Design of a 2.4 GHz High-Performance Up-Conversion Mixer with Current Mirror Topology

In this paper, a low voltage low power up-conversion mixer, designed in a Chartered 0.18 μm RFCMOS technology, is proposed to realize the transmitter front-end in the frequency band of 2.4 GHz. The up-conversion mixer uses the current mirror topology and current-bleeding technique in both the driver and switching stages with a simple degeneration resistor. The proposed mixer converts an input of 100 MHz intermediate frequency (IF) signal to an output of 2.4 GHz radio frequency (RF) signal, with a local oscillator (LO) power of 2 dBm at 2.3 GHz. A comparison with conventional CMOS up-conversion mixer shows that this mixer has advantages of low voltage, low power consumption and high-performance. The post-layout simulation results demonstrate that at 2.4 GHz, the circuit has a conversion gain of 7.1 dB, an input-referred third-order intercept point (IIP3) of 7.3 dBm and a noise figure of 11.9 dB, while drawing only 3.8 mA for the mixer core under a supply voltage of 1.2 V. The chip area including testing pads is only 0.62×0.65 mm2

Direction-of-Arrival Estimation Based on Sparse Recovery with Second-Order Statistics

Traditional direction-of-arrival (DOA) estimation techniques perform Nyquist-rate sampling of the received signals and as a result they require high storage. To reduce sampling ratio, we introduce level-crossing (LC) sampling which captures samples whenever the signal crosses predetermined reference levels, and the LC-based analog-to-digital converter (LC ADC) has been shown to efficiently sample certain classes of signals. In this paper, we focus on the DOA estimation problem by using second-order statistics based on the LC samplings recording on one sensor, along with the synchronous samplings of the another sensors, a sparse angle space scenario can be found by solving an $ell_1$ minimization problem, giving the number of sources and their DOA's. The experimental results show that our proposed method, when compared with some existing norm-based constrained optimization compressive sensing (CS) algorithms, as well as subspace method, improves the DOA estimation performance, while using less samples when compared with Nyquist-rate sampling and reducing sensor activity especially for long time silence signal

Musical interfaces : design and construction of physical manipulatives for musical composition

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaf 19).Currently, musical composition is considered to be a high-level skill that is inaccessible to young children. There is a "high floor" for children who want to create a piece of music because they must learn a way of recording and remembering the notes, their sequence, etc, such as musical notation. Our project explores tangible designs that will make music composition simple to learn and practice while also building an intuition about complex musical concepts. Three original designs of tangible interfaces for musical composition are introduced and the merits and limitations of each are explored using non-functional form models. Audio processing is performed on a peripheral computer running an audio program written specifically for each system. A "Wizard of Oz" approach was used to study user interactions with each design. Music Blocks are designed to be physical representations of inherently intangible musical notes. Each block represents a single note, and the user can modify its pitch and duration by changing the physical shape of the block. They resemble wooden building blocks and suggest the parallels between building structures and the organization of musical compositions and its melody. The Music Glove introduced the idea of using a sound recording instead of a musical note as the musical unit in a composition. This introduced rich ideas about nesting and recursion. At the same time the glove interface highlights the role of personal expression, interaction and affect in musical composition and performance. Here physical inputs of the system were related to the rhythms, tempos, and the tone of the composition. The system was more gestural, performance-oriented and more suited to spontaneous improvising. The Musical Leaves interface is a melding of the concepts for the Music Blocks and Glove. The individual Leaves reflect the modular structure and organization of the composition. At the same time, the Leaves can be manipulated in real-time to change pitch and volume and as a result are deeply expressive and flexible.by Elysa Wan.S.B

A Novel 2.4GHz CMOS Up-Conversion Current-Mode Mixer

In this paper, a low-power up-conversion current-mode mixer, designed in the chartered 0.18-μm RFCMOS technology, is proposed to realize the transmitter front-end in the frequency band of 2.4 GHz. The proposed mixer can convert a 10 MHz intermediate frequency (IF) signal to a 2.4 GHz RF signal, with a local oscillator power of 2 dBm at 2.39 GHz. A comparison with conventional voltage-mode up-conversion mixer shows that this mixer has advantages of low voltage, low power consumption and high performance. Simulation results demonstrate that at 2.4 GHz, the circuit provides 6.5 dB of conversion gain and the input-referred third-order intercept point (IIP3) of 15.3 dBm, while drawing only 5.7 mA from a 1.2V supply voltage. The chip area is only 0.7 mm x 0.8 mm

Dense feature correspondence for video-based endoscope three-dimensional motion tracking

This paper presents an improved video-based endoscope tracking approach on the basis of dense feature correspondence. Currently video-based methods often fail to track the endoscope motion due to low-quality endoscopic video images. To address such failure, we use image texture information to boost the tracking performance. A local image descriptor - DAISY is introduced to efficiently detect dense texture or feature information from endoscopic images. After these dense feature correspondence, we compute relative motion parameters between the previous and current endoscopic images in terms of epipolar geometric analysis. By initializing with the relative motion information, we perform 2-D/3-D or video-volume registration and determine the current endoscope pose information with six degrees of freedom (6DoF) position and orientation parameters. We evaluate our method on clinical datasets. Experimental results demonstrate that our proposed method outperforms state-of-the-art approaches. The tracking error was significantly reduced from 7.77 mm to 4.78 mm. © 2014 IEEE

The effect of comorbid attention-deficit/hyperactivity disorder symptoms on face memory in children with autism spectrum disorder: Insights from transdiagnostic profiles

Face memory impairments are common but heterogeneous in autism spectrum disorder (ASD), which may be influenced by co-occurrence with attention-deficit/hyperactivity disorder (ADHD). Here, we aimed to investigate the phenotype change of face memory in children with ASD comorbid ADHD symptoms, and discuss the potential role of executive function (EF). Ninety-eight children were analyzed in the present study, including ASD- (ASD-only, n = 24), ADHD (n = 23), ASD+ (with ADHD symptoms, n = 23) and neurotypical controls (NTC, n = 28). All participants completed two tests: face encoding and retrieving task and Wisconsin Card Sorting Test (WCST) for measuring face memory and EF, respectively. Results revealed that: compared with the NTC group, children with ASD- exhibited lower accuracy in both face encoding and retrieving, and participants with ASD+ showed lower accuracy only in the retrieving, whereas no differences were found among participants with ADHD. Moreover, in the ASD+ group, face encoding performance was correlated with response perseverative errors (RPE) and failure to maintain sets (FMS) of WCST; significantly, there were no group differences between ASD+ and NTC in these two indices. The transdiagnostic profiles indicated that comorbid ADHD symptoms could modulate the face encoding deficiency of ASD, which may be partially compensated by EF. Shared and distinct intervention strategies to improve social cognition are recommended for children undergoing treatment for each condition

Vertically aligned tin-doped indium oxide nanowire arrays: Epitaxial growth and electron field emission properties

Vertically aligned tin-doped indium oxide (ITO) single-crystalline nanowire arrays are epitaxially grown on ITO/yttrium stabilized zirconia substrates by vapor transport method. Vacuum electron field emission properties of the aligned ITO nanowires are investigated. The turn-on electrical field at a current density of 1 μA/cm21μA∕cm2 is about 2.0 V/μm2.0V∕μm, and the lowest vacuum for an obvious emission is 1×10−1 Pa1×10−1Pa. The good performance of field emission is attributed to the vertically aligned morphology, which has a stronger local electric field due to their orientation parallel to the electric-field direction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87793/2/123102_1.pd