Line-of-sight (LoS) calculation, or detecting where the user is looking at, is expected as a new type of user interfaces, with including the phenomenon of rapid eye movement, so called saccade. However, real-time tracking of saccade is difficult with the conventional image processing systems for their long processing time and latency against the speed of saccade. In this paper, we describe the design of the high speed, low latency LoS calculation image sensor, as well as its preliminary evaluation results. This image sensor has a capability to track the saccade at high frame rate, and generate the LoS calculation results with minimum latency for real-time tracking.
A cyclic TDC can be implemented in a small area with high resolution but it takes long conversion time. To reduce a conversion time, we introduce variable delay circuits that can change a delay time of a pulse. We also introduce calibration techniques, an offset cancellation and delay matching, to improve linearity of the TDC. We confirmed through circuit simulation that the proposed circuit achieves a time resolution of 9.38 ps, dynamic range of 18.7 ns, sampling rate of 2 MS/s, and a power consumption of 11 mW at 1.8 V operation.
In this paper, we describe novel high precision SPICE modeling for triode vacuum tube, which is attracting attention in electronic musical instruments continuously and recently in the field of audio systems. The advantage of proposed high-precision modeling is that it is created considering the difference of space charge distribution originated from the difference of electrode distance between triode tube 12AX7 and 12AU7.
It was found that the characteristic of the space charge change appears within the grid voltage range of minus 1 to plus 1 volt with respect to the grid current vs. grid voltage Ig-Vg curve. In this range, thermal electrons are accelerated from the initial velocity condition of the Maxwell distribution. Based on this analysis, the modulation model formula of the perveance value Gs, which is the key factor of the space charge, is obtained. Subsequently, we extended the model formula to the cathode current vs. plate voltage Is-Vp family curves with the grid voltage as a parameter in consideration of the perveance Gs modulation effects. Finally, Ig-Vp family curve model equation is derived. Comparing the simulation results of the AC characteristics performed using the proposed model equation and the conventional SPICE model equation, the superiority of the new model equation was confirmed.
The on-board microphone with MEMS technology as the condenser microphone is used widely for audio interfaces. We propose the second-order predictive ADC that converts the charge to the digital code directly, without the charge to voltage conversion circuit. In this paper, we show the performance of this ADC using the capacitor array DAC and the DEM method. By the simulation using BASIC programming language, we confirmed that the DEM method improves the SNR degradation.
Switching frequency of a power converter has increased because of recent development of power semiconductor devices. For measurements of switching waveforms in high-frequency power converters, it is important to precisely calibrate skew for an oscilloscope. In order to conduct skew calibration, we fabricate a high-power and high-speed pulse generator using a SiC power MOSFET. The skew of oscilloscope probes is discussed.
We have been proposed on-chip power supply system for a micro system. This power supply system operates application circuit, to achieve a stand-alone chip, referred to as a micro system. In this work, we fabricate the chip to evaluate the on-chip boost power supply that consists of photovoltaic device, ring oscillator and DC-DC boost converter on the same die. The solar cell using N-well and P-substrate outputs about 500 mV and several μW under about 7600 lx lighting. This solar cell generates negative voltage to the P-substrate but the photoelectric conversion efficiency is much higher than the solar cell generates positive voltage. In this work, the integration method is shown to realize the solar cell with negative voltage output and bootstrap charge pump(BSCP) DC-DC converter using triple well technology. The performance of newly designed BSCP DC-DC converter using MIM capacitor and previously designed BSCP DC-DC converter using MOS capacitor are compared. The converter using MIM capacitor shows the much higher voltage conversion ratio than the converter using MOS capacitor. However, designed on-chip power supply system shows a large variation of the output voltage. We discuss the variation and mismatch with simulation considering parasitic capacitances using corner simulation.
A novel architecture of downconverting A-to-D Converter is proposed, which is based on even-harmonic mixer and ΔΣ Time-to-Digital Converter. Analog circuits are minimized by the proposed architecture. As a design study, a test chip of 200 MHz RF signal to baseband downconverter is designed and fabricated. The design uses a standard 0.18 µm CMOS technology, and the simulation results verify the operation of the proposed architecture. Measurement result is presented and it verified the functionality of the fabricated test chip.
Automatic design of analog integrated circuit is in great demand due to the requirement of the reduction of design time. Optimization algorithms are often used for the automatic design. However, because the optimization algorithm is based on the stochastic method and determines the circuit parameters at random, a lot of circuits which do not operate in principle are generated and simulated to find the optimal circuit. These redundant simulations consume time in vain. In this paper, the automatic design method, which achieves to reduce the redundant simulations, of the topology and element values of the comparator circuit, is proposed. For the decision of the topology, simulation results are utilized to determine the topology, which results in the reduction of numbers of simulations. For the decision of element values, Divided Circuit Optimization which performs optimization for each function block is proposed. The reduction of the optimization target means that HSPICE optimization function ensures to converge. Compared with the conventional method, the proposed method can reduce numbers of simulations to 1/30 and simulation time to 1/3.
Conventionally Peltier device has been controlled precisely by pulse driving current. In this study, it is shown that driving Peltier device by DC current controlled by pulse signal increases COP of cooling system with reducing self-heating in the device keeping accurate controlling. In practical application, the DC current driving can be achieved easily by connecting one electric condenser with large capacitance to the Peltier device in parallel. In results of analysis for electric circuit, the DC driving current reduced the self-heating in the Peltier device to conventional calorific power multiplied by driving duty-cycle value. Heat absorption rate in the Peltier device was increased by half of the reduction in the self-heating. Thermal equivalent circuit of Peltier device considered Seebeck effect was proposed to analyzed COP accurately. It was also analyzed COP of system driven by each current by using proposed thermal equivalent circuit. In result of experiment, it was possible to confirm that COP in cooling system using the DC driving current was increased than conventional system. In particular, the COP increased to equal or more than 2.01 times in less than 50% of driving duty cycle.
In the broadband wired communication, it is strongly required to equalize attenuation characteristics in transmission lines. In this paper, the variable attenuator equalizer using 90-degree hybrid coupler is proposed which has the lowest return coefficient. Experimental results show the variable attenuator can be realized in the 700 to 1050MHz frequency range. Further result shows that the attenuation profile can be controlled in real time with variable attenuation equalizer using PIN diode. From these results, adaptive attenuator with variable attenuation characteristics can be realized.
In this paper, a method for expanding the freedom of the circuit design concerned with a first-order passive complex filter including no transformers is proposed. The proposed frequency transformation is obtained by arranging the conventional one for the complex filter using loose coupling transformers. By giving appropriate specifications to the conventional frequency transformation, we can exclude the ideal transformers. The validity of the proposed method is confirmed through experiment.
Body-bias control technique which is useful method with fully-depleted silicon-on-insulator (FD-SOI) transistor circuits for low-power design is employed for an optimization method of the tradeoff between RF performance and current consumption. A 2.4-GHz low-power low-noise amplifier (LNA) is designed with a 28-nm FD-SOI process. By tuning drain current and body-biases, the LNA with low power consumption can be designed while keeping the performance of zero body-bias.
Generally, in electric equipment, a large inrush current flows in the capacitor when the power is turned on. The inrush current causes deposition of terminals and switches, melting of fuses, and so on. Therefore, conventional inrush current prevention circuits using an electrical relay and a controller are provided. However, the use of electrical relay enhances concern about an increase in cost and charge-time. In order to solve these problems, this paper proposes the inrush current prevention circuit without electrical relay. In this paper, the authors examine the effectiveness of the proposed circuit from experimental results.
In this study, we directly measured the tongue force using an artificial finger with built-in two force sensors during sucking, and constructed the system that outputs whether the tongue is peristaltic-like movement or not to the infant toy (baby mobile). This system will help mothers who feeding and rearing infants because it is possible to visually and auditorily confirm the tongue movement of the infant simply by inserting the sensor part into the oral cavity.