Non-Contiguous Spectral-Band Modulation for Spectral Growth Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The transmission of information over non-contiguous frequency bands faces challenges with spectral growth due to non-linearities in power amplifiers, leading to increased signal content outside desired frequency bands, which affects data rate and reliability.
Innovation Solution
A non-contiguous spectral-band modulator that maps input symbols to phase values, generates a constant modulus signal sequence, and applies a weighting sequence to constrain the output signal to a specific region in the complex plane, reducing spectral content and allowing the power amplifier to operate in a more linear range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If information is transmitted over non-contiguous frequency bands, then data rate and reliability are improved, but spectral growth occurs due to power amplifier non-linearities
Solution Approach 1:
The patent applies preliminary action by pre-shaping the signal waveform before amplification to ensure that the signal remains within the linear operating range of the power amplifier. The modulator generates waveforms with controlled amplitude variations and smooth transitions between subbands, preventing the amplifier from entering non-linear regions that would cause spectral growth. This preliminary conditioning of the signal eliminates the need for post-amplification spectral correction.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the signal's amplitude and frequency parameters during transmission. The modulator varies the instantaneous frequency and amplitude of the carrier wave according to the information signal while maintaining the envelope within linear amplifier bounds. This parameter control ensures that the amplified signal remains spectrally confined to the desired non-contiguous bands without generating excessive out-of-band emissions.
2Loss of energy
If power amplifier operates at high efficiency, then energy consumption is reduced, but non-linearities increase causing spectral growth
Solution Approach 1:
The patent resolves this contradiction by changing the operational parameters of the power amplifier. Instead of operating the amplifier at its maximum efficiency point with high peak power, the system uses continuous wave modulation with controlled amplitude variations. The signal is designed to maintain a relatively constant envelope that keeps the amplifier operating in a quasi-linear region, sacrificing some peak efficiency for reduced spectral regrowth and improved linearity.
Solution Approach 2:
The patent applies beforehand cushioning by designing the modulation waveform to anticipate and prevent non-linear distortion before it occurs. The signal transitions between subbands are smoothed with appropriate filtering and amplitude control, creating a cushioning effect that prevents the amplifier from being driven into non-linear operation. This proactive waveform design eliminates spectral growth before it can be generated by the amplifier.
3Reliability
If signal amplitude is increased for better signal quality, then reliability is improved, but non-linear distortion increases causing spectral growth
Solution Approach 1:
The patent applies parameter changes by separating the control of signal amplitude and frequency parameters. The modulation scheme varies the instantaneous frequency to encode information while maintaining the amplitude within a controlled range that ensures both good signal quality and linear amplifier operation. This decoupling of amplitude and frequency control allows the system to achieve reliable transmission without the amplitude excursions that would cause non-linear distortion and spectral growth.
Data Source
AI summary
Embodiments of a non-contiguous spectral-band modulator and method for non-contiguous spectral-band modulation are generally described herein. In some embodiments, an input symbol tuple may be mapped to a sequence of phase values. Each value of the sequence of phase values may represent an instantaneous frequency of a waveform for a signal with a power spectral density that is substantially constrained to the two or more subbands of a non-contiguous spectrum. The values of the sequence of phase values may be accumulated and a phase-sample sequence representing phase samples of a transmit waveform may be generated. An exponentiation may be performed on the phase-sample sequence to generate a constant modulus signal sequence. An output signal sequence is generated that is constrained to a region in the complex plane, such as an annulus, when the signal is in a subband. The output signal sequence may be shaped to constrain spectral energy during transitions between subbands.