Composite BOC Signal Cross Spectral Term Reduction
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Solution Overview
Problem
Existing satellite navigation systems face interference issues due to significant cross spectral terms in the power spectral density of composite binary offset carrier (BOC) signals, which hinder the realization of a common power spectral density for different satellite navigation systems.
Innovation Solution
The method involves generating a composite BOC waveform by arranging the states of first and second BOC signals over subsequent time intervals to be complementary to their current states, thereby reducing or eliminating cross spectral terms and achieving a common power spectral density similar to time division multiplex BOC signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If composite BOC signals are used to modulate carrier signals in satellite navigation systems, then signal transmission capability is improved, but cross spectral terms in the power spectral density increase causing interference
Solution Approach 1:
The patent applies periodic action by using time-division multiplexing to alternately transmit different BOC signals (e.g., BOC(1,1) and BOC(6,1)) in periodic time slots. This periodic transmission structure eliminates cross-spectral terms between different satellite navigation systems while maintaining signal transmission capability, as the signals are separated in time rather than overlapping in frequency.
Solution Approach 2:
The patent segments the composite BOC signal into separate time-division multiplexed components, dividing the transmission into distinct time slots for different BOC signals. This segmentation prevents the spectral overlap that causes interference, allowing each signal component to be transmitted without cross-spectral interference while preserving overall system performance.
2Adaptability or versatility
If multiple BOC signals are combined in composite modulation, then signal versatility is improved, but power spectral density commonality across different satellite navigation systems deteriorates
Solution Approach 1:
The patent uses periodic time-division multiplexing to transmit different BOC signals in alternating time slots, creating a periodic transmission pattern. This approach maintains versatility by supporting multiple BOC signal types while ensuring that the overall power spectral density conforms to a common standard, as the periodic structure prevents spectral contamination between different signal types.
Solution Approach 2:
The patent transitions from frequency-domain multiplexing to time-domain multiplexing, changing the dimension in which multiple signals are combined. By separating signals in the time dimension rather than the frequency dimension, the system achieves both signal versatility and power spectral density commonality, as the time-division approach eliminates cross-spectral terms while maintaining compatibility with common spectral masks.
3Productivity
If conventional composite BOC modulation is used, then signal processing capability is improved, but interference between different satellite navigation systems increases
Solution Approach 1:
The patent implements periodic time-division multiplexing where different BOC signals are transmitted in alternating periodic time slots. This periodic separation eliminates cross-spectral interference between GPS, Galileo, and other satellite navigation systems while maintaining signal processing capability, as receivers can process each signal type independently during its designated time slot without interference from other systems.
Solution Approach 2:
The patent segments the composite signal transmission into separate time-division multiplexed channels for different satellite navigation systems. This segmentation isolates the spectral content of each system, preventing interference while allowing receivers to process each segmented signal component with optimized algorithms tailored to specific BOC signal characteristics.
Data Source
AI summary
Embodiments of the present invention provide a method to produce a modulation signal comprising combining at least two modulation signals, for example, BOCs or derivatives thereof, having portions (chip or a number of chips) thereof with respective relative phases or states ({++,−−} and {+−,−+}) selected such that the average of a plurality of said portions at least reduces cross spectral terms of the composite complex spectrum of said at least two modulation signals.