Passive GPS Fuze Height-of-Burst via Signal Correlation
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Solution Overview
Problem
Existing munition fuze systems face challenges in accurately determining the height-of-burst (HOB) for detonation, particularly when munitions are traveling at high speeds or using commercial/military GPS receivers with slow PRN averaging times, as they often require complex calculations or constant height measurements.
Innovation Solution
A passive HOB fuze system utilizing the difference in time between direct and reflected GPS signals from a single GPS satellite to determine the appropriate height for detonation, eliminating the need for a transmitter and reducing the need for constant height calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex calculations are used to determine HOB based on launch parameters and trajectory, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical calculation systems with an electromagnetic signal-based measurement system. By using GPS signal correlation between direct and reflected paths, the system determines HOB through signal processing rather than complex trajectory calculations, thereby reducing computational complexity while maintaining precision.
Solution Approach 2:
The patent introduces GPS signals as an intermediary medium to determine HOB. Instead of directly calculating trajectory parameters, the system uses the reflected GPS signal as a mediator to indirectly measure the vertical distance to the target surface, simplifying the determination process.
2Measurement precision
If constant height measurements are performed to determine HOB, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary correlation setup by storing the direct GPS signal pattern before the munition reaches the target. This allows the reflected signal to be compared against the pre-stored pattern, eliminating the need for real-time signal processing and rapid repeated measurements, thus reducing time loss while maintaining accuracy.
3Measurement precision
If a transmitter is included in the HOB fuze system to actively measure height, then measurement precision is improved, but weight of moving object increases
Solution Approach 1:
The patent makes the GPS receiver multi-functional by using it for both navigation and HOB determination. Instead of adding a separate transmitter and receiver system, the existing GPS receiver is utilized to process both direct and reflected signals, eliminating the need for additional active transmitters and reducing overall system weight.
Solution Approach 2:
The system uses the naturally occurring reflected GPS signals from the environment rather than requiring an active transmitter. The Earth's surface itself serves as the reflector, and the GPS satellite provides the signal source, allowing the munition to passively determine HOB without carrying additional active components.
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 allows for more accurate and efficient determination of the HOB, adapting to varying speeds and GPS receiver capabilities, and simplifies the calculation process by correlating the time difference between direct and reflected signals to generate a detonation signal.
Implementation Method 1
The second GPS signal being a reflected GPS signal that is a GPS signal from the same satellite after having been reflected by the surface of the earth in the vicinity of the target
Data Source
AI summary
The present invention is directed to fuze system for munition that produces a height-of-burst (HOB) signal using two Global Positioning System (GPS) signals, the first signal being from a particular GPS satellite (the direct GPS signal) and the second signal being the GPS signal from the same GPS satellite after the signal has been reflected from the surface adjacent to the target. In one embodiment, the HOB signal is generated when there is a substantial correlation between the reflected GPS signal and direct GPS delayed by an amount of time that is indicative of the desired HOB.