We propose a single-slope analog-to-digital converter (ADC) with an intermittently working time-to-digital converter (TDC). Applying an n-bit TDC reduces the conversion time by a factor of 2ⁿ, and using multiphase clock signals achieves timing consistency and realizes robust metastability. We focus on the operation time of the TDC. Since a TDC must operate continuously, it requires a large dissipation power. We propose generating the pulse-width modulation (PWM) signal of a single-slope ADC and apply a scheme for limiting the TDC operation period in order to reduce the TDC power dissipation. We designed and fabricated a 12-bit ADC, which consists of a 6-bit TDC and a 6-bit single-slope ADC, by using a 0.18 μm CMOS process. The ADC operated at 100 kS/s consumed 5.5 μW from a 1 V supply. Its INL and DNL were +1.9/-1.9 LSB and +0.5/-0.8 LSB, respectively.

View full abstract

The quantum-inspired evolutionary algorithm (QEA) and QEA with a pair-swap strategy (QEAPS), where each gene is represented by a quantum bit (qubit) in both algorithms, have shown superior search performance to the classical genetic algorithm in the 0-1 knapsack problem. Also, from experimental results for the integer knapsack problem, a novel integer-type gene-coding method that can obtain an integer value as an observation result by assigning multiple qubits in a gene locus has shown superior search performance to the conventional binary-type gene-coding method. However, the integer-type gene-coding method cannot deal with permutations simply. Therefore, we have proposed two interpretation methods that can deal with permutations in order to expand the gene-coding method based on the qubit representation. From the results of a computer experiment using the proposed interpretation methods in the traveling salesman problem, we have clarified that the two proposed interpretation methods can search for the optimal solution, even with the gene-coding method based on the qubit representation. Moreover, there are suitable rotation angles for discovering the optimal solution that depend on the algorithm.

View full abstract

This paper proposes a novel coded spatial modulation technique with nonbinary signaling based on a nonbinary turbo-coding approach. The aim of this work is to improve the average bit error rate (BER) performance over a peak-to-average power ratio (PAPR)-limited channel. The use of nonbinary signaling such as hexagonal quadrature amplitude modulation (HQAM), has been studied as a technique that can mitigate the PAPR. However, it is not suitable for the transmission of binary information because the number of modulation level cannot be given by a power of two, which leads to translation loss from nonbinary to binary numbers. On the other hand, generalized spatial modulation (GSM) has been proposed as an extended version of spatial modulation (SM) and it can boost the transmission rate. However, the number of modulation levels of GSM cannot be given by a power of two. This work proposes to jointly design coded spatial modulation composed of nonbinary signaling and nonbinary SM i.e., GSM, by using nonbinary turbo coding. Simulation results demonstrate the improved BER the proposed coded SM over a PAPR-limited channel.

View full abstract

It is important to quantify and prevent mental fatigue in order to forestall absence from work and death from overwork. In this study, we used “Large-scale Data-based Online Modeling (LOM)”, one of the local modeling methods based on databases, to reproduce the characteristics of fatigue based on information derived from observation of biomedical signs. The subjects in our study were 10 male university students.After assuming a relaxed seated position for 10 minutes, they performed two repeated sessions of a mental arithmetic task for 30 minutes each session with a 30-minute break. Subjective symptoms of feelings of fatigue score were evaluated on a 10-point scale. We measured several biomedical signs and subjective symptoms of feelings of fatigue score. We propose that it is possible to estimate the degree of acute mental fatigue from biomedical signs using the LOM method. We propose a method for determining the reliability of estimating “degree of fatigue” by distance of neighboring data.

View full abstract

An inductor or switch current is necessary to control a boost converter in the continuous conduction mode for high dynamic performance. Sensorless current control of a boost converter reduces its cost, size, and weight. A Luenberger observer (LO) only feeds a linear output estimation error back to the observer. In this paper, a sliding mode observer (SMO), which feeds a nonlinear output estimation error back to the observer, was proposed for the sensorless control of a boost converter to improve its dynamic performance. Simulations by Simulink and practical experiments on an NJU20010 digital signal processor are performed. It is shown that the proposed SMO-based sensorless control of a boost converter maintains better dynamic performance than LO-based sensorless control and conventional sensor-based double-loop Proportional-Integral (PI) control.

View full abstract

In this paper, we consider a formal linearization for multi-output nonlinear systems based on Chebyshev interpolation. Defining a linearization function that consists of Chebyshev polynomials, a given nonlinear dynamic system is transformed into an augmented linear one with respect to this linearization function by Chebyshev interpolation. Introducing a new augmented measurement vector that consists of polynomials of measurement data for a given multidimensional measurement equation, a measurement equation is transformed into an augmented linear one with respect to the linearization function in the same way. A linear estimation theory is applied to these augmented linearized systems and a nonlinear filter is synthesized. In order to show the performance of the method, a tentative estimation problem of a pendulum system is solved, with the results compared with those for the extended Kalman filter as a conventional method.

View full abstract

In this paper, turbo-coded on-off keying (OOK) with differential detection is proposed. The proposed system constitutes the standard turbo code with OOK modulation, differential encoding and a delay detection technique. The purpose of using the differential encoding system is to suppress the influence of background noise in an optical wireless channel (OWC). OOK systems use the threshold detection method to determine the data. In optical intensity modulation/direct detection (IM/DD) systems, disturbances in the channel such as background noise and scintillation make it more difficult to decide the threshold value. Hence, in order to deal with the degradation in the quality of communication due to background noise, a turbo-coded OOK system with differential encoding and delay detection is proposed. The bit error rate (BER) performance of the proposed system is analyzed through computer simulation of an OWC in the presence of background noise, scintillation and avalanche photodiode (APD) noise. In terms of the BER performance, the results of this study show that the proposed system outperforms the conventional turbo-coded OOK system by 2.0 [dBm] at BER=10^-5.

View full abstract