with traditional phased array systems. By spatially distributing side-by-side more than one device, spatial diversity with beamsteering is enabled with an estimated reduction of 1:8 in the number of associated RF-chains. This new concept clearly demonstrates its merit by directly reducing the implementation costs„ RF-chain components and increasing the energy efficiency, specially in larger systems.
- Metamaterial-inspired Flat-Antenna Design for 5G Small-cell Base-Stations Operating at 3.6 GHzPublication . Reis, João R.; Fernandes, Telmo R.; Patrício Carreira Vala, Mário António; Caldeirinha, Rafael F. S.In this paper, a flat-beamsteering antenna for 5G applications is being presented. The antenna, designed to operate at 3.6 GHz (5G new radio (NR) frequency range 1 (FR1) band n78), presents a unique flat form factor which allows easy deployment and low visual impact in 5G dense scenarios. The antenna presents a multi-layer structure where a metamaterial inspired transmitarray enables the two-dimensional (2D) beamsteering, and an array of microstrip patch antennas is utilised as RF source. The use of metamaterials for beamsteering control allows for the reduction of costly and complex phase-shifter networks by using discrete capacitor diodes to control the transmission phase-shifting and subsequently, the direction of the steering. According to simulations, the proposed antenna presents 13.9 dBi of gain, 100 MHz of bandwidth with a maximum steering range of ±20 degrees, achievable in both elevation and azimuth planes, independently.
- STDCC radar at 24 GHz: first measurement trialsPublication . Ferreira Sardo, Andre; Reis, João R.; Duarte, Luis; Leonor, Nuno; Ribeiro, Carlos; Caldeirinha, Rafael F. S.This paper presents the first measurement trials for performance assessment of a real-time and high resolution monostatic radar operating at 24 GHz. The proposed real-time radar, which operates based on the sliding correlation of pseudo-noise (PN) sequences, provides a high time resolution better than 4 ns, useful for moving target identification (MTI) in the presence of highly dense clutter, under harsh environments and severe weather conditions (fog, snow and fire smoke or plume). The STDCC radar target detection capability is demonstrated in this paper, by measuring and identifying the radar data for 4 distinct scenarios, composed of multiple targets (up to 8), inside an anechoic chamber, demonstrating the potential of the proposed radar architecture.
- 5G: performance and evaluation of FS‐FBMC against OFDM for high data rate applications at 60 GHzPublication . Gomes, Rodolfo; VITORINO REIS, JOÃO RICARDO; Al‐Daher, Zaid; Hammoudeh, Akram; Caldeirinha, RafaelThis study presents a frequency spreading filter bank multi-carrier (FS-FBMC) waveform as a potential candidate for the fifth generation (5G) network applications at millimetre-waves (mmWaves). The proposed model is developed based on the orthogonal frequency division multiplexing (OFDM) waveform standardised by IEEE 802.15.3c for 60 GHz high data-rate applications. The effects of non-linearities of power amplifiers (PAs) at 60 GHz for both OFDM and FS-FBMC are presented and compared using a realistic PA model. In particular, the sensitivity of both transmission schemes to the non-linear effects is investigated and its impact on the performance degradation in terms of output-power-backoff, is characterised over typical indoor line-of-sight, kiosk and residential, 60 GHz IEEE channel models. The assessment metrics considered are bit error rate and out-of-band emissions. This study concludes radio access schemes for future communication generations, i.e. 5G may employ OFDM for up-link and FS-FBMC for down-link due to the sensitivity to PA non-linearities of both waveforms.
- Shielding Effectiveness of Log Barriers for Radio Exclusion ZonesPublication . Conniott, W.; VITORINO REIS, JOÃO RICARDO; Leonor, Nuno; Caldeirinha, RafaelThis paper presents the development of new electromagnetic barriers based on wooden poles for application in electromagnetic site shielding. Exposure to electromagnetic radiation becomes a raising concern among the population worldwide, mostly due to the explosion of mobile technologies and services. A number of innovative and highly sustainable barriers made of circular section timber of low industrial processing, based on periodic structure of wooden poles that are stacked in a multi-layer configuration, while allowing visual transparency, is proposed. Immediate applications may be found in electromagnetic barriers that may be placed at intended radio exclusion zones in the [0.7, 2.5] GHz frequency range. © 2018 Institution of Engineering and Technology. All rights reserved.