Low Altitude Target Elevation Detection Using Interference Signal Amplitude

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Solution Overview

Problem

Existing methods for determining the elevation of a target flying at very low altitude, such as drones during landing, face inaccuracies due to multiple signal reflections from the ground, requiring costly and complex hardware or significant calculation capabilities, which are often not feasible for mobile radar systems.

Innovation Solution

A method using an electromagnetic detection system that extracts elevation measurements from the amplitude of interference signals produced by direct and reflected signals, employing sub-arrays of radiating elements and minimizing a specific function to calculate the frequency of the interference signal, allowing for determination of the target's height relative to the ground without requiring extensive hardware or calculation resources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high-resolution adaptive processing operations are used on the received signal, then measurement precision is improved, but device complexity and calculation capability requirements increase significantly

Engineering Contradiction:

Improveelevation measurement precisionVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential information needed for elevation measurement from the received signal by analyzing the interference pattern between direct and reflected signals. Instead of applying comprehensive high-resolution adaptive processing, the method extracts specifically the phase difference information that contains elevation data, thereby achieving precise measurement with reduced computational complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent inverts the conventional approach by not trying to eliminate ground reflections through complex processing, but rather by utilizing the interference pattern created by reflections as a useful signal source. By analyzing the constructive and destructive interference patterns, the system extracts elevation information directly from what was traditionally considered noise or interference.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If the width of the antenna beam is reduced and pointed towards the target, then measurement precision is improved, but device complexity and cost increase due to bulky hardware requirements

Engineering Contradiction:

Improveelevation measurement precisionVSAvoidantenna hardware complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical solution of using a narrow, steerable antenna beam with a signal processing approach. Instead of physically adjusting antenna orientation and width to achieve precise measurements, the method uses electronic analysis of interference patterns from multiple antenna elements to determine elevation, thereby avoiding bulky mechanical hardware while achieving comparable or superior precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If the radar is positioned at a sufficiently high level relative to the ground, then measurement precision is improved, but adaptability decreases due to constraints on radar height in mobile applications

Engineering Contradiction:

Improveelevation measurement precisionVSAvoidmobile radar adaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the measurement parameters by analyzing interference patterns at the existing radar height rather than requiring elevated positioning. By processing the phase and amplitude information from signals reflected off the ground and combining with direct signals, the system achieves accurate elevation measurements regardless of the radar's height above ground, making it adaptable to mobile platforms with constrained mounting heights.

Inventive Principle:

Principle #35Parameter changes

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 method provides accurate elevation determination for targets near the ground, accommodating existing radar models and requiring minimal computational resources, while being applicable to various antenna types and ground conditions, including non-plane and non-horizontal surfaces.

Implementation Method 1

The interference signal is produced by a signal re-emitted directly by the target and a signal re-emitted by the target towards the ground then reflected by the ground towards the radar

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

a signal re-emitted by the target towards the ground then reflected by the ground towards the radar

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS7994964B2Method for determining the position, notably in terms of elevation, of a target flying at very low altitude

Publication Date: 2011.08.09 THALES SA

AI summary

The present invention relates to a method for determining the position notably the elevation of a target flying at very low altitude. An electromagnetic detection system extracts the measurement of the elevation on the basis of the amplitude of the interference signal produced by a signal emitted directly by the target and by a signal emitted by the target towards the ground then reflected by the ground towards the radar. Embodiments of the invention can notably be used within the framework of the guidance of drones in the final landing phase.