Gain Modulation Research Articles

Gain modulation and odor concentration invariance in early olfactory networks.

The broad receptive field of the olfactory receptors constitutes the basis of a combinatorial code that allows animals to detect and discriminate many more odorants than the actual number of receptor types that they express. One drawback is that high odor concentrations recruit lower affinity receptors which can lead to the perception of qualitatively different odors. Here we addressed the contribution that signal-processing in the antennal lobe makes to reduce concentration dependence in odor representation. By means of calcium imaging and pharmacological approach we describe the contribution that GABA receptors play in terms of the amplitude and temporal profiles of the signals that convey odor information from the antennal lobes to higher brain centers. We found that GABA reduces the amplitude of odor elicited signals and the number of glomeruli that are recruited in an odor-concentration-dependent manner. Blocking GABA receptors decreases the correlation among glomerular activity patterns elicited by different concentrations of the same odor. In addition, we built a realistic mathematical model of the antennal lobe that was used to test the viability of the proposed mechanisms and to evaluate the processing properties of the AL network under conditions that cannot be achieved in physiology experiments. Interestingly, even though based on a rather simple topology and cell interactions solely mediated by GABAergic lateral inhibitions, the AL model reproduced key features of the AL response upon different odor concentrations and provides plausible solutions for concentration invariant recognition of odors by artificial sensors.

Design of Sensorless Control System for Permanent Magnet Linear Synchronous Motor Based on Parametric Optimization Super-Twisting Sliding Mode Observer

To improve the chattering problem caused by the terminal sliding mode control (TSMC) and sliding mode observer (SMO) in permanent magnet synchronous linear motor (PMLSM) control systems, this study presents the design of a continuous terminal sliding mode control (CTSMC) controller and an improved SMO. By enhancing the sliding mode surface, CTSMC enhances the dynamic response and robustness of the system. The observer replaces the traditional sliding mode switching law with a super-twisting (ST) algorithm, a twisting algorithm that makes use of the structural characteristics of the second-order sliding mode to ensure output continuity and reduce the observed buffeting. The sliding mode gain of the ST algorithm is optimized using the particle swarm optimization (PSO) algorithm to acquire the optimal parameters and fully exploit the observer’s performance potential. Finally, the proposed method is simulated and tested. The comparison results show that the proposed method boosts the system’s dynamic response and robustness and reduces chattering.

Design and Analysis of a High-Efficiency Resonant Converter for EV Battery Charger

The interest in electric vehicle (EVs) components such as battery, battery chargers, and battery management systems is increasing in parallel with the spread of electric vehicles. One of the most critical of these components is battery chargers. Battery chargers are equipped with DC-DC converters with high efficiency, low cost, and wide output voltage range. In order to provide reliable operation of the battery charger, it is of great importance that the DC-DC converters are operated with a robust and stable controller as well as designed optimally. In this paper, a design method for a CLLC resonant converter-based bidirectional dc-dc converter (BiDC) is presented for a battery charger. The resonant converter, whose design details are presented, suggests a resonant system to be used in battery chargers with fewer components than the CLLLC converter, and similar voltage gain characteristics for bidirectional power flow operations compared to the LLC converter. The design procedure highlights performing the soft switching operation and determining the resonant tank parameters. In addition, the forward mode and reverse mode gain equations required for the system to operate in the desired output voltage range have been presented. The design procedures have been validated with a CLLC BiDC model with ratings of 1 kW, 400 V input / 300-450 V output in the PSIM environment. The performance results reveal that the zero voltage switching (ZVS) has been performed for primary-side MOSFETs under a wide load range.

Few-mode erbium-doped fiber with trench and weak coupling for mode gain equalization based on layered-doping technology.

A few-mode erbium-doped fiber (FM-EDF) with a step refractive index and trench structure is designed and proposed to realize the modal gain equalization of a few-mode erbium-doped fiber amplifier (FM-EDFA). The layered-doping technology is used to reduce the mode gain difference (DMG). The doping radius and doping concentration are adjusted to obtain the optimum FM-EDF structure. When the designed FM-EDF is applied to the FM-EDFA, the DMG of the whole C-band is less than 0.15dB and the DMG is less than 0.12dB at 1550nm. The minimum refractive index difference (Δ n eff) between modes can be calculated according to the refractive index and radius of the fiber core; i.e.,1.35×10-3, which will greatly reduce the coupling between modes in a practical application. Tolerances in the fiber manufacturing process are also considered for reliable FM-EDFA performance. When the doping radius and concentration of each doping layer fluctuate by ±15% based on the precise value, the maximum DMG increases to 1.8dB. In general, DMG can maintain a small value, which is beneficial for application in optical communications systems.

A 2.4 GHz Reconfigurable Cascode/Folded-Cascode Inductive Source Degenerated LNA With Enhanced OP1dB and OIP3 Over Gain Reduction

A 2.4 GHz reconfigurable cascode/folded-cascode inductive source degenerated LNA (ISDLNA) is proposed to implement the variable-gain functionality with enhanced output 1 dB compression point (OP1dB) and output third-order intercept point (OIP3) over the gain reduction, ensuring low noise figure (NF) of sub-1 dB at high gain mode. Depending on the channel condition, the LNA is designed to be operated as the cascode and folded-cascode ISDLNA through the digital switch control to have low NF of around 1 dB at high gain mode and high input P1dB (IP1dB) of greater than -5 dBm at low gain mode, respectively. To avoid the reliability issues caused by the overdriving control voltage of greater than the nominal supply voltage, the transmission gate switch is employed as the common gate stage of the cascode amplifier. In experiments, the proposed variable-gain LNA shows a power gain (S21), input return loss (S11), and NF of 11.8 dB, -31.8 dB, and 1.1 dB at high gain mode, and 5.0 dB, -14.4 dB, and 1.96 dB at low gain mode. In case of the linearity, the proposed LNA shows an IP1dB and input IP3 (IIP3) of -19.2 dBm and -5 dBm at high gain mode, and -5.1 dBm and +4.8 dBm at low gain mode, respectively. The power consumption for two operation modes is the same as 9.6 mW from a 1.2 V supply voltage.

An Intuitive and Noniterative Design Methodology for CLLC Chargers Employing Simplified Operation Modes Model

This paper mainly focuses on the simplified operation modes (SOM) model and resonant parameter design for the CLLC charger. Based on the mathematical and detailed operation waveform assumptions, the voltage gain model expressions and the operation mode boundaries are calculated directly, providing the high efficiency and high reliability of the CLLC converter. The proposed SOM model is more accurate in depicting the voltage gain compared with the conventional fundamental harmonic approximation (FHA) model. Moreover, the SOM model is more intuitive and has less computational complexity than the complicated and unsolvable time-domain model. As for the parameter design process, the inductance ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k$</tex-math></inline-formula> and characteristic impedance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Z_{0}$</tex-math></inline-formula> are selected instead of specific inductances and capacitances. Relying on the SOM model, a step-by-step parameter design methodology is studied, which avoids repetitive iterations and streamlines the procedure. The voltage gain range, efficiency, soft-switching operation, mode boundaries, and system stability are considered comprehensively and realized in this process. The simulations and experiments validate that the proposed SOM model is accurate, and the design methodology is straightforward through a 1-kW CLLC charger prototype with 97% peak efficiency.

Time-Domain Analysis and Optimal Design of LLC-DC Transformers (LLC-DCXs) Considering Discontinuous Conduction Modes

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DC transformers ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DCXs) operate under fixed-frequency and open-loop conditions to achieve high efficiency and are promising converters that can be used in the auxiliary power units (APUs) of electric locomotives. An optimal design method of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DCXs is proposed in this paper. First, the time-domain expressions of the symmetric half-bridge <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with split resonant capacitors are derived. A current increment method is proposed to determine the expressions. Second, the discontinuous conduction mode (DCM) and voltage gain limiting conditions are used to obtain the magnetizing inductance ranges. The converter losses and zero-voltage-switching (ZVS) ranges are considered to determine the final magnetizing inductance. A 10 kW prototype is used as an example, and a detailed parameter design process is implemented. Compared with conventional design methods for the magnetizing inductance, the proposed method can effectively determine the maximum magnetizing inductance for the DCM operation of the converter. The effectiveness of the proposed method is proven by the simulations and experimental results obtained for the 10 kW <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> -DCX prototype. The maximum efficiency of the designed converter is 98.12% under the full load.

Primary somatosensory cortex bidirectionally modulates sensory gain and nociceptive behavior in a layer-specific manner

The primary somatosensory cortex (S1) is a hub for body sensation of both innocuous and noxious signals, yet its role in somatosensation versus pain is debated. Despite known contributions of S1 to sensory gain modulation, its causal involvement in subjective sensory experiences remains elusive. Here, in mouse S1, we reveal the involvement of cortical output neurons in layers 5 (L5) and 6 (L6) in the perception of innocuous and noxious somatosensory signals. We find that L6 activation can drive aversive hypersensitivity and spontaneous nocifensive behavior. Linking behavior to neuronal mechanisms, we find that L6 enhances thalamic somatosensory responses, and in parallel, strongly suppresses L5 neurons. Directly suppressing L5 reproduced the pronociceptive phenotype induced by L6 activation, suggesting an anti-nociceptive function for L5 output. Indeed, L5 activation reduced sensory sensitivity and reversed inflammatory allodynia. Together, these findings reveal a layer-specific and bidirectional role for S1 in modulating subjective sensory experiences.

Gain, not concomitant changes in spatial receptive field properties, improves task performance in a neural network attention model.

Attention allows us to focus sensory processing on behaviorally relevant aspects of the visual world. One potential mechanism of attention is a change in the gain of sensory responses. However, changing gain at early stages could have multiple downstream consequences for visual processing. Which, if any, of these effects can account for the benefits of attention for detection and discrimination? Using a model of primate visual cortex we document how a Gaussian-shaped gain modulation results in changes to spatial tuning properties. Forcing the model to use only these changes failed to produce any benefit in task performance. Instead, we found that gain alone was both necessary and sufficient to explain category detection and discrimination during attention. Our results show how gain can give rise to changes in receptive fields which are not necessary for enhancing task performance.

Recovery of auditory evoked response attentional gain modulation following the first psychotic episode indexes improvements in symptom severity.

Attentional control of auditory N100/M100 gain is reduced in individuals with first-episode psychosis (FEP). Persistent problems with executive modulation of auditory sensory activity may impact multiple aspects of psychosis. As a follow-up to our prior work reporting deficits in attentional M100 gain modulation in auditory cortex, we examined changes in M100 gain modulation longitudinally, and further examined relationships between auditory M100 and symptoms of psychosis. We compared auditory M100 in auditory sensory cortex between 21 FEP and 29 matched healthy participants and between timepoints separated by 220 ± 100 days. Magnetoencephalography data were recorded while participants alternately attended or ignored tones in an auditory oddball task. M100 was measured as the average of 80-140 ms post-stimulus in source-localized evoked responses within bilateral auditory cortex. Symptoms were assessed using the PANSS and PSYRATS. M100 amplitudes, attentional modulation of M100 amplitudes, and symptom severity all improved in FEP over time. Further, improvement in M100 modulation correlated with improvements in negative symptoms (PANSS) as well as physical, cognitive, and emotional components of hallucinations (PSYRATS). Conversely, improvements in the overall size of the M100, rather than the difference between active and passive M100 amplitudes, were related to worsening of positive symptoms (PANSS) and physical components of hallucinations. Results indicate a link between symptoms (particularly auditory hallucinations) and auditory cortex neurophysiology in FEP, where auditory attention and auditory sensation have opposed relationships to symptom change. These findings may inform current models of psychosis etiology and could provide nonpharmaceutical avenues for early intervention.

Application of a new type of super twist sliding mode control in flywheel energy storage

Aiming at the error problem in estimating the speed of a permanent magnet synchronous motor (PMSM) using a sliding mode observer in a flywheel energy storage system, a super twist sliding mode observer (SMO) is used to replace the traditional sliding mode observer. A new saturation function is designed to replace the sign function. In addition, a constant sliding mode gain may lead to a decrease in observation accuracy during speed switching. An adaptive sliding mode gain is proposed to reduce chattering, The accurate estimation of the comprehensive speed range observer is enhanced, and the stability of the proposed observer is proved. On this basis, a super twist sliding mode speed controller is designed to replace the traditional PI controller to improve the observation performance of the system. The flywheel energy storage system’s simulation model is built, and the flywheel energy storage system’s constant speed standby and charging conditions are simulated. The simulation results verify the correctness and effectiveness of the improved super twist sliding mode observer in the flywheel motor.

Model of multiple mode gain competition in self-mixing laser diode

Multiple mode gain competition in self-mixing laser diode has been investigated assisted by output optical spectrum. Experimental results show that multi-peaks appear in self-mixing signals depending on the length of the external cavity. The numbers of self-mixing peak signals are the same as that of the output optical spectrum. Laser multi-mode gain competition model has been established to analyze the multiple mode competition in self-mixing laser diode. Numerical analysis demonstrates that the sub-peak in self-mixing signals is attributed to mode gain competition between different longitudinal laser modes.

Three-Mode Variable-Frequency ZVS Modulation for Four-Switch Buck+Boost Converters With Ultra-High Efficiency

This article introduces a three-mode variable-frequency zero-voltage switching (ZVS) modulation method for the four-switch buck+boost converter. This method makes this circuit concept well suited for applications, such as wireless power charging of electric vehicles, where this circuit operates as a power buffer between the resonant converter and the battery with the function to implement the required charging profile. Herein, the buck+boost converter operation is subdivided into three operating regions according to the converter static voltage gain, i.e., buck-, buck-boost- and boost-type modes. A ZVS turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> triangular current mode (TCM) control is adopted for buck-type and boost-type modes. In the buck-boost-type mode when the input-to-output voltage gain is close to unit, all the possible modulation cases are studied thoroughly based on the phase shift of the two half bridges in a full switching period. The selection of the most suitable modulation scheme is performed to minimize the rms value of the inductor current while taking into account the simplification of the practical implementation. Closed-form equations are derived, which makes it easy to implement in practice. The proposed strategy is described, analyzed, and finally verified through a 3 kW surface mounted device (SMD) silicon carbide (SiC) <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> -based laboratory prototype with designed input voltage of 300–600 V and the typical output voltage of 400 V class battery. The efficiency from the measured results is remarkably high, i.e., between 99.2% and 99.6% in a power range from 1 to 3 kW. Finally, tests for the operating mode transitions demonstrated the feasibility of the proposed modulation method. The power density of this converter is 4.86 kW/L.

Attention biases preferential choice by enhancing an option's value.

Does attending to an option lead to liking it? Though attention-induced valuation is often hypothesized, evidence for this causal link has remained elusive. We test this hypothesis across 2 studies by manipulating attention during a preferential decision and its perceptual analog. In a free-viewing task, attention impacted choice and eye movement pattern in the preferential decision more than the perceptual analog. Similarly, in a controlled-viewing task, attention had a larger effect on choice in the preferential decision than its perceptual analog. Across these experimental manipulations of attention, choice and eye-tracking data provide converging evidence that attention enhances value, and computational modeling further supports this attention-induced valuation hypothesis. A possible explanation for our results is a normalization mechanism where attention induces a gain modulation on an option's representation at both the sensory and value processing levels. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Research on Sensorless Control of Permanent Magnet Synchronous Motor Based on Novel Sliding Mode Observer

In this paper, an improved SMO system is proposed to solve the problems of jitter and poor interference immunity of the conventional SMO system, the system is improved by replacing and adding three new simulation modules. Starting from the ideas of the “quasi-sliding module” and “boundary layer” of sliding mode control theory, by replacing the symbolic function in the conventional observer with an exponential segmentation function, which can effectively suppress the jitter phenomenon. And for different speed motor control application scenarios, a variable sliding mode gain coefficient that can be dynamically changed with the motor speed is used. For the system’s anti-jitter performance to be improved, a variable sliding mode gain coefficient that can be dynamically changed with the motor speed is introduced, which has stronger self-adaptability in different speed scenarios. An improved SMO system is formed by adding three new and improved modules, and this basis is tested experimentally on the MATLAB/Simulink simulation platform. The SMO with the addition of three new modules can be tested by simulation experiments to know that it has stronger anti-disturbance and self-adaptive capabilities under change scenarios such as sudden changes in load torque and sudden changes in speed.

Effects of Weight Gain During Pregnancy in Normal-Weight Women on Changes in the Gut Microbiota of Pregnant Women in the Third Trimester.

With the improvement of living standards and the lack of nutrition awareness during pregnancy, the phenomenon of excessive weight gain (EWG) of pregnancy is increasing. EWG during pregnancy has profound effects on the health of mother and offspring. The role of intestinal flora in regulating metabolic diseases has gradually attracted attention in recent years. The study explored the effect of EWG during pregnancy on gut microbiota, and analyzed the diversity and composition of gut microbiota in pregnant women in third trimester. Fecal samples were collected and divided into: insufficient weight gain (IWG)during pregnancy (group A1, N = 4), and appropriate weight gain (AWG) during pregnancy (group A2, N = 9), and EWG during pregnancy (N = 9 in A3 group). MiSeq high-throughput sequencing technology and bioinformatics analysis were introduced to investigate relationship of gestational weight gain and maternal gut microbiota. General data analysis showed that gestational weight gain and delivery mode have significant differences among the three groups. The overall level and diversity of intestinal microbiota in A1 and A3 group were increased. Composition of gut microbiota has no difference among three groups at the phylum level, but species of gut microbiota were different. Alpha diversity index analysis showed that the richness of A3 group was increased versus A2 group. EWG during pregnancy affects the abundance and proportion of gut microbiota in the third trimester. Therefore, maintaining moderate weight gain during pregnancy helps to maintain intestinal homeostasis.

Perceptual Difficulty Regulates Attentional Gain Modulations in Human Visual Cortex.

Perceptual difficulty is sometimes used to manipulate selective attention. However, these two factors are logically distinct. Selective attention is defined by priority given to specific stimuli based on their behavioral relevance, whereas perceptual difficulty is often determined by perceptual demands required to discriminate relevant stimuli. That said, both perceptual difficulty and selective attention are thought to modulate the gain of neural responses in early sensory areas. Previous studies found that selectively attending to a stimulus or increasing perceptual difficulty enhanced the gain of neurons in visual cortex. However, some other studies suggest that perceptual difficulty can have either a null or even reversed effect on gain modulations in visual cortex. According to Yerkes-Dodson's Law, it is possible that this discrepancy arises because of an interaction between perceptual difficulty and attentional gain modulations yielding a nonlinear inverted-U function. Here, we used EEG to measure modulations in the visual cortex of male and female human participants performing an attention-cueing task where we systematically manipulated perceptual difficulty across blocks of trials. The behavioral and neural data implicate a nonlinear inverted-U relationship between selective attention and perceptual difficulty: a focused-attention cue led to larger response gain in both neural and behavioral data at intermediate difficulty levels compared with when the task was more or less difficult. Moreover, difficulty-related changes in attentional gain positively correlated with those predicted by quantitative modeling of the behavioral data. These findings suggest that perceptual difficulty mediates attention-related changes in perceptual performance via selective neural modulations in human visual cortex.SIGNIFICANCE STATEMENT Both perceptual difficulty and selective attention are thought to influence perceptual performance by modulating response gain in early sensory areas. That said, less is known about how selective attention interacts with perceptual difficulty. Here, we measured neural gain modulations in the visual cortex of human participants performing an attention-cueing task where perceptual difficulty was systematically manipulated. Consistent with Yerkes-Dodson's Law, our behavioral and neural data implicate a nonlinear inverted-U relationship between selective attention and perceptual difficulty. These results suggest that perceptual difficulty mediates attention-related changes in perceptual performance via selective neural modulations in visual cortex, extending our understanding of the attentional operation under different levels of perceptual demands.

A chopper amplifier with a pseudo MOS resistor-based tunable bandwidth for EEG applications

PurposeThe purpose of chopper amplifier is to provide the wideband frequency to support biomedical signals.Design/methodology/approachThis paper proposes a chopper-stabilized amplifier with a cascoded operational transconductance amplifier. The high impedance loop is established using an MOS pseudo resistor and with a tunable MOS capacitor.FindingsThe total power consumption is 451 nW with a supplied voltage of 800 mV. The Gain and common mode rejection ratio are 48 dB and 78 dB, respectively.Research limitations/implicationsAll kinds of real time data analysis was not carried out, only few test samples related to EEG signals are validated because the real time chip was not manufactured due to funding issues.Practical implicationsThe proposed work was validated with Monte-Carlo simulations. There is no external funding for the proposed work. So there is no fabrication for the design. But post simulations are performed.Originality/valueThe high impedance loop is established using an MOS pseudo resistor and with a tunable MOS capacitor. To the best of the author’s knowledge, this concept is completely novel and there are no publications on this work. All the modules designed for chopper amplifier are new concepts.

Generation of 1.3 µm femtosecond pulses by cascaded nonlinear optical gain modulation in phosphosilicate fiber.

Nonlinear optical gain modulation (NOGM) is a simple and effective approach to generate highly coherent ultrafast pulses with a flexible wavelength. In this work, we demonstrate 34 nJ, 170 fs pulse generation at 1319 nm through a piece of phosphorus-doped fiber by two-stage cascaded NOGM with a 1064 nm pulsed pump. Beyond the experiment, numerical results show that 668 nJ, 391 fs pulses at 1.3 µm can be produced with up to 67% conversion efficiency by increasing the pump pulse energy and optimizing the pump pulse duration. This would offer an efficient method to obtain high-energy sub-picosecond laser sources for applications such as multiphoton microscopy.

2.8 μm pulsed Er3+:ZBLAN fiber laser based on external gain modulation

We report the generation of stable pulses in a ∼2.8 μm Er3+:ZBLAN fiber laser by varying the population inversion of active ions with an external 1973 nm auxiliary pump source. When we increase the 976 nm master pump power to beyond the chaotic self-pulsing stage, stable pulse trains can be obtained immediately with the switch-on of the 1973 nm auxiliary pump source. The pulse repetition rate can be tuned from 22.47 kHz to 63.98 kHz by adjusting the 1973 nm pump power, and the corresponding pulse width is varied from 4.47 μs to 1.99 μs. The underlying mechanism of the pulsed Er3+:ZBLAN fiber laser with external gain modulation is also discussed.