Navigation Receiver Using Clock Drift and Velocity for Reduced Transmitter Count
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Solution Overview
Problem
Existing navigation systems require at least four transmitters to determine position, velocity, and time (PVT), which can be unreliable due to factors like transmitter obstruction or failure, and are prone to drift in estimated position.
Innovation Solution
A navigation receiver system that can calculate PVT using signals from fewer than four transmitters by employing a receiver clock with clock bias and drift, a decoder to determine pseudo-ranges and frequencies, and a processing unit that uses known transmitter locations and velocities to determine the receiver's position, velocity, and time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If at least four transmitters are used to determine PVT, then position and time accuracy is maintained, but the system becomes vulnerable to transmitter obstruction or failure
Solution Approach 1:
The patent changes the parameters used for navigation by incorporating receiver velocity and clock drift as known or estimable quantities. This allows the system to solve for position using fewer transmitter signals by reducing the number of unknown variables in the navigation equations, thereby achieving reliable positioning with only three transmitters instead of four
2Adaptability or versatility
If fewer than four transmitters are used, then the impact of obstructions and failures is reduced, but position determination becomes mathematically impossible with traditional methods
Solution Approach 1:
The patent transforms the navigation problem by treating receiver velocity and clock drift as known parameters rather than unknowns to be solved for. This parameter redefinition enables the mathematical solution of position using only three transmitter signals, maintaining measurement precision while improving adaptability to reduced transmitter availability
Solution Approach 2:
The patent introduces receiver velocity and clock drift as intermediary parameters that bridge the gap between limited transmitter signals and accurate position determination. These intermediaries serve as additional constraints that enable the system to solve the navigation equations with fewer transmitters while maintaining accuracy
3Duration of action of moving object
If inertial navigation is used to estimate position, then navigation can continue with fewer transmitters, but drift in position estimates occurs over time
Solution Approach 1:
The patent implements a feedback mechanism where the receiver velocity is used to correct and update the position solution continuously. By incorporating velocity information into the navigation equations, the system can maintain accurate position estimates over time without the drift problems associated with pure inertial navigation, as the velocity feedback continuously constrains the solution
Data Source
AI summary
A system for determining a position of a receiver from as few as two or three transmitters. The receiver may be stationary or moving with a known velocity. The system includes a receiver clock having a clock bias and a clock drift relative to a reference clock and may also include a motion sensor. A decoder receives transmitted signals from a number of transmitters and determine pseudo-ranges and transmitter frequencies therefrom and a processing unit receives the pseudo-ranges, the transmitter frequencies and the receiver velocity and determines the position of the receiver therefrom. When only two transmitters are available, the position of the receiver is determined dependent upon a known receiver clock drift. The system may also determine clock bias and, when three or more transmitters are available, receiver clock drift. The processing unit uses ranging and Doppler equations in combination, and may also use a measured velocity.