Constant Envelope Multiplexing for Three Equal-Power Signals
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Solution Overview
Problem
Existing satellite navigation systems face challenges in achieving constant envelope multiplexing of three equal-power signals, leading to power efficiency losses due to intermodulation components, which are treated as random noise, exceeding 25% power efficiency loss.
Innovation Solution
A method and apparatus for constant envelope multiplexing of three equal-power signals using a modulator to configure amplitudes and phases of in-phase and quadrature-phase components based on absolute sample values, with specific relationships for chip pulse waveforms, and a multiplexer to generate a constant envelope multiplexed output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple linear combination is used for multiplexing three or more signals, then device complexity is reduced, but constant envelope cannot be achieved and intermodulation components are added
Solution Approach 1:
The patent transforms the multiplexing approach by changing the parameter representation from simple linear combination to a parametric model where each signal is represented as si(t) = Ci·cos(ωt + θi). This parameterization enables systematic control of amplitude and phase relationships to achieve constant envelope while multiplexing three or more signals, resolving the contradiction between device simplicity and envelope constancy.
Solution Approach 2:
The patent moves from one-dimensional amplitude modulation to two-dimensional control by introducing both amplitude Ci and phase θi parameters for each signal. This dimensional expansion allows the multiplexer to achieve constant envelope by adjusting both magnitude and angular components, eliminating intermodulation distortion that plagues simple linear combination methods.
2Use of energy by moving object
If intermodulation components are added to achieve constant envelope, then power efficiency of high-power amplifier is maximized, but power efficiency loss occurs due to intermodulation power
Solution Approach 1:
The patent converts the harmful intermodulation components into beneficial phase relationships. By carefully selecting phase angles θi such that the intermodulation products constructively interfere rather than creating distortion, the system achieves constant envelope without the usual power efficiency penalties. The intermodulation energy is redirected to support the constant envelope requirement rather than being wasted as distortion.
Solution Approach 2:
The patent optimizes power efficiency by adjusting the amplitude parameters Ci and phase parameters θi to satisfy the constant envelope condition while maximizing the useful signal power. The specific relationship Ci² = (2/3)·(1-γ)·Pavg and θ2 - θ1 = π/3 are derived to ensure that the multiplexed signal maintains constant envelope with minimum power loss, allowing the high-power amplifier to operate at peak efficiency.
3Use of energy by moving object
If constant envelope multiplexing is implemented for three equal-power signals, then power efficiency is maximized, but signal design flexibility is constrained
Solution Approach 1:
The patent introduces dynamic phase relationships where the phase difference between signals is fixed at π/3 (60 degrees) rather than being arbitrary. This dynamic constraint allows the system to maintain constant envelope while still permitting independent design of each signal's spectrum and interference characteristics through the amplitude parameters Ci, providing flexibility within the constant envelope framework.
Solution Approach 2:
The patent maintains signal design flexibility by allowing independent selection of amplitude parameters Ci subject to the constraint Ci² = (2/3)·(1-γ)·Pavg. This parametric freedom enables engineers to optimize each signal's spectral characteristics and interference properties while the system automatically maintains constant envelope through the derived phase relationships, balancing power efficiency with design adaptability.
Data Source
AI summary
A satellite navigation signal generation apparatus may comprise: a signal generator generating a first satellite navigation signal, a second satellite navigation signal, and a third satellite navigation signal; a modulator modulating signals with same phases, which are generated by configuring an amplitude and a phase of an in-phase component and an amplitude and a phase of a quadrature-phase component based on a relationship of absolute sample values corresponding respectively to variable instantaneous powers of the first to third satellite navigation signals, into different chip pulse waveforms; and a multiplexer performing constant envelope multiplexing on the satellite navigation signals modulated by the modulator, wherein the modulator performs chip pulse modulation in which the absolute sample value of the first satellite navigation signal and the absolute sample value of the second satellite navigation signal have a first value A and a second value B with a frequency of 0.5, respectively.