1,720,965 research outputs found
Response Optimization of Antenna-Coupled FET Detectors for 0.85-to-1-THz Imaging
No full textThis letter presents several configurations of terahertz (THz) pixel structures with different bow-tie antennas and field-effect transistor (FET)-based detectors, implemented in a 0.15-μm standard CMOS technology, operating at a radiation frequency range of 0.85-1 THz for CMOS imaging applications. The innovative FET detector structures are investigated for higher power coupling efficiency with the integrated antennas, aiming to improve the THz detection behavior in terms of responsivity and noise equivalent power. Experimental THz characterization of the fabricated structures provides the guidelines for the future implementation of THz imaging arrays. Images of concealed metallic objects are acquired in a single-pixel mode under continuous THz illuminatio
A Low-Noise Direct Incremental A/D Converter for FET-Based THz Imaging Detectors
No full textThis paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz) detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and noise reduction stage based on a parametric chopper amplifier and a direct analog-to-digital conversion by means of an incremental ΣΔ converter, performing a lock-in operation with modulated sources. The FET detector is integrated with an on-chip antenna operating in the frequency range of 325–375 GHz and compliant with all process design rules. The cascade of the FET THz detector and readout chain is evaluated in terms of responsivity and Noise Equivalent Power (NEP) measurements. The measured readout input-referred noise of 1.6 μ V r m s allows preserving the FET detector sensitivity by achieving a minimum NEP of 376 pW/ Hz in the optimum bias condition, while directly providing a digital output. The integrated readout chain features 65-dB peak-SNR and 80-μ W power consumption from a 1.8-V supply. The area of the antenna-coupled FET detector and the readout chain fits a pixel pitch of 455 μm, which is suitable for pixel array implementation. The proposed THz pixel has been successfully applied for imaging of concealed objects in a paper envelope under continuous-wave illumination
A CMOS Multispectral Imager with Terahertz and Visible Pixels
No full textIn this paper a CMOS image sensor featuring pixels with both THz and visible (VIS) sensing capabilities is presented. The THz-VIS imager includes, in the same focal plane array, 10x10 THz pixels with embedded analog-to-digital conversion and 50x50 VIS active pixels for simultaneous imaging. First images are captured in the THz and in the VIS range
Pixel-level continuous-time incremental sigma-delta A/D converter for THz sensors
No full textA readout channel based on continuous-time incremental sigma-delta analog-to-digital converter for FET-based terahertz (THz) imaging applications was implemented in a 0.15 μm standard CMOS technology. The designed readout circuit is suitable for implementation in pixel arrays due to its compact size and power consumption. The system-level analysis used to define the modulator parameters and to specify its analog building blocks is presented. The loop filter has been realized by using a Gm-C integrator. Circuit linearization techniques have been implemented to improve the linearity of the transconductor cell and reduce the impact of parasitic capacitances. Moreover, chopper stabilization technique is adopted in the loop filter, significantly reducing the low-frequency flicker noise thereby preserving the Noise Equivalent Power (NEP) of the FET detector within the required specifications of minimum detectable signal. The resulting input referred noise voltage is 87.5 nV/√Hz . The incremental ADC achieves 68-dB peak signal-to-noise-and-distortion-ratio (SNDR), equivalent to 11 bits effective resolution over 1 kHz signal bandwidth at 1 MHz sampling frequency. In order to meet the requirements of large sensor arrays, a first order architecture is realized. This leads to lower area occupancy and power consumption. The readout circuit draws 80 μW of power from a supply voltage of 1.8 V. The channel occupies an area of 90 x 273μm2
A noise-efficient, in-pixel readout for FET-based THz detectors with direct incremental A/D conversion
No full textA low-noise readout interface integrated with an antenna-coupled FET-based terahertz (THz) detector is designed and fabricated in a 0.15-μm CMOS standard technology. The implemented readout includes a cascade of a preamplification noise reduction stage based on a parametric chopper amplifier, and a direct analog-to-digital conversion by means of an incremental ΣΔ converter, substituting the lock-in apparatus. The measured input referred noise of 1.6 μVrms allows preserving the FET detector noise performance. The characterization results show that the noise equivalent power (NEP) of the THz detector and readout chain is of 376 pW/√Hz at the optimal bias point while providing directly a digital output. The integrated readout chain features 65 dB maximum SNR and occupies an area of 90 × 300 μm2, with 80 μW power consumption from 1.8 V supply
A CMOS 0.15-μm in-pixel noise reduction technique for readout of antenna-coupled FET-based THz detectors
No full textA test structure comprehending an antenna-coupled FET-based THz detector integrated with readout electronics is designed and fabricated in a 0.15-μm standard CMOS technology. A low-noise preamplification technique has been employed, based on parametric chopper amplifier, substituting the lock-in apparatus and performing direct analog-to-digital conversion by means of an incremental ΣΔ converter. The input-referred noise of 1.6 μVrms is such that the Noise Equivalent Power (NEP) of the FET detector is not degraded. The measured signal-to-noise ratio (SNR) is 65 dB which is equivalent to 10.6 effective number of bits (ENOB). The readout chain area is 90 × 300 μm2. The measured power consumption is 80 μW from 1.8 V supply
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
- …
