1,720,960 research outputs found
Analysis and Design of a Transmitter for Wireless Communications in CMOS Technology
Full text linkThe number of wireless devices has grown tremendously over the last decade. Great technology improvements and novel transceiver architectures and circuits have enabled an astonishingly expanding set of radio-frequency applications.
CMOS technology played a key role in enabling a large-scale diffusion of wireless devices due to its unique advantages in cost and integration. Novel digital-intensive transceivers have taken full advantage of CMOS technology scaling predicted by Moore's law. Die-shrinking has enabled ubiquitous diffusion of low-cost, small form factor and low power wireless devices.
However, Radio Frequency (RF) Power Amplifiers (PA) transceiver functionality is historically implemented in a module which is separated from the CMOS core of the transceiver. The PA is traditionally dictating power and battery life of the transceiver, thus justifying its implementation in a tailored technology. By contrast, a fully integrated CMOS transceiver with no external PA would hugely benefit in terms of reduced area and system complexity.
In this work, a fully integrated prototype of a Switched-Capacitor Power Amplifier (SCPA) has been implemented in a 28nm CMOS technology. The SCPA provides the functionalities of a PA and of a Radio-Frequency Digital-to-Analog Converter (RF-DAC) in a monolithic CMOS device. The switching output stage of the SCPA enables this circuital topology to reach high efficiencies and offers excellent power handling capabilities. In this work, the properties of the SCPA are analyzed in an extensive and detailed dissertation.
Nowadays Wireless Communications operate in a very crowded spectrum, with strict coexistence requirements, thus demanding a strong linearity to the RF-DAC section of the SCPA. A great part of the work of designing a good SCPA is in fact designing a good RF-DAC. To enhance RF-DAC linearity, a precision of the timing of the elements up to the ps range is required. The use of a single core-supply voltage in the whole circuit including the CMOS inverter of the switching output stage enables the use of minimum size devices, improving accuracy and speed in the timing of the elements.
The whole circuit operates therefore on low core-supply voltage. Throughout this work, a detailed analysis carefully describes the electromagnetic structures which maximize power and efficiency of low-voltage SCPAs.
Due to layout issues subsequent to limited available voltages, however, there is a practical limitation in the maximum achievable power of low-voltage SCPAs. In this work, a Multi-Port Monolithic Power Combiner (PC) is introduced to overcome this limitation and further enhance total achieved system power. The PC sums the power of a collection of SCPAs to a single output, allowing higher output powers at a high efficiency. Benefits, drawbacks and design of SCPA PCs are discussed in this work.
The implemented circuit features the combination of four differential SCPAs through a four-way monolithic PC and is simulated to obtain a maximum drain efficiency of 44% at a peak output power of 29dBm on 1.1V supply voltage. Extensive spectrum analysis offers full evaluation of system performances. After exploring state-of-the-art possibilities offered by an advanced 28nm CMOS technology, this work predicts through rigorous theoretical analysis the expected evolution of SCPA performances with the scaling of CMOS Technologies. The encouraging forecast further emphasizes the importance of SCPA circuits for the future of high-performance Wireless Communications
Injection locked ring oscillator based digital-to-time converter and method for providing a filtered interpolated phase signal
No full textApparatus and methods for a digital-to-time converter (DTC) are provided. In an example, a DTC can include a phase interpolator and a ring oscillator. The phase interpolator can be configured to receive digital representations of two or more distinct phase signals, and to interpolate the digital representations of the two or more distinct phase signals to provide an interpolated output phase signal. The ring oscillator can be configured to receive the interpolated phase signal, to lock on to a frequency and a phase of the interpolated output phase signal, and to provide a filtered phase signal
Analysis and design of power and efficiency in third-order matching networks for switched-capacitor power-amplifiers
No full textThis paper presents the design of a matching network (MN) for switched-capacitor PAs (SCPA) optimized for efficiency against required load output power. The presented third-order MN exploits the intrinsic output capacitance of the SCPA, reducing the number of passive components required by the MN. As an example, a MN for a 1.1 V switched capacitor power amplifier has been designed with a bluetooth application in mind. The example MN has been implemented in a 28 nm CMOS RF metal stack and provides 16.7 dBm output power with IL = 1.1 dB at 2.4 GHz in an area of 300 x 300 um^2 when resonated by an SCPA capacitance of 2.3 pF. Further structures have then been implemented and characterized, covering a broader set of applications
A linear model of efficiency for Switched-Capacitor RF Power-Amplifiers
No full textIn this paper, a linear model for intrinsic power and efficiency in Radio-Frequency Switched-Capacitor Power Amplifiers (SCPA) is presented. Given a target output power and frequency of operation this model enables sizing the output stage inverter for maximum efficiency by means of back-of-the-envelope equations. The model is validated by SpectreRF simulations for a low-power CMOS 28nm technology for different frequencies of interest
Analysis and design of a 1.1dB-IL third-order Matching Network for Switched-Capacitor PAs
No full textA Matching Network for a 1.1V Switched Capacitor Power Amplifier has been designed with a Bluetooth Application in mind. The Matching Network has been implemented in a 28nm CMOS RF Metal Stack and provides 16.7dBm output power with IL = 1.1dB at 2.4GHz. A detailed analytical model of power and efficiency of the Matching Network is derived and used for optimal design of the Matching Network. The model shows very good agreement with circuit simulations, and good matching with experimental data as well
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A 28nm Low-Voltage Digital Power-Amplifier for QAM-256 WIFI Applications in 0.5mm2 Area w/ 2D Digital-Pre-Distortion and Package Combiner
No full textThis paper presents a DPA design with a DAT power combiner drawn in the package metallization achieving 26.7dBm maximum output power at 25% PAE using 0.5mm 2 area on die and 0.5mm 2 on package. Thanks to an offline static 2D DPD, an EVM as low as 4.1%at 17.3dBm modulated output power is achieved for a WIFI 2x20MHz, and an EVM of 1.8% at 14.3dBm for a WIFI 20MHz signal is achieved, enabling up to QAM-256 support
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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