Carrier Wave Frequency and Phase Modulation for Multipath Nulling
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Solution Overview
Problem
Radio transmissions experience periodic multipath nulling due to destructive interference between direct and reflected signals, particularly severe for moving transmitters like aircraft and drones, leading to communication losses, especially over calm water at low altitudes and long distances.
Innovation Solution
A communication system that periodically changes the carrier wave frequency or phase to prevent destructive interference, using a processor to anticipate and adjust the frequency or phase based on anticipated nulling conditions, ensuring continuous communication by maintaining signal strength above a minimum S/N level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency hopping is used to mitigate multipath nulling, then communication reliability improves, but system complexity increases and it becomes non-viable when there are fixed available frequencies or the waveform does not lend itself to frequency hopping
Solution Approach 1:
The patent changes the carrier wave frequency parameter periodically according to a predetermined schedule to prevent multipath nulling. Instead of complex frequency hopping across multiple channels, the system systematically varies the carrier frequency within available constraints, achieving reliability improvement without the full complexity of traditional frequency hopping schemes.
Solution Approach 2:
The patent implements periodic frequency or phase adjustments of the carrier wave according to a predetermined schedule. This periodic action prevents multipath nulling by ensuring that the carrier wave parameters change before destructive interference can consistently occur, providing a simpler alternative to continuous frequency hopping.
2Reliability
If the carrier wave frequency is periodically changed to prevent multipath nulling, then communication continuity improves, but signal stability deteriorates due to frequency variations
Solution Approach 1:
The patent applies periodic changes to the carrier wave frequency or phase according to a predetermined schedule. This controlled periodic variation prevents multipath nulling while maintaining signal stability by ensuring changes occur in a predictable, systematic manner rather than randomly, allowing the receiver to track and compensate for the variations.
Solution Approach 2:
The patent uses predetermined schedules for frequency or phase adjustments, where the changes are planned and anticipated in advance. This preliminary action allows both transmitter and receiver to coordinate their operations, maintaining signal stability while preventing multipath nulling through pre-coordinated parameter changes.
3Reliability
If phase adjustment is used to mitigate multipath nulling, then destructive interference is reduced, but system complexity increases due to phase negotiation and coordination requirements
Solution Approach 1:
The patent implements periodic phase adjustments of the carrier wave according to a predetermined schedule. This systematic periodic phase variation prevents multipath nulling by ensuring that phase relationships change before destructive interference can consistently occur, reducing signal quality issues without requiring complex real-time phase negotiation.
Solution Approach 2:
The patent uses predetermined schedules for phase adjustments, where phase changes are planned and coordinated in advance. This preliminary coordination simplifies the system by eliminating the need for complex real-time phase negotiation between transmitter and receiver, while still achieving the goal of reducing destructive 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
The solution effectively mitigates multipath nulling, allowing for continuous data communication even during periods where prior systems would experience complete loss of connectivity, with data recovery codes compensating for minimal data loss and maintaining reliable communication.
Implementation Method 1
reflected signals travel a path that is longer than the direct, line-of-sight path by some multiple of the radio wavelength that causes destructive interference of the carrier wave at the receiver
Implementation Method 2
a communication system periodically adjusts the phase of the carrier wave such that the reflected wave is no longer completely out of phase with the line-of-sight wave
Data Source
AI summary
A communication system periodically changes the carrier wave frequency or phase such that a signal traveling a reflected path no longer destructively interferes with a signal traveling a direct line-of-sight path. The communication system negotiates a periodic frequency or phase shift with a receiver, and then shifts the frequency or phase according to the negotiated schedule to maintain continuous communication.