Compensation Filtering for Constant-Envelope Data Transmission
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Solution Overview
Problem
In data communication systems, especially in mobile communication, frequency multiplexing leads to interference between signals in different channels due to undesired frequency components outside the used transmission channel, which are not effectively suppressed by existing methods, resulting in noise and inefficiencies in power amplification.
Innovation Solution
A method and device that generate a modulated carrier signal with a constant envelope waveform, which is filtered to create a compensation signal that is subtracted from the amplified transmission signal to remove unwanted frequency components, thereby reducing interference without altering the signal's spectral shape or efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency multiplexing is used to allow multiple communication in distinct frequency channels, then communication capacity is improved, but interference between adjacent channels occurs due to undesired frequency components outside the used channel
Solution Approach 1:
The patent extracts and removes the harmful spectral image components from the transmitted signal by generating a compensation signal that contains only these unwanted frequency components and subtracting it from the original signal, thereby eliminating inter-channel interference while preserving the useful signal
Solution Approach 2:
The patent introduces a compensation signal as an intermediary element that mediates between the transmitted signal and the desired clean signal. This compensation signal acts as a subtractive component that removes harmful spectral images without affecting the main signal content
2Productivity
If linear modulation methods (QPSK, 8-PSK, QAM) are used, then data transmission efficiency is improved, but non-linear characteristics of the power amplifier broaden the spectral range and increase back-off requirements
Solution Approach 1:
The patent extracts the harmful spectral broadening effects caused by amplifier non-linearities by generating a compensation signal that contains only the unwanted frequency components, allowing the use of efficient linear modulation methods without suffering from spectral broadening penalties
3Stability of the object's composition
If continuous phase modulation methods with time limited phase pulses are used, then constant envelope waveform is achieved, but the signal spectrum becomes relatively broad
Solution Approach 1:
The patent removes the harmful broad spectral components by generating a compensation signal that contains only the unwanted frequency parts outside the transmission channel and subtracting it from the modulated signal, thereby narrowing the effective spectral range while preserving the constant envelope property
4Object-generated harmful factors
If signals with optimized shape are used to narrow the spectral range, then spectral efficiency is improved, but the transmission method becomes more noise sensitive
Solution Approach 1:
The patent creates a copy of the modulated signal through the compensation path, processes this copy to extract only the unwanted frequency components, and subtracts it from the original signal. This copying approach allows spectral shaping without directly modifying the original signal format, thereby maintaining noise performance
Data Source
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AI summary
A new method for transmitting data (ak) is provided, wherein along a transmission path (2): (i) a modulated carrier signal (s(t)) is generated based on the data (ak) to be transmitted, the carrier signal (s(t)) having a carrier frequency (fS) within a given transmission channel, which is comprised of a number of frequencies (f), and (ii) the modulated carrier signal (s(t)) is amplified to a transmission signal (p(t)), wherein along a compensation path (3): (i) the modulated carrier signal (s(t)) is filtered, whereby the frequency components within the transmission channel are removed, and (ii) at least one of a phase (φ), an amplitude (α) and a delay (τ0) of the filtered signal (sH(t)) is modified thereby generating a compensation signal (c(t)), and wherein the compensation signal (c(t)) is subtracted from the transmission signal (p(t)) thereby generating a compensated transmission signal (v(t)), and wherein the compensated transmission signal (v(t)) is transmitted. Also a respective data transmission device (1, 25, 30) is disclosed.