Akio Tsuneda

Design of binary sequences with tunable exponential autocorrelations and run statistics based on one-dimensional chaotic maps

This paper describes simple design methods of chaotic binary sequences with prescribed exponential autocorrelation properties and run statistics. We employ one-dimensional piecewise monotonic onto maps and a simple threshold function for generating such sequences. Some examples of such designs are also given. Furthermore, bounds on run statistics are discussed and compared to the result for sequences of general binary random variables.

Correlational Properties of Chebyshev Chaotic Sequences

We evaluate dependence of a chaotic real-valued trajectory generated by the Chebyshev map of degree k (≥ 2) by using the kth-order dependency moments. We find that a real-valued trajectory generated by the Chebyshev map of degree k has the kth-order correlated property and the ek(N)-delay correlated property to be defined here. Results for other well-known maps with the equidistributivity property defined in our previous paper are also given briefly.

Design of spreading sequences with negative auto-correlations realizable by nonlinear feedback shift registers

Spreading sequences with a negative auto-correlation for time-delay one are designed based on the Bernoulli and tent maps which are well-known one-dimensional chaotic maps. We also show that maximal-period binary sequences with negative auto-correlation based on such maps with finite bits can be generated by a class of nonlinear feedback shift registers (NFSRs). Furthermore, we perform computer simulations of asynchronous DS/CDMA communications using such negatively auto-correlated spreading sequences.

Design of chaotic binary sequences with good statistical properties based on piecewise linear into maps

This paper shows design of chaotic binary sequences with good statistical properties based on one-dimensional piecewise linear maps. Such chaotic binary sequences are shown to be balanced and i.i.d. (independent and identically distributed). We also realize such sequences by an analog circuit using switched-current (SI) techniques. The statistical properties of the sequences generated by such an analog circuit are also investigated by SPICE simulations.

Performance evaluation of spreading sequences with negative auto-correlation based on chaos theory and Gold sequences

Spreading sequences with appropriate negative auto-correlation can reduce average multiple access interference (MAI) in asynchronous DS/CDMA systems compared with the conventional Gold Sequences generated by linear feedback shift registers (LFSRs). We design spreading sequences with negative auto-correlation based on Gold sequences and the chaos theory for the Bernoulli map. By computer simulations, we evaluate BER performances of asynchronous DS/CDMA systems using the proposed sequences.

Performance evaluation of LFSR-based spreading sequences with negative auto-correlation designed by Chaos theory of modulo-2 added sequences

In asynchronous DS/CDMA systems, spreading sexadquences with appropriate negative auto-correlation properties can outperform conventional LFSR (linear feedback shift regxadister) sequences with respect to bit error rate (BER) perforxadmance. Spreading sequences with negative auto-correlations can be generated by using one-dimensional chaotic maps but their hardware cost is more expensive than LFSRs. In this paper, we design spreading sequences with negative auto-correlation to be generated by LFSRs, which is based on the chaos theory for the Bernoulli chaotic map and modulo-2 added binary sequences. By computer simulations, we evaluate BER performances of asynxadchronous DS/CDMA communication systems using the proposed sequences.

Design and Experiments of a Novel Low-Ripple Cockcroft-Walton AC-to-DC Converter for a Coil-Coupled Passive RFID Tag

A low-ripple diode charge-pump type AC-DC converter based on the Cockcroft-Walton diode multiplier is proposed for coil-coupled passive IC tags in this paper. This circuit is developed as a power supply for passive RFID tags with smart functions such as heart rate detection and/or body temperature measurement. The proposed circuit converts wirelessly induced power to a low-ripple DC voltage suitable for a 13.56 MHz RFID tag. The proposed circuit topology and the principle of operation are explained and treated theoretically by using quasi-equivalent small-signal models. The proposed circuit was implemented on a PCB. And it was confirmed that the proposed circuit provides 3.3 V DC with a ripple of less than 20 mV when a 4Vp-p sinusoidal input is applied. Under this condition, the maximum output power is about 310 μW. The measured results were in good agreement with theoretical and HSPICE simulation results.

A CMOS continuous-time FPAA analog core using automatically-tuned MOS resistors

In this paper, a novel CMOS analog core for continuous-time FPAAs (field programmable analog arrays) is proposed. The proposed analog core consists of CMOS opamps and automatically-tuned MOS resistors. Since MOS resistor values are fixed by a PLL (phase locked loop) technique, the MOS resistors are almost immune to temperature variations and fabrication tolerances. In this analog core, the MOS resistors not only act as linear resistors but also as analog switches.

Design and Evaluation of Spreading Sequences with Negative Auto-Correlations Based on Chaos Theory and LFSR Sequences

Spreading sequences with exponentially vanishing negative auto-correlations can reduce average multiple access interference (MAI) in asynchronous DS/CDMA systems compared with the conventional M-sequences and gold sequences generated by linear feedback shift registers (LFSRs). We design spreading sequences with negative (but not exponentially vanishing) auto-correlations based on M-sequences and Gold sequences, which is also based on the chaos theory for the Bernoulli map. By numerical experiments, we investigate auto-/cross-correlation properties of the proposed sequences.

A Study on Generation of Random Bit Sequences with Post-Processing by Linear Feedback Shift Registers

There are several attempts to use chaotic nonlinear maps for random number generation. Theoretically, some chaotic maps can produce balanced and i.i.d.(independent and identically distributed) binary sequences. However, it is difficult to generate aperiodic sequences with good statistical properties by analog circuits or digital circuits only. In this paper, we propose a simple post-processing by linear feedback shift registers for generating random bit sequences with good statistical properties. Some numerical results including a well-known statistical test (FIPS140-2) are shown.