Current Steering Research Articles

Evaluation Steering and Strategy Performance of Local NGOs in Uganda

This article interrogates the contextual relevance and application of evaluation steering in a strategy implementation discourse by local NGOs in Uganda. The study hinges on the assumption that evaluation outputs from local NGOs are often less utilized due to inept leadership, yet critical programmatic and policy issues of strategic relevance can best be utilized through a steering score. The study’s main purpose was to examine the relationship between evaluation steering and the strategy performance of local NGOs. The study drew findings from a cross-sectional study conducted using quantitative methods. In total, 349 participants comprising of field workers, mid-level staff, and executives from local NGOs from all parts of Uganda, were interviewed using a structured questionnaire. Results of the study showed that there was a positive correlation between evaluation steering and strategy performance constructs of fund stability (r = .243**), community satisfaction (r = .201**), and timeliness (r=.134**). The study concludes that evaluation steering has a high potential to improve fund stability, community satisfaction, and timeliness despite a weaker level of positive correlations. The national NGO bureau and NGO associations should establish executive capacity-building initiatives to support local NGOs to overcome the weakness in the current evaluation steering process. Consultants, volunteers, and NGO forums should advocate for donor resources to deepen organizational development, which supports an effective steering process. Keywords: Evaluation steering, Localization, Strategy performance.

A novel current steering method for targeted spinal cord stimulation.

Spinal Cord Stimulation (SCS) with leads embedded in the epidural space has become a recognized and effective clinical therapy for chronic pain relief. Leads with multiple electrodes placed close to the spinal cord allow targeted stimulation. This paper presents a novel current steering method to achieve targeted spinal cord stimulation by determining the optimal current sourced through a set of electrodes to maximize current density in a specified region of the spinal cord. The method provides a flexibility for personalized pain relief therapy, while minimizing stimulation in unwanted regions. The paper proposes a new optimization problem to achieve current steering. The optimization problem uses a solution of the Poisson equation evaluated using Finite Element Analysis (FEA) over a geometric model of the spinal cord and the embedded leads. The solution to the optimization problem determines the optimal current sourced through a set of electrodes to achieve a targeted stimulation.

Design of 8-Bit Hybrid Current Steering Digital to Analog Converter in a Standard 65nm CMOS Technology

A digital-to-analog converter (DAC) in electronics is a device that transforms digital signals into analog signals. There are various DAC architectures, and DAC's usefulness for a given application is determined by factors like resolution, INL, DNL, power consumption, maximum sampling frequency, and others. Because digital-to-analog conversion may damage a signal, a DAC with negligible faults for the application should be used. The current-steered digital-to-analog converter is well suited for high-speed applications because no buffers are needed for current steering architectures and the output is the total current drawn from the supply. In this paper, an 8-bit hybrid current steering digital-to-analog converter is proposed. Four cascode current sources with different weights are used in this architecture. The UMC 65nm CMOS technology was used to design the digital-to-analog converter. The INL and DNL were +0.19/-0.15 LSB and +0.28/-0.11 LSB respectively. The DAC uses roughly 3.25 mW at a supply voltage of 1.2V and a sample rate of 100 MHz. 12.751 mV was the output voltage at full scale. In comparison to earlier reports, the power, INL, DNL, and chip area used by the digital-to-analog converter in this architecture were significantly lower. It is appropriate for use in portable devices.

Deep Brain Stimulation: When to Test Directional?

Directional deep brain stimulation (DBS) allows for steering of the stimulation field, but extensive and time-consuming testing of all segmented contacts is necessary to identify the possible benefit of steering. It is therefore important to determine under which circumstances directional current steering is advantageous. Fifty two Parkinson's disease patients implanted in the STN with a directional DBS system underwent a standardized monopolar programming session 5 to 9 months after implantation. Individual contacts were tested for a potential advantage of directional stimulation. Results were used to build a prediction model for the selection of ring levels that would benefit from directional stimulation. On average, there was no significant difference in therapeutic window between ring-level contact and best directional contact. However, according to our standardized protocol, 35% of the contacts and 66% of patients had a larger therapeutic window under directional stimulation compared to ring-mode. The segmented contacts warranting directional current steering could be predicted with a sensitivity of 79% and a specificity of 57%. To reduce time required for DBS programming, we recommend additional directional contact testing initially only on ring-level contacts with a therapeutic window of less than 2.0 mA.

A 10-bit CS-DAC using Fully Random Rotation based DEM and code independent output impedance compensation

This article presents a low power high dynamic performance 10-bit Current Steering Digital-to-Analog Converter (CS-DAC), which utilizes a novel Fully Random Rotation-based Dynamic Element Matching (FRR-DEM) technique and Code Independent Impedance Compensation (CIIC) method. The mismatch induced non-linearities are suppressed by proposed FRR-DEM , while at high frequency, the distortion due to code dependent load variation is compensated by CIIC technique to achieve the high Spurious Free Dynamic Range (SFDR). The FRR-DEM efficiently performs the rotation and binary to thermometer conversion of input Upper Least Significant Bits(ULSB) and Most Significant Bits (MSB) in a random fashion. In view of digital area complexity, this randomizer utilizes minimum number of transistors compared to the conventional state-of-the-art DEM DACs without compromising the dynamic performances and also it adds an additional level to averaging out the amplitude mismatch errors. The complete CS-DAC is designed using 180 nm CMOS process and the post-layout mismatch based simulation results are presented. This DAC achieves SFDR of more than 66 dB at 500 MS/s sampling frequency over entire Nyquist band with a 17 dB improvement from the conventional DAC. The proposed DAC acquires an active area of 0.31 mm2 and the post-layout simulated power consumption is 23 mW from a single 1.8 V supply.

Parasitic-Aware Simulation-Based Optimization Design Tool for Current Steering VGAs

Designing millimeter-wave variable gain amplifiers (VGAs) is very challenging owing to the parasitic effects of the interconnects of both active and passive devices. An automated parasitic-aware optimization RF design tool is proposed in this paper to address this challenge. The proposed tool considers the parasitic effects prior to layout. It employs a knowledge-aware optimization technique. The augmentation between parasitic-aware and knowledge-aware techniques speeds up the design process and leads to a design as close to the final design after finalizing the layout. The proposed tool gives limitless and guaranteed converged solutions in a wide range of RF frequencies. A four-bits current steering VGA design is used as a validation of the tool. The tool is tested on three different frequencies using the 65 nm-technology node. The three tested frequencies (7, 10, and 13 GHz) show a root mean square gain error at approximately 0.1 dB and a phase variation at approximately 3.5° within a 16-dB gain control range. To our knowledge, it is the first reported automated design tool for a current steering VGA.

Sweet spots of standard and directional leads in patients with refractory essential tremor: white matter pathways associated with maximal tremor improvement.

In patients with essential tremor (ET) treated with standard deep brain stimulation (sDBS) whose ET had progressed and who no longer received optimal benefit from sDBS, directional deep brain stimulation (dDBS) may provide better tremor control. Current steering may provide better coverage of subcortical structures related to tremor control in patients with ET and significant progression without optimal response to sDBS. This study included 6 patients with ET initially treated with sDBS whose tremor later progressed and who then underwent reimplantation with dDBS to optimize their tremor control. To investigate the differences in the local effects of sDBS and dDBS, the authors generated the volume of tissue activation (VTA) to calculate the sweet spots associated with the best possible tremor control with no side effects. Then, to investigate the anatomical structures associated with maximal tremor control, the white matter pathways of the posterior subthalamic areas (PSAs) were generated and their involvement with the sDBS and dDBS sweet spots was calculated. Tremor improvement was significantly better with dDBS (68.4%) than with sDBS (48.7%) (p = 0.017). The sDBS sweet spot was located within the ventral intermediate nucleus, whereas the sweet spot of the dDBS was mainly located within the PSA. The sweet spots of both sDBS and dDBS involved a similar portion of the cerebellothalamic pathway. However, the dDBS had greater involvement of the pallidofugal pathways than the sDBS. In patients with ET treated with sDBS who later had ET progression, dDBS provided better tremor control, which was related to directionality and a more ventral position. The involvement of both the cerebellothalamic and pallidofugal pathways obtained with dDBS is associated with additional improvement over the sDBS.

Matrix Coupled All-in-One Magnetics for PWM Power Conversion

This article investigates the matrix coupled “all-in-one” magnetic structure that combines both series coupling and parallel coupling for pulse-width modulated (PWM) power conversion. A systematic analysis of the current ripple reduction mechanism is performed. Current ripple steering among asymmetric series coupled windings is discussed. The transient performance of the matrix coupled inductor is demystified, providing insights for analyzing converter dynamics and its large- or small-signal modeling. To quantify the benefits of matrix coupling, a figure of merit is defined by comparing the current ripple of a matrix coupled inductor to that of a discrete inductor given the same transient speed. The comparison results indicate that a higher number of phases and a stronger matrix coupling coefficient amplify the benefits of matrix coupling. A 1 V-to-5 V input, 1 V-to-5 V output, four-phase matrix coupled synchronous SEPIC converter with planar PCB integrated magnetics is built and tested. The matrix coupled SEPIC prototype can support load current up to 185 A at 5 V-to-1 V voltage conversion with a maximum power density over 470 W/in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\text{3}$</tex-math></inline-formula> . Compared to commercial discrete inductors, the matrix coupled inductor has a 5.6 times smaller size and 8.5 times faster transient speed with similar current ripple and current rating. The experimental results validate the matrix coupling concept and the theoretical analysis, opening the possibilities toward wide adoption of ‘‘all-in-one-magnetics” in PWM topologies.

Analysis and Calibration for Wideband Times-2 Interleaved Current-Steering DACs

This work presents analysis and calibration of interleaving and data timing errors that are encountered in modern times-2 interleaved digital-to-analog converters (DACs) with a current-steering (CS) architecture. Such errors corrupt the DAC output spectrum with spectral images that require calibration. We develop an analytical model for the interleaving and data timing errors that we understand are most significant and propose a calibration algorithm that treats all of them. Extensive simulations of the algorithm are made possible by leveraging the speed and accuracy of the analytical model. The algorithm is demonstrated on a commercially-developed 10-bit times-2 interleaved CS-DAC, operating at 40GS/s in 14nm CMOS.

A ZVS Phase-Shift Full-Bridge Converter With Input Current Steering to Reduce EMI Noise

Utilizing an L-C-L network including first primary, a clamping capacitor and second primary, a phase-shift full-bridge converter with input current steering is designed and presented. This proposed converter inherits the advantages of the conventional phase-shift full bridge converter, including d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> noise attenuation via its zero voltage switching operation. Moreover, the current steering technique is realized with the help of a clamping capacitor implemented as a built-in second voltage source to share part of input current resulting in d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> noise reduction. As a result, both d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> and d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> noises can be attenuated and then electromagnetic interference (EMI) performance are improved. A conventional phase-shift full-bridge converter and the proposed converters are built for performance verification with an input from 300 to 390 V, switching frequency 100 kHz, and an output of 24 V, 15 A. Experimental result shows that the input current ripple of the proposed converter can be reduced in half to as small as 2.72 A, as opposed to the 5.20 A by the conventional converter, while the maximum EMI noise is successfully improved to 19.85 dBμV at 300 kHz.

O033 / #241 REAL-WORLD OUTCOMES USING A NOVEL DIRECTIONAL LEAD FROM A MULTICENTER DBS REGISTRY FOR PARKINSON'S DISEASE: TRACK 2: DEEP BRAIN STIMULATION FOR MOVEMENT DISORDERS

Early Deep Brain Stimulation (DBS) systems used ring-shaped electrodes to achieve axial selectivity in stimulation of target tissue. However, directional current steering allows for rotational selectivity (in addition to axial) and has the potential to further improve patient outcomes by avoiding off-target stimulation due to the ability to create a well-defined field around the intended target. Several pilot studies have corroborated the use of directionality and its impact on therapeutic window and adverse effects.

Designing of 8-Gate Fingered GaN HEMT based Frequency Mixer with Enhanced Gain for Wide Band Communication Systems

The reconfigurable mixer plays an important role in both transmitter as well as receiver section in the present wireless and digital communication systems. Also such mixer requires lot of power for up-converting and down-converting the signal without any noise. This paper deals about such type of designing of reconfigurable mixer for wide band communication applications with Gallium Nitride High Electron Mobility Transistor (GaN HEMT). This GaN HEMT transistor solves the requirement of huge power over wide range without any noise. The mixer is designed in the present paper for variable gain conversion along with power consumption trade-off for a wide range of frequency (2–8 GHz) with reconfigurable concept. Applied Wave Research (AWR) simulator was used to design the reconfigurable mixer. The gain is controlled by changing the trans-conductance of the input RF stage, and the current steering in trans-impedance stage. A broadband down-converter mixer is designed that provide different conversion gain, ranging from 25–33.5 dB with two different modes. The large bandwidth of the mixer is achieved by shunting the trans-conductance stage and with various switching stages. The results also show that there is good isolation along with conversion gain of designed reconfigurable mixer, for wide range in various communication applications.

Design of Low-Power High-Speed 8 Bit CMOS Current Steering DAC for AI Applications

This paper describes a current steering 8-bit DAC architecture for low power and high-speed assistance in AI networks. This design is most suitable for 5G and next-generation high-speed communication systems on chip (SoCs). This DAC keeps a constant load current and leads to faster operations in wideband portable device applications. The design is based on weighted current transmission through current mirrors wherein current reduces from MSB to LSB continuously. By choosing a low current for LSB, the power dissipation reduces. Power and area are also reduced by using a 2-bit binary to thermometer decoder. The DAC's integral nonlinearity (INL) and differential nonlinearity (DNL) are found to be within 0.4 and 0.9 LSB, respectively. The DAC's highest operating speed is 1GHz, with a power dissipation of around 24.2 mW with the supply voltage of 1.8v using 180nm CMOS technology.

Effect of stimulation parameters on sequential current-steered stimuli in cochlear implants.

Manipulation of cochlear implant (CI) place pitch was carried out with current steering by stimulating two CI electrodes sequentially. The objective was to investigate whether shifts in activated neural populations could be achieved to produce salient pitch differences and to determine which stimulation parameters would be more effective in steering of current. These were the pulse rate and pulse width of electrical stimuli and the distance between the two current-steering electrodes. Nine CI users participated, and ten ears were tested. The pattern of pitch changes was not consistent across listeners, but the data suggest that individualized selection of stimulation parameters may be used to effect place pitch changes with sequential current steering. Individual analyses showed that pulse width generally had little influence on the effectiveness of current steering with sequential stimuli, while more salient place pitch shifts were often achieved at wider electrode spacing or when the stimulation pulse rate was the same as that indicated on the clinical MAP (the set of stimulation parameters) of the listener. Results imply that current steering may be used in CIs that allow only sequential stimulation to achieve place pitch manipulation.

Current Steering Using Multiple Independent Current Control Deep Brain Stimulation Technology Results in Distinct Neurophysiological Responses in Parkinson's Disease Patients.

BackgroundDeep brain stimulation (DBS) is an effective neuromodulation therapy to treat people with medication-refractory Parkinson’s disease (PD). However, the neural networks affected by DBS are not yet fully understood. Recent studies show that stimulating on different DBS-contacts using a single current source results in distinct EEG-based evoked potentials (EPs), with a peak at 3 ms (P3) associated with dorsolateral subthalamic nucleus stimulation and a peak at 10 ms associated with substantia nigra stimulation. Multiple independent current control (MICC) technology allows the center of the electric field to be moved in between two adjacent DBS-contacts, offering a potential advantage in spatial precision.ObjectiveDetermine if MICC precision targeting results in distinct neurophysiological responses recorded via EEG.Materials and MethodsWe recorded cortical EPs in five hemispheres (four PD patients) using EEG whilst employing MICC to move the electric field from the most dorsal DBS-contact to the most ventral in 15 incremental steps.ResultsThe center of the electric field location had a significant effect on both the P3 and P10 amplitude in all hemispheres where a peak was detected (P3, detected in 4 of 5 hemispheres, p < 0.0001; P10, detected in 5 of 5 hemispheres, p < 0.0001). Post hoc analysis indicated furthermore that MICC technology can significantly refine the resolution of steering.ConclusionUsing MICC to incrementally move the center of the electric field to locations between adjacent DBS-contacts resulted in significantly different neurophysiological responses that may allow further precision of the programming of individual patients.

Intracortical current steering shifts the location of evoked neural activity

Objective. Intracortical visual prostheses are being developed to restore sight in people who are blind. The resolution of artificial vision is dictated by the location, proximity and number of electrodes implanted in the brain. However, increasing electrode count and proximity is traded off against tissue damage. Hence, new stimulation methods are needed that can improve the resolution of artificial vision without increasing the number of electrodes. We investigated whether a technique known as current steering can improve the resolution of artificial vision provided by intracortical prostheses without increasing the number of physical electrodes in the brain. Approach. We explored how the locus of neuronal activation could be steered when low amplitude microstimulation was applied simultaneously to two intracortical electrodes. A 64-channel, four-shank electrode array was implanted into the visual cortex of rats (n = 7). The distribution of charge ranged from single-electrode stimulation (100%:0%) to an equal distribution between the two electrodes (50%:50%), thereby steering the current between the physical electrodes. The stimulating electrode separation varied between 300 and 500 μm. The peak of the evoked activity was defined as the ‘virtual electrode’ location. Main results. Current steering systematically shifted the virtual electrode on average between the stimulating electrodes as the distribution of charge was moved from one stimulating electrode to another. This effect was unclear in single trials due to the limited sampling of neurons. A model that scales the cortical response to each physical electrode when stimulated in isolation predicts the evoked virtual electrode response. Virtual electrodes were found to elicit a neural response as effectively and predictably as physical electrodes within cortical tissue on average. Significance. Current steering could be used to increase the resolution of intracortical electrode arrays without altering the number of physical electrodes which will reduce neural tissue damage, power consumption and potential heat dispersion issues.

A 16-Channel Analog CMOS SiPM With On-Chip Front-End for D-ToF LiDAR

This article presents a 16-channel analog silicon photomultiplier (SiPM) with on-chip front-end for direct time-of-flight (D-ToF) LiDAR applications. The proposed receiver is mainly composed of 16-channel SiPM, variable gain amplifier (VGA) and time-to-digital converter (TDC). Each SiPM channel consists of 256 microcells, and their outputs are connected to a common output terminal in parallel. A novel active quenching circuit is adopted to reduce the long exponential tail in conventional SiPM and enable the capability of multi-echo detection. Current steering circuits are adopted within microcells to make the output current of SiPM immune to SPAD gain variations. The receiver was fabricated in 180-nm HV CMOS technology and integrated into the 16-line LiDAR prototype with optical components. Measurement results show that the sensor is capable of 20 m range imaging with 3 cm accuracy under 40 klux background light conditions. With the mechanical scanning system, a high-resolution image ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$240\times16$ </tex-math></inline-formula> ) can be obtained.

Design of IF-RF-Based Heterodyne Transmitter Using Current Steering DAC with 5.4 GHz Spur-Free Bandwidth

The paper presents an intermediate frequency (IF) radio frequency (RF)-based heterodyne transmitter using current steering DAC. In the proposed design, a single digital AND gate is used as IF mixer and modulator of input data. This IF signal is further mixed with local oscillator signal in the current steering DAC to obtain RF output signal. The AND gate-based IF modulator converts input signal to square wave. This square wave does not contain even harmonics and consists of odd harmonics, which reduces harmonic mixing products. In addition, double differential architecture has been used in current steering DAC to cancel even harmonics. With cancellation of even harmonics in IF and RF signals, the output spectrum consists of only odd multiple of RF output frequency, resulting in spur-free bandwidth of 5.4 GHz for the RF output frequency of 2.4 GHz. The proposed transmitter employs 64-quadrature amplitude modulation which gives an output power of 446 m dBm without a power amplifier. Monte-Carlo simulations have been performed to verify the reliability of the circuit against process and mismatch variations, and it has been found that the circuit parameters are less sensitive to process variations.

Remote-Powered Infrared Indoor Optical Wireless Communication Systems

Near-infrared optical wireless communications (OWCs) have been widely studied in indoor environments, and the beam steering has been widely used to achieve both high-speed and wide coverage. Compared with active steering, the passive method eliminates the need for local power supply at OWC access points. However, current passive beam steering is based on wavelength tuning, which requires precisely controlled and costly tunable lasers. In this letter, we propose a beam-steered indoor OWC system without the need for local power through remote powering, providing the benefits of low power consumption, passive OWC access points, and low-cost. The proposed remote-powered indoor OWC system is experimentally demonstrated with 10 Gb/s OWC provided to users. An indirect remote powering scheme is also proposed and realized to support large-scale OWC access points.

423 Efficacy of an Image-Based Programing Plan in Predicting the Final Stimulation Configuration and Directionality for Subthalamic Nucleus Deep Brain Stimulation

INTRODUCTION: Subthalamic nucleus stimulation (STN-DBS) is a well stablished therapy for Parkinson’s disease (PD). Initial programing of the DBS electrodes may take up to 2 hours in order to determine the contact(s) with the best and worse therapeutic response and thresholds for side effects. Furthermore novel directional electrodes have additional contacts that increase complexity and time to the selection. New image processing techniques allows reconstruction and visualisation of the DBS electrode and adjacent structures in a tridimensional space as well as modeling of the volume of tissue activation (VTA) which in turns helps to infer which contact(s) could be best for the stimulation. METHODS: Forty-four electrodes were evaluated; directional contacts were initially reviewed as a ring. The images were processed using two different methods 1) The spatial position and distance of each electrode contact was assessed in a normalized space with respect to the STN, motor portion of the STN (mSTN) and the corticospinal tract (CST) using the open source toolbox Lead-DBS; 2) The relation of the electrode contacts with the STN was visualized using the Boston Scientific GuideTM XT clinical software which is based on automatic anatomical segmentation. Both methods were independently used to select the best (positive) and worst (negative) stimulation contacts and then compared with the final stimulation plan. RESULTS: A chi-square analysis demonstrated a significant association between the IBP and the final therapeutic configuration (p&lt;0.05). The test sensitivity was 95%-97.3%, specificity 85.7%-83.87%, positive predictive value 86.3%-87.8%, negative predictive value 94.7%-96.3%, and accuracy 90.2%-91.2% using the research and clinical methods respectively. In a subsequent analysis the selection of the directional contact(s) was investigated in 5 patients (6 electrodes) using current steering. In 89%-78% of the cases the contact(s) selected based on the IBP was part of the final configuration. CONCLUSION: An Imaged-based programing plan could be used as an initial guide to predict the best electrode configuration in order to reduce the programing time, this may translate in better use of hospital resources, improve the patient comfort and may avoid further adjustments in programing.