Surface RF Transmitter System for VTOL Location
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Solution Overview
Problem
Existing navigation systems for VTOL aircraft, such as GPS and ILS, are unreliable in GPS-denied environments and unsuitable for precise location determination during takeoff and landing, especially in urban areas where GPS signaling is attenuated or interfered with, and ILS is costly and complex.
Innovation Solution
A surface-based ultrawideband multistatic positioning system using a set of RF transmitter nodes that output a sequence of pulses with predefined inter-pulse delays, allowing for precise location determination of vehicles by measuring propagation times, reducing multipath interference, and providing an alternative to GPS for navigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GPS is used for navigation, then location determination is provided, but reliability deteriorates in GPS-denied environments and urban areas with signal attenuation
Solution Approach 1:
The patent introduces an intermediary positioning system using terrestrial RF transmitter nodes as mediators between the vehicle and the positioning function. When GPS signals are unavailable, the vehicle receives RF pulses from ground-based transmitter nodes and calculates its position based on time difference of arrival, serving as an alternative information pathway that bypasses the blocked GPS signal route.
Solution Approach 2:
The system changes the fundamental parameter of signal propagation medium from space-based radio waves (GPS) to ground-based RF pulses with specific characteristics (ultrawideband, long inter-pulse delays). This parameter change enables operation in GPS-denied environments by utilizing a different physical layer approach with pulses separated by more than 1 microsecond to reduce multipath interference.
2Ease of operation
If ILS is used for takeoff and landing, then navigation assistance is provided, but device complexity and cost increase
Solution Approach 1:
The patent segments the positioning function into distributed, independent RF transmitter nodes deployed at different locations rather than a monolithic ILS system. Each node operates independently, transmitting RF pulses that the vehicle receives and processes. This segmentation reduces overall system complexity while providing the necessary navigation assistance for takeoff and landing operations.
Solution Approach 2:
The system replaces the complex electromagnetic field-based ILS with a simpler time-domain pulse transmission system. Instead of maintaining continuous electromagnetic fields and interpreting field strength variations, the vehicle measures time differences of arrival of discrete RF pulses, substituting a mechanically simpler timing measurement approach for the more complex field-based ILS methodology.
3Productivity
If short inter-pulse delays are used, then transmission efficiency is improved, but multipath interference increases
Solution Approach 1:
The system applies preliminary anti-action by pre-establishing a minimum inter-pulse delay of more than 1 microsecond before transmitting successive RF pulses. This predetermined timing separation proactively prevents multipath interference from previous pulses from overlapping with subsequent pulses, eliminating the harmful effect before it can occur rather than attempting to mitigate it after the fact.
Solution Approach 2:
The system employs periodic transmission of RF pulses with regular intervals exceeding 1 microsecond between consecutive pulses from the same transmitter node. This periodic action with sufficient spacing allows the electromagnetic environment to settle between pulses, preventing accumulation of multipath interference while maintaining consistent positioning updates for the vehicle.
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 system enables accurate location determination of VTOL aircraft with an error of less than a foot, even in GPS-denied environments, by using ultrawideband pulses with long inter-pulse delays to reduce interference, facilitating safe takeoff and landing operations.
Implementation Method 1
a set of radio frequency (RF) transmitter nodes that, when deployed at different respective locations, are configured to output a sequence of respective RF pulses
Implementation Method 2
determining propagation times that indicative respective amounts of time taken by the set of RF pulses to directly propagate to the vehicle
Data Source
AI summary
A surface-based transmitter system for assisting determination of vehicle location is presented. The system comprises a set of radio frequency (RF) transmitter nodes that, when deployed at different respective locations, are configured to output a sequence of respective RF pulses with a predefined inter-pulse delay between each pair of consecutive RF pulses in the sequence, wherein the pre-defined inter-pulse delay is longer than 1 microsecond. The set of RF transmitter nodes include at least a first RF transmitter node, a second RF transmitter node, a third RF transmitter node, and a fourth RF transmitter node, which are configured to output a first RF pulse, a second RF pulse, a third RF pulse, and a fourth RF pulse, respectively, of the sequence of RF pulses.