Chaotic Spread Spectrum Signal Constant Envelope Modulation
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Solution Overview
Problem
Existing communication systems with fixed operational parameters are inefficient and susceptible to interference, particularly in non-line-of-sight channels, and suffer from low throughput due to the limitations of analog chaotic circuits and high peak-to-average power ratio (PAPR) in chaotic spread spectrum signals.
Innovation Solution
A communication method using a chaotic spread spectrum system with a spreading sequence of constant magnitude and variable phase angle, dynamically adjusting the peak-to-average power ratio (PAPR) based on signal-to-interference ratio, to enhance transmitter gain and resistance to interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If analog chaotic circuits are used to generate chaotic signals, then chaotic communication systems can be implemented, but the throughput is limited due to circuit drift requiring constant state information transfer
Solution Approach 1:
The patent replaces analog chaotic circuits with a digital chaotic signal generator that uses a nonlinear congruential generator with modular arithmetic operations. This substitution eliminates the drift problem inherent in analog circuits, allowing for higher data throughput without requiring constant state information transfer for synchronization, as the digital system maintains stability through its mathematical structure
Solution Approach 2:
The patent changes the fundamental parameter of chaotic signal generation from analog continuous-time circuits to digital discrete-time mathematical operations. By using modular arithmetic and nonlinear congruential generators, the system achieves parameter stability without drift, enabling higher throughput while maintaining synchronization reliability through deterministic digital operations
2Productivity
If chaotic spread spectrum signals are transmitted with high average power, then data throughput is improved, but signal distortion increases due to high peak-to-average power ratio
Solution Approach 1:
The patent applies constant envelope modulation to the chaotic spread spectrum signal, changing the amplitude parameter to remain constant while varying only the phase. This parameter change eliminates signal distortion caused by high peak-to-average power ratio, allowing the system to transmit at high average power levels without distortion, thereby improving data throughput
Solution Approach 2:
The patent transitions from varying the amplitude dimension of the signal to varying the phase dimension while maintaining constant amplitude. This dimensional shift moves the signal variation from the amplitude domain to the phase domain, eliminating peak power issues while preserving the chaotic spread spectrum properties needed for high throughput communication
3Ease of manufacture
If conventional PRNG is used to generate spreading codes, then digital implementation is achieved, but cyclostationary features reduce security and robustness
Solution Approach 1:
The patent changes the mathematical parameters of the number generator by using a nonlinear congruential generator with modular arithmetic operations instead of a conventional linear PRNG. This parameter change eliminates the cyclostationary features present in conventional PRNG outputs, providing truly random-like sequences that enhance security and robustness while maintaining full digital implementation
Solution Approach 2:
The patent substitutes the conventional linear PRNG mechanism with a nonlinear chaotic map based on modular arithmetic. This substitution replaces the predictable, cyclostationary output of conventional PRNG with a digitally implemented chaotic sequence that has superior randomness properties, enhancing security while maintaining digital implementation ease
Data Source
AI summary
Systems (100) and methods (700) for providing a communications link with a power-limited communication transmitter (102) positioned remotely from an intended receiver system (104). The methods involve channel encoding a carrier signal with data provided at the power-limited communication transmitter to form an information signal. The methods also involve generating a chaotic spreading sequence based on a chaotic number sequence. The chaotic spreading sequence has a magnitude that is constant and a variable arbitrary phase angle comprising phase values which are uniformly distributed over a predetermined range of angles. A spread spectrum signal is formed by multiplying the information signal by the chaotic spreading sequence. The spread spectrum signal has an adjustable amplitude characteristic and a zero autocorrelation. The spread spectrum signal is transmitted from the power-limited communication transmitter to the intended receiver system.