Carrier Signal Extraction for Suppressed and Mixed Modulation
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Solution Overview
Problem
Existing carrier modulation techniques face challenges in efficiently extracting and managing carrier signals from modulated signals, particularly when the carrier is suppressed or when little a priori information about the modulated signal is available, limiting the ability to combine different modulation types on a single carrier frequency and increasing bandwidth effectively.
Innovation Solution
The method involves detecting the center frequency of an input signal, generating a difference signal with a signal generator, and modifying the frequency of a second signal to extract and modulate the carrier signal with a transpositional modulation (TM) signal, allowing for the combination and separation of TM signals from traditional modulation schemes without interfering with existing signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional modulation techniques are used, then information can be transmitted, but the carrier signal cannot be efficiently extracted when suppressed or when little a priori information is available
Solution Approach 1:
The patent creates a universal carrier extraction system that works across multiple modulation types (AM, FM, PM, QAM, OFDM) without requiring modulation-specific processing. The system uses general-purpose operations like FFT, autocorrelation, and zero-crossing detection that are applicable to any modulated signal, making the extraction method versatile and adaptable to different modulation schemes while maintaining high accuracy
Solution Approach 2:
The system extracts carrier signals from the modulated signal itself using intrinsic properties of the signal (symmetry, periodicity, spectral characteristics) without requiring external reference signals or prior knowledge of the modulation type. The modulated signal serves its own carrier extraction needs through self-contained processing operations
2Quantity of substance
If carrier signals are suppressed in modulated signals, then bandwidth efficiency is improved, but the ability to extract and manage carrier signals deteriorates
Solution Approach 1:
The patent replaces direct carrier signal presence (mechanical/physical carrier) with mathematical/signal processing methods to detect and reconstruct the carrier. Instead of relying on the physical carrier being present in the transmitted signal, the system uses computational techniques (FFT, autocorrelation, zero-crossing detection) to mathematically derive the carrier frequency and reconstruct the carrier signal from the modulated signal's spectral characteristics
Solution Approach 2:
The system combines multiple signal processing techniques (FFT for spectral analysis, autocorrelation for periodicity detection, zero-crossing detection for frequency estimation) to create a composite extraction method that is more robust than any single technique alone, enabling accurate carrier recovery even when the carrier is completely suppressed
3Quantity of substance
If multiple modulation types are combined on a single carrier frequency, then bandwidth utilization is increased, but signal separation and management become more complex
Solution Approach 1:
The patent segments the combined modulated signal into individual modulation components through systematic processing: first extracting the carrier frequency from the composite signal, then using this carrier as a reference to separately demodulate and identify each modulation type present. This segmentation approach breaks down the complex separation task into manageable steps, reducing overall system complexity while enabling multi-modulation support
Data Source
AI summary
Methods, systems, and apparatus for detecting a center frequency of an input signal, the input signal including a carrier signal modulated with a modulation signal. Detecting a frequency of a second signal. Determining a difference signal between the center frequency of the input signal and the frequency of the second signal. Modifying the frequency of the second signal based on the difference signal to provide the carrier signal. And, outputting the carrier signal.