Carrier Extraction Circuit for Shared TM and Modulated Signals
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Solution Overview
Problem
Existing modulation techniques struggle to efficiently combine and separate transpositional modulation (TM) signals with traditional modulation signals on the same carrier, often requiring a priori information about the carrier signal and being limited by interference and bandwidth constraints.
Innovation Solution
The method involves extracting a carrier signal from a modulated input, modifying its frequency using a difference signal, and combining it with a TM signal, allowing for the transmission and reception of TM signals without interfering with traditional modulation schemes, using a CAREX circuit and heterodyning to maintain minimal frequency difference and separate the TM signal effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carrier suppression is used to increase bandwidth efficiency, then spectral efficiency is improved, but carrier extraction becomes difficult without a priori information
Solution Approach 1:
The patent introduces an intermediary frequency estimation process that acts as a mediator between the suppressed carrier signal and the extraction process. By estimating the center frequency of the modulated signal and using it to generate a local oscillator signal, the system creates an intermediary reference that enables carrier extraction without requiring the carrier to be present in the transmitted signal.
Solution Approach 2:
The patent replaces the mechanical approach of directly extracting the carrier from the modulated signal with an electronic signal processing approach. Instead of relying on the physical presence of the carrier, the system uses digital signal processing techniques including frequency estimation, local oscillator generation, and mixing to electronically reconstruct and extract the carrier signal.
2Productivity
If multiple modulation signals are combined on a single carrier frequency, then bandwidth utilization is improved, but signal interference increases
Solution Approach 1:
The patent segments the combined modulated signal into separate components by estimating the center frequency and using it to generate distinct local oscillator signals for each modulation type. This frequency-based segmentation allows different modulation signals (QAM, PSK, FM) to be separated and processed independently, eliminating interference while maintaining bandwidth efficiency.
Solution Approach 2:
The patent implements feedback through an iterative frequency estimation and adjustment process. The system estimates the center frequency, generates local oscillator signals, processes the modulated signals, and uses the results to refine frequency estimates for subsequent processing. This feedback mechanism ensures accurate separation of combined signals and minimizes interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases bandwidth by allowing two differently modulated signals to share a carrier frequency, enables carrier extraction with minimal information about the modulated signal, and separates TM signals from traditional modulation without interference, appearing as noise to non-TM receivers.
Implementation Method 1
multiplying the input signal with a third signal to create a fourth signal, and converting the fourth signal into a direct current (DC) voltage signal representing the center frequency of the modulated signal by integrating the fourth signal
Implementation Method 2
modifying the frequency of the second signal based on the difference signal to provide the carrier signal
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.