Constant Radius Orthogonal Walsh Modulation for RF Power Efficiency
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Solution Overview
Problem
Current radio systems face performance limitations due to peak-to-average power ratio issues in RF amplifiers, especially in high-capacity and robust communication networks, where constant envelope waveforms are desirable but often result in reduced capacity and efficiency, particularly in battery-operated devices.
Innovation Solution
The implementation of a transmitter and receiver system using constant radius orthogonal Walsh modulation, which employs a Fast Walsh Transform to encode and frequency spread communications symbols, combined with frequency modulation and a square root raised cosine filter to limit bandwidth and reduce peak-to-average power ratio, while maintaining a constant envelope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If constant envelope waveforms are used, then power efficiency is improved, but capacity is reduced
Solution Approach 1:
The patent segments the frequency spectrum into multiple orthogonal frequency components (subcarriers) and distributes data across these segments using Walsh-Hadamard coding. This allows the system to maintain constant envelope while achieving high capacity through frequency diversity and orthogonal signaling.
Solution Approach 2:
The patent transitions from time-domain modulation to frequency-domain modulation by using orthogonal frequency components. This dimensional shift enables constant envelope waveforms to carry information through frequency variations rather than amplitude variations, resolving the capacity limitation.
2Device complexity
If traditional GMSK techniques are used, then implementation simplicity is maintained, but performance is limited
Solution Approach 1:
The patent replaces traditional time-domain GMSK modulation with frequency-domain orthogonal Walsh-Hadamard modulation. This substitution uses mathematical transforms (Fast Walsh-Hadamard Transform) instead of complex analog modulation circuits, achieving superior performance with comparable or simpler digital implementation.
Solution Approach 2:
The patent changes the fundamental modulation parameter from phase/ amplitude (GMSK) to frequency and orthogonal coding (Walsh-Hadamard). This parameter transformation enables higher spectral efficiency and robustness while maintaining implementation simplicity through digital signal processing.
3Use of energy by moving object
If peak-to-average power ratio is reduced, then power efficiency is improved, but data rate is reduced
Solution Approach 1:
The patent segments data into multiple parallel Walsh-Hadamard coded streams that are transmitted simultaneously across different frequency components. This segmentation allows the system to achieve high data rates through parallel transmission while maintaining constant envelope and low peak-to-average power ratio.
Solution Approach 2:
The patent uses periodic Walsh-Hadamard coding sequences that repeat every symbol period. This periodic structure enables efficient power distribution across time and frequency, maintaining constant envelope while achieving high spectral efficiency through the periodic orthogonal coding pattern.
Data Source
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AI summary
A radio device includes a transmitter having a modulator for generating M-PAM communications symbols containing communications data. A Fast Walsh Transform circuit orthogonally encodes and band-spreads the communications symbols using the Fast Walsh Transform. A frequency modulation circuit frequency modulates the communications symbols wherein a constant radius orthogonal Walsh modulated communications signal containing the communications data is generated.