A Novel Highly-efficient Amplification Scheme for Satellite Communications Pedro Viegas, Joao Guerreiro, Hugo Serra, Ricardo Madeira, Pedro Morgado, Ricardo Laires, Rui Dinis, Paulo Montezuma, Joao Pedro Oliveira 2021 IEEE International Conference on Communications Workshops Icc Workshops 2021 Proceedings, 2021 It is widely known that satellite communications require highly-efficient transmission structures. This is even more important in the forward link, since the available power at the transponders is limited. For that purpose, having a highly-efficient amplification scheme is critical. However, since the spectral-efficient transmission techniques (e.g. single-carrier modulations with large constellations or multicarrier modulations) present a large peak-to-average power ratio (PAPR), high amplification efficiency is very difficult to obtain. In fact, a linear amplification of such techniques requires high back-offs, which significantly degrades the amplification efficiency. In this work, a novel amplification scheme based on the use of multiple parallel highly-efficient power amplifiers (PAs) is presented, which is suitable for satellite communications. This amplification scheme is based on the decomposition of a high-PAPR signal into a set of constant-envelope components that are individually amplifying and efficiently combined. As it is demonstrated with a set of performance results of a QDA prototype operating with multicarrier signals, the proposed amplification scheme presents a large amplification efficiency, while preserving the linearity of the transmitted signals.1
A Highly-Efficient Amplification Scheme for OFDM Signals Pedro Viegas, Joao Guerreiro, Rui Dinis, Paulo Montezuma, Joao Pedro Oliveira, Ricardo Laires, Pedro Morgado, Hugo Serra, Ricardo Madeira IEEE Vehicular Technology Conference, 2021 The need for higher data rates in wireless communications has resulted in a significant effort in what regards to the design of transmission techniques and waveforms. This design can be very challenging thanks to the strong trade-off between the spectral efficiency and the energy efficiency, which comes from the fact that spectral-efficient waveforms usually presents a very large peak-to-average power ratio (PAPR), requiring a linear amplification for preserving the linearity of the transmitted signals. Nevertheless, obtaining spectral- and energy-efficient wireless communications will undoubtedly be one of the main challenges of both 5G and beyond 5G (B5G) systems. In this work, we propose a new amplification scheme named quantized digital amplification (QDA). The QDA is based on the decomposition of a high-PAPR signal into constant-envelope components and allows to obtain very high energy efficiencies, being suitable for spectrally-efficient transmission techniques such as orthogonal frequency-division multiplexing (OFDM). By presenting a set of results of the QDA’s prototype, we demonstrate that it is possible to obtain amplification efficiencies way above the ones of the state-of-the art amplification schemes, while preserving the linearity of the transmitted signals. 1
Quantized Digital Amplification with combination over the air - Achieving maximum efficiency on communication links between long range UAVs and satellites Paulo Montezuma, Ricardo Madeira, Hugo Serra, Pedro Viegas, Rui Dinis, Joao Oliveira, Joao Guerreiro Proceedings IEEE Military Communications Conference MILCOM, 2021 Uplink high throughput is essential to assure good situational awareness in Unmanned Aerial Vehicles (UAVs) mission. For that purpose larger bandwidths should be combined with the maximum possible spectral efficiency at the uplink. This leads to the use of multilevel broadband modulations with high Peak-to-Average Power Ratio (PAPR) values that may compromise the power amplification efficiency of current amplification technologies. High efficiency can be assured in these links with a new amplification scheme based on the Quantized Digital Amplification (QDA) technique that combines broadband support with both low complexity and high energy efficiency of signal power amplification stage. Spectral efficiency is also assured due to the QDA capacity to deal efficiently with multilevel modulations with high PAPRs, commonly used to assure high spectral efficiencies. The several cases analyzed here show the effectiveness and the robustness of the new technique to support efficiently the signal amplification in these links.
A Novel Highly-Efficient Amplification Scheme for Wireless Communications in a CathLab Environment Pedro Viegas, Hugo Serra, Joao Guerreiro, Ricardo Madeira, David Borges, Rui Dinis, Paulo Montezuma, Joao Pedro Oliveira, Luis M. Campos, Marko Beko IEEE Access, 2021 Wireless communication systems are being considered for medical applications to facilitate the doctors’ operation and the quality of the medical procedures. A demonstrative example of this is the catheterization laboratory (CathLab), where it is desirable to replace the existent wired connections by wireless alternatives. However, there are some challenging requirements that need to be fulfilled by the wireless link, especially for intra-vascular ultra-sound (IVUS) systems, since the images acquired by the catheter should be transmitted with very high data rate and low latency, together with the highest possible amplification efficiency, to increase the battery life. The communication requirements can be achieved with latest the Wi-Fi standard IEEE 802.11ax (Wi-Fi 6). However, since Wi-Fi is based on orthogonal frequency division multiplexing (OFDM) waveforms, the transmitted signals present high envelope fluctuations, leading to amplification difficulties due to the nonlinear distortion effects and low energy efficiency. In this paper, we present an innovative amplification scheme named quantized digital amplification (QDA). It is shown that the QDA allows a quasi-linear amplification of IEEE 802.11ax signals while maintaining a very high energy efficiency. To demonstrate this, a QDA prototype and a set of performance results, regarding both the linearity of the transmitted signals and the energy efficiency, are presented.
A 130 nm CMOS Power Management Unit with a Multi-Ratio Core SC DC-DC Converter for a Supercapacitor Power Supply Ricardo Madeira, Joao P. Oliveira, Nuno Paulino IEEE Transactions on Circuits and Systems II Express Briefs, 2018 In recent years, switched capacitor (SC) DC–DC converters have been gaining interest as an attractive solution for implementing power management solutions in small scale low power systems, such as Internet of Things remote sensor nodes. Since switch capacitor circuits can be fully integrated in bulk CMOS technology, the number of external components is reduced, thus decreasing both the production costs and the volume of the system. This brief presents a power management unit using a multi-ratio SC DC–DC converter, and its controlling circuits, designed in a 130 nm bulk CMOS technology occupying an area of 0.138 mm2. It provides a constant supply voltage of 0.9 V for a maximum output power of 1 mW, from an input supercapacitor voltage ranging from 1.2 to 2.3 V. The measured results show a conversion efficiency peak of 80.4%.
Live Demonstration: An Automated Test Bench for an 130nm SC DC-DC Converter Ricardo Madeira, Nuno Correia, Joao Pedro Oliveira, Nuno Paulino Proceedings IEEE International Symposium on Circuits and Systems, 2018 In this demonstration a test bench is presented to test and exhibit the operation of a Switched Capacitor DC-DC converter, designed in 130nm CMOS technology. The converter generates a stable 0.9 V from an input voltage range of 1.2 to 2.3 V, that is provided by a supercapacitor power supply charged by a PV cell. The demonstration allows to select between different loads to change the output power level of the converter (up to 1 mW of output power). The voltages and currents of the input and output of the converter are measured in real time in order to create a real time graphical visualization of the several parameters of the converter.
A low power quadrature class D LC oscillator with 0.4V supply Andre Bispo, Filipe Quendera, Ricardo Madeira, Joao P. Oliveira, Luis B. Oliveira Proceedings of the 21st International Conference on Mixed Design of Integrated Circuits and Systems Mixdes 2014, 2014
