1,720,969 research outputs found
An UMTS ΣΔ fractional synthesizer with 200 kHz bandwidth and -128 dBc/Hz @ 1 MHz using spurs compensation and linearization techniques
No full textThis paper describes a general study on spurs generation in fractional synthesis and techniques for their reduction. This theory has been verified with the realization of two IC prototypes fabricated in 0.18 μm CMOS, targeting UMTS-WCDMA specifications, both with a frequency resolution of 35 Hz. The first one is a fully integrated (1.9×1.6 mm2) 2.1 GHz ΣΔ synthesizer burning 19 mW, with 600 kHz 3 dB closed loop bandwidth. Its spur performance is limited by non-linear effects. This limitation has been overcome by linearization techniques implemented in a second chip with external VCO and loop filter. This synthesizer achieves -128 dBc/Hz @ 1 MHz offset with a 200 kHz 3 dB closed loop bandwidth
Method of adjusting the resonance frequency of an L-C resonant circuit and resonant circuit
No full textAn L-C resonant circuit with an adjustable resonance frequency, having a capacitor and a first inductor electrically coupled together and a second inductor magnetically coupled to the first inductor. Additionally, there is a control circuit to sense a signal representing a first current flowing through the first inductor and to force through the second inductor a second current that is a replica of the first current for setting the adjustable resonance frequency of the L-C resonant circuit
A Magnetically Tuned Quadrature Oscillator
No full textContinuous frequency tuning by control of the magnetic field of a transformer—capacitor tank, in a selective oscillator, is explored in this work. A quadrature generator is built connecting two identical transformer—capacitor oscillator cells in a feedback loop. The topology itself assures the currents in the transformer windings are aligned in phase, while their relative amplitude determines, via magnetic coupling, oscillators’ tank reactance,i.e., oscillation frequency. This paper introduces the idea, analyzesoscillation amplitude, frequency tuning band, phase noise, and phase accuracy, and discusses design and experiments. Prototypes,realized in 65 nm CMOS, employing MOS varactors to further extend operation bandwidth, show the following performances:3.2 GHz and 7.3 GHz minimum and maximum oscillation orequency, respectively. Phase noise figure of merit of 176.5 dBat 3.2 GHz and 170.5 dB at 6.4 GHz is observed, with 24 mWmaximum power consumption and 1.5 maximum deviation fromquadrature
A Multi-Standard WLAN RF Front-End Transmitter with Single-Spiral Dual-Resonant Tank Loads
No full textThis paper describes a radio frequency (RF) front end transmitter for wireless LAN (WLAN), designed for the most common standards, integrated in digital CMOS 0.18mum technology. It covers 802.11a/b/g specifications, concurrently working in the 2.5GHz and 5-6GHz frequency ranges. An innovative solution for the design of the LC tank allows to use a single-spiral inductor in dual resonant tank, with a strong reduction in die area. The dual band RF transmitter size is only 1mm, the smallest ever reported in literatur
A 700-kHz bandwidth Sigma-Delta fractional synthesizer with spurs compensation and linearization techniques for WCDMA applications
No full textA ΣΔ fractional-N frequency synthesizer targeting WCDMA receiver specifications is presented. Through spurs compensation and linearization techniques, the PLL bandwidth is significantly extended with only a slight increase in the integrated phase noise. In a 0.18-μm standard digital CMOS technology a fully integrated prototype with 2.1-GHz output frequency and 35 Hz resolution has an area of 3.4 mm2 PADs included, and it consumes 28 mW. With a 3-dB closed-loop bandwidth of 700 kHz, the settling time is only 7 μs. The integrated phase noise plus spurs is -45 dBc for the first WCDMA channel (1 kHz to 1.94 MHz) and -65 dBc for the second channel (2.5 to 6.34 MHz) with a worst case in-band (unfiltered) fractional spur of -60 dBc. Given the extremely large bandwidth, the synthesizer could be used also for TX direct modulation over a broad band. The choice of such a large bandwidth, however, still limits the spur performance. A slightly smaller bandwidth would fulfill WCDMA requirements. This has been shown in a second prototype, using the same architecture but employing an external loop filter and VCO for greater flexibility and ease of testing
A 19mW 2.2GHz Fully Integrated CMOS Sigma Delta Fractional Synthesiser With 35Hz Frequency Step and Quantization Noise Compensation
No full textA fully integrated 0.18μm CMOS ΣΔ fractional synthesizer targeting 3G wireless terminals applications is presented. This work is a practical example of a more general study on frequency fractional synthesis. A simple linear model of the system is presented and used to simulate different ΣΔ modulators topologies and to evaluate the effects of circuits non-idealities particularly on output spurious tones. Phase Frequency Detector (PFD) and Charge Pump (CP) non-linearity effects are analysed in details, the obtained results are confirmed by measurement. Solutions to overcome these limitations are given. At last, a ΣΔ quantization noise compensation technique is presented allowing to break the trade-off between Phase Locked Loop (PLL) bandwidth and high frequency noise regrowth
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
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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