Gain Control Stage Research Articles

저전력 가변 이득 증폭기 설계

This paper presents a low-power variable gain amplifier (VGA) for the automotive radar. The proposed VGA comprises a gain control stage and an amplifier stage with active inductors. The gain control stage on the circuit is designed to be adjustable in 5 steps from 0 dB to 20 dB. The chip area can be reduced using an active inductor. This circuit also has a lower power dissipation, which reduces slow vibrations. The VGA is fabricated by TSMC 0.13 μm CMOS process. In comparison to conventional research results, the proposed VGA showed a lower power consumption of 17.88 mW, a low noise figure of less than 3.424 dB, and a relatively low active area of 0.034 mm².

Effects of compression channel number and linked compression on masked lateralization performance in simulated bilateral cochlear implant listening

Bilateral cochlear implants (CIs) are becoming increasingly common. It is hoped for bilateral CI users that audibility in quiet will be complemented by performance benefits in everyday binaural listening tasks, like location-identification of a speech talker presented amid other talkers. While normal-hearing (NH) listeners have typically performed well in such kinds of tasks, bilateral CI users have performed poorly. It is possible that, for bilateral CI users, better performances can be attained through a re-thinking of device signal-processing strategies. In particular, we are interested in evaluating alternatives to single-channel independent compression, as is typically applied at the automatic gain control (AGC) stage. Specifically, we test the hypothesis that for simulated bilateral CI users (listeners with both NH and hearing impairments, HI), lower rms-error in a masked lateralization task will be achieved for multi-channel AGC and linked AGC, than for single-channel independent AGC, with and without pre-emphasis filtering, and for low and high compression thresholds. Preliminary data suggest a lower rms-error for linked compression than for independent compression, in conjunction with no detrimental effect of multi-channel compression. These data support the possibility of linked AGC with multi-channel AGC as an alternative to independent AGC in bilateral CI listening.

OLT Receiver for Power Normalization of Burst OFDM Signals Enabling OFDM/TDMA-PON

An optical line terminal receiver, composed of an optical gain-control stage based on an optical coherent detection followed by an electrical front-end amplifier, is verified to be able to normalize upstream burst orthogonal frequency division multiplexing (OFDM) signals with different power levels, thus alleviating a substantial limiting factor in OFDM/time division multiplexing access-passive optical network (PON) system development. A receiver dynamic range of 25 dB and system power budget of 29 dB are achieved. Experiments confirm that the receiver meets the linearity requirement posed by OFDM signals while satisfying the dynamic range and power budget specified by the current PON standards.

A 3.8 GHz programmable gain amplifier with a 0.1 dB gain step

A broadband programmable gain amplifier (PGA) with a small gain step and low gain error has been designed in 0.13 μm CMOS technology. The PGA was implemented with open-loop architecture to provide wide bandwidth. A two-stage gain control method, which consists of a resistor ladder attenuator and an active fine gain control stage, provides the small gain step. A look-up table based gain control method is introduced in the fine gain control stage to lower the gain error. The proposed PGA shows a decibel-linear variable gain from −4 to 20 dB with a gain step of 0.1 dB and a gain error less than ±0.05 dB. The 3-dB bandwidth and maximum IIP3 are 3.8 GHz and 17 dBm, respectively.

Binocular contrast discrimination needs monocular multiplicative noise

We report the surprising result that although binocular vs monocular viewing of a sinusoidal grating has approximately the same perceived contrast, contrast discrimination is ͩ0;2 better for binocular viewing. We argue that the most plausible class of models with this property has a gain control stage with ocular crosstalk whereby the effective contrast of each eye is halved (see Ding and Sperling, 2006), followed by multiplicative noise, and then the summation of the two eyes' signals and noise going to the decision stage. To pin down the model, we performed three experiments using identical stimuli to measure perceived phase, perceived contrast, and contrast discrimination of a cyclopean sinewave. On each trial, horizontal sinewaves (0.68 cpd) were presented independently to the two eyes using a mirror stereoscope. Perceived phase was measured using a paradigm adapted from Ding and Sperling (2006). (The perceived phase is sensitive to the ratio of right and left eye contrasts and is important for pinning down the gain control parameters.) Perceived contrast was measured by matching the contrast of a binocular grating to a monocular standard. Contrast discrimination was measured with both pedestal and test sinewaves either in the same eye (monocular), in different eyes (dichoptic), or in both eyes (binocular). A modified Ding-Sperling model (Ding, Klein and Levi, in press) plus a contrast discrimination mechanism were used to fit all three data sets simultaneously. We tested four different model configurations: multiplicative noise or a non-linear contrast transducer could be either inserted before or after the combination site. Only multiplicative noise inserted before the combination site was able to account for the data. Meeting abstract presented at VSS 2013

A SiGe HBT Variable Gain Amplifier for Wireless Receiver System with On-Chip Filter

A using SiGe HBT variable gain amplifier (VGA) with filtering for wireless receiver system is presented in this paper. The VGA consists of three stages. The first stage is the gain control stage, and the second stage is the fixed gain stage. The third is the GM-C filter. The VGA is driven by a 3.3-V power supply, and linear gain control range varying is from 26 dB to 62dB. When control voltage varies from 0 to 1.8V. The input 1-dB compression point is -4dBm at minimum gain. The VGA is fabricated in a 0.5 μm = 80GHz and =90GHz silicon germanium heterojunction transistor technology.

Readout electronics for the SiPM tracking plane in the NEXT-1 prototype

NEXT is a new experiment to search for neutrinoless double beta decay using a 100kg radio-pure high-pressure gaseous xenon TPC with electroluminescence readout. A large-scale prototype with a SiPM tracking plane has been built. The primary electron paths can be reconstructed from time-resolved measurements of the light that arrives to the SiPM plane. Our approach is to measure how many photons have reached each SiPM sensor each microsecond with a gated integrator. We have designed and tested a 16-channel front-end board that includes the analog paths and a digital section. Each analog path consists of three different stages: a transimpedance amplifier, a gated integrator and an offset and gain control stage. Measurements show good linearity and the ability to detect single photoelectrons.

Diverse mechanisms of contrast normalization in primary visual cortex

Contrast normalization models are extremely successful at describing the responses of neurons in visual cortex. They consist of two stages. A linear spatio-temporal filter (the receptive field) generates stimulus selectivity, such as orientation and direction preference. A non-selective, contrast-dependent, gain-control stage then normalizes the output of the linear filter. The models can quantitatively describe a variety of response nonlinearities, including contrast saturation, contrast invariance of orientation tuning, cross-orientation suppression, contrast-dependent changes in preferred temporal frequency, and modulation of neuronal responses by attention. In the standard model of contrast normalization, the normalization step is performed by a contrast-dependent shunting inhibition, which scales the size of the EPSPs generated at the linear stage. This shunt must be large, contrast-dependent, and only weakly selective for stimulus orientation and direction. Because we have rarely observed inhibition of this description in intracellular recordings from simple cells, we have investigated alternative mechanisms that might underlie contrast normalization. We applied the measured responses of LGN neurons to a feed-forward model of a simple cell that includes a variety of nonlinear properties of neurons and synapses that we measured directly. These include spike threshold, contrast saturation in the LGN responses, synaptic depression, contrast-dependent changes in trial-to-trial variability, and diversity in the timing of LGN responses. The model makes predictions of the synaptic input to simple cells, which we then compared to the membrane potential responses of simple cells recorded intracellularly in vivo. The model is highly constrained, with only two free parameters: the number of presynaptic LGN cells, and the aspect ratio of the simple cell subfield. And yet nearly all of observed aspects of contrast normalization emerge with considerable precision. We conclude that while the brain may find it advantageous to implement contrast normalization in the spike output of cortical simple cells, it uses a variety of underlying mechanisms to do so.

Adaptation and gain pool summation: alternative models and masking data

Foley [J. Opt. Soc. Am. A 11 (1994) 1710] has proposed an influential psychophysical model of masking in which mask components in a contrast gain pool are raised to an exponent before summation and divisive inhibition. We tested this summation rule in experiments in which contrast detection thresholds were measured for a vertical 1 c/deg (or 2 c/deg) sine-wave component in the presence of a 3 c/deg (or 6 c/deg) mask that had either a single component oriented at −45° or a pair of components oriented at ±45°. Contrary to the predictions of Foley's model 3, we found that for masks of moderate contrast and above, threshold elevation was predicted by linear summation of the mask components in the inhibitory stage of the contrast gain pool. We built this feature into two new models, referred to as the early adaptation model and the hybrid model. In the early adaptation model, contrast adaptation controls a threshold-like nonlinearity on the output of otherwise linear pathways that provide the excitatory and inhibitory inputs to a gain control stage. The hybrid model involves nonlinear and nonadaptable routes to excitatory and inhibitory stages as well as an adaptable linear route. With only six free parameters, both models provide excellent fits to the masking and adaptation data of Foley and Chen [Vision Res. 37 (1997) 2779] but unlike Foley and Chen's model, are able to do so with only one adaptation parameter. However, only the hybrid model is able to capture the features of Foley's (1994) pedestal plus orthogonal fixed mask data. We conclude that (1) linear summation of inhibitory components is a feature of contrast masking, and (2) that the main aftereffect of spatial adaptation on contrast increment thresholds can be assigned to a single site.

A high-performance monolithic IF amplifier incorporating electronic gain control

A direct-coupled monolithic IF amplifier that incorporates an active gain control stage and exhibits a power gain of 50 dB and an AGC range of 60 dB at 50 MHz is described. This circuit has negligible change in either input or output admittance, and has excellent signal linearity over the full range of gain control. Experimental and theoretical analyses are made of the large signal response, stability, available gain, and noise behavior of the circuit. An application to color television is discussed in which the functions of the 45-MHz IF amplifier and the dc-AGC circuitry are fabricated on a single die.