Chaotic Amplitude Modulation Signal Generation
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Solution Overview
Problem
Conventional spread spectrum communications signals are vulnerable to security compromise due to detectable statistical, higher order, and cyclostationary features, and amplitude modulated waveforms can induce unwanted detection due to cyclostationary features, limiting data throughput and security.
Innovation Solution
Generating a chaotic amplitude modulated signal with a constant power envelope using orthogonal chaotic spreading sequences and discrete time baseband modulation, such as quadrature amplitude modulation, to create a signal with no detectable cyclostationary features, thereby enhancing security and data throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If amplitude modulation is used to increase data throughput, then data throughput is improved, but cyclostationary features are introduced that compromise security
Solution Approach 1:
The patent applies parameter changes by transforming the amplitude modulation signal into a constant envelope representation. Specifically, the signal is converted from varying amplitude PAM symbols to a constant envelope format where the information is encoded in phase or frequency rather than amplitude, thereby eliminating cyclostationary features while preserving data throughput capability
Solution Approach 2:
The patent substitutes the traditional amplitude-based modulation mechanism with a phase or frequency-based mechanism. By replacing amplitude variation with phase/frequency modulation, the system achieves high data throughput without introducing detectable cyclostationary features, thus resolving the security throughput tradeoff
2Object-affected harmful factors
If PSK modulation is used to eliminate cyclostationary features, then security is improved, but data throughput is limited
Solution Approach 1:
The patent creates a universal signal representation that can accommodate multiple modulation schemes while maintaining constant envelope properties. The constant envelope signal framework serves as a universal basis that can encode information through various mechanisms (phase, frequency, time-varying phase) without introducing cyclostationary features, thereby achieving high throughput without sacrificing security
3Ease of manufacture
If conventional pseudorandom sequences are used for spreading, then implementation is simple, but statistical and higher order features make the signal vulnerable to detection
Solution Approach 1:
The patent transforms the statistical properties of the spreading sequence by converting it from a conventional pseudorandom sequence with detectable higher-order moments to a chaotic sequence with specifically engineered statistical properties. The chaotic sequence is designed to have zero skewness and excess kurtosis, eliminating detectable features while maintaining the spreading function
Solution Approach 2:
The patent creates a chaotic spreading sequence that copies the essential spreading function of conventional pseudorandom sequences while possessing fundamentally different statistical properties. The chaotic sequence replicates the noise-like characteristics and spreading capability without the detectable cyclostationary and higher-order features present in conventional sequences
Data Source
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AI summary
Systems (400, 500, 600) and methods (300) for generating a chaotic amplitude modulated signal absent of cyclostationary features by preserving a constant variance. The methods involve: generating a PAM signal including pulse amplitude modulation having a periodically changing amplitude; generating a first part of a constant power envelope signal (FPCPES) by dividing the PAM signal by a square root of a magnitude of the PAM signal; generating a second part of the constant power envelope signal (SPCPES) having a magnitude equal to a square root of one minus the magnitude of the PAM signal; and generating first and second spreading sequences (FSS and SSS). The methods also involve combining the FPCPES with the FSS to generate a first product signal (FPS) and combining the SPCPES with the SSS to generate a second product signal (SPS). A constant power envelope signal is generated using the FPS and SPS.