Shortwave Demodulation via Multi-Carrier Signal Merging
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Solution Overview
Problem
Shortwave band communication is unstable due to the constantly changing state of the ionosphere, affecting radio wave transmission quality as radio waves may pass through or be reflected by the ionosphere, and their behavior varies with frequency, leading to inconsistent signal reception.
Innovation Solution
A demodulation method and apparatus that detects and extracts signals from multiple carrier waves, generates a target demodulation signal by comparing waveforms of received signals, and performs demodulation to improve signal accuracy and stability, using a communication system with transmitters and receivers that superimpose messages on carrier waves and transmit them at different times based on a schedule.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If shortwave band communication uses ionosphere reflection for long-distance transmission, then transmission distance is extended, but transmission stability deteriorates due to constantly changing ionosphere state
Solution Approach 1:
The patent combines signals from multiple carrier waves (first carrier wave and second carrier wave) transmitted at different times into a single demodulation signal. By superimposing multiple extracted signals and performing unified demodulation, the system merges redundant information to achieve more stable communication despite ionospheric variations.
Solution Approach 2:
The patent performs preliminary extraction of signals from multiple carrier waves before demodulation. The extraction unit extracts signals from both first and second carrier waves in advance, storing them for subsequent combination and demodulation processes, which helps mitigate the effects of ionospheric changes before they fully impact the communication quality.
2Measurement precision
If multiple carrier waves are transmitted at different times, then signal accuracy is improved through waveform comparison, but communication time increases
Solution Approach 1:
The patent maintains continuous communication by overlapping transmission time periods of the first and second carrier waves. The transmission time periods are configured to overlap, ensuring that useful communication action continues without interruption while enabling signal comparison and combination for improved accuracy.
Solution Approach 2:
The patent transmits redundant information through multiple carrier waves with overlapping time periods. This excessive transmission of the same message through different carriers allows for signal comparison and combination, improving signal accuracy at the cost of additional transmission time and resources.
Data Source
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AI summary
A non-transitory computer-readable recording medium on which a program is recorded for a causing a processor to execute a demodulation process. The demodulation process includes detecting a preamble of a wireless signal transmitted from a first transmission station by way of a short wavelength carrier wave, extracting a first signal superimposed on the short wavelength carrier wave, the first signal being extracted from a wireless signal that is identified in accordance with the detection of the preamble, extracting a second signal superimposed on a carrier wave transmitted from a second transmission station, and performing demodulation on a target demodulation signal obtained by superimposing the first signal on the second signal.