Abstract: Spread spectrum transmission of information is performed using chaotic signals. Direct chaotic communication systems in which information is input to chaotic signal generated directly in information transmission frequency band, are achieved by forming broadband information carrier necessary for transmission and using a chaotic dynamic system whose structure is synthesized in advance in accordance with predetermined characteristics of broadband information carrier to cause chaotic dynamic system to provide operation of forming the broadband information carrier in form of a chaotic information carrier having prescribed spectral characteristics.

Abstract: A signal generator, a signal generation method, and a communication system using the same are provided. The signal generator includes a plurality of nonlinear elements which are connected in a ring; and a signal distributor which is arranged in the ring to form a closed loop, feeds part of a signal to one of the plurality of the nonlinear elements, and outputs signal generated by one of the plurality of nonlinear elements. The method includes arranging a plurality of nonlinear elements connected in a ring; inputting a signal to one of the nonlinear elements; amplifying the signal; receiving the amplified signal and generating a harmonic component of a frequency; clipping the signal; and feeding part of the signal back to one of the nonlinear elements and outputting a remainder of the signal. The system includes a chaotic signal generator; a signal distributor; a modulator; and a transmission circuit.

Abstract: Provided is an apparatus and a method of measuring a distance between devices using a low clock frequency signal. The apparatus includes clock frequency generators, counters, a controller and a calculator for determining the distance based on clock signal overlap. Radio waves are transmitted and a number of clocks of a clock signal having a clock frequency b are counted, and if the transmitted radio waves are received again, a number of clocks of a clock signal having a clock frequency a are counted. If the clock signals having the clock frequencies a and b overlap with each other, counting of the numbers of the clocks of the clock signals having the frequencies b and a stops, and the distance is measured using the count values of the clock signals having the clock frequencies a and b. As a result, number of clocks of clock signals having low clock frequencies with a uniform difference can be counted to precisely measure a distance.

Abstract: A preamble generating method which includes computing (N) chaotic samples; transforming the (N) chaotic samples into (N) binary values of certain bits, respectively, and computing a chaotic sequence bit successively using the (N) binary values; and generating a preamble based on the chaotic sequence bit. By using the sequence bit from the chaotic samples, a plurality of preambles with optimum auto-correlation and cross-correlation properties is generated.