Chaotic Communication System with Modulation of Nonlinear Elements
First Claim
1. A method of transmitting information, comprising the steps of:
- (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 by;
generating a chaotic carrier signal that oscillates about one of two equilibrium points in the current-voltage phase space; 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 by causing both equilibrium points to shift in the current-voltage phase space.
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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
61 Claims
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1. 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 by;
generating a chaotic carrier signal that oscillates about one of two equilibrium points in the current-voltage phase space; 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 by causing both equilibrium points to shift in the current-voltage phase space. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 39, 42, 45, 48, 51)
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12. 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 that includes means for switching a plurality of resistive values. - View Dependent Claims (13, 14, 15, 16, 17, 40, 43, 46, 49, 52)
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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, wherein the chaotic circuit comprises a diode circuit that exhibits a negative piecewise linear resistance; 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. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 41, 44, 47, 50, 53)
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26. 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;
an op amp coupled between the first and second circuit terminals through a resistive network;
a fourth resistor coupled to the resistive network; and
a switch that couples the fourth resistor into the resistive network, thus changing a slope of the piecewise linear current-voltage characteristic of the nonlinear circuit element in response to an information signal, 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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27. 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 carrier signal with the information signal using a chaotic trajectory shifting technique by changing a non-reactive resistive value in a chaotic circuit element to cause a strange attractor trajectory shift; and
(3) transmitting the chaotic trajectory shift-keyed signal generated in step (2) to the base station. - View Dependent Claims (28, 29, 30, 31, 32, 61)
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33. 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;
a low-pass filter coupled to the output of the switch; and
a summing circuit coupled between the switch and the low-pass filter, wherein the summing circuit sums the output from the switch. - View Dependent Claims (34, 35)
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36. 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;
(4) transmitting the selected output from step (3); and
(5) filtering the output selected in step (3). - View Dependent Claims (37, 38)
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54. 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 by changing a nonreactive circuit value in a chaotic circuit coupled to a resistor that defines the current-voltage load line; and
(4) transmitting the chaotic carrier signal shifted in step (3). - View Dependent Claims (55)
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56. 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) by using a direct current power supply and an attenuator circuit; and
(3) matching the amplitude and impedance of the signal obtained from step (2) to the communications channel. - View Dependent Claims (57)
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58. 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, wherein the communications channel comprises a radio frequency channel. - View Dependent Claims (59, 60)
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Specification