Frequency-Modulated Signal Transmission via Pilot Tone Offset
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Solution Overview
Problem
In radio transmission systems, frequency-modulated signals are often extinguished at the receiving antenna due to multipath propagation, leading to increased noise floors and loss of the transmitted signal, particularly in static channels where the carrier frequency remains unchanged.
Innovation Solution
A transmitting apparatus that generates a pilot tone with a frequency outside the range of the modulating useful signal, ensuring a minimum frequency deviation and combining it with the useful signal to create a frequency-modulated signal, thereby preventing signal extinction by varying the carrier frequency even in static channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency modulation is used to transmit signals, then the signal can be modulated to carry information, but the carrier signal may be extinguished at the receiving antenna due to multipath propagation
Solution Approach 1:
The patent applies parameter changes by introducing a pilot tone with a specific frequency offset from the carrier frequency. This frequency offset parameter is designed to be outside the frequency range of the modulating useful signal, causing the frequency-modulated signal to vary its frequency range over time. This prevents the signal from being extinguished at the receiving antenna by ensuring the carrier frequency never remains static at a single point, thereby avoiding multipath propagation issues while maintaining reliable signal transmission.
2Device complexity
If the carrier frequency is kept constant in static channels, then the transmission is simple, but the carrier may linger at the extinguishing frequency causing interference
Solution Approach 1:
The patent implements periodic action by having the frequency-modulated signal continuously vary its frequency range through the superposition of the pilot tone and useful signal. The pilot tone's frequency, being outside the useful signal's frequency range, ensures the combined signal's frequency constantly changes rather than remaining static. This periodic frequency variation prevents the carrier from lingering at extinguishing frequencies, eliminating interference while maintaining relatively simple transmission system architecture.
3Measurement precision
If pilot tones are used for channel estimation in digital transmission, then the channel transfer function can be estimated, but the pilot tones are evaluated differently from analog transmission methods
Solution Approach 1:
The patent applies universality by designing the pilot tone to serve multiple functions simultaneously: (1) it acts as a reference signal for channel estimation, (2) it prevents signal extinction by varying the frequency range of the frequency-modulated signal, and (3) it enables interference spike correction through linear interpolation. The pilot tone's frequency is specifically chosen to be outside the useful signal's frequency range, allowing it to perform these multiple functions without interfering with the useful signal transmission, thus simplifying signal evaluation while maintaining precise channel estimation.
Data Source
AI summary
A transmitting apparatus for transmitting a frequency-modulated signal is provided. The transmitting apparatus includes a pilot tone generation device for generating a pilot tone. The transmitting apparatus also includes a modulation device for obtaining the generated pilot tone and a modulating useful signal and for generating a frequency-modulated signal based on a combination of the generated pilot tone and the modulating useful signal. The generated pilot tone has a frequency outside a frequency range of the modulating useful signal in order to vary a frequency range of the frequency-modulated signal.