Constant Envelope Walsh Modulation for RF Power Efficiency
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Solution Overview
Problem
Current radio systems face challenges in maintaining constant envelope waveforms while achieving adequate capacity and robustness, particularly in high-performance radio networks and handheld devices, where peak-to-average power ratio limitations restrict the efficiency of RF amplifiers.
Innovation Solution
The implementation of a transmitter and receiver system using Fast Walsh Transform (FWT) for orthogonal Walsh modulation, which spreads data evenly over frequencies, combined with FM modulation and a square root raised cosine filter to reduce peak-to-average power ratio, and a phase demodulator with phase unwrapping to maintain constant envelope and increase capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If constant envelope waveforms are used to improve power amplifier efficiency, then power efficiency is improved, but capacity and robustness deteriorate
Solution Approach 1:
The data stream is segmented into multiple parallel channels using orthogonal Walsh functions. Each channel carries a portion of the data and is modulated independently. This segmentation allows the system to maintain constant envelope properties while increasing overall capacity through parallel transmission paths.
Solution Approach 2:
The patent transitions from single-carrier modulation to multi-carrier orthogonal modulation using Walsh functions. By adding the dimension of orthogonality in the frequency domain, the system achieves both constant envelope maintenance and enhanced capacity through multiple orthogonal channels that can be independently processed.
2Use of energy by moving object
If peak-to-average power ratio is reduced to improve amplifier efficiency, then power efficiency is improved, but signal capacity deteriorates
Solution Approach 1:
The patent changes the modulation parameter from conventional amplitude or phase modulation to constant envelope orthogonal Walsh modulation. By using Walsh functions with constant amplitude properties and orthogonal characteristics, the system achieves low peak-to-average power ratio while maintaining high signal capacity through the orthogonality of multiple channels.
Solution Approach 2:
The patent combines multiple orthogonal Walsh channels into a composite modulated signal. Each channel contributes to the overall capacity while the composite signal maintains constant envelope properties. This composite approach allows the system to achieve both power efficiency and high signal capacity simultaneously.
3Productivity
If orthogonal Walsh modulation is used to increase capacity, then data rate is improved, but complexity of modulation scheme increases
Solution Approach 1:
The patent applies preliminary orthogonal encoding using Walsh functions at the transmitter before transmission. The orthogonal codes are pre-assigned to different channels, and the modulation scheme uses these pre-defined orthogonal sequences. This preliminary action simplifies the transmission process while enabling high capacity through orthogonal multiplexing.
Solution Approach 2:
The patent introduces orthogonal Walsh functions as intermediary carriers for data transmission. These Walsh functions serve as mediators that enable multiple data streams to be transmitted simultaneously without interference. The orthogonal properties of these intermediary functions simplify the separation and processing of multiple channels at the receiver.
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 a communications symbol using the Fast Walsh Transform. A frequency modulation circuit frequency modulates the communications symbols wherein a constant envelope orthogonal Walsh modulated communications signal is generated having a plurality of orthogonal waveforms each forming a separate Walsh communications channel.