A survey on nonlinear analog-to-digital converters

Denić

Measurement Science Review

2017

Optical rotary encoders generate nonlinear sine and cosine signals in response to a change of angular position that is being measured. Due to the nonlinear shape of encoder output signals, encoder sensitivity to very small changes of angular position is low, causing a poor measurement accuracy level. To improve the optical encoder sensitivity and to increase its accuracy, an improved linearization circuit based on pseudo-linear signal generation and its further linearization with the two-stage piecewise linear analog-to-digital converter is presented in this paper. The proposed linearization circuit is composed of a mixed-signal circuit, which generates analog pseudo-linear signal and determines the first four bits of the final digital result, and the two-stage piecewise linear analog-to-digital converter, which performs simultaneous linearization and digitalization of the pseudo-linear signal. As a result, the maximal value of the absolute measurement error equals to 3.77168·10 -5 [rad] (0.00216°) over the full measurement range of 2π [rad].

“…The TSPLADC is a generalpurpose linearization circuit, i.e. by reprogramming its transfer function any sensor type can be linearized [8]- [15]. Fig.1.…”

Section: Proposed Linearization Circuitmentioning

confidence: 99%

An Improved Linearization Circuit Used for Optical Rotary Encoders

Denić

Measurement Science Review

2017

“…One of the most common causes of a measuring system low accuracy is nonlinearity of a sensing element. There are many techniques developed to compensate a sensor nonlinearity, but the linearization with a two-stage piecewise linear analog-to-digital converter (two-stage PWL ADC) has proved to be one of the most effective [1]- [4]. In particular, the sensor linearization is performed simultaneously with the signal digitalization, i.e.…”

Section: Introductionmentioning

confidence: 99%

A Cost-effective Method for Resolution Increase of the Twostage Piecewise Linear ADC Used for Sensor Linearization

Measurement Science Review

Denić

2016

A cost-effective method for resolution increase of a two-stage piecewise linear analog-to-digital converter used for sensor linearization is proposed in this paper. In both conversion stages flash analog-to-digital converters are employed. Resolution increase by one bit per conversion stage is performed by introducing one additional comparator in front of each of two flash analog-to-digital converters, while the converters’ resolutions remain the same. As a result, the number of employed comparators, as well as the circuit complexity and the power consumption originating from employed comparators are for almost 50 % lower in comparison to the same parameters referring to the linearization circuit of the conventional design and of the same resolution. Since the number of employed comparators is significantly reduced according to the proposed method, special modifications of the linearization circuit are needed in order to properly adjust reference voltages of employed comparators.

“…This is done under the assumption that the entire input full-scale range (FSR) carries equal amounts of useful information and thus any input value needs to be converted with the same resolution. However, there are many applications where specific regions of the input FSR are of higher interest than the rest, where non-linear ADCs (NLADCs) can be advantageous because of reduced bit-rate, lower conversion energy, and increased dynamic range [1][2][3][4][5]. Logarithmic ADCs based on the m-law have been extensively used in speech and imaging applications to mimic human organ response [3,4].…”

mentioning

confidence: 99%

“…However, there are many applications where specific regions of the input FSR are of higher interest than the rest, where non-linear ADCs (NLADCs) can be advantageous because of reduced bit-rate, lower conversion energy, and increased dynamic range [1][2][3][4][5]. Logarithmic ADCs based on the m-law have been extensively used in speech and imaging applications to mimic human organ response [3,4]. Other areas where NLADCs can be used include nuclear science, robotics, and non-linearity correction in sensors and front-end amplifiers [1,4,5].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Two‐step, piecewise‐linear SAR ADC with programmable transfer function

Sengupta

Johnston

2019

Electron. lett.

A 7-bit successive approximation register (SAR) analogue-to-digital converter (ADC) with programmable transfer functions is presented. Building upon prior art, a two-step successive approximation technique is used to implement a piecewise-linear approximation of the desired transfer function. However, unlike previous implementations of SAR-based non-linear ADCs, the proposed work demonstrates programmability of arbitrary non-linear transfer functions, thus making it suitable for a wide range of low-bandwidth applications. Simulation results from a proof-of-concept design in a standard 180 nm CMOS process are presented to validate the proposed idea.