Chaotic communication system and method using modulation of nonreactive circuit elements
First Claim
1. A chaotic receiver comprising:
- an input terminal that receives a modulated chaotic signal;
an oscillator coupled to the input terminal;
a chaotic circuit comprising a capacitor and a negative resistance circuit;
a gain control amplifier coupled between the oscillator and the chaotic circuit, wherein the gain control amplifier amplifies a voltage present at the oscillator before it reaches the chaotic circuit;
a synchronizing resistor coupled between the input terminal and the chaotic circuit; and
a detection circuit, coupled to the synchronizing resistor, wherein the detection circuit detects periods of synchronization and non-synchronization between the modulated chaotic signal and the chaotic circuit and generates an output corresponding to periods of synchronization and non-synchronization.
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Accused Products
Abstract
A chaotic communication system employs transmitting and receiving chaotic oscillating circuits. One improvement to first-generation systems is the ability to modulate a nonreactive element in the transmitting circuit, thus increasing modulation bandwidth. Other features include insertion of a gain control amplifier in a chaotic receiver; signal filtering in chaotic transmitters and receivers; use of chaotic modulation techniques for cellular telephony applications; dual-transmitter and receiver systems; a dual receiver synchronization detector; interfaces to communication systems; analog chaotic signal modulation; use of multiple chaotic transmitters and receivers; digital algorithm improvement using a cube-law nonlinear component; a Gb-only receiver; a Gb-only transmitter; and positive slope transmitter and receiver systems.
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Citations
33 Claims
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1. A chaotic receiver comprising:
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an input terminal that receives a modulated chaotic signal; an oscillator coupled to the input terminal; a chaotic circuit comprising a capacitor and a negative resistance circuit; a gain control amplifier coupled between the oscillator and the chaotic circuit, wherein the gain control amplifier amplifies a voltage present at the oscillator before it reaches the chaotic circuit; a synchronizing resistor coupled between the input terminal and the chaotic circuit; and a detection circuit, coupled to the synchronizing resistor, wherein the detection circuit detects periods of synchronization and non-synchronization between the modulated chaotic signal and the chaotic circuit and generates an output corresponding to periods of synchronization and non-synchronization.
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2. A chaotic receiver, comprising:
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an input terminal that receives a modulated chaotic signal; an oscillator circuit coupled to the input terminal; a first chaotic circuit coupled to the oscillator circuit and tuned to a first strange attractor; a second chaotic circuit coupled to the oscillator circuit and tuned to a second strange attractor; and means for detecting a difference between the modulated chaotic signal received at the input terminal and respective signals generated by the first and second chaotic circuits. - View Dependent Claims (3)
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4. A method of demodulating a signal modulated according to a chaotic trajectory shift-keying technique, comprising the steps of:
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(1) receiving a modulated chaotic signal modulated according to a chaotic trajectory shift-keying technique; (2) using the modulated chaotic signal to drive an oscillator; (3) using the modulated chaotic signal and an output of the oscillator to drive a first chaotic circuit tuned to a first strange attractor; (4) using the modulated chaotic signal and an output of the oscillator circuit to drive a second chaotic circuit tuned to a second strange attractor; and (5) detecting a difference between the modulated chaotic signal and respective signals generated by the first and second chaotic circuits. - View Dependent Claims (5)
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6. A chaotic receiver, comprising:
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an input terminal that receives a modulated chaotic signal; an oscillator coupled to the input terminal; a first chaotic circuit coupled to the oscillator and tuned to a first strange attractor; a second chaotic circuit coupled to the oscillator circuit and tuned to a second strange attractor; and a detector circuit coupled to the first and second chaotic circuits, wherein the detector circuit subtracts signals present at the first and second chaotic circuits and generates an absolute value signal based on the subtracted signal.
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7. A method of demodulating a signal modulated according to a trajectory shift-keying technique, comprising the steps of:
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(1) receiving a modulated chaotic signal; (2) using the modulated chaotic signal to drive an oscillator circuit; (3) using the modulated chaotic signal and an output of the oscillator circuit to drive a first chaotic circuit comprising a first nonlinear circuit element and tuned to a first strange attractor; (4) using the modulated chaotic signal and an output of the oscillator circuit to drive a second chaotic circuit comprising a second nonlinear circuit element and tuned to a second strange attractor; and (5) detecting a difference between first and second signals present at the first and second chaotic circuits, respectively, by subtracting the first and second signals and generating an absolute value thereof.
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8. A chaotic receiver comprising:
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an input terminal that receives a modulated chaotic signal; an oscillator circuit coupled to the input terminal and driven by the modulated chaotic signal; a chaotic circuit comprising an upper slope circuit that implements a first current-voltage function in an upper quadrant of a current-voltage response plane and a lower slope circuit that implements a second current-voltage function in a lower quadrant of the current-voltage response plane, wherein the first and second current-voltage functions have a different voltage offset, and wherein the upper and lower slope circuits cooperate with the oscillator circuit to generate a local chaotic signal; a synchronizing circuit, coupled to the oscillator circuit and the chaotic circuit, wherein the synchronizing circuit detects differences between the modulated chaotic signal at the input terminal and the local chaotic signal; and a detector coupled to the synchronizing circuit which detects periods of synchronization and non-synchronization. - View Dependent Claims (9, 10, 11)
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12. A method of demodulating a chaotically modulated signal, comprising the steps of:
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(1) receiving the chaotically modulated signal; (2) applying the signal received in step (1) to an oscillator through a resistor that defines a load line; (3) applying the signal applied to the oscillator in step (2) to first and second slope detector circuits each of which defines a linear current-voltage function that intercepts the load line in a different quadrant of a current-voltage plane; (4) applying respective outputs of the first and second slope detector circuits to a synchronizing resistor circuit that generates voltage differences corresponding to differences between each respective slope detector circuit and the chaotically modulated signal received in step (1); and (5) detecting an output from the synchronizing resistor circuit to provide a demodulated signal. - View Dependent Claims (13)
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14. A method of demodulating a chaotically modulated signal, comprising the steps of:
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(1) receiving the chaotically modulated signal; (2) applying the signal received in step (1) to an oscillator through a resistor that defines a current-voltage load line; (3) applying the signal applied to the oscillator in step (2) to a slope detector circuit that exhibits a current slope function opposite in polarity to that of the load line and which intersects the load line at an equilibrium point corresponding to an equilibrium point of a transmitter; (4) generating a difference signal representing a difference between the chaotically modulated signal received in step (1) and the output of the slope detector circuit; and (5) recovering an information signal on the basis of the difference signal generated in step (4). - View Dependent Claims (15)
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16. A method of transmitting information, comprising the steps of:
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(1) generating a chaotic carrier signal that causes a voltage to oscillate chaotically about a first equilibrium point in a current-voltage phase space of a circuit that exhibits a current-voltage characteristic curve on which the first equilibrium point falls; and (2) changing, in response to an information signal, a non-reactive resistive value in the circuit and thereby causing the first equilibrium point to shift to a shifted first equilibrium point in the current-voltage phase space.
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17. A chaotic transmitting circuit, comprising:
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an oscillator circuit; a resistor coupled to the oscillator circuit; a chaotic circuit, coupled to the oscillator circuit through the resistor, wherein the chaotic circuit exhibits a current-voltage characteristic shape having a slope that intersects a load line defined by the resistor and provides an equilibrium point about which a voltage oscillates chaotically; and means for changing the slope exhibited by the chaotic circuit in accordance with an information signal.
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18. A chaotic transmitting circuit, comprising:
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an oscillator circuit; a resistor coupled to the oscillator circuit; a chaotic circuit coupled to the oscillator circuit through the resistor, wherein the chaotic circuit exhibits a current-voltage characteristic shape having a slope that intersects a load line defined by the resistor and provides an equilibrium point about which a voltage oscillates chaotically; and a switch coupled to the chaotic circuit, wherein the switch changes a nonreactive resistive value in the chaotic circuit in accordance with an information signal and thereby causes the first equilibrium point to shift to a shifted first equilibrium point.
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19. A nonlinear circuit element for use in a chaotic transmitter, comprising:
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a first pair of diodes coupled in series and biased in a forward direction with respect to first and second circuit terminals; a second pair of diodes coupled in series and biased in a reverse direction with respect to the first and second circuit terminals; a first resistor coupled between the first pair of diodes and one of the circuit terminals; a second resistor coupled between the second pair of diodes and one of the circuit terminals; and an op amp coupled between the first and second circuit terminals through a resistive network; wherein the first resistor, the second resistor, and the resistive network have values selected to bias the nonlinear circuit element such that it exhibits a piecewise linear current-voltage characteristic across the first and second terminals.
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20. A chaotic transmitter, comprising:
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an oscillator; a resistor coupled to the oscillator; a chaotic circuit comprising a negative resistance, wherein the chaotic circuit is coupled to the oscillator circuit through the resistor; an isolation amplifier coupled to the chaotic circuit; a filter coupled to the output of the isolation amplifier that limits a frequency bandwidth present at the chaotic circuit; and means for modulating a circuit element of the chaotic transmitter in accordance with an information signal.
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21. A chaotic telephone device comprising:
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a chaotic transmitter that receives a first information signal and generates in response thereto a first chaotic trajectory shifted signal modulated in accordance with the first information signal; a chaotic receiver that receives a second chaotic trajectory shifted signal modulated in accordance with a second information signal and generates in response thereto a demodulated version of the second chaotic trajectory shifted signal; and an interface circuit that couples the chaotic transmitter and chaotic receiver to a radio-frequency telephone circuit, wherein the radio-frequency telephone circuit communicates with a ground-based telephone network through one or more radio frequency transmission stations.
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22. A method of communicating between a portable telephone device and a base station, comprising the steps of:
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(1) generating an information signal at the portable telephone device; (2) modulating a chaotic earner signal with the information signal using a chaotic trajectory shifting technique; (3) transmitting the chaotic trajectory shift-keyed signal generated in step (2) to the base station; and (4) in the base station, demodulating the transmitted signal to recover the information signal.
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23. A chaotic transmitter, comprising:
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a first chaotic circuit that generates a first chaotic signal having a first strange attractor trajectory; a second chaotic circuit that generates a second chaotic signal having a second strange attractor trajectory different from that of the first strange attractor trajectory; a switch coupled to the first and second chaotic circuits, wherein the switch selects either the first chaotic signal or the second chaotic signal in response to an information signal; and a low-pass filter coupled to the output of the switch.
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24. A method of transmitting an information signal, comprising the steps of:
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(1) generating a first chaotic signal comprising at least one strange attractor that oscillates about a first equilibrium point; (2) generating a second chaotic signal comprising at least a second strange attractor that oscillates about a second equilibrium point; (3) in response to the information signal, selecting an output of either the first chaotic signal or the second chaotic signal; and (4) transmitting the selected output from step (3).
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25. A method of transmitting information, comprising the steps of:
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(1) in response to receiving a time-varying N-bit code representing a unit of information, selecting a corresponding one of a plurality of 2N transmitters each of which generates a chaotic strange attractor signal that is distinct from others in the plurality of 2N transmitters; and (2) transmitting through a communications channel the chaotic strange attractor signal selected in step (1).
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26. A method of recovering information transmitted through a communication channel, comprising the steps of:
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(1) receiving a time-varying signal comprising discrete portions of each of a plurality of chaotic strange attractor signals; (2) matching the signal received in step (1) to one of a plurality of 2N receivers each of which is tuned to a different strange attractor signal; and (3) on the basis of the receiver matched in step (2), generating an N-bit code.
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27. A transmitting system capable of transmitting N bits of information, comprising:
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a plurality of 2N transmitters each of which generates a chaotic strange attractor signal that is distinct from others in the plurality of 2N transmitters; a switch which, in response to receiving a time-varying N-bit code representing a unit of information, selects a corresponding one of the plurality of 2N transmitters; and a transmission circuit that transmits the selected chaotic strange attractor signal across a transmission channel.
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28. A method of transmitting information, comprising the steps of:
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(1) generating a chaotic carrier signal characterized by a voltage that oscillates chaotically about a first equilibrium point in a current-voltage plane, wherein the first equilibrium point is defined by an intersection of a current-voltage load line having a first slope and a current-voltage slope line having a second slope opposite in polarity to that the of the first slope; (2) in response to a time-varying information signal comprising an N-bit symbol, selecting one of a plurality of 2N equilibrium points defined by successive intersections of a plurality of current-voltage slope lines having slopes opposite to that of the load line and that intersect the load line at different points; (3) shifting the first equilibrium point to the one selected equilibrium point such that the chaotic carrier signal oscillates chaotically about the one selected equilibrium point; and (4) transmitting the chaotic carrier signal shifted in step (3).
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29. Apparatus for transmitting a modulated chaotic signal, comprising:
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a computer that generates, in response to an information signal, a digital word comprising N bits; a digital-to-analog converter, coupled to the computer, that converts the digital word into an analog signal selected from one of 2N possible signal levels; and means for converting the analog signal into a chaotically oscillating signal that oscillates about a current-voltage equilibrium point defined by an intersection of a resistive load line and a current-voltage function uniquely defined by the analog signal.
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30. A method of interfacing a chaotic transmitting circuit to a communications channel without using a frequency filter, comprising the steps of:
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(1) buffering an output of the chaotic transmitting circuit to isolate the chaotic transmitting circuit from the communications channel; (2) removing a direct current voltage component from the buffered output obtained in step (1); and (3) matching the amplitude and impedance of the signal obtained from step (2) to the communications channel.
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31. Apparatus for interfacing a chaotic transmitting circuit to a communications channel without using a frequency filter, comprising:
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an isolation circuit that buffers an output of the chaotic transmitting circuit from the communications channel; a direct current power supply coupled to the isolation circuit through a resistor, wherein the direct current power supply subtracts a direct current voltage from the output of the isolation circuit; and an attenuator circuit, coupled to the direct current power supply, wherein the attenuator circuit attenuates a signal present at the direct current power supply prior to being introduced into the communications channel.
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32. A method of interfacing a chaotic receiving circuit to a communications channel without using a frequency filter, comprising the steps of:
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(1) buffering a modulated chaotic signal received from the communications channel to isolate the chaotic receiving circuit from the communications channel; (2) amplifying the buffered signal; and (3) adding a direct current component to the amplified buffered signal obtained in step (2), wherein the direct current component corresponds to a direct current component subtracted at a corresponding transmitter.
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33. Apparatus for interfacing a chaotic receiving circuit to a communications channel without using a frequency filter, comprising:
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a buffering circuit that buffers a modulated chaotic signal received from the communications channel to isolate the chaotic receiving circuit from the communications channel; an amplifier coupled to the buffering circuit that amplifies an output of the buffering circuit; and a direct current voltage offset circuit coupled to the amplifier, wherein the direct current voltage offset circuit adds a direct current component to the amplified buffered signal, wherein the direct current component corresponds to a direct current component subtracted at a corresponding transmitter.
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Specification